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Corvette Modifications
Corvette Modifications
I don't know exactly how this section should be formatted, so for now if you send me your details I'll just add them to one of the appropriate files below according to year. I'll put your name and email address with it so others can ask more specific questions, unless you request that I not include it. I'd like to also get some info about comparisons of various parts, such as the muffler numbers that have been posted before. Longer articles, or those that are applicable to more than one generation are listed at the end.
Modifications by year...
- 1953-1962 C1 / Straight Axles
- 1963-1967 C2 / Midyears / Sting Rays
- 1968-1982 C3 / Sharks / Stingrays
- 1984-1996 C4 / Clamshell / ???
- 1997-up C5 / Late Model
- Noel Carboni's Customized 82 Collectors Edition.
- Removing the body from your '53-'62 corvette.
- Making your Corvette lighter.
- Removing the rear suspension/drivetrain components from your Shark.
- A recipe for a 300 hp L98.
Performance mods for 1953-1962
Engine Modifications
From Jerry Galang, jg@acti.com:i have a 1959 modified corvette; 1974 LT1 engine 3/4 clay cam solid lifters edelbrock intake holly 750 mallory dual point headman headers b&m 3 speed 456 rear modified front end, no teeth, bobbed, 62 grill chrome roll bar
Suspension Modifications
Body Modifications
Performance mods for 1963-1967
Mike Cobine's midyear '66 race carEngine Modifications
Suspension Modifications
From: Mike Ennis: mennis@PICA.ARMY.MILI put the Richmond 6-speed in my '66 but it is not a big block car. I used the stock drive shaft and transmission mount, but had to make a new mount bracket. The midyear trans mount bracket is not the same as the '68 and later brackets. You can use the original bracket mounting points, so you don't have to modify the frame crossmember at all. It's pretty easy to make a new bracket out of 1/8" steel plate with minor welding. I can send you my drawing if you want it. The rubber mount itself works fine if you trim the corners off a little for clearance. The drive shaft is O.K. except for changing the front yoke to match the Richmond output splines.
The console required about a 1/2 X 1" piece to be removed from the trans tunnel and the console itself at the left rear corner where the stock unit tapers in toward the center line. I bought an old console to cut up and saved my original one.
The shifter is a tight fit in the opening and required some persuasion and minor trimming of the tunnel to get it in. Also, the reverse gear shift arm interferes with the tunnel and I had to cut a relief hole in the side of the tunnel which I covered with a wedge-shaped piece of sheet metal screwed over the opening. It's alongside the seat and doesn't show.
I used the stock pressure plate but had to change to the 26(?) spline clutch disc.
The speedometer cable works allright but it is a challenge to install it -- very tight clearance to the tunnel.
All in all the job was more work than I expected but that almost always seems to be the case, doesn't it? I am very happy with the way the car performs with this set up, but I should warn you that the Richmond trans is noisy and the shifter is stiff -- i.e., I can't flat shift from 2nd to 3rd or 4th to 5th. I am using the stock 3.08 rear and that ratio is very good for the street with the low (3.27) first gear of the trans.
If you have any other questions just ask. Have fun!
Body Modifications
Performance mods for 1968-1982
Engine Modifications
From Bill Jurasz, bjurasz@ti.comHere goes the scoop on my '80:
It started out as a stock 1980 L48 4-speed with 3.08 posi. The motor, exhaust and ignition have since been redone. The motor is a new unit from Auto Center in Dallas Texas. It is a new 4-bolt block, forged rods, cast aluminum pistons, L98 aluminum Corvette heads, 9.5:1 compression. Intake is an Edlebrock Performer EGR. Carb is a Carburetor Shop Stage-II QuadrJet. On the factory exhaust, minus the catalytic, the car turned a best of 14.79, averaging about 14.89. The next major modifications made including a whole new exhaust (Blackjack AK5000 headers, 2.5" pipes, single 3" catalytic, DynoMax Super Turbos), a new iginition (Performance Distributors Street/Strip HEI), reconnecting the factory dual snorkel intake, and adding a K&N. Best e.t. dropped to a 14.22, averaging in around 14.29.
According to the AutoCenter literature, the motor is rated 300hp and 350 ft-lbs. The cam is a dual pattern cam (.442"/.465" lift, 288/298 duration, 112 degrees spread). It idles very well with high vacuum (near 20"). I run it to 5500rpms between shifts. It consumes some oil, but nothing out of the ordinary for a small block. With a stock '80 L48 running the quarter in the high-15s, I've added about 110hp and dropped nearly 1.5 seconds off my time! This motor has also seen four 15-hour at-a-time road trips on the highway without any complaints and with decent mileage.
My recommendations for carbureted vehicles:
- Carburetor Shop Stage-II QuadraJet
- Factory 1980 dual-snorkel fresh air intake and K&N
- Headers and DynoMax Super Turbos, plus the biggest cat. you can find
- Performance Distributors Street/Strip HEI ignition
- A decent cam, such as a Comp Cams 268H
- Mild head work
- Balanced crank/rods/pistons
- Forged pistons ONLY if you plan to go over 6000rpms or use nitrous
From: Noel Carboni: ncarboni@ccmail.racal.com
The engine is a 417 CI small block Chevy, which was created from a 2-bolt 400 block bored .030 over and outfitted with a special Speed-O-Motive offset-ground crank. I deburred everything and installed oil-drainback filters, mounted up a Melling high volume oil pump, installed Clevite (Michigan) 77 bearings, and slopped on lots of sealant to keep the leaks at a minimum.
I bought Dart II iron heads and put a hundred or so hours (some of which was learning time) into porting and polishing them. The compression ratio works out to about 10.5:1, which seems to be just below the practical detonation limit for iron heads and 93 octane premium. The pistons are Arias forged, and the cam is an Iskendarian hydraulic with 280 degree off-seat duration (232 degrees at 0.050), 0.480 inch lift, and a 109 degree lobe centerline. Rhoads lifters effectively reduce the valve duration at low RPM, and a Cloyes double roller timing chain coordinates everything. I believe, however, that this combination could use more valve lift, and I'll be using a higher lift roller cam and/or higher ratio rockers for my next engine.
On top is a F.I.R.S.T. (Fuel Injection Research System Technology) TPI system, which sports a huge throttle body and runners. This replaced the TBI (Throttle Body Injection) system originally shipped with the car. It is rated to flow enough fuel/air for 450 HP. Sadly, I think the manufacturer (IMPCO aka AirSensors, a California-based firm) has gone out of business. I wonder where I'll get my next mass-airflow sensor... Anyone need a ported TBI intake with all the goodies?
The TPI has its own computer, nestled in the glovebox, which provides buttons to select parameters and a knob to adjust them. Tweaking this thing turns out to be a fun way to pass the time at stoplights, with the runs between serving as tests.
The existing GM ECM (Electronic Control Module, or "computer" by another name) still manages spark timing. I reverse-engineered the ECM tables from the ROM (Intel 2532 EPROM compatible pinout) and did a lot of seat of the pants testing to determine the optimum curves for avoiding detonation and making Mustang drivers feel bad.
Blackjack AK5000 headers wrapped with Thermotech insulation carry the hot gasses out into a dual 2 1/2" exhaust (2 cats). The insulation saves a lot of wear and tear on engine compartment goodies, not to mention the hood paint.
The engine idles well (although a bit rough below 900 RPM) and pulls strongly from 1500 to 5500 RPM. It really kicks you in the pants at 3000 (it smokes the tires in 1st AND 2nd gear)! This mandates a conservative approach to driving in the rain or in any traction-limited situation (a la always)!
From: "Michael H. Shaffer"
I used to work for Summit Racing in the Engine Development department, so if anyone has any Fuel Injection Technical Questions or general Engine Technical questions I would be willing to answer them.
74 Corvette Coupe Specs.
- Base Coat Clear Coat Bright Red
- Ceramic Coated Side Pipes
- Daytona Rear Wing
- 355 Engine
- Summit Stage II connecting rods
- Custom "swirl patterned" Aluminum Keith Black Pistons
- Hydraulic Roller .510 in/.490ex lift 282 dur
- Ported Trick Flow Aluminum Heads 2.05/1.62
- First TPI Induction/ Ported & Polished
- GNX Fuel Injectors, Flow rated and balanced
- DFI ECM
- MSD 6AL Ignition/W MSD Blaster Coil & Distributer
Suspension Modifications
From: Noel Carboni: ncarboni@ccmail.racal.comTransmission, Drive Train, and Suspension (getting the go to the ground)
If you remember, the 1982 model only shipped with a 700R4 4-speed overdrive automatic. 1982 was early in that transmission's design lifetime, and (you other 1982 owners probably guessed this already) it ground itself into little metal particles at about 60,000 miles, still coupled to the original unmodified 350 engine. What to do?
I bought a Doug Nash 5 speed, way back before Richmond Gear bought them out and began making a 6 speed (sigh). I also got a Centerforce dual friction clutch setup and a bizillion '80/'81 Corvette manual transmission parts from GM. Everything from the backup light switch to the Z-bar stud on the engine to the clutch/brake pedal linkage had to be dealt with. The GM dealership parts guy began giving me wholesale prices because I was such a regular customer.
I got a shortened drive shaft and special U-joints (one is even Chrysler sized, for Chrysler's sake). The cross-member didn't fit, so I got a late '70s part from a junkyard and modified the transmission mount. Since this cross-member has holes for exhaust pipes on each side (rather than a hump on one side) I had to spring for a custom-bent exhaust system (anybody ever notice that the word "custom" is gold-plated?). The list just goes on and on of big and little things that had to be done. What an exercise, BUT IT WAS WORTH IT!!! The Hurst is pure pleasure to shift, the exhaust note is healthy, the tire smoke impresses the guy behind, etc. This is the way GM should have built the car in the first place. Come to think of it, late model 'Vettes have a lot of these attributes...
Now I had this problem. I kept breaking my differential. The first time, I literally broke the housing into 3 distinct pieces. Let me tell you, it was an expensive sound. I searched far and wide (at the time not having Internet access) and found a little shop in Delray Beach, FL, near my home called (I think) Florida Corvette Calipers or Florida Precision Calipers (at least I know how to drive there). They built me a replacement with a new housing and hardened gears, but in about 6 months I broke off a couple of teeth (another expensive sound). Finally, the owner, Carl, who knows metallurgy, sent off for "special FAA machine shop" gears that I haven't been able to break yet. I'm now using synthetic gear lube, too.
Vette Products keeps my car from dragging on the road and from running into stopped semis and guard rails. I love sending money to these guys:
VP made me a 400 lb fiberglass rear spring to replace my Gymkhana steel spring (to my chiropractor's chagrin). I installed a VP 3/4" rear anti-sway bar and polyurethane bushings for the trailing arms, the spring end links, sway-bar links, the camber arms (struts?), and all of the other squishy parts. I originally put Koni shocks (adjusted to max stiffness) all around, but a broken half-shaft U-joint mandated replacement rear shocks, so I'm now riding on Carrera rears. Its a bit squeaky (due to the poly bushings), but boy does it corner. I can enter a corner 15 or 20 MPH too fast and just go around it! I've left a lot of late model cars in the dust at on-ramps and the like, which usually results in some puzzled expressions (and an inner feeling of joy) should they ever catch up to me.
One thing I'm thinking about doing now is replacing my 550 lb front coils, A-arms, etc. with a VP transverse fiberglass monospring system. This should reduce the unsprung weight a good bit and improve handling over not-so-smooth surfaces, not to mention refresh my bushings. Also, VP updated their rear setup to provide a dual mount for the '82 aluminum cross-truss. I might have to check that one out as well.
I have VP brake calipers in the front and the original (believe it or not) GM calipers in the rear. I'm running carbon-metallic pads all around and all of calipers are plumbed with steel braided brake line. I'm using the VP heavier-than-stock rotors mated with lighter-than-stock hubs. Silicone brake fluid keeps the corrosion down and the boil temperature up. The car stops true and really SHORT. This setup has saved my buns from a crash on several occasions. The only thing I worry about now is being hit by the car behind, but there usually isn't anybody close behind...
For those of you considering carbon-metallic pads, one warning: The friction characteristics change slightly as they get hotter (they grab more when hot). This isn't a problem when you learn to expect it, but please don't let it surprise you when you first put them in. Also, contrary to popular lore, they make a LOT of black brake dust (but don't seem to wear very fast - interesting).
BF Goodrich Comp TA 255-60-HR4s ($85 apiece installed!) are carrying me through the corners, although I can go a lot faster than the 129MPH H speed rating (alas, but where?). These are the best 15" street tires I have ever had, and I sure like the price as compared to those for 16" and 17" rims!
Body Modifications
From: Ross Jones <rossjones@ti.com>
Her name is Shamu, and she is a 1973, 454 (engine was balanced and blueprinted, no other mod's), automatic, T-tops, with a major paint job consisting of 4 shades of blue, pearlized white, and black, with some gold pin-stripping.
The interior has been changed to black leather and black carpeting.
The wheels and tires have been altered to larger sizes and much of the engine has been chromed. The front has been changed, nose clip is different, and the back bumper is painted black.
A little history: the previous owner had most of this work done and showed the car (which accounts for the low miles when I got it last year of ~43,000). The car is originally from the Dallas area (Garland) and has always been here. That owner died and his father got the car, but did not want to drive it. He stored it until a machanic I know got ahold of it and fixed it up, as it had not be properly stored.
About that time I was in the market for my first Corvette and went to talk with Jim, the machanic, about Vettes since I knew he fixes/restores them as a side line to his normal auto shop business. After talking to me about what I was looking for, I wanted a 70's, a/c, good condition, he pointed this one out to me. It is really different, and I'm sure many purist would be scratching their heads. But I liked it, and the price was okay. By the way, all the numbers match.
I know it's a bit different, but its a Corvette, and my first!! I love it. I love driving it!! I love to show it (to anyone). I've never had a car I love as much; even my first: a 57 Chevy.
My wife, named her because of the paint job, and it has stuck.
Best regards,Ross Jones
Member of LSCC (Lone Star Corvette Club)
Plano, TX (Just north of Big D)
Performance mods for 1984-1996
Engine Modifications
Greg Crowe, '85 and '92
Michael Shaffer, '87
Dan Durbin, '91
Chris Adamec, '92
Michael J. Bird, '92
Jerry Forbes, '93
Michael Eckhaus, '93
Craig A. Thompson, '93
Suspension Modifications
Body Modifications
J. Carlos Fox, '92
Performance mods for 1997-up
Engine Modifications
Suspension Modifications
Body Modifications
How To Make Your 1963 to 1982 Corvette Lighter
by Mike "Doc" Cobine 70373.2450@compuserve.com or cobine@cig.mot.comCorvettes, although fiberglass bodied, are heavy vehicles. When the 1963 appeared, it was 3015 pounds, slightly lighter than the '61 and '62 Corvettes, yet still heavier than the ones before. By 1968, the weight had increased to 3210 pounds and continued to climb to 3529 in 1975. At 3572, 1978 was the heaviest year as Chevy put it on a diet since someone finally realized that weight was counterproductive to gas mileage, braking, handling, and acceleration. By 1981, the Corvette was back down to 3307 although it jumped right back up to 3342 in '82, the last of the Sting Ray/Stingray chassis.
In 1980 at Road America for the Can Am, I met a guy with a '68 Coupe that was considerably lighter. He claimed it was 2200 lbs. And he drove it there. He bought his '68 new and was disappointed to be beaten constantly by the Cobras. His contention was the only reason the Cobras were beating Vettes was due to about 800 lbs difference. so he lightened his.
The Corvette has a lot of fat in it so you can lighten it a lot. My '66 weighes roughly 2700 and that is with a bunch of welding, steel gussets, and roll cage tubing. So you could shave a few hundred but at what price, both in dollars and in comfort?
Here's some ideas.
Engine
- aluminum block - ~ $2500
- aluminum heads ~ $750
- aluminum intake (if you have the iron one) ~ $150
- aluminum water pump ~$80
- tube headers
- aluminum flywheel or 12 lb nodular iron Chevy flywheel
- aluminum accessory brackets
- aluminum radiator
- removal of radiator core steel support (make an aluminum one)
Body
- removal of entire air conditioning system (evap, cond, dry, comp, lines)
- removal of heater system
- removal of hidden headlights (use fixed lights)
- removal of hood mechanism (use hood pins)
- removal of vacuum reservoir
- removal of 5 mph bumper assemblies (leave skins on)
- removal of bumpers and brackets
- removal of spare tire and carrier
- removal of steel header bar under front nose (replace with homemade fiberglass item)
- removal of hood frame
- removal of inner fenders
- removal of your steel floor '76 up (not sure how you do that, other than throw body away and start with a '75 back body)
- replace factory fiberglass front with lightweight aftermarket front
- removal of birdcage inside the body
- removal of door hinges and striker plates
- change to smaller battery
Interior
- removal of door beams or replace with pre-'73 doors
- removal of window crank mechanism or power windows (use a strap to lift window)
- removal of window glass if not needed
- removal of T top inner panels
- removal of convertible top and frame
- removal of hardtop inner panels
- replace hardtop window with plexiglass
- removal of tilt/tele wheel for standard one
- removal of stock seats for racing buckets
- removal of storage compartment doors
- removal of all interior trim, door panels, etc.
- removal of radio
- removal of stock instruments
Suspension
- change to fiberglass spring in rear
- change the front to a transverse fiberglass spring
- change A arms to tube type (check circle track magazines)
- change the iron rear end to the 80 up aluminum diff. and crossmember
- change to newer aluminum half shafts (fabrication reqd.)
- change to newer aluminum driveshaft (fabrication reqd.)
- replace stock camber rods with tube adjustable ones
- remove center cross member and replace with lightweight tube
- change from steel rally wheels to alum mags
- change from steel belted tires to fabric belted
Doc
'63-'82 Rear Suspension Removal
by Mike "Doc" Cobine 70373.2450@compuserve.com corvettedoc@geocities.comSooner or later, most people end up having to remove the rear suspension of their Sting Ray/Stingray. The basic chassis is the same for '63 to '82 but the '80-82 cars have a different, and possibly easier to remove, differential mounting method.
Since you want to work on separate components (You don't want to lug 350 lbs of rear suspension onto your bench vise), you are better off disassembling it in the car piece by piece.
The most common reason to remove the rear suspension is to replace a worn out or broken part. You can use this to remove all or just the parts you need. If you are removing the differential to change gears or replace as it is broken, you do not need to remove the trailing arms. Also, if you are removing the trailing arms to replace bearings or bushings, you do not need to remove the differential. This is a rough sketch of what you need to do:
- Support your Corvette on sturdy jack stands. Use good ones unless you
are very good at bench pressing 2000 lbs. The newspapers seem to like
putting in pictures that have a set of legs sticking out from under a car
after a cheap jackstand has collapsed.
CAUTION - do not run the car on the jackstands and DO NOT engage any gear with the engine running. The rear axle is at a severe angle at the limits of the u-joints and may cause severe damage. - Remove the rear tires.
- Remove the exhaust pipes and mufflers.
- Remove the spare tire carrier.
- Remove the rear sway bar, if you have one.
- Remove the half shafts. If original, there are French locks that fold over the bolt heads to keep them tight on the outside flange. Remove these to remove the four bolts. Install new French locks when you reassemble.
- Remove the spring. Use a floor jack to hold the spring, remove the nut and bolt on the end, and let the jack back down. I typically clamp Visegrips (R) on the leaf where it can wedge against the end of another leaf so the jack has something to grip and not slip. Do Not use a bottle jack but a roll around floor jack. A bottle jack could tip over and be flung by the spring.
- When both ends are loose, remove the 4 center bolts at the differential
mounting plate, if you are removing the differential. If you are only
removing the trailing arms, you can leave the spring.
CAUTION: The steel spring is heavy, roughly 50 lbs. You may want to have some help to remove it. - Remove the shocks. You will need to jack under the trailing arm slightly to remove pressure on the shock. Lower the arm slowly after you remove the shock so it rests in the frame stop.
- Remove the camber strut rods at the shock end and the 4 bolts in center to the diff. You must remove the shock mount to remove the outer end of the camber rod. Do not hammer on the mount as you can destroy the threads and possibly break it.
- Remove the brake lines. You need to disconnect the rubber hoses to the trailing arms and the emergency brake cable.
- Remove the trailing arm front bolt. Expect this to take longer than you can imagine as they are usually rusted in and there is little space to work. Renting a reciprocating saw with a hacksaw blade (several) can make life easier. Many find that it is easy to use a cutting torch to cut the shims and bolt out and then just replace the old bushings. If you are removing the arm, it is probably because the front bushings are bad so they are possibly correct in their method. Just use care to not set the Corvette on fire and have someone standing by with either a fire extinguisher or a water hose.
- Disconnect the driveshaft at the diff. Remove the diff front mount.
- 1963-1979 - Choose whether you cut some holes in the rear floor or take
three times as long. If your rear crossmember has been removed before, it
may remove easily. If not, it can be quite firmly attached.
There are 4 bolts from above that hold the diff to the crossmember accessible ONLY through the floor. Two small holes, quick patch afterwards, and you are in and out. Actually, the location is such that nothing splashes through this hole anyway and the carpet will cover it nicely. If you run stock under the car exhaust, you will wish to seal it to prevent carbon monoxide from entering the car.
The other way can be quick or it can take forever. You remove the diff and crossmember as a unit. Have the floor jack about 1" under the diff. Remove the 2 bolts in the cups. Use the biggest crowbar you can find to pry the crossmember off the cups that hold it.
CAUTION - The diff and crossmember are very heavy and can do severe damage to you if they fall. DO NOT lay under the car while doing this. - 1980-1982 - The crossmember and differential cover are one item. The
mounting of the crossmember is located on horizontal bolts rather than on
verticla cups and the removal is sometimes easier. After removing the two
bolts, you may still need to pry on the ends to get them out of the mounting
bracket.
CAUTION - The diff and crossmember are very heavy and can do severe damage to you if they fall. DO NOT lay under the car while doing this.
Doc
Recipe for a 300HP L98
My car:
- '90 convertible
- Auto
- Pulley set (Was 3-pulley, but...)
- modified air filter lid
- 160 thermostat
- high-flow filter element
- air foil
- 52mm throttle body
- cleaned up plenum entry and interior and matched to runners
- 1.6 full-roller rockers on both intake and exhaust, with guide plates
- no pre-cats
- no cats
- Flowmasters
- 3.31 or 3.54 rear (never did check which one it was. It's out of an early six-speed)
- 285 GCSs
- custom prom
- matched 24# injectors (out of a Ford. Cheaper than GM stockers, even for he matched set)
- GM ignition and GM "black" wires (as good as Accel in my use, and cheaper)
- Adjustable fuel pressure regulator, at 45lbs with vacuum line attached
- Oh, and most important, a vanity license plate. Gotta have one, ya know!
- In other words, the usual bolt-ons, except for the rear end.
Last time I actually ran it on a drag strip was at Beech Bend during the 94 reunion. 13.80 @ 99 mph. 60ft was 2.08. I won't tell you how slow my reaction time was--but since it was only time trials it didn't make any difference. The car is a little quicker now; maybe 13.6-13.7? I estimate the horsepower to be right at 300, given that et and MPH.
And it hasn't idled correctly since I put the rockers on. Cooincidence? Don't know. Cottrell says in his book that 1.6's on the exhaust "show no real improvement and reduce idle quality". He was talking about an 87 (I think), but my experience backs that up. I can't speak for any other year, but on my 90, it does make the idle rougher.
I put the matched injectors on it because I could get them at a good price, and I needed to replace the GM 22s anyway. (It's amazing to how a car with 20K miles on it can need new injectors, but there they were, some leaking, some with high resistance...).
The throttle body and some of the other stuff is there because I'm sneaking up on the price of a "big mouth" manifold base, cam, larger runners, headers, and heads. (And a 383? Or maybe I'll just say screw it, and get a supercharger). I can only afford to do a little at a time--and besides, I like to see how much difference each of these changes makes.
I've been through four chips. One of the downsides of going at it a step at a time is that you need to re-do the chip fairly often. I started with a Hypertech. I've also had TPIS. Seems as if Hypertech put a lot of advance into their chips, as well as the mixture change. Both also change the manner in which the converter locks up. Anyway, with either, there was some change in the upper mid-range that you could feel, but in retrospect, I'm not sure it was worth $400. Now, of course, I need the chip. It won't run correctly with the stock one anymore
I feel essentially the same way about the damn mufflers. Not worth the money or noise on an otherwise stock car, but necessary after you do a couple of other changes.
Air foil? Who knows? I don't think that anyone's butt is sensitive enough to tell whether it's there or not--but it *seems* as if it should help, and it's cheap.
Easily, the most noticeable change I've made is the rear gear. I think a ratio in the mid-3's is nearly perfect for the street. Even back in my hot rodding days, I was running 3.55's and 3.70's when others were thinking that 4.10's and 4.56's were the hot setup. I can't see it, unless your power peak is way up there--and it ain't on TPI motors, unless you've done a bunch to 'em, like getting rid of the GM TPI runners and manifold, a la Accel Super Ram, or TPIS mini-ram. I haven't, and won't. My "thing" is for it to always appear totally stock at first glance, and to be completely driveable with very little compromise necessary.
Second most effective? I'd say it was the exhaust setup. But if you do that, you *will* need a chip made for you.
Why the high fuel pressure? Don't know. It just runs best there, so that's where it stays. Your mileage may vary, as they say. I've heard of guys running them as high as mine or more, but not too many do.
It used to like to have it's initial advance set at 8-10, but since the last chip, I set it at 6. We put a faster rate into the chip, and it seems to like it. I think we could even use a little more, since on cool days my Diacom doesn't show me too much retarding going on. Maybe I should push it a little higher? My engine does seem to run a little cooler now that I use Red Line Water Wetter (Thanks Hib), so maybe I can handle a little more initial? I always did like to run a lot of initial advance whenever I could get away with it.
Diacom also says I've got a few fat spots in the fuel curve at WOT. In a couple of places mid-range it goes to 11.2:1. I like to stay in the 12:1 range at WOT. I'll fix it one of these days. I could back off on the fuel pressure, but then it'd lean out in other places, so we'll change the curve in the chip.
Diacom is a great piece of software. If you've got a laptop PC, you ought to have Diacom. They (used to?) sell two versions. Only major difference was one would record several minutes of engine data, and would print graphs, while the other one would only record 20 seconds or so of data, and did not print. Difference in prices was substantial. I just print the graphs out of a spreadsheet program. Does a better job anyway. And I don't need "minutes" of engine data. A hint: Diacom doesn't like to run on really fast cpus. I run it on an old 386-16 laptop that I had around, and it works fine. You could pick up one of those for $100, if you looked in the paper hard. It is really neat to drive down the road and be able to actually *see* all of those read-outs changing in real time. After you get used to it, you can see wheelspin, converter flash, slippage, etc. Now if I just had a Vericom...
Throttle response is "right there". No bog, no problems. The 60-foot times indicate that I'm not having any real traction problems. (I use the "stab it from idle" launch technique). I might get it down to 1.9 or so, but it seems to me that that's about as good as it's likely to get.
Supposed to be that the 90-up TPS is self-setting so it doesn't make any real difference that it's .57-.64 volts when the throttle's closed, but by golly mine seems to "know the difference", and it likes to be in the .65-.67 range. I run more Initial Air than the book calls for, to smooth the idle some and avoid stalling, and with the non-adjusting TPS I just set it as low as the slot will allow. That works out to be about right.
Oh! The pulleys. The damn thing idled too slowly to keep the battery charged with the full set of three, and you can't really set the idle up too much with an auto car, so I replaced the alternator pulley out of the set with the stock one. Works fine now. Does it make it faster? Nah, not really, but you know, all of those little changes might just be worth something some day when I finally work my way up to the 383..
I've not invested any money in the trans. I'd like to maybe get a mild shift kit, mostly for the adjustable shift points. Right now, I pull the cable out a click or two at the throttle linkage. (What the hell's the name of that cable? I've forgotten.TCC? Anyway, it goes from the throttle linkage to the valve body on the trans). Pulling it out a little works to lower the shift point to 4900-5000, but I don't feel it's good for the trans to be driving it around like that all the time. It seems to slip a little more than it should at part-throttle shifts. If I adjust the cable the way it's supposed to be, the things shifts at 5300-5400 RPM. I think that's too high for my motor. Anyway, I pull it out when I want to to go fast, and put it back when I don't.
This has been a little long. (I do ramble). Sorry. Hope it helps someone, somewhere.
WOT = Wide Open Throttle
TPS = Throttle Position Sensor
TCC = Transmission Control Cable(???)
Cottrell = Myron Cottrell; owner of TPIS (TPI Specialities)
Beech Bend = Beech Bend Raceway Park, near Bowling Green Kentucky, and the
Corvette plant. The location of the National Corvette Reunion in the past,
(and again in the future, thankfully).
