1980 Corvette L-48: I need some performance help from you guys/gals!

[zackm58941]

Hi again, after recently installing a set of headers on my vette (l-48) I now find myself asking the same question that I know many have also asked. Whats next?!? First off, this is what I have done so far: Edelbroke Pro Flow Air Intake, Accel Igniton Coil and Distributor, Dynomax Headers, Dynomax Ultra Flow SS Mufflers, catalytic converter delete (track only) and Comp Cams 1.52 Roller Rockers. The car does perform better vs its stock form but I'd like some more. I noticed the sprak plugs inticated a rich mixture when I had them out for the header install so I think re-jetting/carb rebuild on my Q-Jet is first. I have seen kits on Summit Racing.com and Jegs.com but from what I understand these are just to get them back to OE performance, right? I was woundering if anyone could recommend a rebuild and jet kit that would work well with the mods I have done so far and sort of "pull" it all together. Now that I have asked that one, what would the next step be for raising overall engine performance without sacrificing driveability too much? Camshaft and heads come to mind but there are so many choices out there that I cannot make up my mind, would anyone have any specific sugestions for my specific engine and performance mods? I know this is a lot but I have gotten some really good help from people on this site before and I'm sure there is someone that can point me in the right direction. Thanks in advance for any help!!!

Zack

 

[JHL]

I had an 80 4 speed with a mild comp cam in it, i just bought some new neddles for the secondery barrels of the quadrajet, a few pounds and 5 minutes to fit and a big difference under WOT. I am sure any parts shop will get you the right ones.

J.

 

[turvette]

We are an "older" couple who just purchased a 1980 'vette from a local fellow. We are the 3rd owners. It has always been garaged. Great paint, near showroom condition. The leather is starting to dry out and crack. (It is a dark cherry red interior). The engine idles a little rough -- minor things here and there. We would like to make contact with someone on the Oregon Coast that has a similiar product. We are in Seaside. 'Looking forward to hearing from you.

 

[Glensgages]

..... Now that I have asked that one, what would the next step be for raising overall engine performance without sacrificing driveability too much? Camshaft and heads come to mind but there are so many choices out there that I cannot make up my mind, would anyone have any specific sugestions for my specific engine and performance mods?

You ask a thousand different people about a particular combination, you'll get 1000 different responses.....

To-date, I think you've only scratched the surface (performance-wise) by playing with the intake and exhaust:
choose a hydraulic cam with approx .450" lift, 216*-220* duration at .050" lift, and 112*-114* LSA, and set of 64cc cylinder heads with 2.020" intake/1.600" exhaust valves.

This cam would idle smoothly-enough to operate your vacuum-assisted options, yet pull right up to 5500+ RPM, probably the safe limit for your cast-crank/junk-rod/cast piston rotating assembly, and work fine with your OEM torque converter, too:
the increased compression-ratio alone (by going to 64cc heads) will gain approx 20-25 HP, and the larger valves will allow more air-flow

My '79 Z28 got 18 MPG on the highway, yet ran 14-thirties @ 97 MPH (open-headers, and 3.42 gears on 225/70R15 UNIROYALS), running straight SUNOCO94 or AMOCO93 with a similar combination, and I think you might really like it!

Glen...

 

[81 Corvette]

rear gears will make a difference as well. Not sure what you have, but i went for 2.87 to 3.54 and they made for a nice off the line improvement.

if you want to work on the motor, it boils down to heads and cam unless you want to do an entire rebuild, then its a blank sheet.

i'm getting to your situation, and need to start looking at heads and cam as well for mine

 

[Jack]

I noticed the sprak plugs inticated a rich mixture when I had them out for the header install so I think re-jetting/carb rebuild on my Q-Jet is first.Zack

ZACK:
It seems you looked at plugs BEFORE you installed headers. If so, I suggest you take another look at plugs ... mixture might've changed a good bit with the exhaust changes. Do this before you proceed with carb.

The prior cam suggestion and gear suggestion are good ones. If you're not up for pulling the intake & radiator for cam change, you could simply change out the timing set for a 3-keyway set ... BUT ... install it in the Advanced position ... this will build a bit more compression and will increase bottom to mid range giddyup ... but you'll probably lose some at top end. As with exhaust, any changes in cam timing or profile can affect jetting requirements.
JACK:gap

 

[zackm58941]

I wanna thank everyone for voicing their opinions and giving me ideas where to go next! I believe when I looked up all the stuff that is on my car now, I had the 3.36 gears in the rear with the close ratio manual tranny. I dont think I will play with gearing just yet though... I will probably go along the lines of what Glensgages sugested:

To-date, I think you've only scratched the surface (performance-wise) by playing with the intake and exhaust:
choose a hydraulic cam with approx .450" lift, 216*-220* duration at .050" lift, and 112*-114* LSA, and set of 64cc cylinder heads with 2.020" intake/1.600" exhaust valves.

This cam would idle smoothly-enough to operate your vacuum-assisted options, yet pull right up to 5500+ RPM, probably the safe limit for your cast-crank/junk-rod/cast piston rotating assembly, and work fine with your OEM torque converter, too:
the increased compression-ratio alone (by going to 64cc heads) will gain approx 20-25 HP, and the larger valves will allow more air-flow

My '79 Z28 got 18 MPG on the highway, yet ran 14-thirties @ 97 MPH (open-headers, and 3.42 gears on 225/70R15 UNIROYALS), running straight SUNOCO94 or AMOCO93 with a similar combination, and I think you might really like it!

I think (very soon after something like this is done) I will pull the engine out and tear it down to have it machined .030" over and have more of a performance oriented rebuild kit put in. Not totaly sure yet but that is probably the road I'm gonna eventually go down. One other thing, I have seen in Summit's catalog the Edelbrock's performance combo kits where it comes with a set of their aluminum heads, cam and lifters, performer RPM intake and AVS carb. My question is could this be something that would let me achieve performance results with? I know that the specs on everything really needs to be known but I cant seem to find it but if anyone has seen these kits then please let me know!! I wanna thank everyone again for all the advice and help, I really do appreciate it!

Zack

 

[Glensgages]

..... One other thing, I have seen in Summit's catalog the Edelbrock's performance combo kits where it comes with a set of their aluminum heads, cam and lifters, performer RPM intake and AVS carb. My question is could this be something that would let me achieve performance results with? I know that the specs on everything really needs to be known but I cant seem to find it but if anyone has seen these kits then please let me know!! I wanna thank everyone again for all the advice and help, I really do appreciate it!

Zack

'Most' of the manufacturers who sell combinations/kits have matched the components to each-other (i.e.: nobody's gonna sell you a dual-plane intake and a big solid-roller cam in 'kit'-form).

Edelbrock's aluminum heads are very nice pieces:
my buddy's hot-rod shop uses them on many 12 and 13-second hot-street cars each year, and for less than $1000, they are hard to beat.

Contact Edelbrock direct, explain what you have, what you want to have, listen to what they have to say, and take their advice.

As 81 Corvette stated, deeper gears will drastically help your off-the-line acceleration numbers, and you say you are already " 3.36 gears in the rear with the close ratio manual tranny "
(A source-book I have says the only 4-gear offered in '80 was a wide-ratio 2.88/1.91/1.33/1:1 transmission, and was matched with 3.07:1 rear-gearing.....?)
:confused

Either-way, don't be afraid of running 3.73s with that bottom-end, as that gearing came as OEM in 4-speed Z28s from '77-'79/'80.

 

[zackm58941]

Hi, I looked at this site for the exact gearing that I'm pretty sure I have. http://www.100megsfree4.com/corvette/1980/vet80.htm . I will deffinetly have to call Edelbrock and see what they have that will work with my car. Thanks.

 

[Glensgages]

zackm58941:
I don't know what to say about which 4-speed you have in your '80 Corvette.
:confused
I know that the "Corvette Black Book", which is 'supposed' to-be correct, lists no M21 transmission in '80.

By the late-'70s, GM wasn't offering too-many optional drive-train packages:
my guess is that (possibly) all '80 4-gears got the wide-ratio transmission, which would assist the wimpy 305 CID get off the line better, and make for spirited performance from the 'standard' L-48 in 1st Gear, too.

As-far-as which rear-gear your car has, we've BOTH possibly over-looked something:
seeing as your car is a stick, it may've had the ring and pinion replaced by a previous owner (too many nights at the 'Stop-Light Nationals'?), or by a prior owner to get better mileage, and there's no-telling if it has been replaced with the SAME ratios or not.

Truth-is, we DON'T positively know the gear-ratio inside your 25-year-old carrier, do we?

Because it seems you are giving this project careful fore-thought and planning, you might wanna give that (lack of gear-ratio info) some consideration before you contact any manufacturer/vendor.....

 

[zackm58941]

Honestly, I dont know exactly what gears I have so I will have to wait to find that answer until I have the engine out and rebuild the tranny and possibly the rear end too. So I guess until then I will put all gearing discusions aside until I kno what I have and where I can go.

At least I know one thing though, my dad was the only owner of this car and when it was given to me when I was 15 after his passing... I never really got to ask him about this one too much but I wish he would have kept his 1969 stingray BB and a bunch of other vettes he had. I still have all of the photos of all the corvette's he had and I'll have to scan them into the computer when I'm home for thanksgiving next week and post them. Thanks.