454 performance #@!###
Thread Starter
Instructor
Joined: Oct 2004
Posts: 185
Likes: 0
From: kill devil hills nc
454 performance #@!###
I bought a 1971 454 LS5 project car last year. The engine was rebuild by the previous owner. He stated that the engine was beefed up a little. At the time of purchase the engine did not run due to no carb, radiator or wiring. I have been putting the car back together and should get my body back from the paint shop soon. Before the body goes back on I want to ensure the engine is ready to go. I wanted to exchange the stock manifold for a perormer 2.0. In dioing this I found out that the car has:
1) Ported intake and heads.
2) H581P high performace pistons-domed with 11:1 compression. .30 over
3) pwr max hydr cam. 133802. 222/234@.050"
4) stock quadrajet carb
The guy at the engine shop said that this car would/should have a holley 750 CFM (at least) installed and needs High octane gas. My question is-- I want a car I can drive around on weekends and am not overly concerned with HP. Is this car set up for racing??? Can I keep the pistons and cam shaft in it and use it as a driver or should I change them out to more stock ones??
Thanks
1) Ported intake and heads.
2) H581P high performace pistons-domed with 11:1 compression. .30 over
3) pwr max hydr cam. 133802. 222/234@.050"
4) stock quadrajet carb
The guy at the engine shop said that this car would/should have a holley 750 CFM (at least) installed and needs High octane gas. My question is-- I want a car I can drive around on weekends and am not overly concerned with HP. Is this car set up for racing??? Can I keep the pistons and cam shaft in it and use it as a driver or should I change them out to more stock ones??
Thanks
Melting Slicks
Joined: May 2001
Posts: 2,131
Likes: 4
From: May help you? You can sure as hell try!
The stated compression is a bit high. Depending on the combustion chamber volume,the true compression is most likely lower than stated. BB Chevies used open (~119 cc) and closed (~100 cc) chamber heads so stated compression ratio based on piston specs means nothing.
The camshaft you have is perfect for a street motor. The cam I'm running in my 427 is very close in specs to yours and performs wonderfully.
The setup you have sounds like it will drive and perform very nicely on the street.
The camshaft you have is perfect for a street motor. The cam I'm running in my 427 is very close in specs to yours and performs wonderfully.
The setup you have sounds like it will drive and perform very nicely on the street.
Instructor
Joined: Oct 2005
Posts: 143
Likes: 0
From: Independence MO
11:1 will ping on todays gas!! If you only drive it a little then racing gas at $7.00 a gallon should not be too much of a problem. It should run good!! 
Thread Starter
Instructor
Joined: Oct 2004
Posts: 185
Likes: 0
From: kill devil hills nc
The stated compression is a bit high. Depending on the combustion chamber volume,the true compression is most likely lower than stated. BB Chevies used open (~119 cc) and closed (~100 cc) chamber heads so stated compression ratio based on piston specs means nothing.
The camshaft you have is perfect for a street motor. The cam I'm running in my 427 is very close in specs to yours and performs wonderfully.
The setup you have sounds like it will drive and perform very nicely on the street.
The camshaft you have is perfect for a street motor. The cam I'm running in my 427 is very close in specs to yours and performs wonderfully.
The setup you have sounds like it will drive and perform very nicely on the street.
Melting Slicks
Joined: May 2001
Posts: 2,131
Likes: 4
From: May help you? You can sure as hell try!
If your Q-jet carb is in good condition, use it. The Q-jet is an excellent carb! The rated CFM on a Q-jet is 750 which is plenty for the 454 buildup you have. What cylinder heads are you running? Without that information, it's hard to estimate where your compression ratio is.
My 427 is built to ~10.5:1 and it runs fine on Sunoco 94 without any additives. Personally, I've found that octane boosters do very little, if anything.
My 427 is built to ~10.5:1 and it runs fine on Sunoco 94 without any additives. Personally, I've found that octane boosters do very little, if anything.
Thread Starter
Instructor
Joined: Oct 2004
Posts: 185
Likes: 0
From: kill devil hills nc
If your Q-jet carb is in good condition, use it. The Q-jet is an excellent carb! The rated CFM on a Q-jet is 750 which is plenty for the 454 buildup you have. What cylinder heads are you running? Without that information, it's hard to estimate where your compression ratio is.
My 427 is built to ~10.5:1 and it runs fine on Sunoco 94 without any additives. Personally, I've found that octane boosters do very little, if anything.
My 427 is built to ~10.5:1 and it runs fine on Sunoco 94 without any additives. Personally, I've found that octane boosters do very little, if anything.
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
You need to figure out what heads you have. What number are they? If they are 101cc units you can get a set of open chamber heads to lower the compression some. Use the thickest gasket you can find.
You can also get more camshaft to help bleed off pressure at lower RPM's. Something with about 240 degrees intake duration at .050" lift should help.
The Rochester carburetor is a 750 CFM unit of superior design. No reason to change it.
BigBlockk
Later.....
You can also get more camshaft to help bleed off pressure at lower RPM's. Something with about 240 degrees intake duration at .050" lift should help.
The Rochester carburetor is a 750 CFM unit of superior design. No reason to change it.
BigBlockk
Later.....
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
11-1 is completely operational and safe to run with pump premium. Addatives are not necessary and most of them are worthless and even if you found one, all it would do is increase the average price per gallon of 93/94. 
Racer
Joined: Mar 2000
Posts: 352
Likes: 0
From: Frisco, TX
As others have stated, we need to know the casting number of your heads to get a better idea of what your true compression ratio might be. Also, can you tell if the block has been decked? Look for the numbers stamped on the front of the block, if they are still there, then most likely the block has not been decked. The reason that I ask about the block is that we found Zwede's 71 LS-5 block was all over the map on deck height with some pistons over .040 down in the hole. This will contribute to a lower than advertised compression ratio as well. It turns out that large and somewhat variable piston to deck clearances were very common for original GM castings. The aftermarket blocks such has World and Dart castings don't seem to have this problem.
Melting Slicks
Joined: May 2001
Posts: 2,131
Likes: 4
From: May help you? You can sure as hell try!
Ok, did some cipherin' on what I suspect is your combo. With the pistons you listed (which are Speed Pro hypereutectics by the way) at 0.030 overbore, and pistons down in the hole by 0.020, and 0.040 thick head gasket, your compression is at 10.12:1. If your pistons are even with the deck, it's around 10.5:1. Either situation should be fine with pump gas premium. This is assuming you are running typical '71 LS5 cylinder heads which should come in at around 119 cc's. If larger valves were installed and the chambers cut back slightly, the combustion chamber volume may be a bit larger and the CR a little lower. The LS-5 was available in '70 with the small chamber heads but I don't think the pistons you have are compatible with those because of dome interference.
It sounds like the engine you have will make a real nice street motor.
It sounds like the engine you have will make a real nice street motor.
Pro
Joined: Dec 2006
Posts: 582
Likes: 3
From: Glen Allen (Richmond) Virginia
octane
Worst case is to stop by the local speed shop and pick up a couple of cans of racing fuel. When you fill your car up just leave room for a 2 gal top off with the racing fuel when you get home. You will never hear a ping and your average cost per gal will not be that high.
Advanced
Joined: Aug 2006
Posts: 50
Likes: 0
Hehe i used to buy 120 or so octane gas from one of my cousins that worked for a place that built race cars.. damn that gas would make anything run like a demon from hell.. ^_^ mix it with a little premium get an octane of about 103. Start smokin some tires..
Thread Starter
Instructor
Joined: Oct 2004
Posts: 185
Likes: 0
From: kill devil hills nc
The only question I have left is the carb. I am staying with the Q-jet but how should I set it up?? what size jets primary-62,64,66,69 ??? and what metering rods?? The carb I have is actually a Edlebrock Q jet that is pretty rough. Should I buy a new one with the correct specs or rebuild this one??
Instructor
Joined: Oct 2005
Posts: 143
Likes: 0
From: Independence MO