too much compression with these heads??
Thread Starter
Instructor
Joined: Mar 2002
Posts: 247
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From: las vegas nv
too much compression with these heads??
hi guys. have a 77 l48, bone stock except for duals and a performer intake. want to go sr torquer heads with a cc 262 cam. the chambers on the heads are 67 cc's. will this be too small compared to the 76 cc heads that are on it?? have talked to a few local guys and have varied answers as to how much compression will raise. some say 1/2 a point , some say over a point. whats the true skinny here fellas???? just looking for a nice streetable driver here, not a srip car. thanks for any input. regards, fng
oh , car is an auto with 308s.
oh , car is an auto with 308s.
Drifting
Joined: Dec 1999
Posts: 1,462
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From: Reno nevada
Re: too much compression with these heads?? (FNG)
Your going to raise it nearly 1 point from mid 8 to mid 9. I don't know the exact cc of the L-48 pistons.
It one of the better things that you can do to gain power. More air flow and higher compression. I'm running @10.7 compression with iron heads and a good cam
It one of the better things that you can do to gain power. More air flow and higher compression. I'm running @10.7 compression with iron heads and a good cam
Burning Brakes
Joined: Mar 2001
Posts: 1,211
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From: Nashville TN
Re: too much compression with these heads?? (FNG)
You could go with late model L-98 Corvette aluminum heads. they have 58cc chambers, will give you even more compression. For the size cam you are running they should flow enough air. Higher compression helps you to build low end torque, very desirable in a street car.
Pro
Joined: Sep 2002
Posts: 690
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From: near Memphis TN
Re: too much compression with these heads?? (Kevin Mason)
Running L98 heads with flat top pistons. No problems so far with 93 octane fuel. Compression at 10.7.
Also using a strong cam to bleed off some of the compression.
Also using a strong cam to bleed off some of the compression.
Le Mans Master
Joined: Aug 2000
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From: Semper ubi, sub ubi
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Re: too much compression with these heads?? (FNG)
You'll end up with a nice running car and should be able to run 36 degrees advance on 91 octane with no problems. Add some Dynomax headers and decent exhaust and you should have a car that will probably run in the low 14's and drive real nice on the street. It's going to be a nice setup!
Get a 2000-2200 rpm torque convertor to really pick that TH400 up and get it operatiing in the torque band of your engine.
Get a 2000-2200 rpm torque convertor to really pick that TH400 up and get it operatiing in the torque band of your engine.
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Re: too much compression with these heads?? (Kevin Mason)
Any idea where to find a used set of L-98 heads? Junkyards never seem to have them.
Le Mans Master
Joined: Jul 1999
Posts: 9,206
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From: Sewell NJ
Re: too much compression with these heads?? (FNG)
I have the stock block, pistons, and crank on my 74 l-48 with the SR Torquer 67cc heads and it runs very nice. You may end up with a little less than 1 point increase increase in compression depending on the head gasket. The original head gasket is a steel shim gasket. If you replace the heads and use the same type gasket you will get about 1 point increase. But if you replace the heads and use one of the composition gaskets that are much thicker than the steel shim you will gain less compression, probably on the order of .5 to .75 increase depending on the gasket. i have no ignition problems or pinging with mine running 36 degrees advance and 93 octane. Do it, you'll like it. :thumbs:
Thread Starter
Instructor
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From: las vegas nv
Re: too much compression with these heads?? (Smokehouse69)
thanks fellas. appreciate the input.
smokehouse....thanks. just what im looking for. a decent streeter with a little grunt. never know when you may have to teach someone some manners :blueangel:
thanks again to all that replied. guess its time to get on the phone and whip out the plastic. best regards, fng
smokehouse....thanks. just what im looking for. a decent streeter with a little grunt. never know when you may have to teach someone some manners :blueangel:
thanks again to all that replied. guess its time to get on the phone and whip out the plastic. best regards, fng
Le Mans Master
Joined: Oct 2002
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From: Las Vegas - Just stop perpetuating myths please.
Re: too much compression with these heads?? (FNG)
:cool: That’s pretty much the combo I got FNG. I really gave it a try to measure piston volume at TDC with the block in the car. Yes now I know why it’s not measured that way. Any ways I don’t see high c.r. as a problem with the 67cc WP heads. In fact I went for a little more compression using a steel shim gasket. This thinner gasket also produces a correct quench height for a few more ponies – better fuel mix/burn and tolerates higher c.r. (cheaper gaskets too). Just get that block surface cleanie clean and use Permatex spray sealer on gaskets.
I’m impressed with the WP torquers I bought from Performance Chevy Products in Phoenix, AZ. (602)254-9586. Got mine pocket ported and painted for $850 and shipping was free. They unshrouded the large 2.02”, 1.60” valves (67cc chambers measured 68-69cc). Just demand umbrella valve seals.
That’s a great cam choice. And if you’re running stock exhaust you may want an even shorter duration cam. And for max mid-range torque the Isky Mega cam on 108 lobe sep. angle is optimum for Chevy 350. :hurray:
I’m impressed with the WP torquers I bought from Performance Chevy Products in Phoenix, AZ. (602)254-9586. Got mine pocket ported and painted for $850 and shipping was free. They unshrouded the large 2.02”, 1.60” valves (67cc chambers measured 68-69cc). Just demand umbrella valve seals.
That’s a great cam choice. And if you’re running stock exhaust you may want an even shorter duration cam. And for max mid-range torque the Isky Mega cam on 108 lobe sep. angle is optimum for Chevy 350. :hurray: