More L48 questions
Thread Starter
Melting Slicks
Joined: Jul 2000
Posts: 2,107
Likes: 14
From: Lancaster PA
More L48 questions
I am in the process of rebulding the 73 L48. The heads are 993's. Are these worth using? I was talking to an engine rebuilder at Carlisle and he said he would put in flat top pistons and put on heads from a 307 cid that measure 55cc with big valves installed. This would put compression right around 10:1. I don't want to spend a ton of $ because I don't know how long I will be keeping this car. Do any of you have any reccomendations on a budget rebuild with a boost in HP. Thanks very much, Craig 
Drifting
Joined: Mar 2001
Posts: 1,395
Likes: 6
From: Indiana
Re: More L48 questions (CF6873)
Putting 2.02 valves in an otherwise poor casting won't really do a lot of good. The compression will help, but there are much better heads that are very cheap on the market right now. Chevrolet still offers replacement heads used on 70-72 Lt-1's. These will flow better than what you have and are only about $500 per pair complete with guideplates ,springs and valves. I believe they are 64cc, but I'm not sure. With flat top pistons, you would be at about 10.0:1 .You can also get the Vortec heads for slightly more and these things will outflow just about any stock casting ever made. Unfortunately, you will need a matching intake so the cost will begin to add up. There are also the S/R torqer heads, which I have, that are about 800 complete per pair. These work very well and create a lot of low end torque. The money you spend reworking an old pair of heads would go a long way towards a new set.
Tom
Tom
Race Director
Joined: Apr 1999
Posts: 15,136
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From: NM
Re: More L48 questions (CF6873)
any reccomendations on a budget rebuild
tom...
[Modified by Tom73, 10:07 PM 8/27/2001]
Le Mans Master
Joined: Sep 2000
Posts: 9,078
Likes: 7
From: DFW TX
Cruise-In VII Veteran
St. Jude Donor '07
Re: More L48 questions (Tom73)
Look around for some L-98 vette heads. Cheap, alum., and 55 cc combustion chambers. I posted a pair on ebay for $100 bucks the other day. :cheers:
Drifting
Joined: Nov 2000
Posts: 1,428
Likes: 0
Re: More L48 questions (Budman78)
Firmly believe that Tom73 has you on the right track...I did all of those mods last winter (save Q-Jet rebuild) and results were very impressive compared to stock, w/o much cash outlay. Pulls strong out to Redline and sounds like a Vette while its doing it.....On junk gas. :lol:
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Re: More L48 questions (CF6873)
Craig
993s are very good stock heads. 10 C/R will probably be too high for iron heads. You badly need another cam. Manual or auto. needed for cam.
:cool:
993s are very good stock heads. 10 C/R will probably be too high for iron heads. You badly need another cam. Manual or auto. needed for cam.
:cool:
Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
Re: More L48 questions (Ganey)
993's are excellent cast iron heads. They have plenty of material for porting and are considered 'heavy castings'. They were offered in late 70's and early 80's on the Target motors as a replacement head. They put the light casting heads to shame. Only drawback is the 76cc chamber (too large) and fact they are cast iron (compression limitations).
Burning Brakes
Joined: Dec 2000
Posts: 1,183
Likes: 2
From: Des Moines Iowa
Re: More L48 questions (CF6873)
All of these replys are right on target. 993s are great stock castings, much better than the 882s or 624s, as Ted H said, they have a lot of 'meat' on them and CAN be both ported and milled. Do NOT go with the smaller 307 cast iron heads, they have a lot of cracking and valve stem problems, and will NOT flow as good as your current stock 993 heads. I agree that 10:1 is too high a CR for cast iron heads, don't believe you should go above 9:1, or maybe 9.5:1. IF the bottom end of your engine is OK/good, then agree the best low budget performance increase investment would be in headers, tune-up, camshaft/valve springs/seals/timing chain&gears.
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Thread Starter
Melting Slicks
Joined: Jul 2000
Posts: 2,107
Likes: 14
From: Lancaster PA
Re: More L48 questions (john's '81 mouse)
Thanks very much for the replies. The info on here is great.
Tom 73; The motor does need a rebuild, it had lots of blowby. When I removed the pistons the rings were stuck on them, no springyness,(is that a word)?
Ganey; it is a 4 spd. with a 3:36 rear. Cam suggestion?
Are the flat top hypereutectic pistons a good idea? What compression will I have with the new pistons and the 993 heads?
By the way these heads have new Crane springs on them and full roller rockers. There was a new Crane cam in it, but Crane said it should be used only with over 10.5:1 compression. I don't think I'll go there.
thank again, Craig :cheers:
Tom 73; The motor does need a rebuild, it had lots of blowby. When I removed the pistons the rings were stuck on them, no springyness,(is that a word)?
Ganey; it is a 4 spd. with a 3:36 rear. Cam suggestion?
Are the flat top hypereutectic pistons a good idea? What compression will I have with the new pistons and the 993 heads?
By the way these heads have new Crane springs on them and full roller rockers. There was a new Crane cam in it, but Crane said it should be used only with over 10.5:1 compression. I don't think I'll go there.
thank again, Craig :cheers:
