L83/L98 head swap
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Joined: Dec 2012
Posts: 55
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L83/L98 head swap
New to the forum, I assume this questions's been covered before, but didn't get the info I ws looking for with a search.
Considering swapping my stock iron heads on the 84 L83 with L98 aluminum heads from a 1988 L98 I've got access to. 2 questions:
(1) Are the center bolt holes in the 88 heads compatible with the earlier 84 manifold? I know they switched at some point, but not sure when.
(2) Knowing the swap of 78cc to 58cc will raise compression to near 11:1 on my L83, does anyone have experience or knowlege of using thicker head gaskets to mitigate some of the compression rise?
Thanks, many more questions to come. BTW, If there is a specific forum more focused on the 82/84CFI, please let me know.
Considering swapping my stock iron heads on the 84 L83 with L98 aluminum heads from a 1988 L98 I've got access to. 2 questions:
(1) Are the center bolt holes in the 88 heads compatible with the earlier 84 manifold? I know they switched at some point, but not sure when.
(2) Knowing the swap of 78cc to 58cc will raise compression to near 11:1 on my L83, does anyone have experience or knowlege of using thicker head gaskets to mitigate some of the compression rise?
Thanks, many more questions to come. BTW, If there is a specific forum more focused on the 82/84CFI, please let me know.
Drifting
Joined: Mar 2006
Posts: 1,263
Likes: 188
From: Wabasha Mn
I believe the 86 aluminum heads have the same bolt pattern as your crossfire intake but the 87 and up heads had the different bolt pattern and center bolt valve covers. On my 84 I got rid of the factory 624 heads and bought some Summit cast iron 152123 large valve heads(made by Dart) for $630. They are 72 cc heads with .525 lift springs, screw in studs and modern fast burn angle plug design. Even with the aluminum heads you want to use the restrictive intake ports of the crossfire intake will impede any meaningful performance increase. I went with a carb conversion , a more agressive camshaft, true dual exhaust with no cat and the Summit heads and am very happy with the large power increase. Maybe you can get the whole 88 TPI set up along with the heads.
Drifting
Joined: May 2006
Posts: 1,428
Likes: 7
From: Chewelah Wa
Most people do not realize that the iron 624 heads actually flow more than 113 heads. The weight savings might be worth half a tenth in the quarter. So not worth it. The 113's take to porting much easier (but expensive), if further mods are in the future. I am sure a few peeps have tried running 113's and flat top pistons, but it sounds like too much compression to me. Better off throwing some thin gaskets on the 624's.
Instructor
Joined: Oct 2010
Posts: 215
Likes: 1
Im trying the renegade intake with the edelbrock performer heads. I really think you have to research all the things you want to do before you plunk down the bucks. The 113 heads and the 624 heads have the same intake manifold bolt pattern the center ones go straight in at the same angle as the outside ones
Thread Starter
Advanced
Joined: Dec 2012
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Im trying the renegade intake with the edelbrock performer heads. I really think you have to research all the things you want to do before you plunk down the bucks. The 113 heads and the 624 heads have the same intake manifold bolt pattern the center ones go straight in at the same angle as the outside ones
What are you doing with your throttle bodies if I may ask?
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Drifting
Joined: May 2006
Posts: 1,428
Likes: 7
From: Chewelah Wa
Yes, and if he goes this route, he needs to make sure that he doesn't use the typical replacement felpro, which is .039. Those Summit iron heads that Wilcar has on his, would be perfect for this build IMO. I believe member "Coupeguy" had some 113's on top of some flat top pistons, I believe he may have used 2 gaskets? It's been awhile.
Drifting
Joined: Mar 2006
Posts: 1,263
Likes: 188
From: Wabasha Mn
The 624 thin cast heads are very prone to cracking on the exhaust valves near the heat crossover and most tech forums and Chevy high performance books state that the 624 heads are the worst of the worst heads to use and are not worth sinking any money into for a performance application. Maybe that is why I have not had one bite on my 624's for $99 on craigstist!!!!! One mechanic stated that out of 10 sets of 624's you might get one pair that is not cracked.
Melting Slicks
Joined: Feb 2005
Posts: 2,057
Likes: 5
From: Bay Shore, NY
The 624 thin cast heads are very prone to cracking on the exhaust valves near the heat crossover and most tech forums and Chevy high performance books state that the 624 heads are the worst of the worst heads to use and are not worth sinking any money into for a performance application. Maybe that is why I have not had one bite on my 624's for $99 on craigstist!!!!! One mechanic stated that out of 10 sets of 624's you might get one pair that is not cracked.
Safety Car
Joined: Apr 2005
Posts: 3,624
Likes: 431
From: Dale City VA
The factory hyd roller cam is reason enough.
Will
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Advanced
Joined: Dec 2012
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Most people do not realize that the iron 624 heads actually flow more than 113 heads. The weight savings might be worth half a tenth in the quarter. So not worth it. The 113's take to porting much easier (but expensive), if further mods are in the future. I am sure a few peeps have tried running 113's and flat top pistons, but it sounds like too much compression to me. Better off throwing some thin gaskets on the 624's.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
New to the forum, I assume this questions's been covered before, but didn't get the info I ws looking for with a search.
Considering swapping my stock iron heads on the 84 L83 with L98 aluminum heads from a 1988 L98 I've got access to. 2 questions:
(1) Are the center bolt holes in the 88 heads compatible with the earlier 84 manifold? I know they switched at some point, but not sure when.
(2) Knowing the swap of 78cc to 58cc will raise compression to near 11:1 on my L83, does anyone have experience or knowlege of using thicker head gaskets to mitigate some of the compression rise?
Thanks, many more questions to come. BTW, If there is a specific forum more focused on the 82/84CFI, please let me know.
Considering swapping my stock iron heads on the 84 L83 with L98 aluminum heads from a 1988 L98 I've got access to. 2 questions:
(1) Are the center bolt holes in the 88 heads compatible with the earlier 84 manifold? I know they switched at some point, but not sure when.
(2) Knowing the swap of 78cc to 58cc will raise compression to near 11:1 on my L83, does anyone have experience or knowlege of using thicker head gaskets to mitigate some of the compression rise?
Thanks, many more questions to come. BTW, If there is a specific forum more focused on the 82/84CFI, please let me know.
2. No. It does work though. Check your push-rod length with the new gaskets.
Le Mans Master
Joined: May 2006
Posts: 7,708
Likes: 266
From: indy indiana
its my understanding that the 113 heads do NOT flow much more than the old iron heads or even the old fuelie heads. They are better because of the swirl port chambers and intake port velocity, working the exhaust ports give good results on these heads. they are 22 pounds lighter...062 vortec heads are much better...said to be the best heads Chevy ever made .
Le Mans Master
Joined: Nov 2009
Posts: 6,882
Likes: 234
From: Bangkok, Thailand
I would seriously consider the GM Fast Burn heads. I just installed a set on my 91 and am very happy with them. The only problem I ran into with them is that they DO NOT accept center bolt valve covers. The shape of the gasket rail doesn't match up to the centerbolt pattern. You may also need to have your intake ports welded up to cover the taller port, but look carefull - the floor of the ports also had a mismatch.
Thread Starter
Advanced
Joined: Dec 2012
Posts: 55
Likes: 5
its my understanding that the 113 heads do NOT flow much more than the old iron heads or even the old fuelie heads. They are better because of the swirl port chambers and intake port velocity, working the exhaust ports give good results on these heads. they are 22 pounds lighter...062 vortec heads are much better...said to be the best heads Chevy ever made .
Drifting
Joined: May 2006
Posts: 1,428
Likes: 7
From: Chewelah Wa
Gary, the flow on all these heads is well documented. The 113's probably should not be used with flat top pistons w/ 58 CC chambers. 64 CC chambers would be as low as I would go on an aluminum head and 72 on anything iron. The exhaust is D port on the 113's, so you would need D port exhaust. You may be limited with your stock intake as to the size of intake ports on your heads. Many aftermarket aluminum heads have a 1206 size port, which your stock intake will not cover up. I am thinking maybe you could run a 1205 port, if you can port out a stock CFI manifold that far. Your intake is less than the size of a 1204 port. Edelbrock RPMs or E streets would be a good choice, but they are D port exhaust. A set of LT1 exhaust manifolds would fit these well. EDIT E Streets are square port, RPM's D port.
Last edited by powerpigz-51; Dec 20, 2012 at 09:33 PM.
Instructor
Joined: Oct 2010
Posts: 215
Likes: 1
I had my throttle bodies bored by extreme efi I am really going slow on this rebuild/refresh but the throttle bodies seem to be done very nicely but I still need a few weeks to finish so I cant comment on how they work yet.Ive taken a few pics but I havent posted any yet.