my freind and I are contemplating putting L98 heads and an LT1 cam on his L05 1988 firebird. has anyone done this before? what head gaskets will work with this? as far as we can tell this is the only issue but if anyone knows of another reason that this unlikely marriage should not occur please speak now or forever hold your piece , thanks for the help

 

A simple search would have resulting in you knowing the combustion chambers of L98 heads are much bigger and you will lose compression, probably resulting in a HP loss or at least a reduction in efficiency. :Edit. I thought you said L03, if it is a L05 350 then I think it could work ok if all the pieces bolt up and match.

 

Well is it an LO3 or an LO5? IF it's a 350 than the heads will be an improvement. If an LO3 than you'll lose to much compression. If it's an LO3 get some 305 TPI heads, they flow MUCH better.
Alex

 

Swapping TPI heads for TBI heads is a JOKE... Neither are really "BETTER" in stock form. In fact the improved burn of the swirl ports and higher flowing exhaust ports INCREASE the torque from idle-4,500 rpm on a STOCK engine.

 

my simple search resulted in nothing, maybe if i had an hour to sit on the comp and sort through all the stuff that wasnt pertinent then the "simple search" would have helped. i called SDPC and they told me the combustion chambers are exactly the same, i read in CHP that the 5.0L CC were 56 so if that was the truth this would only be about a 2 tenths of a compression point drop which would not be all that bad considering stock CR is 9.3 to 1 the chambers in a L05 are 65cc the L98 are 58 so if this were an L05 which it is NOT then this would actually raise compression 7 tenths bringing it to approx 10 to 1 which would probably net more horsepower just from that alone... anyway though it is an L03 and the valves on the L98 heads are indeed bigger so that would mean at the very least a slight flow increase. i have also read somewhere that the 5.0L heads have 52cc so that would mean a 6 tenth point loss which would be approx 8.7 to 1 which is still decent and would work fine with pump gas, but would it produce more power? the basic question here is will an LT1 cam and L98 heads make more power on a 305 and what head gaskets should you use... i thought it pretty much pointless to use different 5.0L heads because next year the plan is for the L98 shortblock to be stroked and this was just told hold off till then when we will reuse all the topend on that, so maybe what your saying is the LT1 cam would work well in the L03 without a head swap? and in that case, would we need to change the stock springs or are they good with around .460" lift? thanks in advance

 

will an LT1 cam and aluminum L98 heads (58cc) make more power on a 305 and what head gaskets should you use?

 

LO3 187 casting heads are 58cc just like the Aluminium L98 133 casting. Though aluminium likes a little more compression.
Piston to head should be >= .040 in and < .050 in. Factory piston to deck is around 0.025, in wich case 0.015 head gasket would be good. FEL-PRO 1094 has a 4.100 bore, not sure there is another .015 gasket for aluminium heads with a smaller bore.
Best is you read the "New to TBI" and "Ultimate LT1 cam" in the TBI forum to get the idea.

 

YES.
Aluminum 350 heads on iron block take Fel-Pro 1010 headgaskets.
http://www.jegs.com/i/Fel+Pro/375/1010/10002/-1

For more power do some pocket porting, get a performance valve-job, and upgrade to better valvesprings and higher ratio rocker arms.
Also be sure to use hardened washers under the heads of your head-bolts.

 

For some reason I recall 350 heads not being applicable to a 305 block because the bore is .24" less, which would cause the valves to hit the cylinder walls?

 

You might recall hearing that, but it isn't true.

 

awesome info and exactly what i was looking for, thanks to all of you, oh and its not TBI Fast just so u know

 

Thanks for clarifying, lol

Because a L05 is the RPO code for a TBI 350 and 1988 was a TBI year. But glad you have it running on some other form of intake.

If youl look for a set of L98 Aluminum heads, find you some off of a late, late model ZZ4 engine, probably 2006 and up. They are the BEST you will find down to factory port and bowl work done on them.

 

yeah the block is L05 sorry for not being more clear

 

Thats said to be true for the 2.02/1.60 valves (its the intake valves that will hit) but if those heads have the stock-sized valves, then its not a problem. Stock was 1.94/1.50

 

You might find a little inspiration in this:

https://www.thirdgen.org/forums/memb...engineers.html

I went a little bit heavier than the LT1 cam, but I think it would also be a great choice. My cam specs are a bit closer to the LT4 cam.


Be sure and read my notes on spark plugs and brackets. I used the GM Performance Composite head gasket, should work just fine.

Here's a little teaser for you



-Levi

 

Cam----INT / EXT
Stock LT1---202@ .450/ 207 @ .450 (1.5RR)--- 117 LSA
Stock LT4--- 203@ .476/ 210@ .480 (1.6RR)--- 115 LSA
CCA-07-500 --- 206@ .480/ 212@ .488 (1.5RR)--- 112 LSA --- 1000-5000 <-- My cam

 

cant wait to see what it runs