ok i have some heads off of a 86 lg4 z28, i really dont have much money right now, so im looking for the cheapest power possible. (ive been bitten by the drag racing bug and i want to go faster) my question is this. are these heads good enough to port and make some decent power, can i reuse the valves or would it be better to go with some 1.94's 1.50s? i will of course replace the valve springs, and go with some 1.6 ratio rockers. Also is it possible to port the stock intake, and make any type of difference in top end power? what im shooting for is 300 hp with my 305, then im gonna build an engine with 96 more cubic inches my mods are in my sig, can i hit 300 hp with these heads and rockers? will i at least be close? thanks

 

You might be able to hit it....


But you're reallllllllllllllllllllllly going to need to port.

I dont mean bowl work/combustion chamber work/ gasket match. I mean remove alot of material untill you're up 20+cc from where you started, if not more. Again.. HEAVILY porting will have benifits, I ported and siamesed my TPI intake, It really doesn't resemble tpi any more in power, it doesn't have ungodly low end and dead high rpm, it just kinda has a strong mid with a better upper end, and the low end is just enough to get it moving

Considering youre playing with less displacement You're going to need to take that into consideration if you want to siamese (I probably wouldn't recommend it) you pretty much just need to make everything wider, cleaner, and gasket matched.

If you haven't ported before let me know and i can reffer you to some good online material before you start.

 

no, ive never done it before, how much do you think i should port them? so i should leave the intake alone for now? thanks for the help

 

http://www.sa-motorsports.com/diyport.htm

^ good begining guide, there's more but thats the starting point.


and yes port your intake, most deffinatly, just be cautious about siamesing it, that might kill to much low end on your 305.

 

so should i do more than a gasket match and bowl blend, should i upgrade to 1.94 1.50 valves? also would it help to go with some 1.6 ratio rockers at the same time, i alrady have a mild cam. one more thing, are there any articles about porting your intake? thanks

 

In the tech articles section of this site there's an article on porting and siamesing your intake... porting is fine again, but I dont think you'd be happy with siamesing a 305, you'd just be giving up to much...

1.94's are up to you, and your budget, same with 1.6rr's, a new cam is almost cheaper than the rockers plus you can increase duration and decrease LSA if need be.

 

would it be a significant power increase to go with the 1.94 1.50s? and ive already done one cam swap, thats enough for one 305 im just looking for more mid-high power, and not looking to lose any down low. thanks

 

sounds like you've got your power needs sorted out, for your benifit keep the mindset of not loosing low end because thats your umpf right there. I dont think 1.94's would be "significant" to me significant is .2 or better and there's just only so much you can do with stock heads...


With that being said one board member went to the absolute extreme, he's put together a multipart porting project on i believe some L98 heads, I haven't seen the thread come up too recently, maybe i'll dig it up and see if there was some progress, but he had the aid of experience, the tools, and a flow bench. Without that stock heads will always perform like stock heads, dont get me wrong there will be gains, but please dont dump to much money into them.

I bought a set of sportsman II's for around $600 100% ready to go.

Maybe you should see if you can dig up some aluminum L98's? That gives you a better starting point, so that you'll have a better ending point

Not trying to steer you off your plans, just suggestions.

 

here ya go man i found it

This link has more than enough information, this guy did some great work, and at hte bottom of that link i had posted the aluminum L98 porting tutorial that I found very well writen, it even includes some info on back cutting valves (another thing to consider if you have a steady hand)


Read it over, even if you dont plan on going so far, the info is invaluable

https://www.thirdgen.org/techbb2/sho...n+head+project

 

i was really thinking about the l98 vette heads, b/c they have the valves and cc's that i want, ready to go, the problem is i dont want to pay $1000 for a set. I would really like to find some used ones. that is actually the most desirable set of heads for me. But im looking at my budget and it doesnt allow for $1000 heads. but if anybody sees a set for $650 or less let me know. thanks

 

Before I bought my sportsmans I constnatly saw the aluminum L98's going for $500-$700, usually used buth freshly machined.


try ebay, the classifieds here, and on other GM message boards.


They're out there, my heads were a steal.