manifolds or headers how fast can i go?

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shoebox1.1

New member
guys im new here and dont even have a syclone or typhoon but what i do have is a 1980 pontiac sunbird (chevy monza) that im building a turbo 4.3 for! i have a running engine that my friend built for naturally aspirated use but im taking this running 260rwhp engine and putting a 63 mm turbo on it. this is going to be a light, street strip pump gas car that should be lots of fun. heres the question--- i can build or modify shorty headers or run some kind of manifolds. i know syty manifolds or headers are going to be harder to find that purple hen's teeth!!!! :) looking at 88-95 bravada manifolds they look good flowing and at least close to what you guys have. heres the link-- www.stevensparts.com/CHEV EXHAUST MANIFOLDS.htm how fast can you go with factory manifolds ? 11's 10's dare i say 9's ?? lol is there any gain with extrude hone work? i have a very good porter that could really prep this manifolds... i was told by a well respected syty vendor that 450 crank horse was about it with factory manifolds......... im shooting for 450 rwhp! tell me your manifold and or header stories thanks! gus
 
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turbodig

turbodig

Active member
Re: manifolds or headers how fast can i go?

shoebox1.1 said:
guys im new here and dont even have a syclone or typhoon but what i do have is a 1980 pontiac sunbird (chevy monza) that im building a turbo 4.3 for! i have a running engine that my friend built for naturally aspirated use but im taking this running 260rwhp engine and putting a 63 mm turbo on it. this is going to be a light, street strip pump gas car that should be lots of fun. heres the question--- i can build or modify shorty headers or run some kind of manifolds. i know syty manifolds or headers are going to be harder to find that purple hen's teeth!!!! :) looking at 88-95 bravada manifolds they look good flowing and at least close to what you guys have. heres the link-- www.stevensparts.com/CHEV EXHAUST MANIFOLDS.htm how fast can you go with factory manifolds ? 11's 10's dare i say 9's ?? lol is there any gain with extrude hone work? i have a very good porter that could really prep this manifolds... i was told by a well respected syty vendor that 450 crank horse was about it with factory manifolds......... im shooting for 450 rwhp! tell me your manifold and or header stories thanks! gus
Click to expand...

Factory manifolds have gone well into the 10s, 600 HP +.... you should have no problem
supporting the HP you describe. Other factors will limit you before the manifolds.

Light weight car should be able to get to the 10s easily, given a good tune. You didn't mention the intake you plan on using? ECM, engine management?

Your NA cam will likely be wrong for the turbo.

What trans are you looking at... 400?
 
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shoebox1.1

New member
Re: manifolds or headers how fast can i go?

thanks for the reply and telling me what i wanted to hear! its actually not efi... this engine has ported bowtie raised runner heads and a single 4 bbl crossram! the cam is a roller 224 500 111lsa. its a true 10.7cr i know its high and the cam is wrong but im building the whole rest of the combo now and then build another shortblock. stall is 3000 flash and gear is 3.23's car should weight no more than 3200 race weight fully loaded. the manifolds( bravada lets say) will probably need to be at least port matched.. my heads have been opened up pretty good. im kind of looking at some s10 shorties on ebay.. obx brand 1.750 primary. i think manifolds would be easiest to fab the hot side. i am going to have a nice intercooler, blow through carb and methanol injection. i plan on no more that 10 psi in this state and later (lower cr) going 20 psi
 
turbodig

turbodig

Active member
Re: manifolds or headers how fast can i go?

shoebox1.1 said:
thanks for the reply and telling me what i wanted to hear! its actually not efi... this engine has ported bowtie raised runner heads and a single 4 bbl crossram! the cam is a roller 224 500 111lsa. its a true 10.7cr i know its high and the cam is wrong but im building the whole rest of the combo now and then build another shortblock. stall is 3000 flash and gear is 3.23's car should weight no more than 3200 race weight fully loaded. the manifolds( bravada lets say) will probably need to be at least port matched.. my heads have been opened up pretty good. im kind of looking at some s10 shorties on ebay.. obx brand 1.750 primary. i think manifolds would be easiest to fab the hot side. i am going to have a nice intercooler, blow through carb and methanol injection. i plan on no more that 10 psi in this state and later (lower cr) going 20 psi
Click to expand...

I was assuming you meant a 4.3 v6... where did you find a cross-ram? Or do you mean the box-plenum style manifold that usually accompanied the bowtie heads?

You'll have problems with angle plugs and those manifolds, I suspect. They're made for straight plugs. Also, any headers designed for straight plug might not work with angle plug.

Depending on the design of your pistons, you should be able to get by with that CR. Might get tough running 93 pump gas without the ability to control timing with an ECM...

That seems awful heavy for that car... I was thinking sub 3000#.
 
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shoebox1.1

New member
Re: manifolds or headers how fast can i go?

i think sub 3000 is very do~able i just wanted to be conservative :) they are 2 eye brow flat tops, and i plan on running limited total timing.. lets say 24 all in around 2k. it is the box intake made just for my heads and the 18 degree. i didnt think about the manifolds hitting the plugs...hummm well i think its worth a trip to the pick your part yard and pull a manifold,take some measurements and check port size and porting ability. i do like the "pros" of running manifolds. custom headers are a viable option. i actually have some that came with this motor that i could use the flanges and collectors and some of the tubing. are most fast syty's with manifolds ported or extrude honed? thanks! gus
 
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