Hi Gang, can anybody help me out here, if I have my heads ported and capable of flowing 330 cfm. Is the throttle body going to be the bottle neck? We recently had a manifold ported and it looks and flows much better than before.

I would have thought that there is some sorted of calc that can be done as to sizing of a single throttle body required for a 5 litre motor spinning to a max of 7200 rpm. I have seen a few calcs for individual throttle bodies but I don't think they directly apply. What is the diameter of the stardard throttle body versus the big bore one?

Thanks Greg

 

Greg,

Think Mark Anderson had one done and saw no HP increase on his stroker. Don't know if he tried it since the new intake manifold.

 

Have you ported the heads on that 84 S2? I'd be interested to hear about it if you did.

 

I have a pair of 84 - 86 Euro S heads that I have gasket matched, smoothed & opened the ports below the valve and smoothed the exhaust port where the steel tube insert ends. The ports were pretty close in matching the gaskets, but awful below the valves and in the exhaust port where the aluminum butts up to the steel sleeves. I still need to replace the guides and have a valve job done. I'm planning on putting them on my recently acquired 81 Euro S 5 sp.
I also have a pair of the later 84 - 86 Euro S cams I plan on running. If pulling the cam towers wasn't such a pain, it would be interesting to see how the car runs first replacing the heads and later adding the 84 - 86 cams.

 

First, we need to know more about your equipment. are we talking you have a 81 euro S now, and you are asking about porting the throttle body?
remember, the euro S throttle body vs the US throttle body for the US 80-84 is 2.7 vs 3.3" diameter at the butterfly. HUGE difference. side by side, the smaller one looks like a baby brother.

next, dont get too caught up with the S4 intake mods that do and dont work, as the 5 liter 4 valve system is totally different, plus, Anderson had done things to his, and its a 6.5 liter anyway, that didnt give gains.

On the 2 valve type, i saw 43hp going from stock intake stuff, to euro intake stuff with the 82 euro cam. scot with his 82 US 4.5 went from 200hp to 218hp with the euro stuff only, (no cams)

YOU CANT PORT the US throttle body. its basically junk. toss it out and get a euro throttle body. entirely differnet casting and if you were to try and port it out to even close to euro spec, you would not have anything left !!!!! (ie cant be done! not enough meat to begin with.)

I have the euro throttle body and extrude honed runners that are also externally polished for sale (for a US 84 F1 equiv. system) Let me know if you are in need of the throttle body.

need more information on what you are trying to do. Basically, a euro throttle body or the 4valve 85 and 4 valve S4 throttle bodies are BIG, in the range of 3.5" diameter. changes to them are not showiing much gains. However, the euro 2 valve system is a HUGE improvement on flow not only with the runners, but the throttle body, plennum and of course on the heads, bigger valves and ports.

3.5" of throttle body can support well over 400hp at the wheels to answer your question directly.

think of the US 80-84 throttle body as a 50% restrictor plate!

Mk

 

totally differnent situation. different intake, different heads, TB, etc , and of course as you say, it was a stroker too. However, his engine and Joe fans are in the 500hp rear wheel range now. all of the mods are probably working together now, as he has changed manifold, throttle body, heads valves, compression, displacement, MAF config, etc.

If we are talking 2 valve, there are lots of gains to be made with TB and intake.

my US 4.7 liter went from 200rear wheel hp with a set of headers, to 243hp at the rears with only the euro intake and euro 82 S cam change. (on an engine that was at 150,000miles and had very low compression i.e. 175 rear wheel starting stock)

MK

 

Sorry guys I should have been clearer, the engine is a GT engine. It is in my sig. The intake valves will either be 39 mm or 40 mm, any thoughts on this also.

Thanks Greg

 

Appreciate your info Sterling, Mark are you saying I need the bigger body for a high revving 5 liter? The engine will have some custom cams also. The work done on the manifold is just so that I can be thorough. So I will port match it etc. I also thought about filling in areas around the trumpets to smooth the transitions, this is not big dollar stuff so if it doesn't achieve much no big deal.

Back to the throttle bodies, if you had ITBs you would have eight 50 mm bodies, since I have a single I only have one 74 mm one, as I mentioned before it seems small, doesn't it?

Thanks Greg