I have 350 that was originally built and intended to carbureted with AFR 190cc heads, 9.3 to 1 compression and a XR282HR CompCam. I am considering swapping this motor into an 89 IROC with a TPI 350 but I want to keep the TPI setup and install a modified LT1 intake for more HP at higher rpm.

Question 1:
When it comes to fuel injection, I read all this talk about heads that have a swirl and tumble effect (i.e. Vortec, Fast Burn). To add to the confusion, I hear that TPI heads don’t have this effect... Do Air Flow Research 190cc heads have this swirl and tumble effect? If not, how well will Air Flow Research 190cc heads flow with EFI? Can I get 420 HP with this EFI setup?

Question 2:
Since the XR282HR CompCam has lobe separation of 110, this cam is said to be for carb use... However, If I had a custom ground cam milled with the same specs only with a 112 lobe separation, how this work fine on a TPI/LT1 EFI system? BTW cam specs are:
Dur @ .050 is 230 intake, 236 exhaust
Lift 1.5 rocker is 510 intake, .520 exhaust
Lobe separation 110

Thanks

 

anyone?

 

Swirl/tumble isn't the end-all be-all of making power. I have no idea if AFR heads promote that kind of mixture motion but I know the older TPI heads did not. They do flow a lot more than stock TPI heads and flow is never a bad thing. Plenty of EFI setups out there with AFR heads on top of them making good power.

I would say that cam on a wider 112* LSA would be pretty well suited to a modified LT-1 intake with EFI. However, your compression is marginal for that much duration. Bottom end performance is likely to be a bit "soggy." For that much cam I'd rather see you up around 10:1

 

I ran 190cc AFR heads in my 92, they work great with TPI

 

Thanks guys. I am glad to hear some of you running TPI have had success with AFR / TPI combo. I am new to modding out an EFI system and I was not too sure if there was some black magic to intake runner design for Fuel injectioned heads.

 

BTW, with this EFI combo would it be unrealistic to expect 410 - 420 HP?

 

i was under the impression that AFR heads were the best out there for small block power and are used ALOT for EFI.. ie superram TPI miniram, etc.... i dont see how they would hurt the output of a motor

 

With an LT-1 intake and proper tuning it's very do-able. Certainly the heads aren't going to be the bottleneck.

 

Good call! Don't forget about EXHAUST. If you have the factory stuff... you will be shooting yourself in the foot. I'd go with a good set of headers, a hi-flow cat, and 3 inch all the way around!

 

CHP's extensive series (which you can read online) of head flow data show that the AFRs have excellent swirl. EDIT: CHP did extensive flow measurements, but the swirl testing was actually done by GMHTP, as reposted here.
My bad.

The only TPI head listed among CHP's data is the 113 casting from GMPP. This is a revised casting that has the raised D-shape exhaust port, and revised valve seats, so the flow data are much better than prior unported aluminum L98 heads, and especially better than any of the stock iron L98 heads (083 casting). I don't know if the 083 iron heads had adequate swirl; probably ok but probably not as good as the 193 swirl port heads for obvious reasons.

Swirl is important because it's what makes the air:fuel mixture burn quickly in the cylinder. With low swirl you need a lot of ignition advance to make sure that you burn the mix in the engine and not in the exhaust manifold (fuel+air, by themselves, burn slowly), and a lot of advance means you are pushing down on the piston while the piston is still rising to TDC. So good swirl reduces the need for a lot of ignition advance. It's true that swirl is not the be-all end-all of intake flow, because high swirl with little flow also means reduced power. You need both flow and swirl, and that's why Vizard (among others) say that there is more to head performance than just raw flow numbers.

HRM got 420+ fwhp from iron LT1 heads (same basic casting as the L31 iron Vortec) and the GM HOT cam, so you should be able to easily equal that with the AFRs, a similar cam, and the LT1 intake manifold. I agree on the exhaust comment too (you need something there that won't choke the rest of the engine).

HTH.

 

Thanks for the reply guys… I wasn't sure if EFI required a head specifically designed for mixing the air and fuel. As a carbed engine, these head run great. I just hope to get the same results with I convert to EFI. And by what I am hearing, it sounds very encouraging. BTW, I already took care of my exhaust. I'm Running Headers and 3 inch pipe. I just need to learn about PROM programming/burning.

I wonder if 110 lobe separation is too little for EFI. I could switch to 112 lobe separation but it seems like a lot of work just for 2 degrees of LS.

Couldn't I just keep my current XR282HR cam with 110? Current Vacuum hangs around 9-10 inches. Would it be a bad idea?

How would an EFI system behave with a cam that has 110 lobe separation?