Under what conditions would after market runners be a good investment for a TPI engine? I am researching upgrading the TPI system to my 5.0 Litre TPI engine. After consulting with everyone and researching this website I decided against a larger throttle body. Do the stock runners produce enough of an airflow impedment to warrent upgrading. I am sure the answer is dependent upon how much upgrading one has done to their engine. I have a new GM 5.0 Litre engine with a Comp Cam installed, Headman Hedders, catalytic converts removed and a Walker Super Turbo exhaust system. I am considering a Holley AFPR, porting the plenum and Accel fuel injectors to replace the OEM Multi Tek injectors. I do not think I will change the stock intake manifold or port/change the heads. I know there is an issue with differnet length runners adjusting torque/horsepower at different RPM ranges. However, with what I am contempting should I consider runners. There are several companies including SLP and Edelbrock which makes runners for these engines.

The biggest restriction is the manifold. That should be first.

You can find 'em used for less than a lot of aftermarket runners.

If you're patient, you can find complete porter manifolds and plenums and aftermarket runners for under $500. ...if you're patient
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For runners, I beleive Arizona Speed and Marine have proven to flow best over the whole RPM band. I think SLP flowed best at HIGH RPM's but lost the most torque. The other fit somewhere in between IIRC.

There's a flowchart somewhere around here on TGO. I'll see if I can find it.

All you would need to do for your combination would be port the plenum and get a good AFPR. If you wanted to squeeze a few more horses, you could remove the lip at the entry point on the base and clean it up (not really porting it,, just smoothing things out). If you do all this, you've increased the efficiency of the intake tract enough that you don't need runners with the 305 and stock heads. Larger cammed engines and cars with higher numerical gear ratio and stall speed could see a small benefit from runners. Still,,, considering the cost of the large tube runners ($375+) and how much time you would have to spend modifying a set of SLP runner ($260 + a number of hours grinding),,, it wouldn't be worth it right now in my opinion,, that is if your cam's intake duration is under 224 degrees @ .050 lift.

Yeah, what he said.

I must be behind alot. Whats that about?

Oh you don't wanna know man. Nightmares for the most part if you are a rookie.
I was going to get a set of LPE runners and a base but decided to go after another set up.
I agree the runners will not net you much of a gain with what you have. Not worth the $$$. Spend it on other mods, like a Holly AFPR, ign. box, a shift kit for the tranny(love the kick)oh and from what I have heard stay away from the Accel injectors and you will be ok.

Thanks for your comments. I will use them in consultation with my mechanic.

Here are the specifications of my cam from the card that was provided with the cam:

Gross Value Lift: (intake) .48 (exhaust) .487
Duration at 0.50: (intake) 206 (exhaust) 212
Lobe Lift: (intake) .3200 (exhaust) .3250

Lobe Seperation: 110.0

The TPI system including the OEM fuel injectors were swapped over to the new GM engine. The injectors have about 205,000 km on them so I think I should consider new injectors with this project as I have already had to replace one a couple of years ago. If not Accel, what are some good 19 lbs/hr injectors? Holley or Bosch are good names. I have also installed a K&N airfilter, removered the MAF screens from the recently installed Bosch MAF sensor, done a throttle body coolant by pass and though not relevant to this discussion installed an MSD pro-billet distributor and blaster coil. Once this intake project is complete I will install a custom PROM and an Edelbrock strut tower brace. I think that will complete my engine modifications. Then I will begin on the transmission and differential but that will be in a year or two. Oh, I recently had a LUK clutch installed. Soon the car will be back to the shape it was in, or better, when I bought it in May 1989. Thanks for your advise.

That's a fairly mild cam, with the one questionable value being the LSA. The lower the number, the harder it is for EFI to get it to run properly, especially at idle. An LSA of 112 is commonly considered to be the miimal LSA value for fuel injected motors trying to run in closed loop.

Just my two cents on the topic..... (YMMV, of course!).

And I also agree with the "stay away from Accel injectors" statement. SVO injectors are the most commonly used ones. LS1's appear good too (just trying a set of those myself), but they're probably too much for a built 305.

Good Luck, and let us know what you end up doing and how it turns out!


- Vern

P,S. - I hope you're doing the custom prom yourself and not buying one somewhere. Most of the 3rd party ones are real junk!

I have a dyno graph, I just need to look it up.

tada
https://www.thirdgen.org/techbb2/att...postid=1750460

AS&M large tube runners flow somewhere near 245cfm each. But when you add the base that drops the numbers significantly. Its the same with all TPI setups though.

For the money you'd spend on a set of AS&M runners and an aftermarket base I'd just put the money into a HSR or converted LT1 intake. Both will make your car faster for less invested money.

Unless you can find these parts cheap. If you can get them cheap then I say go for it!

The SLP product represented there is a prototype intake they called the ShortRam. It's not the SLP runners,, it looks more like the Speed and Performance "Ram" intake,,, that looks like the StealthRam. There would be VERY little difference in the power curves from the StealthRam and the SLP product dynoed.

The dyno mule was a stock 350 TPI engine,,,, and the intake system that really pumped up the torque for this mild combination was the ASM system,,, that used a ported stock GM base and the large long tube runners. The TPiS unit was the Big Mouth base and the Semi-Siamesed runners that did too little too late. If I had to pick any of these intakes for a stock or basically stock 350 I'd go with the First unit myself. The ASM set up faired well,,, but that FIRST unit has much more potential to work better on more radical set ups to come later.

I think I will pursue the Ford SVO fuel injectors. I saw some 19 lb/hr EV-1 fuel injectors at Summit Racing part number FMS-M9593C302 for $209.88. Are these the Ford SVO fuel injectors people are recommending?

Brought forward for the Summit/Cam thread for cross referencing purposes.

The 19# injectors are the factory size for a 305. A 350 would need 22# in close to factory configuration. I'm using 28# LS-1 injectors in my 383 Super Ram set-up....

I have a factory 5.0 Litre engine with the modifications I have mentioned and the ones I plan. So I guess I will stick with the 19 lbs/hr injectors.