Guys,

I have a 1991 camaro z28 with a 305 tpi.

I have been looking at the slp performance website, and I am thinking of buying the intake runners they sell for my car, they seem like a pretty simple thing to install myself, and am I right in thinking they should bump up the performance a little?

Also at the same time I am thinking I should swap out my throttle body for a bigger capacity one, seeming as though I will be under the hood anyway. But they sell a couple of different ones, a 52mm and a 58mm. Are they both compatible? What should I go for?

Thanks

Pete

 

On a stock 305 you probably won't see any gain with the slp runners, and definately stay away from either of the larger throttle bodies. If your car is stock, think about doing headers/exhaust first.

 

The airflow design of the intake manifold, runners, plenum and throttle body were designed to accommodate the 5.0 liter engine. That is to say as the 5.0 liter exists the stock TPI system flows enough air and fuel/air mixture to meet the requirements of a 5.0 liter engine. Adding extra flow ability to the runners, manifold and throttle body will not let any more air/fuel mixture get into the cylinders. Further, the runners are that particular size to permit a particular action to occur to deliver a larger air/fuel mixture to be inputted in the cylinders for a 5.0 liter engine. This is where the “tuned” of the Tuned Port Injection comes in. Altering the length and diameter will not only not produce any more air/fuel getting into the cylinder it will affected this second aspect of this part of the fuel induction system. If you put on bigger flowing heads, headers and/or a cam to a 5.0 liter engine you could then maybe consider better flowing runners and/or manifold to handle the engine’s ability to draw more air/fuel mixture. Although, I have not seen any published articles documenting that.

Where you can consider better flowing or bigger runners and manifold is where a TPI system is bolted on top of a 350, a modified 350, a 383 or even bigger displacement engine. There the engine is drawing a bigger volume of air/fuel mixture than the stock TPI was designed to handle.

 

The exhaust is a bigger restriction on a 305 TPI automatic than the intake is.

Replace that, first.

 

I'm running the SLP runners along with their old tri-y headers. I'm also running an old Edelbrock lower manifold. Port matched plenum.

The butt dyno tells me that the engine isn't as "peaky". Either the torque curve flattened out as advertised or it actually lowered the peak torque a bit.

I installed the headers before I touched the intake side. The headers did more to uncork the engine than the intake mods.

IMO, no gain. Looks cool though.

BTW, the intake mods were purly in response to a warped lower manifold. I really wasn't looking for any gains but I was young and had money to blow.

 

If the engine is stock start by upgrading the exhaust.

 

If you get the SLP runners, they will actually hurt your performance until you port the base to match.

The larger TB doesnt help until you get to the VERY high rpms. Look at where you normally drive your motor and see how high your rpms actually go. I doubt you spin it high enough for this to help.