I have searched through all the posts and read the tech article on siamesing the SLP runners completely from top to bottom and 5 inches into the port opening on the intake. I have the Completely New B-body 350 from Jim Pace, (9.6:1, PM rods, etc.) 24# SVO injectors and the LT4 HOT cam kit with springs and rockers for my second project (89 formula 350). I wanted to know if this porting would be Extremely beneficial or not. How does it affect driveability and fuel mileage? I have read that the Vaccuum drops some but it also does witht the HOT cam. BTW this car already has the full SLP exhaust (1 3/4 headers, dual cats and cat-back) If this works well (great!) on this car, I will do the same mods to my TPIS Big Mouth intake and change to SLP runners from the TPIS Large tubes on my 383 in the GTA.... All replies would be GREATLY appreciated!

 

Any body with this set-up??? Any pro's or con's would be great.....

Kevin Graham

 

it would be very benificial!
what you are doing is making the runner length shorter thus making your intake act more like a lt1/miniram intake.
i have siamesed my intake about 1.5 inches and have stock runners and noticed a difference.
driveability will be just the same and you may loose a little vaccume at idle but it won't be bad
Andrew

 

Thanks! Anyone else have any thoughts on this set-up? I dont want to go to the trouble of hacking up my intake and find that its a bear to drive and have to by a new intake. I have the HOT cam kit in my 383 with the TPIS Large ubes and Big Mouth intake in my '89 GTA, and I love it... Just wanted to try something new on this project.....1989 Formula 350

Kevin

 

Well, my engine has the SLP runners on it. I siamesed the plenum outlets for the runners to match the SLP siamesed ones (siamesed the plenum). I also port matched every intake (and the headers sort of) component in the system. I ported the runners down about one inch farther then where they are stock and radiused the entry areas where they meet the plenum. I still have a stock base on my car at this point as well, but I ported it out quite a bit as well. I did virtually all of the mods to my engine all at one time when I built it, so it is really hard to say what mod did what. But my setup pulls pretty nicely to around 5500 rpm at this point (damn the inaccurate factory tach ...grrrrr). I'm sure that the stock ported base and the rather smallish primaries of the Edelbrock TES headers are limiting my system quite a bit. But I will likely go to a MiniRam if I do anything more to the intake system (If/when you get into PROM burning, the MiniRam becomes a lot more affordable). And my hopefully near future plans call for some Hooker SC 1 3/4" primary, long tube headers, with a Mufflex Y-pipe, as soon as I can afford them.

I also run the LT4 Hot Cam. I really don't think the intake mods will be the limiting factor as far as how much vacuum your engine will pull goes. The cam is what usually controls that - or at least it has the biggest input on it. My engine will pull around 14" of Hg at idle with the idle set to (a rather low rpm for the cam) 650 rpm. With the proper PROM tuning, the driveability of my setup has become virtually perfect. The idle is expectedly choppy (love it), but the overall manners have become extremely palatable. It takes a while to adjust all of the PROM calibrations to where you want them/they need to be with a radicalish cam and the like, but you can get it to behave very nicely on the street. If your main worry is about the driveability of the engine, you really need to get into burning your own PROMs.

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1987 GTA L98 MD8
355, TFS Heads, LT4 Hot Cam
My GTA

The Minnesota F-body Club