Mr. Notorious

iTrader: (1)

I picked up a set of siamesed runner from a forum user. Out of the box but in great shape. I guess I should have done a little more research, but why is it than only the first 2" of the runner from the plenum is siamesed, and then it divides into individual ports again?

And my other question is the gasket. I plan and port matching everything, but the gaskets they send with the runners have individual ports (if that makes sense). In other words if I matched the "oval-ish" shape of the runners to the upper plenum, there would be a verticle divider from where the gasket thinks it's going into two ports. Is it okay to just cut the gasket to fit the plenum even though the gasket came with the runners?

Since I plan on having the die-grinder out anyways, is there anything major I should touch up in the stock lower manifold, aftermarket runners, and upper plenum to help feed the 383 some air while I'm at it? It'll be equipped with holley's 52mm blade throttle body... I don't want to cut the wall off the runner like some people do and pull out the spool gun and weld the aluminum back up again however.

d4nk

iTrader: (2)

I used to have the TPI system on my 383. With all aftermarket parts and a lot of die grinder work, it still choked the snot out of the motor. I siameesed the upper plenum, removed the egr walls by the throttle body, opened up the SLP runners devider wall on both ends, along with a edelbrock lower. In my opinion it wasnt worth all the effort. Instead I opted for a carb and rpm air gap manifold and have been much happier with the results. I would look more into a fast system or something along those lines if your looking for performance with the EFI.

Mr. Notorious

iTrader: (1)

Gotcya thanks for the reply. I'm not expecting miracles, it's just that my labor is free. My motor won't be revving over 5000rpm anyways so I'm not trying to pinch every ounce of flow out of this system. Just do a decent amount of port work where it could use it.

Thanks for the suggestion, I've had a carb on this for 4 years already. It's time for FI for where I'm at, I'm a control freak and there's nothing like the throttle control these setups are capable of for their price

Guess thats normal that siamesed runners aren't fully siamesed. Just seems weird to me...

Drac0nic

Yeah cut the gaskets if you cut the head entrances and have siamesed runners. Besides that SLP style runners are really meant to be ported and not used out of the box in my opinion anyways. Siamese the base too as well as as much of the runner as you can get to without going further. I am wanting to cut/weld my base and see how that goes. but we shall see. That is a lot of work.

Mr. Notorious

iTrader: (1)

Sounds like a plan. Any idea why they siamesed one pair of runners down to the intake, but not the other pair. The pair of runners that runs with the EGR passage isn't siamesed. I'm just trying to understand a little more of the theory involved with these before I go porting everything? It just doesn't make sense to me why they designed these this way. Anyone have any insight?