Technical Theory : Plenum Design

[CNCguy]

I have started making an intake also. It wont have the low end that Brads will have though. I dont have the hood clearance issues like most of you guys so I took the easy route. Below is a pic... but once again I came up short since I didnt have a cute kid to model with it.

Marc

[1QUICKHATCH]

Cool! let us know how it works! what are you going to use for a tb?

[Anonymous]

Hey CNCguy, why do your runners kinda aim backwards? Why not just go straight into the actual plenum instead of at an angle?

btw it looks good, kinda looks like a marine motor. Those collectors look "headersbyed style" to me, are they?

[XLR8ING]

Very nice Marc! I wish we all the room to make whatever we really wanted instead of always having to comprimise.

[CNCguy]

Thanks for the props guys

I will be mounting a 75mm TB at the opposite end of the motor. I angled the runners towards the TB to try to improve flow as well as keeping them longer. This isnt the optimal design but should be quite an improvement over stock. One consideration was to raise the plenum which would have lengthened the runners.

If you look closely you will see that I have switched to a RWD timing chain cover. By doing this, it cleans up the front of the motor, moves the waterpump and it gives me more options on where I can mount my alternator. I needed it moved so I would have room to put on a billet set of valve covers.

The collectors were made by myself from 3 peices of tubing. The headers have picked up some surface rust from being handled too much. After a final decision is made on whether to turbo or not, the collector flanges will be made. Afterwards they will be ceramic coated.

Give me some feedback on what would look better. the plenum being powder coated or ceramic coated.

Marc

[GPXSS]

def powder coated.. any candy color would look awesome.

[bszopi]

Well, we did a test fit of my plenum on Tat's car at the meet (since he had the plenum off anyway). Came up with a couple issues... First, the flanges will need to be trimmed up some since one of the corners runs into the PS pump. Second, I'll need to redo the orientation of 2 of the runners because the last one also runs into the PS pump (damn power steering!!!). And finally, it doesn't clear the hood. But man is it close!! Looks like its about a 1/2" too tall. But, with just a small cowl, it could easily be kept under the hood. And a small cowl wouldn't be very gawdy looking either, so that's nice. So now I have to figure out how I'm gonna make it clear the PS pump. Guess I should have listened to Chris about just tacking it up first... Damn you Chris!!

[RidgeRunner]

That intake and those headers just look plain damn MEAN! Very nice.

And finally, it doesn't clear the hood. But man is it close!! Looks like its about a 1/2" too tall. But, with just a small cowl, it could easily be kept under the hood. And a small cowl wouldn't be very gawdy looking either, so that's nice.

Cowl hood on a L body? We're gonna hafta start calling you Taz! :P

[bszopi]

http://www.usbody.com/Pages_Cars/87-Beretta.htm

So no, it won't be a 4" cowl like Taz's... :P

[Anonymous]

I didn't know that the TB would be at the end that the runners pointed to, I was thinking it'd be at the other end. So yes that angle for the runners is good.

I would powdercoat it. Ceramic coatings are better cuz they can handle the heat of headers, but they are not famous for looks.

[EspanolaGuitarista]

Where do you get a 4" cowl for a Beretta? IF I had one I could make a kick-ass intake. Like the Jaguar 4.0L v-8. Great job on all your guy's stuff. I'm really impressed. This is what hot rodding is all about, making your parts. Any candy-ass can pick parts out of magazine and write a check to have it built. Keep up the good work!

[v6h.o.]

Very nice work Marc! damn im impressed with the work and projects that are coming out and being produced by the 660 crowd! very cool indeed.

cant wait to start on my intake manifold and plenum for my car now...

yes i agree powder coat it. would look really good that way.

[pocket-rocket]

Well Brad, I stayed up an hour more then I wanted searching through my pics from my camera to try to find a pic of the plenum off of my wife's T-bird (besides, it was a good reason to finish off the last of my 4 beers I had here, lol). It's basically the way you want to make your intake, with the plenum underneith. On big difference (besides the obvious extra 2 cyl.) was that on the Ford Modular engine (cough *crap!* cough) is that it is a true OHC engine, so there is no jerk over lifter valley screwy design like the LQ1. They wrapped the runners around the plenum pretty tightly, though, and the TB is on the back of it, on a 180* elbow so that it faces forward. I will keep looking to see if I still have it because it kinda looked cool. At least her car didn't have the plastic one!

[EspanolaGuitarista]

How long are the runners on the bottom half? I like the way CNCguy built his. How much more runner length to get to the optimum tuned length we discussed? How do I get a 4 in. cowl?

[bszopi]

I was playing with the idea of adding a small riser plate between uper and lower to slightly lengthen the runners wich would be the easiest way for longer runners but are limited by hood clearence.

Doesn't do anything... I've already tried it.

As far as the lower runner length, I have it written down somewhere, but IIRC, it should be right around 12". As far as the cowl, any fiberglass or steel cowl can be added to the hood. Just take a little work to make it look right.