Edelbrock makes an intake manifold for the GM 60 degree V6 engines. They come in two pieces, upper and lower.

There are two choices for the upper part, one for a 4bbl carb and another for a 2bbl carb.

Both uppers work in conjunction with the same lower intake manifold.

Here's the weird part. Edelbrock designed the lower intake with two different runner sizes - the theory being that one cylinder bank gets smaller runners to boost bottom end torque, while the other head gets larger intake runners to boost the upper end.

Supposedly this fine engineering all comes together when used with their TES headers which also have different sized tubes matched to the intake runners to maximize flow.

Do any of you think this is a bunch of bull?

Have you ever heard of a similar approach on any other engine/s?

Glen,

Edelbrock has always found some way of doing things differently.... Back in the late 50's thier 3X2 intakes were dual plane yet both sides had an upper and lower plane ..but not in the normal way...you have to see one.... back in the 60's they went with the " swept runner " design that was used on the C4B and C3BX type manifolds where they had the 4 outside runners swept really long and the 4 inside runners were very short...... They used to make a Tunnel Ram that had the runners different sizes....where the air would enter the intake port 4 runner exits were shorter than the other 4...this produced a sort of dam or wall...they also had some with runners with a slanted saw tooth pattern in them...both of these last two were suposedly to help reduce " reversion ".... They didnt last long.
They designed the SP2P.... they just went too far on the small side with that one... but that was a didfferent ers when the SP2P was designed...

But they are not afraid to push the envelope if they think there may be something to be gained from it...Sometimes they get it right and sometimes it's not so great...

As for your specific situation I havent seen one so cant really comment on it....But it doesnt surprise me that they did something different.

I always wondered what would happen if you put a rectangle port head on one side and an oval port on the other.

Similar idea, I guess.

Tim.

What they are trying to do is make a V-8 think it is really two four bangers!! One that is hi-po and the other that is not quite as hi-po!! This in turn creates different torque points per cylinder bank and when you add them together the motor is supposed to have a higher and wider torque curve then making everything one way or the other..

I can't say if it works or not but do know stepped headers fall into this cat. as do running 1.5 and 1.6 ratio rockers on different valves..

pdq67

Thanks for the replies.

I got a decent deal on an unused one from ebay, but was unaware of the different runners at that time. Their TES headers won't work for what I'm trying to do, so I'm having second thoughts.

The way I figure it induction is induction and this bottom end cylinder bank and upper end cylinder bank business is more of a compromise than a benefit.

Does anyone make a cam with different lobe profiles for each head? Not that I know of...

The bad thing is this is the only aftermarket intake in current production.

I'll try to get some pics and post them so you can see what I mean. I've never posted a pic here before, so it might be up by Wednesday. ;)

Glen ,

Actually someone used to make a cam something like that.... I have a 1973 Sig Erson cataolg and they used to make this thing called the " Tri Flow " camshaft for the BBC....

The theory went something like this.... the first BBC RP heads left a bit to be desired....2.19 intake and 1.72 exh... and of course the " Good port / bad port " thing going on makeing for less than optimum mixture distribution.....

So they came up with this idea that the different ports needed different cam timing to try to help even this mess all out.... so they made up several different cams..... check out these specs...this is one camshaft.Old part # 124731 ... TF 60

Cylinders 1,4,5,8 :
intake timing 40-80 ..lash .028 .560 lift 300 dur.
exhaus timing 88-47 ..lash .030 .600 lift 315 dur.

Clyinders 2,3,6,7 :
intake timing 47-83 ..lash .028 .580 lift 310 dur.
exhaus timing 86-49 ..lash .030 .600 lift 315 dur.

Hows that for diffewrent thinking.....

Then when Chevy decided to update the heads and came out with different port vol and runner shapes as well as larger 1.84/1.88 ex valve and open chambers these series of lobes were quietly dropped from thier catalog !!


TronDD ,

On that Tunnel Ram I mentioned as I recall they were large and small on both sides...so like cyl 1 and 3 ... 1 had what was basically a large oval runner exit and #3 had the normal rectangular port exit !! right nect to each other... same thing on the other pairings....They basically tried to make the manifold cure a problem most likely caused by the cam timing.

Al,
Erson's approach with different lobe designs makes perfect sense to me, especially since their goal was to even A/F distribution into all cylinders. I'm just surprised that someone went to the trouble. It does seem to me that said cam would only work well with the intake manifold it was designed to work with since one of the big challenges of intake design is equal distribution.
It doesn't seem farfetched at all to try to get the intake as close as possible, then even out the discrepancies with different valve timing for each cylinder. The impractical part is that with that approach each intake would warrant its own matching cam, and greatly limit the usable applications for the cam, which would make it a very nonprofitable even if it was the best thing out there.

Looks like Erson had a lot of R&D go down the drain when Chevy switched head design - bet that made them happy.

But Edelbrock wasn't trying to even things out - from what I've read their intentions were to design the intake in such a way where the two heads have different power curves. It's the rob Peter to pay Paul deal.

I'll try to get some pics of the intake later on.

You do the same thing on a SB when you use 1.6 rockers on the corner cylinders and 1.5 rockers on the inner four!!

Seems it takes longer to get the air/fuel out to the corner cylinders so you up their timimg a schosh with the higher ratio rockers..

At least I think that is the theory, but now we have SB2.2 heads and such!!!

pdq67

Ya it certinally was a different approach to the problem....and I agree that with a different intake you would likely need a different cam also .. useing this idea.....In this catalog they only had 4 " Tri Flow " cams..the one I showed there was the smallest one.... they had as large as 314/320/330 deg cams..... Race only type stuf...

The Cylinder head offset on the BBC is a bit larger than the Cylinder Head offset on the SBC.The smaller offset of the SBC makes it easier to place the intake runners and make them more equal in length and in flow... with the larger offset and staggered valve locations on the BBC and beings they wanted/needed spread exh ports and paired intakes....add to the fact that air flow studies were not very advanced back then....It's no wonder they had problems but they also knew this new BBC had major potential !!

Sig Erson did alot of research on this with CR Axtell on his flow bench.... Flow benches were very uncommon back then.... Anyhoo these guys worked this all out and came up with this idea.....But they ofcourse didnt know that Chevy was working on basically the same thing but in correcting the heads....There really wasnt a whole lot that Chevy did to the intake manifolds back then....the early one had 4 drilled holes and the later a divided plenum and milling the plenum divider on the L88/Zl-1 intakes.... They couldnt also know about the dual pattern L-88/ZL-1 cams also that Chevy released....

Got to give them credit for trying...even if it ultimatly failed...... But they certinally were not alone in the failier department.... But thats all part of R&D...you are going to try stuff that fails.... You'll never win if you fear failing....
Offy " Dual Port " intakes ,Crowers " Gas mileage " system with 14-1 comp and a tiny cam with late opening and real real late closing with a normal exh... the"Tungston Hydro Catalist" those screens that went under the throttle bores to break up the A/F better.... The Tornado intake swirl generator ect ect ect.... All wizzy stuff that failed....

As to the Edelbrock idea of have the two different heads make different power curves.... well I dont know but that seems like the wrong approach... but I know nothing about that engine and what it responds to.....

I remember there were a couple of Cam companies who refused to grind cams for the GM Vega engines... as they had cyl heads that were so poor that they didnt respond to cam changes the way that most engines do... others jumped right in and made cams for them.... Now about the only Vegas you see are S/G cars with V8's in them....

Anyhoo I certinally cant speak for Edelbrock on what their idea was on this one...I have no idea...

69LS1,

Glad you mentioned the Crower thing b/c it was an interesting study to say the least!!

IMHO, I figure the Offy dual port is a winner like the SP-2P IF and it's a BIG IF used in the proper applications..

AND I don't think even Mr. Duntov figured out why the Holley-Z manifold that was a single plane with a port between the #7 and #8 ports worked so good!!

pdq67