standup

What are the consequences of using an LS6 intake manifold (designed for rectangular port heads) with Edelbrock RPM heads....(the Edelbrock literature says their heads are oval port but flow like rectangular port) ??????

shafrs3

Fuel pooling at the lip between the head and the intake.

itsonlyairandfuel

I've done it with no noticable problems. In fact it ran pretty good. Ron B.

73, Dark Blue 454

Actually Edelbrock calls these heads "roval" port,..which I guess is a "tweener". But why not spend $150 and get the matching intake? Having a big stair-step in the runner can't be good.

kaiserbud

I am in the process of changing from Chevy OEM Rectangular Ports Heads to Brodix RaceRite Oval Ports. I did not want to deal with the mismatch on the intake, so I bought an AirGap Oval Manifold to maintain best flow. Isn't that what it is all about?
Here are the Brodix #'s:
RaceRite BB Oval: 270cc Intake/119cc Chamber, Flow 340 Intake/236 Exhaust
RaceRite BB Rect: 294cc Intake/119cc Chamber, Flow 342 Intake/236 Exhaust
Their website data: http://www.brodix.com/heads/raceritebb.html

I am by no means an expert, but from what I read/was told, the flow on the oval is actually faster with the volume being very close. The oval is more streetable and the rectangular might be better for REALLY high rpms.....guys - be gentle.......

standup

That would be too simple .....you're right about the step, because the heads and intake are not matched and I'm now sure there's going to be lots of metal interference......staying with the stock or L36 manifold means I have to use a Q-Jet.....I'd buy the Performer 2-0manifold, but not sure if it will fit under the stock BB hood ?????

Thanks for the Brodix link, haven't seen those heads before ....I've got a stock mid 70's 454 and I'm sure I'm going to need small (110cc minimum) heads to build compression because I didn't want to go into the bottom end.....I may have to anyway because I've got flat top pistons ???????

Do you have an L88 hood to get the AirGap manifold in there ????? If not tell me how it's done....

standup

BTW, what I'm trying to acheive is a top end rebuild on a stock '77 454 motor....which is probably no more than 8.5:1 compression with 113cc chamber heads.....

....so I want to change heads, cam, intake & carb to improve low end torque...and it all has to fit under the stock BB hood.....

Little Mouse

Take a look at the edelbrock performer high compression 454-0,
part #60499, it has 100cc comb. chambers, 219/188
valves, 290 runner.

standup

Those are the exact heads I'm looking at.....just need to make sure a low rise, Holley based intake will fit under my BB hood....I've already been told I should have bought an L88 hood to "widen my horizons"..... ...but I'd like to make this work without having to change the hood....again....

kaiserbud

StandUp - I do have an L88 hood - very happy with extra clearance and especially the looks

sxr6

Standup; word is useing the rect intake works just fine on a oval head just doesn't work worth poop the other way.
Assuming you have stock flat tops that are 16-20 thou down the holes you need small cc heads to get any decent compression. The flattops in my 454 are down 16 thou & with 101cc (290) heads & a 020 steel head gasket my compression works out to just under 9-1.

yellow-fever

I have a stock 74 454 and am also contemplating either a top end rebuild with the 100cc Edelbrock heads, new cam, carb, etc. and I also want to keep it all under the stock hood. I have done the homework and found that there are 2 and exactly 2 manifolds that will work in our situation: (1) LS-6, which will give a port-mismatch with the oval heads but I am told actually works fine, OR: (2) Edelbrock Torker II, which is not a good manifold in any way. It has very small runners and and open plenum design (?).

My choice was the LS-6 manifold. Found a NOS one on Ebay in perfect condition. Now the only thing I have to figure out is what ttpe of shape my short block is in. If it needs a rebuild, I will probably pull out the entire motor and drop in a ZZ502, using the LS-6 manifold on it.

I will be interested to follow along with your project, standup, as we are trying to do exactly the same thing with our cars.

Wrencher

I'm running a rectangle port 3x2 manifold on my stock oval port heads with no problems. Is it perfect performance wise? No, but until I install the LS-7 heads and a better cam, it'll work and I get to drive it. I put about 500-800 miles a month on mine and try to limit down time

Hans