bbc small vs large oval ports

[68bowtie]

looking for the difference in bbc port size. i have three big block chevy engine books, and i can't find the answer... most literature just refers to "oval" vs "square" ports, but doesn't differentiate between small vs. large ovals.

i'm trying to find an intake manifold to match my 1973 "049" heads, which are oval ports. the inlets to my heads measure roughly 1.73" wide and 2.00" tall. i'm considering the edelbrock 2161 (link below) but if you read the fine print it says the ports are 1.70"x1.68". some of the reviews on the 2161 comment that they are for "peanut" ports. when you search on summit you can sort by "oval port" or "large oval port". do i need to stick to the "large" designation? that limits my choices big time (at least on summit). most the manifold specs don't list the port dimensions... hoping someone can point me in the right direction.

https://www.summitracing.com/parts/edl-2161

[Tom Vogel]

I would post this exact question on the racing section. I believe the intake manifold you reference will fit on your heads however it would probably help is you port match.

[regan wilson]

You have a good set of oval port heads. They are passenger car heads and can be ported and fitted with bigger valves to make some pretty good power.(500 plus)

The intake you are looking at is for a truck head. They were designed with a small port for low rpm torque. They came on big block pickups and 366-427 tall decks that were made for lower rpm towing.

I would find an intake that would be compatible for an LS5 454. LS5 was the lower hp 454 in a 70 Chevelle. LS6 was the bad boy square port 450hp 454 in the 70 Chevelle.

The intake you are looking at could possibly be ported to match your heads but it might make for a thin casting. I would look for something else.

Hope this helps.

[68bowtie]

yes that's helpful thanks. that answers my question.

[Redline novdog]

Yes you have the large oval ports. Awesome cheap power with very little work. "049" heads are very good heads!!!!

[Mike C]

The Edelbrock intake you mention is for either peanut port (almost round) and the large ovals. Even having smaller ports than the heads, it flows WAY better than the GM low profile intake.

The GM performance parts intake can be bought port matched, then you can port match your heads to equal that.

But unless you are going for max effort, the Perfomer intake is a great solution.

Full disclosure, I originally bought the Edelbrock Performer but subsequently bought the GM intake that is port matched. I will port my 290 small chamber ovals to match.

The GM intake is the same as the Performer RPM. Probably made by Edelbrock from best I can tell. I am going to paint it and would have ground off "Edelbrock" if I ran their intake on my sleeper. But I will just leave the bowtie on the intake as it comes from GM.

[68bowtie]

Originally Posted by Mike C

The Edelbrock intake you mention is for either peanut port (almost round) and the large ovals. Even having smaller ports than the heads, it flows WAY better than the GM low profile intake.

The GM performance parts intake can be bought port matched, then you can port match your heads to equal that.

But unless you are going for max effort, the Perfomer intake is a great solution.

Full disclosure, I originally bought the Edelbrock Performer but subsequently bought the GM intake that is port matched. I will port my 290 small chamber ovals to match.

The GM intake is the same as the Performer RPM. Probably made by Edelbrock from best I can tell. I am going to paint it and would have ground off "Edelbrock" if I ran their intake on my sleeper. But I will just leave the bowtie on the intake as it comes from GM.

is this what you're talking about?

http://www.gmperformancemotor.com/parts/12363420.html

[Mike C]

Yes. You can get standard as cast and they sell a port matched one. Standard is probably the way to go. I am second guessing my own choice...

[Aus69c20]

I'll second the Gm performance manifold.

I purchased the edelbrock and was ready to fit it before I double checked the port dimensions and realised it was slightly different. Went back and swapped it for the as cast Gm manifold and the dimensions were perfect.

As bonus it looks better in a stock looking engine bay. Painted orange you barely notice it.

[Mike C]

Just to make sure you caught it the first time, the GM intake is the same as the Performer RPM, and NOT the standard Performer intake.

And as I said above, the port size isn't what kills the flow relative to the GM intake but the "pancake" style design of the factory intake and it's lack of any plenum volume. With a stock cam and a 396-402" engine the standard Performer will be fine.

With a bigger motor and/or more cam the RPM or GM intake would be better.


My build is a .030 over 427 with the smallest nitrous hydraulic roller that Comp makes, 224/236 at .050. on 113 deg lobe sep.

My intent is to run through a set of angle milled big block Corvette exhaust manifolds so the extra duration of the N20 cam to offset not running headers.

[davepl]

If you're getting later parts (like GMPP stuff) keep in mind there are also "roval" ports, which are larger oval ports. They're from the ZZ502 and I have a couple of manifolds that fit them, so they're out there, and you could well run across one thinking its a normal oval port... but it's not.

[68bowtie]

thanks guys. i like the performer rpm for my setup (396, 060 domed pistons, XE268H cam).