Intake manifold options for a big inch small block Chevy

[quickcat]

I am looking for further manifold options for a 427 ci small block Chevy that I have built for a friend. He had an Accel Super Ram on an engine before and wanted to run one again so that is what we put on it. Well the dyno results were proving to be disappointing so I am trying to come up with a better intake without going to a modified carb intake or a sheetmetal race piece.

The engine is a World aluminum 4.125 bore block with a 4 inch stroke crank (427 cid) and Brodix CNC ported heads with 2.10 in/1.60ex valves and 210cc intake runners, and 10.5:1 compression. The cam will probably peak out at 5500 but it may go higher (the Super Ram was obscuring the engine's true potential). It will be in a 1970 Vette with a TKO behind it. We are running the FAST XFI injection system on it.

The only manifold I can think of is the TPIS Mini Ram but I don't know if it will move the air we need either. This is just a big engine and I am concerned that there are not many choices out there that are big enough for it.

Thanks.

Matt

[Kenova]

I believe most aftermarket injection manifolds are geared toward the lower RPM ranges on smaller engines (350 to 383 ). To give the 427 SBC the air it wants, I think you may need to use a carb manifold set up for injection.
To find the manifold that suits your purpose, you could try a few with carburation, select the one that works best and have it converted to EFI. I have no real experience with induction systems, but I think a port matched Victor Jr. may be a good place to start.

Ken

[funcars]

You can buy a victor manifold that already has injector ports and there are lots of others you can convert. Torque won't be a problem so a singleplane is a good choice.

[andrewb70]

How about the Holley Stealth Ram?

Andrew

[Mike Norris]

Most of the stealth ram manifolds will run out of air for sure.

The Beck and Hogan LSx style sheet metal manifolds are rgeat but can be pricey for sure.

The new FAST manifold and rail kit may be just what you need. It claims to run from 4500-8500 ona SBC, but considering the 427 cubes, I would say to 7500 or maybe 8000.

I can get you the FAST manifold and rail kit for about $450.

Or I can have Wilson add injector bungs and rails/stanchions for about $595.

Hope this helps.

Mike Norris

[GetMore]

Hijack here, but on a similar note:
I've got a small block 409 (.040" over 400) that will probably spin to 7,000 rpm. What kind of manifold might work on this?
I've got a GM Ram Jet from when I was using standard Vortec heads and keeping the rpm down. Now I'm not sure how much of a restriction it'll be. Maybe Extrude-Honing it will help?

[Mike Norris]

I think you will be in the same boat also. I looked a little bit but could not find an RPM or HP rarting for the Ram Jet manifold. Extrude hone will help, but I do not see it going to that RPM well. You may be pleasantly surprised but i would not bet on it. If you can find the RPM range and HP potential, that will help quite a bit.

Mike Norris

[Blown353]

FYI, an out of the box SBC StealthRam flows about 250-255cfm per port-- at least mine did. So it will certainly be a limit on a big-inch SBC as it flows less than the intake ports on most decent 23 degree heads.

After major extrude honing and a sheetmetal upper plenum with extended bellmouth runners my stealthram now flows just over 305cfm per port-- which is much more in line with the kind of flow numbers a worked 23 degree head can achieve.

So a Stealthram can work... but it will take a lot of money to do it. So much so you'd be better going off with a converted single plane if you're looking to save a few bucks, and if not a custom sheetmetal job would be the best option.

Short of spending $2500+ on a sheetmetal intake, my recommendation would be to buy a Victor Jr. EFI and then run either an elbow and a monoblade or a 4-hole TB.

[DeltaT]

Edelbrock has a Super Victor EFI that's meant for high rpm (8500) use.

Jim

[GetMore]

I checked, and the intake ports on my heads only flowed 244 cfm. Would this mean that maybe the StealthRam intake would work?

I am using ported Bowtie Vortec 180 heads. I know the ports on the Ram Jet intake are smaller than those on the ported heads.

If I remember correcly, the person that chose the cam grind for me said it'd make max power at 6500, but it'd still pull to 7000.

Mike, have you got any more information on those LSx-style manifolds? Perhaps a link? I tried searching for them and couldn't find any.

[GetMore]

Should the manifold runner flow match or be close to the head runner flow?

[Chevy]

FYI, an out of the box SBC StealthRam flows about 250-255cfm per port-- at least mine did. So it will certainly be a limit on a big-inch SBC as it flows less than the intake ports on most decent 23 degree heads.

After major extrude honing and a sheetmetal upper plenum with extended bellmouth runners my stealthram now flows just over 305cfm per port-- which is much more in line with the kind of flow numbers a worked 23 degree head can achieve.

So a Stealthram can work... but it will take a lot of money to do it. So much so you'd be better going off with a converted single plane if you're looking to save a few bucks, and if not a custom sheetmetal job would be the best option.

Short of spending $2500+ on a sheetmetal intake, my recommendation would be to buy a Victor Jr. EFI and then run either an elbow and a monoblade or a 4-hole TB.
Blown, does that mean out of the box you flow 250X2=500 cfm total? Not sure how many ports you count the stealth ram as total.

Thanks in advance for answer.

[John S]

I'm running a 427SCB with the Stealth ram and yes, it does limit the engine. I've been researching a new intake and the new Super Victor EFI manifold seems to be the way to go, I plan on topping that with the FAST 1300cfm throttle body.

[vetteoz]

FYI, an out of the box SBC StealthRam flows about 250-255cfm per port-- at least mine did.

Interesting , they are listed on most sites as 275cfm.

[Motown 454]

In Chevy High Performance 's September issue they test 16 small block manifolds. You could check them out to get an idea on which will be best for you.
Wayne

[Blown353]

Interesting , they are listed on most sites as 275cfm.

Some flowbenches are more "forgiving" than others, just like some dynos are more forgiving than others... :hmm:

We flowed my intake and heads on the same bench, which is the ideal setup as there isn't any disparity between flowbench numbers. My stealthram (which I've had about 4 years now) was nowhere near 275cfm out of the box.

It's still a good intake IMO but for naturally aspirated applications that are high RPM, big cubes, or has good heads (or any combination of the above) it will be a limiting factor if left in out of the box condition.

[Taylor1969]

How about the Holley Stealth Ram?

Andrew


:twothumbs


Steathram w/ LT1 throttlebody and megasquirt

:hail:

(for my 383 it is my choice)... maybe as others have said, those extra 50 cubes will kill it.