ZZ454 Carb spacer carb size exhaust size
 

I am in the process of having a ZZ454 installed in my 68 Camaro. I have an almost brand new Holley square bore 750 dp that sat on top of a 4 hole spacer over a single plane intake on the old 454. I have 2” hooker headers and 2 1/2” exhaust out the back. I want to dial this in as much as possible....the motor was dyno’d with a 770 carb. So I am assuming I won’t see much of a difference at all with the carb size (I know there are some variables here, so I am assuming this in “general” terms). I have a clearance issue with the hood with the new motor, so I will not using the spacer have an affect? Last, how much will the 2 1/2” exhaust affect my HP? Thank you in advance for your responses....and Merry Christmas!

I don't see a problem as long as it's not on top of a spread bore intake.
The exhaust should be fine as long as you have mufflers that flow well enough.
Pretty much what I had on my '69 Camaro back in the day with a 427,long tube 2" tube headers with 2 1/2" exhaust and turbo muffs.
I ran a Holley 750 double pumper on a twisted torker intake like this one, had the rectangular port heads and solid lifter cam.
She ran like a scalded dog!


https://cimg6.ibsrv.net/gimg/camarof...20f75c9382.jpg

Thanks for the reply..... the intake does have dual planes.... not an open plenum like your picture.....so this is where the confusion begins.... is an open plenum better suited to a spread bore or a square bore carb? My intake is dual plane, but the separation doesn’t come all the way to the top of the intake....there is a gap about 3/4” of an inch in the splitter below the top surface of the intake. I hope that makes sense. Most of them that I see have the splitter between front and rear on the intake coming all the way to the top of the intake.

Ahh I see, your first post said you have a single plane but as long as the butterflies open all the way without hitting the splitter you should be fine.
I take it you are using a different intake than you had on the old 454? Why not just use the old intake? Are they both the same port design either oval or rectangle?
I'd rather have a single plane with a double pumper myself but I'm no expert either so maybe someone more well informed will chime in on the differences pro or con.
The Edelbrock I pictured worked great on my car but I did have hood clearance issues and had to change hoods to a cowl induction style.

Here's a good read,I learned a bit about the ZZ454. https://www.hotrod.com/articles/best-induction-combo/

My 427 had rectangle port heads and a much bigger cam,very different animal.

Sorry about the single plane thing.... that was dumb! I am going to run this set up a while and see what’s what. At some point I may step some things up a bit like a cam, but I like the fact that the engine is a complete package and I have baseline Dino results to work with. It also has a nice warranty as is! Looks like we will break the motor in on Wednesday....big day! Thanks for the info, and I will check out that article link now.

The 'dual-plane' manifold will be the better fit for you as one should build torque for the street. The one pictured is for high rpm in building horsepower.
The reduced center wall is for balancing both sides of plenum for a better vacuum signal, read steady, to the power valve rather than a choppy signal of a completely divided plenum.
Building torque is at a lower RPM requires long runners, both intake and exhaust sides.
Torque is the action pegging the 'Seat-O-Pants' meter.

thank you! I have gotten a lot of feedback, and it all seems to align with the build that Chevy created with this crate motor. We fired it up for a couple of seconds last week....just required a bump of the key (and it was cold that day!). I am hoping to have it back on the road Friday of this week.....fingers crossed! Thank you for the reply....Happy New Year!

All true although I never had a problem finding enough seat of the pants torque with my 427 and that intake even with the solid lifter cam.
Sure not like the DZ 302's. lol big blocks come by it pretty easy

Tell those who I have beaten with a DZ302 in a '64 Impala . Above 4000 RPM, it pulled.
Their faces told the story as I, at least, stayed along side of them. Great memories.