jaybird81

I am going to be pulling the stock motor from my 81 and going with a one I built up from another car as a kid. The motor has an Edlebrock performer rpm manifold which is a square-bore setup. I had a holley carb on it, but I want to use the rochester (non-computer) carb on the car now. Looks like all I need is a $20 adapter. there are several ones to choose from on different performance websites. I've come to you guys for some guidance. I know there are guys out there running beefed up motors and sticking with the quadrajets, what adapters are you using? I have a stock hood did any one have any clearance issues with the extra height? Any advice you could give me would be greatly appreciated. I am really excited about getting a lot more power in the car and since the motor was built a while ago, it's not costing me a lot of money. Just a set o headers and this adapter. I would really not like to have to buy a new carb.

billla

Used spread-bore Edelbrock Performers can be had pretty cheap on auction sites.

Jeff_Keryk

Like Billa sez, use the correct manifold and you will be better off.

glen242

Edelbrock does make a spread bore Performer RPM manifold. I have one on my '76.

My previous Performer (not rpm) would handle both types of carbs.

7t9l82

i believe the performer air gap can be had with a spread bore, an RPM air gap cannot.

wilcar

If your 81 is stock then why not use the stock q jet aluminum intake you already have? Performer rpm is taller than a performer and you will likely have clearance issues if you try put a q jet adapter on it. The stock q jet intake flows just as well as a performer intake so I would keep it.

7T1vette

Adapters that go from spread-bore to square-bore, or vice versa, don't work very well. And, they add height to the carb so that it might not fit under your hood. Spend a few more buck$ and buy a used (or new) intake manifold that is made for the carb you choose.

jaybird81

I appreciate all the advice. Thanks. Looks like the general opinion here is get the right carb for the manifold I want to use or get the right manifold for the carb I want to use.
Is this true? Is the stock manifold on the 81 Vette comparable to a performer Edlebrock manifold? Now that I think about it the manifold might just be a performer not a performer RPM. I have to check the next time I am out there. If it is just a performer, is the stock one just as good. The motor I am using is a 350 that has been bored .030 over has 10:25 /1 forged piston a competition cams 280H cam and I'll be using headman full length headers dual exhaust flow master mufflers. So I guess regardless of the intake I use it's still going to have noticeably more power than the stock 190 HP motor.

68post

Performer RPM Spreadbore #7104 , I need a good used one also.

wilcar

I have read several articles that state there is little difference on a mild street engine between a stock q jet intake and a performer intake. Do you know what heads are on the engine you are installing? A comp 280 cam will be pretty doggy on the low end unless you have some decent rear gears and a 4 speed or a 2500 stall in an automatic. If you are using stock heads the 280 cam will not give you the power it is capable of at higher rpm' s due to the restrictive flow of the stock heads.

Jeff_Keryk

The Performer manifold will accept square or spread bore carbs.

jaybird81

I built that motor in High school back in 95, so I don't remember everything. I do remember cc'ing them and they were like 76 cc I think, and they are 1.94's not like 202's. They were what came on the motor which was out of a 71 full size chevy. The pistons I went with combined with the specs of the heads gave me a compression ration of 10.25:1. The car had a 2500 rpm stall converter and 3.55:1 gears. It was a 72 chevelle. It didn't bog and the car was pretty fast ( for a 17 year old), maybe I wasn't getting everything out of the cam, but it was enough power for me. The vette I have it's going in I converted to a 4 speed but has the stock auto gears. I'm thinking I'll need to do the gears down the road but I'll wait and see how it runs with the new motor before doing that. Like I said, It has to be a noticable improvement over the stock 190 HP

wilcar

It may work out fine for you with 10.25 c r and the 4 speed, let us know how it works out.

v2racing

I think the gears will be a little steep for that cam. 3.55 gears would probably be a good choice to make it a lot more fun and let it cruise more in it's RPM range.