spread-bore carb to square-bore manifold
Thread Starter
Racer
Joined: Sep 2002
Posts: 357
Likes: 0
From: Sayville New York
spread-bore carb to square-bore manifold
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 $20 adapter. there are several ones to choose from on different performance websites. I've come to you guys for some guidance. I know there are guys out there running beefed up motors and sticking with the quadrajets, what adapters are you using? I have a stock hood did any one have any clearance issues with the extra height? Any advice you could give me would be greatly appreciated. I am really excited about getting a lot more power in the car and since the motor was built a while ago, it's not costing me a lot of money. Just a set o headers and this adapter. I would really not like to have to buy a new carb.
Melting Slicks
Joined: Apr 1999
Posts: 2,010
Likes: 3
From: Moon Twp. PA USA
Drifting
Joined: Mar 2006
Posts: 1,263
Likes: 188
From: Wabasha Mn
If your 81 is stock then why not use the stock q jet aluminum intake you already have? Performer rpm is taller than a performer and you will likely have clearance issues if you try put a q jet adapter on it. The stock q jet intake flows just as well as a performer intake so I would keep it.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Adapters that go from spread-bore to square-bore, or vice versa, don't work very well. And, they add height to the carb so that it might not fit under your hood. Spend a few more buck$ and buy a used (or new) intake manifold that is made for the carb you choose.
Thread Starter
Racer
Joined: Sep 2002
Posts: 357
Likes: 0
From: Sayville New York
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.
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.
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Drifting
Joined: Mar 2006
Posts: 1,263
Likes: 188
From: Wabasha Mn
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.
Thread Starter
Racer
Joined: Sep 2002
Posts: 357
Likes: 0
From: Sayville New York
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.
Melting Slicks
Joined: Mar 2008
Posts: 2,666
Likes: 289
From: Spring Park MN
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