bmcnitt

Well I just dove into my first "major" project. I took the intake manifold off today and that may not seem like a big deal but I didn't know what an intake was 5 months ago so I got my hands full. I am following JohnZ's article on BarryK's website so if you guys are out there thanks, cause I wouldn't even attempt this without your help. Anyhow I really dont understand the significance of the spread bore/square bore thing. I thought my carb ( 4175 Holley - Quadrajet replacement) was a spreadbore and I know my new edelbrock is a squarebore. I was expecting I would need a spread to square spacer. However when I got my holley and intake off they looked different then what I was expecting. To make a long story short here are my old and new manifolds, do I need a spread to square spacer or can I put my Holley straight on the edelbrock. Thanks for your help.

Plasticman

Yes, and that will take up vertical space which you may not have (besides not being the best for optimum air/fuel flow).

Best to get the correct matching carb for that new manifold.

Just try mounting the old carb on the new manifold should answer your question. Doubt it will mount at all due to mounting hole mismatch (and opening the secondaries should not work either - secondary plates will stop when they strike the manifold).

Take a look at the below website, and scroll down to the Performer Manifold (Idle-5500 rpm). You can see the bulges in the carb opening for the larger secondary throttle plates of the spreadbore, plus the dual set of mounting holes.
Your manifold does not have either feature (and is only for the square bore carbs).

http://www.edelbrock.com/automotive_...lds_main.shtml

I am guessing, but is your new manifold the #2703 (Performer EPS with oil fill tube)?
Edelbrock recommends a 500 to 650 cfm carb. That can be an Edelbrock (Carter design AFB), or a Holley, or one of the offshoots like a Demon or Barry Grant.

Here is Edelbrock's carb page:

http://www.edelbrock.com/automotive_...ess_main.shtml

Plasticman

bmcnitt

Thanks, yeah it is the 2703 and the oil fill tube is the reason I bought it. I want to stay with the oil fill tube and I didn't want to mess with getting the oil fill bored out on the rpm. Not worried that much about clearence cause I have a stinger hood and about 2" to play with. I am worried about performance and not having a spacer screw that up. I should be able to send this back to summit since I havent installed it, maybe i should go back w/ the rpm air-gap and get it bored out. I got afraid of that because someone told me the fill tube hole had to be tapered and I didn't know if the local machine shop guys would do it right without any specs?

bmcnitt

Anyone out there using a spread to square spacer/adapter, any comments on you results?

Plasticman

1st question to ask yourself is what is the current rpm band of the components in the engine, and what is it's intended use (RPM band wise).

If it is a base engine running the base low lift cam and low compression ratio, then the intake you have is pretty good. If it is one of the SHP engines, then you need an intake with a higher RPM band, such as the Performer RPM. Don't mismatch them, unless you plan on making further changes later. Best to match components for their intended use.

Adapter plates do work, but not the best match (just a method of getting from point A to Point B, but not the shortest or best path). Adding plenum volume (by adding a straight spacer), can actually help upper RPM band power, but at the same time hurts the lower end (especially throttle response). But the flow path through a spreadbore to square bore spacer involves a mismatch from the carb secondaries down to the intake runners which can see some separation of fuel from the air/fuel flow stream (resulting in fuel puddling in the bottom of the plenum).

And the flow through a spreadbore carb is almost never as equalized as a square bore from cylinder to cylinder at full throttle (you will not see spreadbores used in competition unless they are mandated by sanctioning rules).

Plasticman

bmcnitt

Thanks for your help Plasticman. It basically just seems like there isn't anything out there for me cause I wanted an idle - 5500rpm intake that has a fill tube. I don't want to change my valve covers to have the fill there. The performers dont have the blank for a fill tube bore out. My engine was originally a 250hp 327, not sure about now. I would like to put some AFR heads on and a better cam and try to build it up to a 400 hp type engine but with that being said it is a cruising type car and idle - 4000rpm is what I really care about. I don't see myself hardly ever driving this thing over 80mph.

bmcnitt

I guess the edelbrock performer does have an oil fill boss, maybe I will trade in for that and stay w/ my holley. Really wanted the air gap but those are the ones w/ no oil fill hole/boss.

wesmigletz

The RPM Q-Jet is a nice intake, but it does have a large plenum. There is a pad for a fill tube. I ran one on the 383 in my truck. It may not be ideal for a stock engine, but it leaves room for the engine to "grow" so to speak.

http://store.summitracing.com/partde...4&autoview=sku

Wes

1COOL60

Edelbrock used to make a squarebore/Q-jet adapter plate that was less than a 1/4" thick. I used one to put an AFB on a Perfomer manifold. I would think it will work to put the 4175 on the sqarebore manifold. Also, I had a 4175 years ago that I put on a 454 '71 Vette. IIRC, the secondaries of the 4175 are much samller than a Q-jet, so I don't think the secondary butterflies will hit the manifold.

If you are interested, I believe I still have that Edelbrock adapter plate. If you want to go that route, let me know and you can try it out.

bmcnitt

Yeah I'm interested, do you know what the part number is. I don't see a spacer that trim on summit. They tend to be .75 to 1 inch thick. That is causing problems cause even with a my stinger hood I don't have much room left. Plus I have been testing it out using 3/4" wood as a spacer just to see what it looks like and it looks weird. I found a guy selling a square bore edelbrock on craigs list for $200 but then i am thinking why am I buying a carb when my holley runs great. I decided tonight to keep the holley. Yeah if you can tell me where you bought that spacer i would love to try one, nothing to lose really.

Plasticman

I checked the usual sources, and did not see any less than 3/4" thick. I did make one for a Torker intake (for adapting a Q-Jet) that was 7/16" thick, but I also blended the intake to smooth the transistion from the Q-Jet secondaries into the plenum. In other words, I hogged out the intake opening to match the secondaries as much as possible. I could not go out further (and hence the need for the 7/16" plate) due to the thinness on the sides of the manifold in the secondary plate area. With that combination, 7/16" was as thin I thought practical (in that application).

But as I mentioned in a previous post, tuning the huge secondaries to match the smaller primaries is really difficult, and I was never pleased with the tune (some cylinders always ran richer than others at full song), and I played with it a lot!

Here is the Edelbrock adapter page for ref.
http://www.edelbrock.com/automotive_..._spacers.shtml

Think you would be best to bite the bullet and pop for a new carb, or get the correct spreadbore intake. You might want to run an insulator gasket between the carb and manifold anyway, and it does not sound like you have room for that either.

I have seen guys have their manifolds machined for the fill tube, and they were not tapered holes. The fill tubes I have seen have a very slight taper towards where they seat in the manifold, and should provide a pretty good seal (especially if some Permatex or Loctite was added during installation). The only caution is not to have too tight an interference fit (you don't want to crack that new manifold).

Plasticman

bmcnitt

Yeah I agree, the oil fill tube port in this 2703 is not tapered. I have changed my mind a thousand times but i like my holley so I may buy a performer, I believe its a 2101. Problem is I have dinged up this 2703 enough from messing around with it that it wouldn't be fair to try to return it as new to Summit. I may just cut my losses and sell it for half price on craigs list. I don't want to try to save $100 and end up with a setup i don't like. I dont see where it does anything but would this thin Wieand bracket accomplish what i am trying to - http://www.jegs.com/i/Weiand/925/9006/10002/-1

Plasticman

The problem I see is where are you going to thread in the holes for mounting the carb (in that thin spacer)? A spreadbore has a different bolt spacing than the square bore carbs, and the Performer square bore intakes do not have the optional (spreadbore) bolt pattern. Looking at the square bore Performer intakes, there is not sufficient meat for the spreadbore bolt pattern to be drilled & tapped (for those mounting holes), so those threads need to be in the spacer. And then how do you bolt the spacer & carb to the intake?
http://www.edelbrock.com/automotive_...ormer-sb.shtml

Another "plus" for the spreadbore Performer is that it is lower than the square bore version by .22".

Plasticman

blubu

you can either buy a plate that adapts it form a quad to a holley sq pattern
Or you could throw the spreadbore to the next kid you see and buy a sq bore holley
Spacer is optional if you have clearance

1COOL60

Try Edelbrock number 2731. Adapts spread bore carb to square bore manifolds. Edelbrock catalog says it is 1/16" thick. I have (or had) the number 2732, which is pictured. 1/16" thick sounds right. I didn't take the time to look for it last night. If you want, I will dig it up.

Here is a link to the Edelbrock catalog:
http://www.edelbrock.com/automotive_..._spacers.shtml

Good luck.

66rag427

Maybe I misunderstood the question but the edlebrock should run a square bore without a spacer. Mine will run square or spread.

bmcnitt

Great, thanks I just ordered one. I already ordered a performer 2101 but if this works i will send it back and I won't have to worry about boring anything out which is great. I never caught this model on summit because they have a type-o on their site. It says .625" thick instead of .0625". Appreciate it, if this works you saved me atleast $100 depending on what I would have been able to get for my 2703 on craigs list.

Plasticman

What is it going to bolt to? The square bore pattern intake you have does not have the same bolt pattern as a spreadbore carb. Unless that spreadbore Holley has holes for both patterns, I don't see how it would work.

Plasticman

bmcnitt

Yeah, the more I look at it I don't really see how it will work? Not sure. The 2101 is also on the way so one way or another I should be able to get this thing back together.

Plasticman

I know what the Edelbrock description states for that adapter, but those adapters are normally used to mount a square bore carb onto a Performer 2101 or other spreadbore intake. Not the other way around (not a spreadbore carb onto a square bore intake).

The adapter opening shown is square, not 2 large and 2 small as for a spreadbore. It is used to block off and seal the larger spreadbore intake's plenum opening, so that is it sealed from outside air. Otherwise, just bolting a square bore carb onto a spreadbore intake will end up with a massive vacuum leak. They "use to" include one of those plates with every dual pattern intake (and maybe they still do).

Plasticman