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Old 01-20-2011, 07:56 PM
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pontiac 400 build question

Ok this my first post.

I have a 71 pontiac 400, 4x heads 98cc chambers 1.96 1.66 valves
The heads are currently at the machine shop and I have a descision
To either put in the stock 1.96 1.66 size valves or upgrade to the 2.11 1.77
Valves. Mind you I have a performer rpm edelbrock cam 470 470 lift 230 240 duration
With a 113 lobe seperation. The suggested head is an edelbrock aluminum head
With those vavles. But here's the twist my machinist said those valves might hit the
Piston.

Also kinda a side question. I should run the matching intake, but I have a
Chance to get a dual quad intake with two 390 holleys. I have always wanted
Dual quads, but never understood the need for them.

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Old 01-20-2011, 08:01 PM
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Hi. Welcome to the site.
What are you putting the engine in? What is the gear ratio, what trans and is it for street ? strip?
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Old 01-20-2011, 08:28 PM
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Hahaha I'm actually putting it in a 88 firebird 373
700r4 converter I haven't picked and was wondering
On stall speed?
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Old 01-20-2011, 08:49 PM
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Go for it! You definitely will want the bigger valves in the head for sure. The valves shouldn't hit the pistons if they are bigger, they should hit the lip of the cylinder if any issues come up. If they hit the pistons its a piston or cam issue I would guess and the smaller ones would hit as well. That's the same cam I chose and I like it alot. You will defintely want a higher stall I say 2500+ stall converter and that rear gear is perfect. I have 6x-8 heads and mine were 2.11 int. 1.66 exhaust and if I did it over again I would definitely open them up to 1.77 on the exhaust side. Make sure he mills them accordingly to get you to 9.0-9.6 to 1 compression also. I ran 1.5 ratio roller tip rockers from comp but if you want to run the 1.6s you will have to have him elongate the pushrod holes also or you will be SOL. As far as dual quads go, i'm not really a big fan due to trying to get them to idle right. They do look impressive but look even better and BELONG on a supercharger. I ran a single edelbrock 750 but I really hated it and switched to my 800cfm quadrajet and haven't looked back since. Pontiacs love qjets!
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Old 01-20-2011, 11:08 PM
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^ bump for QJets on Ponchos, an Edelbrock 750 is ruining my life right now and when my QJet is built it will go to the recycle bin.
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Old 01-21-2011, 12:14 AM
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The edelbrock isn't a good choice? I have a new 750 cfm. How bad could it run?
Ok one more question hahaha. For a torque converter should I run a anti-balloon
Plate?
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Old 01-21-2011, 01:49 AM
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You need no anti balloon plate unless you're gonna hit it hard w/N2O.

You will need to port the valve pocket below the 2.11" intakes to remove the mismatch that will be there from the smaller valve. There are reamers that will cut part of this out, but there needs to be hand work done to make them right.

I wouldn't worry so much about the exhaust side, even if you left them at 1.66". Hell, I ran 6X-4's on a fairly aggressive 455 and ran mid 12's w/ease. And using a Performer (not RPM) w/a 650 CFM 4777.
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Old 01-21-2011, 01:55 AM
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Quote:
Originally Posted by howesbird
I have always wanted
Dual quads, but never understood the need for them.
There is no "need" for them- other than the looks, that is. There is NO performance advantage, that's for sure.
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Old 01-21-2011, 09:04 AM
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I have a 100 shot. Its a wet shot like the smallest u can do. The shop I go to said my motor will eat it up. Is a 100 shot a big enough shot to need a anti balloon plate?
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Old 01-21-2011, 09:09 AM
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Quote:
Originally Posted by howesbird
Is a 100 shot a big enough shot to need a anti balloon plate?
Not even close.
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Old 01-21-2011, 09:19 AM
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Sweet thanks so much for the advice guys. Looks like I'm in the market
For some valves, a torque converter 2500+ stall, and a performer rpm
Intake lol
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Old 01-21-2011, 09:23 AM
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Quote:
Originally Posted by howesbird
Sweet thanks so much for the advice guys. Looks like I'm in the market
For some valves, a torque converter 2500+ stall, and a performer rpm
Intake lol
You could try posting your "Want Ads" in the Classified section, found at the top of the page. It's free.

Who knows, you might get lucky.
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Old 01-21-2011, 08:17 PM
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As far as the edelbrock 750, it will run smooth and great until you put it up against a well tuned qjet. Out of the box they will run and idle smooth but the snap acceleration and throttle response suck! Not to mention bad gas mileage and non adjustable secondarys. The qjet wins hands down unless you don't really care about what i have mentioned above, then the edelbrock it is. I would choose holley as a second choice but its your engine. I had my qjet rebuilt and just added an electric choke themostat and it runs and especially starts flawlessly. Love it when the huge secondarys open up!
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Old 01-22-2011, 11:20 AM
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everyone speaks bad on edelcraps and qjets, the only problem with them is that the owner does not know how to run them properly.

edelbrocks will run great as a daily driver. there simple to rebuild IMO.
no power valves to blow, but will lean out when cornering hard.
there not very peformance oriented. and yes is a square bore so when you hit WOT you dont get the flow of a q-jet or spread bore holley.
yes im defending edel's even tho i call em edelcraps, because they last a while, ive swapped them so many times and they work great.

q-jets on the other hand i have not had much luck with. i know from my buddy that it takes a special breed to make a q-jet run great. but when you get it perfect, they are awesome.

holleys just piss me off! floats always sticking, one backfire and your changing powervalves. but they have proven themselvs on the strip and street.

dual carburation in your case will just give you 2x the headache an 850 will give you more flow and less headaches. edel, holley, and q-jets all have 850 cfm carbs.or in that range.

i myself am stepping up to a hillborn mechanical injection. havnt slapped it on yet, but soon the time will come!
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