[jarretts70]

I'm building a 455 for my GTO. Typical street engine - 9.4 cr, ram air exhaust manifolds, etc...it will run a Q-jet with tweaks I learned from Cliff's book.

The only intake manifold I have on hand is an old P4B - it's in nice shape, so I could use it. I'd need an adapter to run the Q-jet. Is it worth it or should I just try pick up an original iron manifold? There is one for sale on marketplace - its a '68 casting for 50$. The drawback is it's a couple hours away. Opinions?

[b-man]

Sell the P4B.

Use the proceeds to buy gas for a road trip to score that iron intake and maybe have some nice conversation with a new Pontiac friend while you’re there.

No adapter, proven performance intake.

[PAUL K]

I just put a P4B on my Super Duty to test. So far it seems good. No reason you can't run a P4B. Of course I had to make it look factory.

There are several versions. Some are tight with an HEI. You have to watch out the the correct throttle bracket provisions, also the water necks were clocked in a couple of different positions. The P4B sits slightly lower that an OEM manifold and the carb flange is flat, so you should have room for the Q-jet adaptor.

[higgenslake]

PM sent

[steve25]

That’s the only aftermarket street type intake I never had on one of my motors so I can’t offer much in the way of options.

Like Paul posted it is lower in height then the iron intake and this must have a effect on the amount of top end the manifold produces, and since your running a big 455 this may be a concern.

I would still go get the iron intake because you just never know.
I had a spare one on my shelf for 2 decades collecting dust and was just about to sell it off when I picked up a car that needed one, so I was glad I had it and especially since back then I picked it up for 10 bucks and the cost of them had at that point shot up a lot.

Just be sure it is a 68, as you do not want a 67 but for resto purposes.

[Half-Inch Stud]

Spreadbore P4B is good. Spread Adaptor ah meh. Factory 68-70 iron ought be the good start. Cut water log for future trials.

[77 TRASHCAN]

Some non spread bore P4B's have a enlarged flange area on the sides of the secondary throttle bores, I've seen in pictures of many of these intakes.

I wonder if there's enough material there to grind clearance needed for Quadrajet secondary throttle blades?

Although not all have the extra material present.

There's seemingly many versions of this intake...

[Sirrotica]

Over the years, when about the only aluminum intake available for a Pontiac was the P4B, I've used them with a plate and a Q Jet on many of my own cars (race, and street) as well as customer cars.

Back in the early 70s there were pretty slim pickens for Pontiac intakes. As a result many times I've used the factory intakes because the wallet, or class rules, dictated keeping the prices down, or you had to run cast iron intakes. Come to find out, that they were a pretty good choice. Pontiac built a efficient design right out of the box.

One nice thing is the P4B with an adapter plate, it works on T/As with the shaker scoop, and with the correct one you can still use the HEI distributor on the later ones. I've never run across a P4B that was designed to bolt directly to a Q Jet, but have seen pictures of them on this board.

[Lee]

P4B did quite well in my chassis dyno testing, against a Holley Street Dominator, Tomahawk, and a Torker II. All were stock, except for removing water crossover.

This is an 8.3:1 455, unported 66 heads, and a square bore throttle body EFI system. After seeing 100+ internet experts say that TBI systems NEEDED a single plane (with zero actual data to support their claim), I decided to test for myself.

Not sure how the P4B would perform with an adapter, though.

[jarretts70]

This P4B defiantly doesn't have enough material on the carb flange to allow enlarging the bores to work with a Q-jet....I haven't tried, but it looks like an HEI would clear. I don't love using carb adapters, but if the P4B is lower than a factory intake adding a adapter would add plenum volume, which might help.

My combo is a 455 block - I had to have it sleeved, so it's stock bore. 6X-4 heads with very mild port/bowl work and 1.77 exhaust valves. Comp xtreme energy 274 camshaft. Nothing crazy. 91 octane is easy to get here, and 94 is at some stations so I don't believe I'll have issues with fuel.

[jarretts70]

I know the factory intake performs well & would work fine in my application. But I like the idea of saving some weight.

[Sirrotica]

Edelbrock has made many renditions of the P4B over the years, some of the later intakes did reduce the size of the rear runners to allow use of an HEI distributor. Probably the most common ones are the early ones, which don't allow the use of the HEI without some modification to the runners, and the smaller mounting pad that doesn't allow the use of a Q Jet without a plate.

Cliff Ruggles did some testing with the P4B back awhile ago, here's the link to the original post about all the variants, and performance of the intakes he tested.

https://forums.maxperformanceinc.com...ight=Cliff+P4B

It's 15 pages long, but still a good read!

There are a few P4B intakes for sale on E Bay currently, pricing seems pretty high, averaging about $175.

[steve25]

Here’s the info for the P-4B out of a 1970 Edelbrock catalog.

Looking at the rear of the manifold I would think that the number 8 and 7 runner would need to have been modified on the later ones to clear a HEI.

The number 8 runner being on the hirise top plenum likely would not have lost much performance capability, but the lower number 7 probably took a good hit.

Note the cfm carbs there recommending!

[Formulas]

the stickey points for me and P4B have been PCV hookup and throttle bracket

if your carb has a 3/8 fitting front and back then power brakes and PCV will get full plenum siginal instead of single runner

[steve25]

In 1970 Edelbrock also made a 4BJ version of this intake which was made for I Q-jet.

It’s likely that this version of the manifold with its bigger secondary side plenum would have out powered the square Bore version assuming the same cfm rated carbs where used.

[carbking]

Peformance is a function of both mass (weight) and power.

I would be interested in a real world test to see if the vehicle performance with the P4B/adapter was better or worse than the iron intake.

With the P4B, lose a few pounds, lose several horsepower; what is the end result on performance?

I second B-man's suggestion.

Jon

[steve25]

The P-4B tips the scale at 15 lbs, if I am not mistaken a iron intake only has to make 1 more Hp to negate the difference at least straight line performance wise.

Doesn’t seem like a hard thing to pull off.

[1968GTO421]

My apologies to The OP, not trying to hi-lack . I acquired a P-4B secveral yerars before I happened to find my GTO. The GTO has a 428 with 6X-4 heads (stock) and a Performer (not RPM) intake. I am curous if keeping the Peformer would be better or worse than using the P-4B. Thoughts?

(I suffered a shoulder injury a while back and am able to deal with the aluminum intakes' weight but the iron intake would mess me up even though it would be better power wise.)

Thanks!

[b-man]

Other than the aluminum intake weight aiding in assembly for some of us who may risk injury tossing an iron intake into the engine compartment I don’t see knocking 20 pounds off of the front of a 3800 pound car being that much of an incentive.

If you aren’t physically able to install the iron intake, invite a friend over for lunch to do the heavy lifting and git ‘er done.

I like using stock components whenever possible mainly because everything fits, no messing around with throttle cables, PCV hoses or fuel lines.

Not to mention the Pontiac engineering department gifted us with essentially a race design intake, a slightly modified 421 Super Duty intake. Not many other factory iron 4-barrel intakes are worth using, consider yourselves lucky.

[Dragncar]

Originally Posted by 1968GTO421

My apologies to The OP, not trying to hi-lack . I acquired a P-4B secveral yerars before I happened to find my GTO. The GTO has a 428 with 6X-4 heads (stock) and a Performer (not RPM) intake. I am curous if keeping the Peformer would be better or worse than using the P-4B. Thoughts?

(I suffered a shoulder injury a while back and am able to deal with the aluminum intakes' weight but the iron intake would mess me up even though it would be better power wise.)

Thanks!

Run the P4B on a 428. The Peformer is a good performance for a 350, thats about it.
A 400 will run worse with a Performer vs iron Q jet intake. So a 428, worse yet.
I have a P4B and actually have some pretty big runners on them. You 428 will like it, if you have enough cam.