Mutilated Stock Intake Manifold
 

So... much... grinding...

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I wanted a spreadbore intake manifold that flows well, fits under the low profile shaker of my '77 Trans Am, has the required bolt holes for an OEM-style AC compressor, accommodates my Q-jet throttle linkage, looks nice, and weighs less than stock.

I agonized endlessly, went back and forth multiple times, even bought multiple intake manifolds. I have a Performer, a Ram-Air IV/HO-replica, and a Crosswind on hand. So much money spent. NONE of these alternatives met all my requirements. Some were missing bolt holes to accommodate the AC or the throttle bracket, some were too tall and couldn't easily be shortened, some were horrendously bad casting quality, some weren't conducive to the power levels I was aiming for.

So finally I just chose to mutilate my stock manifold. I know it fits, all the bolt holes are there, and it can be ported to flow more than enough to meet my needs. With all the grinding and cutting, I've removed over 15 pounds of weight. And I can pair it with an aluminum water crossover, which weighs less than a pound. It's still significantly heavier than the all-aluminum manifolds, but that's a trade-off I can live with.

I wish someone would produce one of these exactly like this in aluminum and good quality casting.

Now it's off to SD Performance for CNC porting!

Grind away! Holy crap. That had to have taken at least 6 hours...

Interesting solution...
Kinda like it.

I'll be getting it cleaned and blasted so the surface is more even. But I'm really happy with the result.

Nice work.

I remember reading in the H-O Racing engine book where they said often the best intake for your Pontiac performance engine is the stock one.

For the majority of street Pontiacs this rings true.

Yes, but maybe not that one. It has the restricted secondaries.

EVERY flow test has shown that those make no actual difference in real life. And anyways, they'll be ported away

Intake Uptake '75-'78 Edition
Do You Need to Modify Your'75-'78 Pontiac Four-Barrel Intake Manifold for Best Performance?

https://www.motortrend.com/how-to/hp...take-manifold/



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That 75 and later intake you spent so much time on I believe the floor of the port is higher to accommodate the EGR circuit.

I had great results with the old fat runner Edelbrock P4B QJ and according to Rocky Rotella the flow is better than a stock intake.

Wow. That was a lot of work if you did that with a grinder. Looking good. I wondered what one of those would look like with the cross over removed.

I did one of those intake’s earlier this year. When I first started I wasn’t sure what I was getting myself into. I have to say, after I opened up the secondaries and ported matched it to RA4 sized 1014s felpro’s I was shocked how cavernous that intake is. The plenums are a little deeper than all the earlier Qjet intakes I have a seen. When PMD re-engineered the plenum for the second generation EGR after 1975 they dropped the plenum down and made it deeper to make room for the exh port running up to the top. All you have to do is grind and blend where the egr was coming into the plenum, connect the primaries and secondaries, and it really opens up. When you port match the exits and open up a couple places where the boss’s for the intake bolts are it becomes a totally different intake. I don’t how much or if the secondaries are actually a restriction, Rocky’s article indicated that they are not. I opened mine up anyway.

Looks like it will perform, even though the interior still looks as-cast. I'd use it.

The EGR causes the side wall to tuck in a little bit, as can be seen on the top view picture, but the floor is actually slightly lower than non-EGR manifolds to make up for that. Actual volume remains the same, but there's slightly less room on that side between the manifold and the valley pan as a result. I compared the floor with the one on my RA-IV/HO reproduction, and this one is definitely lower than that.

The Edelbrock Performer intake that I have on hand has tiny runners, and some of them have huge bosses running through them that would make porting difficult. The casting itself is excellent quality, but its design is crippled.

why did you cut through the center of the front bolt holes?
how do you plan to block off the exhaust cross over in the heads?

That's why I use the earlier Edelbrock PB4 QJ

I wanted the aluminum water crossover to be attached with 4 bolts rather than 2, that one will also have 2 half-holes so that 2 of the bolts are shared between the two parts but they're still separate and the water crossover will no longer dictate where the intake manifold must exist.

I'm running KRE D-ports. No exhaust crossover holes.

I used an acetylene torch to remove the water crossover (the casting is THICK there), a chop saw with abrasive cutting disc for a couple of longer cuts (see the tiny knick on the left side of the carb flange where I cut too far), a 5" corded angle grinder with a thick wheel, and 2 air die grinders with metal bits (one straight, one angled).

These are in-progress shots where I just got done removing the exhaust crossover:

https://i.ibb.co/d4M8zBK/process-1.jpg
https://i.ibb.co/7WG9H4q/knick-on-plenum.jpg
https://i.ibb.co/9GBZjBb/shaved-4.jpg

You can see how thick the casting is in places. I ended up removing those fins on the bottom of the plenum and grinding that whole outside surface smooth.

keep in mind the RA/HO repro intakes plenum floor is not as deep as GM intakes, rocky rotella measured them & showed about 1/8-3/16 less depth, i compared my 1970 iron intake to a 71 HO GM intake & the HO is not as deep, both were fully ported by SD.

In my case it's a full 1/4" difference on the short side. That HO intake manifold is one of the worst casting jobs I've ever seen in my life. There's no obvious core shift in mine, the quality is just horrendous on both the inside and outside. I refuse to use it. I don't even want its water crossover, it looks awful. I'll likely take the one from the Crosswind. I have an older one that has the water crossover still attached so I can cut it off where I need to.

Shaker455 do you have any thoughts on the effect of the gap under the primaries on the carb signal? It seems backwards to me too have the divider drop on the primaries instead of the secondaries? I am running the drop on the primaries like the pictures show. But I wonder if I shouldn’t put the EGR plate under the carb back in, cover the EGR holes in the plate and cut down the divider on the secondaries?

I recall Rocky flowing the PB4. It did really well.

From what I've read elsewhere, they don't have a noticeable effect, but I was planning to build that back up with a spacer after the porting is done

Figure the NHRA stocker folks are running deep in the 11s with those unported!

I would be curious to know if removing that much material had any effect whether the intake stayed straight and didnt warp.
Wouldnt think so. But a straight edge should tell us.

Jim Hand found decades ago that having that divider flush with the primaries of the carb was very beneficial to part throttle drivability (better carb signal), and then just cutting down the back portion of the divider. Not only just having the front of the divider flush with the primary of the carb, but also keeping the diameter of the primaries on the intake the same as the carb base. This turned out to be the best combo that Jim ran for many years.

That is generally how I modify all these intakes and it works exceptionally well, and easily supports over 500hp with either the iron or aluminum version.

So are the pure stock and factory stock guys at the muscle car drags.

Ported they are into the 9's.

I was worried about that, especially with the acetylene torch cutting. But I placed the intake manifold on the heads and everything is perfectly flat and straight. That casting is SOLID, there's a good reason it weighs 45+ pounds as-cast.

Even if it wasn't perfectly straight, having the center section of the mounting flange removed allows greater flexibility to accommodate any twist in the runners as the bolts are tightened down, and any wave would be taken up by the gaskets. This isn't a boosted application, so sealing isn't difficult.

The carb flange is also still perfectly flat, but the carb gasket would take up any unevenness even if it wasn't.

Just to be clear, despite all the material I've removed, this is no lightweight intake manifold. The Crosswind aluminum manifold weighs about 10 pounds as-cast, and that's with the water crossover attached. The Edelbrock Performer weighs 15 pounds as-cast. The HO reproduction weighs 8 pounds as-cast. My endless hours of grinding on this cast iron manifold resulted in a 27 pound part, without a water crossover. It's still VERY hefty and VERY stout, even if it's significantly lighter than it used to be. I'm guessing porting will remove another pound or so.

Jay, after many Performer & Performer RPM divider mods allowing snap install for any configuration & ease of testing, I found fully divided on primary's shows best signal.

I still have my RPM I machined a snap in T-bone for the rear divider

Here's the Fat runner P4B QJ i.put on my 67 GP

Yeah that looks completely different from the current Performer. Why isn't that still in production? What's the reasoning behind stickimg with the defective design? I don't get it...

Having said that, it looks like it's missing some threaded holes that my stock manifold was using. I won't know for sure until I have everything assembled again

Since this seems to be more interesting to people than I expected it to be, here's a few more detail pictures along with a comparison to the RAIV/HO reproduction manifold, which is the closest cousin I have on hand.

Here's the underneath, side-by-side. Really illustrates the difference in the EGR area.
https://i.ibb.co/hFy2km8/bottom-comparison.jpg

The EGR hole is blatantly obvious here. I'll plug it after the manifold is ported, either with aluminum or JB Weld. Can also see where those fins used to be. I'm still planning a final finishing of the surface to get it more smooth once the paint's been stripped off.
https://i.ibb.co/xM6X5Jk/20221102-125017.jpg

Compared to the older design.
https://i.ibb.co/nnwhFgM/20221102-125021.jpg

Front comparison.
https://i.ibb.co/st9hDpd/20221102-124957.jpg

Rear comparison.
https://i.ibb.co/JzNMXPB/20221102-125007-HDR.jpg

P4B QJ was designed before the energy crisis in mid 70's with generous runner volume, the Performer we know today is the end result of the crisis.

This intake made the car much smoother over the factory 4-bbl Carter carb intake

Got it media blasted. Now the little nick where my chop saw went in a little too far is especially noticeable :rolleyes: Time to get it sent out for porting!

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Is Dave at SD Performance taking on new work? I thought he was still playing catch up on what he had? His website still says no new work!

WE ARE WORKING IN THE SHOP AS MUCH AS POSSIBLE WITH A FOCUS ON CATCHING UP ON EXISTING JOBS. WE ARE NOT TAKING ON ANY NEW WORK UNTIL FURTHER NOTICE AS OUR PRIORITY IS TO CATCH UP AND GET OUR CYLINDER HEAD BUILD SCHEDULE BACK ON TRACK AS WELL AS DEAL WITH REPAIRS AND CLEANUP ON OUR PROPERTY AFTER BEING HIT BY A LANDSLIDE LAST FALL. THANKS FOR YOUR PATIENCE AND UNDERSTANDING, WE HOPE TO BE TAKING NEW ORDERS LATER THIS FALL.

Just a note on dual plane intakes and dividers. It is best to leave the divider intact and full height. At most you can remove a small portion of it between the secondaries, but that is more easily accomplished by just using an open gasket under the carb. The Olds Q-jet gasket is solid across the front and open between the secondaries. They are apprx .160" thick so two stacked together works well. You can also use a 1/4" thick four hole gasket and snip it out between the secondaries.

I've lost count of how many dividers I've had to make and install where someone following good on-line advice ground most of or all of it down. The symptoms from doing this can be minro to severe. Usually you will get a HUGE stumble/hesitation/bog going quickly to full throttle with good traction. Once past "transition" they work OK and may even show a few more HP way up at the shift point.

The dyno and drag stip tells us from the testing I've done that spending a bunch of time with the divider does next to nothing but leaving it in place improves throttle "feel" in the "normal" driving range.

Same thing with spacers, fully open was HORRIBLE for all testing, dyno, street and at the track. Fully divided was OK, four hole not that great, and semi-open (similiar to what Jim Hand used on his 455) the overal winner everyplace.......FWIW......

Theres a few PB4s. Some have narrow runners like a Performer and some, I think the older ones, have fat tapered runners. Some are square flanged and some are for Spreadbore carbs. The thicker runners ones are preferable for hi-perf use. I recall the dyno of the EGR intake showed little difference compared to the non EGR intake. The D shape to the secondaries is to reduce/inhibit reversion into the carb. I can't comment on the lip around the primaries. Must help exhaust distribution of the EGR function. If you are using 6X heads in a build and want to use the cast iron intake, look for the 72 version. It fits the later heads exhaust crossover correctly but has no EGR. The choke design is different but as long as you have the right rod it works the same. I already did it.

Could have just used an intake gasket with a crossover block-off insert and got the same result with a lot less work.

saved 15+ lbs & looks way cooler

That machined divider is really cool!

Every kid needs a hobby I guess but now he has to cobble together block off plates or run a separate exhaust crossover.

instead of being negative, it would be better to actually read his comments & see that hes using KRE Dports that dont have an exhaust crossover... :rolleyes:

I've been concerned about that message on their website. The second landslide occurred in the fall of 2019 (I think...).
3 years is quite a while to NOT be taking in any new business.
I sent Dave a PM to his user name, here about a week ago. No response, so far.
There's some folks, here that would like to do some business with him.
I'm really disappointed that he quit working on iron heads, but he WAS still doing iron intakes.

Anyone here have a connection to Dave?? I know there's a lot on Canadian members here!!!
If he'd just give use some kind of an idea of what's going on, that would set us all at ease. Dave's work IS the absolute best!!!

OK. So this is an exercise in "improving the aesthetics" then. Now I really don't get it but to each his own.

i talked with dave via email in feb 21 about doing some Eheads i have, he was taking new work at that time. not sure on the date he posted that message.

improving aesthetics, saving some weight & having a factory intake that will fit all accessories & when ported will out perform the other intakes he has. whats not to get?

i've seen a few iron intakes cut up like that on here before, was considering doing it for my SD ported iron intake too but found a real HO intake ported by SD before doing all that work.

Dave's website, in the past. Didn't seem to.get updated very often at all. So I nds like that hasn't changed.

Nope, clearly you don't.

But you definitely get it.

How much extra horsepower & torque is there to be gained by porting the iron intake and at what power level? That is in addition to gasket matching the port exits and opening up the runners to gasket size and removing bolt bosses.

I doubt there's much to be gained on a stock application. The as-cast stock manifold seems to top out around 5500rpm and 300hp or so. Below that, it's not enough of a restriction that porting it would help anything. But I'm running it on KRE aluminum heads with 10.25:1 compression ratio and a decent roller cam with a freshly machined block. I'm hoping for about 450hp. The stock manifold can be ported to support up to 600hp.

"How much extra horsepower & torque is there to be gained by porting the iron intake and at what power level?"

I spent several years porting/modifying my factory iron intake taking every chance it was off the engine to make modifications to it. Along the way it was dyno tested several times and never disappointed. I also did some back to back track testing and it did very well there. Around 2004 I sent it to Dave at SD so he could do a CNC scan and use it to port factory intakes sent there.

On a pretty stout 428 build it made 6 more HP than a port matched Edelbrock RPM intake, no spacer used on either one. That engine had 10.6 to 1 compression, KRE aluminum "D" port heads, and a custom ground 236/242 @ .050" HR camshaft. Back to back on the dyno with no other changes the RPM made 491hp, a modified HO "re-pop" intake made 487hp, and my iron intake made 497hp.

At an HPP "shootout" we tested a Tomohawk intake against the iron intake It faired poorly without a 1" spacer on it and really liked my Holley 850 cfm carb vs the Q-jet. The only pass where it ran faster (MPH) over the modified stock intake was using a 1" spacer and Holley 4781-2 850DP carb. That combo was a solid 2mph faster than all other runs. The iron intake w/o a spacer was still the overall winner in ET besting that combo by .03 seconds as it ran quicker in 60' with a much harder launch.

The problem we have here with aftermarket intakes is lack of choices that fit and work well with these engines. The RPM is a nice piece, but too tall for many set-ups with some "cobbling" to use it or you have to put a drop base air cleaner on the carb moving the air cleaner lid WAy too close to the carburetor and pinching off more power than you ever hoped to gain with the bigger/taller intake.

The T-II is EXCELLENT if you are using a square flange carb and will rival the Victor intake to 600hp or so but it REQUIRES at least a 1" spacer on it and square flange carb.

The Performer is a "turd" and not even on my list unless you have a 350 build with 7.5 to 1 compression and it's not going to make chit for power right to start with. The Performer is a very poor choice for a 455 build and starts to become restrictive past 400hp or so. I've ran into issues trying to street, track and dyno test them so it's not even on my list anyplace. Of course every time I put that info up here someone Googles to the brink of extinction and finds someone someplace who made 8 zilliion HP with one on a 540CID build just to muddy the water and downplay my results testing them. Sadly the folks who do that have don't even have a Pontiac powered car that moves and/or have never tested a Performer intake on anything.

In any case we are left with very few choices for good intakes at the stock flange height. The HO is a nice part but the re-pops have very poor port alignment and serious miss-match at the gasket openings. It would have been nice if the folks who put up the money for that effort had spent a few minutes with some epoxy and a sanding roll and straightened all that up........IMHO.........

Looks to me like Speed master is making an aluminum intake with this mod. Even has a small section taken out between the secondaries.

Not sure what the rest of the intake is patterned after? Says mid rise.