[Tom Vaught]

TAFF2, THAT IS A OUTSTANDING EXAMPLE OF FABRICATION!

Very nice work there. Buick manifolds had a design that somewhat resembled what you have done and I always wondered why OFFU never offered a similar runner design for the Pontiac (with the Port Devider). EXCELLENT ATTACK ANGLES!

Tom V.

Did you also mill away the Head runner divider to the head bold boss?

[charlie66]

Originally Posted by taff2

Single plane manifold with a big open runner between the carb plenums. Before and after pics. Carb hat/box halfway through construction.

I didn't realize that you could cut the dividers out and have it still work right! Very interesting. I just learned something . Thank you!

[johnta1]

I have a question for everyone In regards to whether or not my plenum is too small. When im on the break tying to build boost , what happens is the needle on the gage shakes really bad. It moves back and forth from 1 to 6 psi until it gets to 10 psi where it goes dead steady all the up from there. My question is , is it that the plenum doesn't have enough area for the air , so as the pulsations from each valve closing pushing back to the next valve pushing back is shocking and disturbing the small area of air in the plenum where if it was larger it would have more cushion with less disruption , almost like tossing a rock in a small body of water and having more disturbance then it would in a big body of water.

I would say that is what is causing it?

I would do as Bruce said and go at least 1.5 times, personally with a 4 cylinder engine I'd start at twice as big.
The 4 bangers need all the plenum they can get and with the pulsing I can't imagine it helping the turbo vanes any?

How is the turbo inlet configured now?
(and the path from turbo to the intake?)

Also, the intake ports need to be as straight of a shot to the head port/valve as can be made.

[charlie66]

Originally Posted by Tom Vaught

A bigger volume will dampen the pulsations for sure. Was the engine doing the same thing before you went to the bigger turbo?

Tom V.

Its not bigger on the compressor side just the exhaust side. Old turbo was a 7668 new is a 6870.

It might have been doing it , but I don't really 100% remember ..

[charlie66]

Originally Posted by johnta1

I would say that is what is causing it?

I would do as Bruce said and go at least 1.5 times, personally with a 4 cylinder engine I'd start at twice as big.
The 4 bangers need all the plenum they can get and with the pulsing I can't imagine it helping the turbo vanes any?

How is the turbo inlet configured now?
(and the path from turbo to the intake?)

Also, the intake ports need to be as straight of a shot to the head port/valve as can be made.

Here are some pictures of the way it is now, The only difference is it has a better turbo on it now.

[charlie66]

The manifold it half a Torker 2 with plenum mods

[johnta1]

I agree that a modified Wentzler tunnel ram would be very good improvement if you don't get another intake made.

Possibly a lot cheaper than a sheet metal intake.



How big is the intercooler?

[charlie66]

Originally Posted by johnta1

I agree that a modified Wentzler tunnel ram would be very good improvement if you don't get another intake made.

Possibly a lot cheaper than a sheet metal intake.



How big is the intercooler?

its the top one on the page .. Good for 1000 hp...

http://www.treadstoneperformance.com...ers&f_start=20

[charlie66]

Originally Posted by johnta1

I agree that a modified Wentzler tunnel ram would be very good improvement if you don't get another intake made.

Possibly a lot cheaper than a sheet metal intake.



How big is the intercooler?

If im going to make a new one it will be sheet metal...the one I made took a really long time to make it work right..

[JSPONT]

Originally Posted by taff2

Single plane manifold with a big open runner between the carb plenums. Before and after pics. Carb hat/box halfway through construction.

That's the photos I wanted, thank you for sharing, that was thinking outside the box!!

[charlie66]

Originally Posted by taff2

Single plane manifold with a big open runner between the carb plenums. Before and after pics. Carb hat/box halfway through construction.

With having no divider between the 2 ports how is the off boost drivability ? Does one steel from the other . Wouldn't it take the individual velocity away from them ? How is it just cursing a round?

[johnta1]

Does one steel from the other . Wouldn't it take the individual velocity away from them ? How is it just cursing a round?

That's what I would wonder about also.
(especially for your 4 cylinder)

The tuned length would be who knows with no runner basically?

With your 4 cylinder the individual runners to the plenum may be more critical?
(with a V8 the problem wouldn't be as bad?)

[charlie66]

Originally Posted by johnta1

That's what I would wonder about also.
(especially for your 4 cylinder)

The tuned length would be who knows with no runner basically?

With your 4 cylinder the individual runners to the plenum may be more critical?
(with a V8 the problem wouldn't be as bad?)

I think you're right. Thanks for saying something because was considering maybe trying it..

[charlie66]

It just dawned on me that my elbow probably adds to my plenum size. So I guess I have to figure that in too. Maybe my plenum isn't the problem at all? Would I get a bouncy boost gage needle if I had a exhaust leak?

[taff2]

Thanks Tom, yeah, I milled away the head port divider walls, not right down to the bolt boss (I milled them about 1.5" down as per your advice).there is now a lovely straight shot to the back of the valves from the intake plenum.
Charlie, the engine idles nicely and there doesn't seem to be any charge robbing (reading off the plugs), cruising is fine too, I was expecting it to be soggy down low but it's not bad at all. The carbs are Holley 600 double pumpers too, I would have liked 450's but couldn't get them.
That is one cool 4 pot motor!

[Tom Vaught]

With a Modified Firing order I believe that you could have a firing order where there would be no robbing of the fuel from one common port (like the 5/7 cylinder firing order).

Tom V.

[Tom Vaught]

I looked at your deal again Charlie and your 4 cylinder engine (with the cylinder head mounted on the passenger side of the vehicle is a NATURAL for the center divider removal modification. You would always be drawing air and fuel from either the front pair of runners or the rear pair of intake runners but never twice from the same runner pair.

I have attached a image of the Pontiac Firing order 9when using a stock camshaft firing order.

Charlie's head is on the passenger bank (the 2-4-6-8 numbered bank). If we say the cylinders 6 & 8 are the "Upper Cylinders" and cylinders 2 & 4 are the
"Lower Cylinders" we can go thru the Pontiac firing order. 1 - 8- 4 - 3 - 6 - 5 - 7 - 2

Starting off: 1 (is not used), 8 (is a Upper), 4 (is a Lower), 3 (is not used), 6 (is a Upper), 5 & 7 (are not used), 2 (is a Lower).

So the pattern is Upper, Lower, Upper, Lower then it starts again Upper, Lower, Upper, Lower, ..........

So you could remove the divider wall between the "Upper" Runners and the divider wall between the "Lower" Intake runners you will never
have robbing of the Air/Fuel Mixture between the two cylinders next to each other. So you could do a TAFF mod without any issues.

Understand??

Tom V.

[BruceWilkie]

Originally Posted by charlie66

It just dawned on me that my elbow probably adds to my plenum size. So I guess I have to figure that in too. Maybe my plenum isn't the problem at all? Would I get a bouncy boost gage needle if I had a exhaust leak?

Everything between throttle and runners is plenum area.

[Tom Vaught]

Charlie, did you read the post above?

It looks like you could remove the dividing wall of the paired runners and not have an issue. Do to the unique 4 cylinder firing pulses.

And yes, the plenum elbow is probably adding another 80-90% volume to your system.

Tom V.

[johnta1]

It would be interesting to hear John M's views on the intake.