I thought that it had more to do with the fact that those injectors are furthest back on the rails and received slightly less fuel in the stock configuration? I could be wrong there, just speculation that I've heard. Maybe its a combination of the two?

 

That has been one of my theories, but no factual information to back it up other than, after I put aftermarket FR and moved the regulator up front I know for a fact the car ran more consistent and didn't foul the plugs as quick or often etc...

 

I did see something that made me wonder on the cylinder 7 problem. When you put the intake on backwards and race it, cylinder 7 still gets damaged first.


Kurt

 

Interesting. What's your theory? Firing order or?

Also to throw my .02 in, I vote for the factory composite intake

 

Not positive what causes it, but to get a Motorola cup car to live on pump gas in the race, we changed the water flow in the heads. I ran a 346 engine on the engine dyno at 6000rpm steady state for 10 minutes at a time with 02 sensors in all 8 header tubes, and we could not see any a/f problem with the rear cylinders.


Kurt

 

Well, I'm going to try a gmpp intake with an Arrons fabbed elbow .I didn't have either so not a tremendous difference in price.Its hard to decide which one when there are so many different opinons and choices.This is mine, I will try it and see what happens.Looks great but thats just a plus,I would not use it just based on that.I am using heads and cam on the large side and it just seems to go better with these.I just think any thing you can do to enhance the overall flow of your engine will help,forced induction or not.If this is the wrong decision it wont be the first time I made the wrong one,we will see what happens.

 

Hot spot at the rear cylinders ?

If using all four steam vent tubes...is it still a problem ?

 

Now THAT is interesting. Makes one wonder how or why you would try that...twin turbo car with the IC in the pass seat area?

And even more good data to ponder. Now you have me questioning my reasons for changing from a FAST to a Vic Jr......thanks for sharing Kurt!

 

what about a wilson manifold. i know price is an issue. but i am planing on running that with my car. should be 12psi on strret and 18psi on track. wilson has told me that it would be a great manifold. and wilson helped make the fast.

so i think it is worth the money for the wilson manifold. a fast 90 ported for tony is like a total of 1600. so after puting 8,000 in the motor. what is another 900. no sense in going cheap now.

 

Agree what about the Wilson billet bank intake or a Beck Intake for forced induction.

 

The problem looks to be water flow related to me. Kinda getting off track from the original post.....


Kurt

 

Wilson said their intake would be great.....

Im not knocking the product...but dont ya think they might say this ?

The sheet metal intakes do look superb, and I'd love one myself, even if only for looks. But unless there was a huge benefit, it is hard to justify that money on looks alone.

I seen a test recently on a custom fabbed intake in Aussieland. They did back to back dyno's, and while it was a prototype, they actually lost something like 15hp. They openly admitted this, and said they will re-design, and have another go. It did look stunning though.
Cant recall which forum though...probably one of the Aussie ones.

 

yes your right they might say this. but that is why i stated the part about wilson and the f.a.s.t. wilson helped design that intake.

and next wilson aint a protype. they been around awhile.

 

Well this is true for forced induction, as I said earlier, the optimal FI intakes are high flow units. Runner dimensions are useless for pulse tuning, it's all about CFM. But N/A, flow is secondary to pulse tuning.

 

True, but LS engines have TONS of intake flow. The exhaust seems to be the restriction from what I've seen. That restriction plus the long intakes probably helps explains why they make the huge torque numbers they do.

It just seemed intuitive to me that those long runners would give the back cyls less air, caused to some extent by the pulses traveling back up from the cyls disrupting flow & mixing exhaust gasses with the fresh air & gas. Hence my purchase of a Vic Jr & interest in this thread.

And for once I disagree with you Kurt. This is one of the most imformative intake manifold threads I've seen in some time....due in large part to your posts.

 

LS1s don't really make huge torque numbers, at least not in respect to what they do north of 3,000rpm. The torque they do have doesn't really come from the intake or exhaust, it comes from one thing--displacement. And the LS1 isn't exactly lacking in that department. To an extent, intake manifolds, headers, cams, heads, and all that other jaz doesn't really have an affect on low-speed torque, until they are tuned specifically for it. All these high flow, short runner heads don't hurt low end torque, they just don't help it any, so people feel like they've hurt low end. And the LS6 intake is tuned quite well for the LS1's 3,000-6,000 band.

I honestly have no experience on why the back cylinders starve. I haven't looked into it, nor do I plan on it in the near future.

Sorry I'm missing r's, the r key on my laptop doesn't register half the time.

 

Good information about the water flow. I have not run 8 widebands myself but every time I've pulled plugs after a wot pull all 8 have looked identical. (with factory type intake manifold).

 

If the back cylinders got less air they would run rich, not lean. If the problem was realated to the intake it would be because the no. 7 cylinder is getting more air. Now the vic Jr DOES NOT have equal length runners. The front and backs are slightly longer.

 

Some people believe the factory style intakes result in air packing the back cyls due to the velocity that it has...shoots straight in & bounces off the back. It would be interesting to have a clear top made for a FAST & inject smoke & see what's happening. Tho at the flow rate we're all worried about, you probably wouldn't be able to tell.

Regardless, a Vic should give a more equal distribution, & too much air or fuel could cause a problem.....

 

Ive read about this too, I just don't think it would make any significant difference in the amount of air the cylinder recives. 427's water flow idea makes much more sense to me. Also the fact that when a factory style intake is turned backwards the no. 7 still gets hurt first. The dyno testing with 8 widebands kind of backs it up too. If anything I think the factory style intakes give the best distribution but the single planes are capable of flowing more.
Maby someone could flow an ls6 with about 2000 cfm going into it and measure the flow at all the ports.