Intake swap thought

[yevgenievich]

Oh gotcha. Basically if the airflow levels out or drops off and the MAP is steady the restriction is after the plenum. If the MAP drops it is before the plenum. A restriction after the plenum could be cam timing, cylinder head flow, intake port flow, intake port length or even exhaust restriction. My restriction is ahead of the throttle body. I pinpointed it by running speed density and removing intake parts until I found it.

Maybe my completely stock set of cats and stock muffler is a restriction after all then...
Back to sticking pressure guages in to the exhaust pipe. Still Interested to see how your set up works. Would have bought one of those intakes if they were in stock back when I really needed one.

 

[L31MaxExpress]

I wouldn't call it short runner either, but I think it's going to hurt your low end torque a little bit, which it sounded like was a priority for you. Be interesting to see the before and after numbers.

I am more after mid-range torque. 1,500-6,000 rpm give or take a little. Torque at 1,000-2,000 rpm mean very little to me. My converter stalls 2,800 rpm and as soon as I roll into the throttle the engine is up a bit in RPM. At 70 mph I am turning 2,200 rpm. I found a comparison between the short runner Ramjet intake and the L31 Marine crossram with the external injectors. Both comparisons start at 2,500 rpm and go to 5,000 rpm. From 2,500-2,700 rpm the intakes are equal. At 2,700 rpm the Ramjet starts pulling ahead. At 4,800 rpm the Ramjet intake is 61 hp up on the marine intake. Same 350, same camshaft, same heads, same 9.1:1 compression. Only difference in the long block is 1.6:1 full roller rockers on the Ramjet which are good for at most 20 hp.

On a secondary note the shorter runner may actually help kill off the cylinder charge in the 2,000-2,500 rpm where I had to pull a bit of timing.

 

[L31MaxExpress]

Maybe my completely stock set of cats and stock muffler is a restriction after all then...
Back to sticking pressure guages in to the exhaust pipe. Still Interested to see how your set up works. Would have bought one of those intakes if they were in stock back when I really needed one.

If I get lucky enough that mine shows up undamaged I will definitely let you guys know the results.

 

[Supercharged111]

Shouldn't MAF fall off after peak HP too?

 

[L31MaxExpress]

Shouldn't MAF fall off after peak HP too?

Yes but that is from the combination of things I mentioned. Cam timing, cylinder head flow, runner length, etc, etc. What I was getting at is if the MAF flow holds steady or falls off and the MAP reading stays high, the engine is just not moving air vs being starved by an intake tract restriction.

 

[Supercharged111]

Yes but that is from the combination of things I mentioned. Cam timing, cylinder head flow, runner length, etc, etc. What I was getting at is if the MAF flow holds steady or falls off and the MAP reading stays high, the engine is just not moving air vs being starved by an intake tract restriction.

That's what I was thinking even though you didn't EXPRESSly state it.

 

[yevgenievich]

I wonder if if map number would represent restriction coming in to the intake plenum, and not necessarily indicate if the intake plenum it self is a restriction.

 

[L31MaxExpress]

I wonder if if map number would represent restriction coming in to the intake plenum, and not necessarily indicate if the intake plenum it self is a restriction.

That could depend on the MAP sensors placement. With the MAP in the rear if I looked at it without stripping down the air inlet, I could have easily blamed it on the fuel spider blocking airflow to the rear 4 cylinders. However the internal plenum are is huge compared to that 90* air cleaner adapter on top of the throttle body. The airflow just does not want to make that 90* turn into the throttle body in that bonnet that is only 1" wide above the throttle body. I ran into a similar restriction on the 99 Suburban my brother had and my 99 Tahoe with the 305. Its one of the reasons I really like the Volant air intake. It has a nicely radiused tube that bolts to the throttle body. I do not even have enough room above my throttle body to get a cobra head there.

 

[L31MaxExpress]

3.5" Cobra head for reference. Trust me I tried.

You must be registered for see images attach

 

[0xDEADBEEF]

I am more after mid-range torque. 1,500-6,000 rpm give or take a little. Torque at 1,000-2,000 rpm mean very little to me. My converter stalls 2,800 rpm and as soon as I roll into the throttle the engine is up a bit in RPM. At 70 mph I am turning 2,200 rpm. I found a comparison between the short runner Ramjet intake and the L31 Marine crossram with the external injectors. Both comparisons start at 2,500 rpm and go to 5,000 rpm. From 2,500-2,700 rpm the intakes are equal. At 2,700 rpm the Ramjet starts pulling ahead. At 4,800 rpm the Ramjet intake is 61 hp up on the marine intake. Same 350, same camshaft, same heads, same 9.1:1 compression. Only difference in the long block is 1.6:1 full roller rockers on the Ramjet which are good for at most 20 hp.

On a secondary note the shorter runner may actually help kill off the cylinder charge in the 2,000-2,500 rpm where I had to pull a bit of timing.

That would definitely be the intake I would choose between those 2.

I don't know if there's a real definition for mid-range torque, but to me I think 3k-4k rpms on a typical V8. 1500-6000 is pert'near a full sweep in a lot of engines.