pcguy2u

Here's a pic of an intake manifold that I'm contemplating modifying:




Considering cutting out about 1/2" of the bridge between the two black marks - which raises some questions:

1. Will this increase the potential for higher RPM?
2. Is 1/2" a good number?
3. What would you stuff into the manifold to keep debris from falling into the guts?
4. Anyone have any suggestions as to how to make the cut? Is there a blade for a dremel that might work? Or what would you use?
5. Is this a good idea or should I just get a RPM manifold?

427Hotrod

Need to know about the combo.

If you want to try it before you do it..stick a 1/2" carb spacer on it and see how it acts first.

What are you trying to accomplish? More high RPM power?

If you cut on it..best to remove from the motor..but you can fill the intake with shaving cream and it will catch most of the metal. Then vacuum it all out of there. Or stuff something down in there and seal with playdoh around edges..or grease.



JIM

pcguy2u

The goal is 11.5 secs.

The combo is not finally determined at the moment and the HP is still unknown, but it looks like the 350 will put down about 325 at the flywheel and it has a TH350 with a 3000 stall. Have 3.73 posi and at the moment the tires are 23.4" street tires on 15" rims and I want to try it that way before changing to a drag radial – that way I’ll have a better idea of what I need.

Here are some theoreticals for 11.43 seconds:

Vehicle Weight: 2800
(in pounds)
Assumed HP: 325
(at the flywheel)
1/4 Mile Top End Speed: 115
Required RPM through lights: 5800
Assumed Gear Ratio: 3.73
Tire Diameter (Height): 25

With the 23” tires, the RPM required is 6100+- with 3.73 gears

In any case, it looks like something greater than 5500 will be required.

Thanks for the cutting tips. I have posted this same thread in the H-body forum and the conventional thinking is that there is little to gain.

Have the carb off for a rebuild and proper setup for the cam, power valve and vacuum secondaries spring tension. Hope to run this at least once before the season ends next month.

427Hotrod

Even at 2800 lbs (is that with driver and fuel?)....I think I'd plan on more HP to go mid 11's.

If you think back to a dead stock base LT-1 C4....that only weighs a few hundred pounds more...a really good one with a good driver would run real low 13's...maybe high 12's with traction. That was 300 *new style* HP. An average LS type C-5 would put around 300-325 to the wheels..which is a lot closer to 400 or so crank HP. They might run similar times ( I remember spanking many of them with my old above mentioned C4 even though they should have walked away from me). I just had to work the stick trans and hope they snoozed a little! But even from a roll...the LT-1 hung well.

Your plan for MPH and ET's align...but again...I'd plan more HP in the *real world* to actually get there unless you are running in below sea level air *cave air* etc.

Street stuff brings lots of compromises.


JIM

383vett

I would run the car first to establish a baseline before cutting. A die grinder will work. A mill would be better if the manifold is off the motor.

pcguy2u

Thanks for that Jim - lots of unknowns here, weight and HP in particular. Weight is a max number and HP is a minimum number. With the cam that appears to be in this beast, I would bet on 400HP, but only time will tell. With the weather closing in and the last track event at Infineon/Sonoma Raceway being on the 15th, think its going to wait until spring.