I did a search on all the spacer questions and most seem to be related to putting them on a stock motor. I have a 7116 RPM Vortec manifold, NOT the air gap. I noticed the airgap manifolds have the divider cut down, and I assume it is to help with top end horsepower. My car pulls hard but has problems getting past 6000 rpm. I was looking into putting a 1 inch open spacer to help the motor breath better on the topend. Low end doesn't really matter that much since I have a manual and I will be launching at 3500 anyway. My buddy has a similar setup to me (355 HOT cam Vortec)and he pulls it to 6500 easy. The only difference is he has a single plane intake. I also know the RPM manifolds are supposed to pull from 1500 to 6500 but mine seems to come up short, I need advice on whether or not to purchase a spacer???Thanks

BTW: The HOT cam is supposed to pull to 6500 rpm and I have the proper valve springs. And I don't want a single plane manifold.

 

The HOT cam will pull to 6500 when used in an LT-1/LT-4 that has VERY SHORT intake runners. Like 3" long. They really help prop up the RPM range. With a longer runner intake like your RPM dual plane you're not going to get quite the same RPM potential out of it.

This is not to say that a spacer is a bad idea. Quite the contrary. You may find it doesn't really want to rev much higher but your midrange torque may jump up quite a bit. How upset would you be if you found that to be the result? Probably not very upset. Try it out. Worst case, you still learned something.

BTW- you're getting some decent times out of that combo right now. Obviously, you know how to spec-out a combo and tune it. So you should be familiar with the "try it and see" approach to installing new go-fast parts.

 

why not?

i mean you just described the EXACT reason they exist.

for motors that want to turn high RPMs like that without regard for bottom end power.

 

I am looking for a quick track-only solution to help me beat my buddy (need one tenth) but I want it to run stong on the low end for when I am on the street and I don't want to be swapping manifolds a lot.

I just thought of something; how would a single plane do with a 4-hole spacer?

 

run her rich and hook up a sneeky pete system... :lala:

im going to share somthing with you thats 100% totally against popular belief and im sure someone will argue with me about it.

i have never felt a loss in my butt dyno on the street with a single plane intake. there. i said it. i run a single plane on the street.

so while i never FEEL the loss, i probly did lose a ftlb or two... meanwhile i gained power at the track.... now i am running more cubes then a 305, but ive done this with a 327, 350, and 400 without issue....

 

There you go tempting me to get a new manifold. I like that cause it sounds like it will work, I don't like that cause I have no will power and I will look into/ probably buy a manifold now, LOL

 

My experience is not very different from Mr. Dude. Single plane only fell off at very low RPMs- like below 2500-2800. Above that I am hard pressed to tell the difference until very high RPMs (6000+). Again, expect no miracles. We're talking relatively small incrememtal improvements on the top end. It probably won't give you an "oh wow!" kinda improvement.

Again, put it in the "try it and see" category. Swapping an intake is pretty easy to do. Maybe buy a used Vic Jr. off ebay for cheap and see how she does. I, myself, rarely buy new parts becuase I don't want to drop hundreds and find out I gained nothing or saw little improvement. That way I can resell the parts again and be even-money except for my time and labor.

 

i could tempt you with other stuff first.


now this is somthing that people i know do. i think its a BAD idea. i do NOT do this to my car, even just at the strip for one run.
it does work, but i DONT reccomend it.
that said.... you could pull your air filter element off for the run down the strip.

you can also take off the belt... however, you can easily overheat your car that way.
meaning if you do that, you'll have to push it thru the staging lanes, and not fire it up until you're ready to stage and run. only do this if the motor is cool too.
(this is why im putting a electric pump in... i can just flip the switch off when im ready to go)
the downsides to the belt mod:
its temporary. you cant do this anywhere but the strip.
its a PAIN to steer. because the power steering pump isnt turning.
and lastly, it MAY make you slower if your battery isnt fully charged. some cars need the alternator running to get a good run down the strip. this is just one of thoes "try and see how the car likes it" kind of things.

another thing i would do is everything you can to hook out of the hole.. thats where a close race is won. (well technicly the finish line is where its won, but getting a good start puts you off to... well a good start) [im soo funny]


rather then list more stuff, why dont you tell me what you do when you goto the track, and i'll tell yea what i think your missing...

 

To increase the top end of your motor with a dual plane manifold to be more like a single plane will take more than a spacer.

Because of the divided manifold plenum you can use a much larger carb. 600cfm is restrictive on a motor like yours. a modified 750cfm would work well (820cfm).

You can also shorten the dividing wall in the top of the plenum. ( allows each cylinder to breath off all 4 venturii)

install a larger cam. 230 to 240@.050"

like this one

Or this other one

 

Spacers aren't an across the board fix.
I've seen motors lose power on the dyno with the addition of a spacer.