2" spacer....waste of time/$$??

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6sally6
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2" spacer....waste of time/$$??

Post by 6sally6 »

My pardoner has a 74 Nova...3.73:1 gear....turbo 350...383 stroker...650 DP Holley...."healthy" street roller cam (hydraulic)...gear drive...the whole 9 yards.
He's thinking a 2" open spacer will make a big difference in power/torque/butt-O-meter power. I'm kinda :roll: ...no so sure.
For a street application/car show cruiser....Is it worth the trouble?
How much bigger should we jet it?
What can he expect?
6sally6
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Re: 2" spacer....waste of time/$$??

Post by mag2555 »

What intake manifold is being run and what heads and what if anything has been done to the heads?

I have seen where what would be too large of a 4 bbl Carb by 100 cfm placed on a 1” spacer then on a duel plane intake that was dead above 5400 rpm turn in another 12 hp with no loss in bottom end torque , so ya just never know!
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Re: 2" spacer....waste of time/$$??

Post by Walter R. Malik »

6sally6 wrote: Wed May 05, 2021 6:14 pm My pardoner has a 74 Nova...3.73:1 gear....turbo 350...383 stroker...650 DP Holley...."healthy" street roller cam (hydraulic)...gear drive...the whole 9 yards.
He's thinking a 2" open spacer will make a big difference in power/torque/butt-O-meter power. I'm kinda :roll: ...no so sure.
For a street application/car show cruiser....Is it worth the trouble?
How much bigger should we jet it?
What can he expect?
6sally6
It could be ... maybe not ... maybe a different combination of spacers would be best and maybe not.
Unless it all gets tested, it will merely be a guess.
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Re: 2" spacer....waste of time/$$??

Post by BOOT »

Like many things results may vary
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Re: 2" spacer....waste of time/$$??

Post by rustbucket79 »

I’ve tested enough spacers on enough combinations to tell you there is no constant. I’ve tried a 2” open on just a few engines that I thought would warrant it, never made enough difference. Now if you just want a reason to have to cut the hood... :mrgreen:
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Re: 2" spacer....waste of time/$$??

Post by bob460 »

This one made 36hp........... =D> ...........but as said every engine is different.

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Re: 2" spacer....waste of time/$$??

Post by 1980RS »

In testing last fall I found that my peanut port headed BBC with the Holley Strip Dominator intake liked the 2" 4 hole tapered spacer the best. 1 week later when I switched to an RPM intake manifold the 2" spacer slowed the car down 2 tenths. I then put an open 1" spacer and the car picked up the 2 tenths plus another tenth. I have always picked up at least 1 tenth on a dual plane with a 1" open spacer, single plane intake are hit or miss for me with a spacer.
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Re: 2" spacer....waste of time/$$??

Post by mag2555 »

It's seems a lot hinges on if the motor needs more plenum volume to dampen reversion pluses and to lower in coming Carb air speed to slow it which allows more air volume to better make the turn into the tops of the runners.

As posted up many times here, its a matter of trying different set up's!
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Re: 2" spacer....waste of time/$$??

Post by Camaromeo »

in 80% of cases i came across its the following pattern:

a dual plane benefits from a 1-2" open spacer

a single plane benefits from a 1-2" 4 hole tapered spacer

The smaller (maybe even undersized) the intake is in relation to the hp-level initially, the more it benefits from a spacer and its growing size.
You basically add intake size / plenum volume. Its like upsizing you headers.
You shift the breathing sweet spot a little more up in the rpm range, rersulting in more TQ at higher RPM so more HP results from it..

Its trial and error, what size is the best.
For kind of spacer, not so much, its much lesser the case.
Mostly only extrem high horsepower engines just need open spacers on top of single planes.
And mostly only very short stroke small displacement engines with very big dual plane intakes benefit from 4 hole spacers on top of them..
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Re: 2" spacer....waste of time/$$??

Post by F-BIRD'88 »

Before you invest your hard earned money consider making up home made test carb spacers that you can stack up and test for effect.. Old 1/2" old 5/8" partical board, cabinet board , plywood.
On a dual plane consider trying a combo divided spacer where the deep side of the plenum gets 2 holes and the shallow side gets a siamesed D shape..
Can use a common 4 hole carb gasket as a pattern.

On a single plane street motor you can intergrate a steel/aluminim plate plenum divider that is held in place by the carb spacer. Test for effect...
Try them all. See what works.

Worst case you'll have some interesting wall art or firewood.
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Re: 2" spacer....waste of time/$$??

Post by skinny z »

1980RS wrote: Thu May 06, 2021 1:19 am. I have always picked up at least 1 tenth on a dual plane with a 1" open spacer...
Camaromeo wrote: Thu May 06, 2021 6:57 am in 80% of cases i came across its the following pattern:

a dual plane benefits from a 1-2" open spacer...



Does this hold true with a cut out divider as is the RPM Air Gap? I've seen results such as yours when the divider is complete (Performer IIRC) but have heard the reverse when the divider is cut.
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Re: 2" spacer....waste of time/$$??

Post by F-BIRD'88 »

..... Then,when you go to buy the carb spacer(s) it needs, make sure one is a nitrous plate.😁
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Re: 2" spacer....waste of time/$$??

Post by 1980RS »

skinny z wrote: Thu May 06, 2021 11:51 am
1980RS wrote: Thu May 06, 2021 1:19 am. I have always picked up at least 1 tenth on a dual plane with a 1" open spacer...
Camaromeo wrote: Thu May 06, 2021 6:57 am in 80% of cases i came across its the following pattern:

a dual plane benefits from a 1-2" open spacer...



Does this hold true with a cut out divider as is the RPM Air Gap? I've seen results such as yours when the divider is complete (Performer IIRC) but have heard the reverse when the divider is cut.
Can't say I have ever tried that before. My 358 has an Air Gap on it now with the divider cut down so next time I go out I will have to test that one for sure.
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Re: 2" spacer....waste of time/$$??

Post by skinny z »

1980RS wrote: Thu May 06, 2021 3:26 pm
skinny z wrote: Thu May 06, 2021 11:51 am
1980RS wrote: Thu May 06, 2021 1:19 am. I have always picked up at least 1 tenth on a dual plane with a 1" open spacer...
Camaromeo wrote: Thu May 06, 2021 6:57 am in 80% of cases i came across its the following pattern:

a dual plane benefits from a 1-2" open spacer...



Does this hold true with a cut out divider as is the RPM Air Gap? I've seen results such as yours when the divider is complete (Performer IIRC) but have heard the reverse when the divider is cut.
Can't say I have ever tried that before. My 358 has an Air Gap on it now with the divider cut down so next time I go out I will have to test that one for sure.
Noting that every car is different, it would still be interesting to know your results.
Two options exist for me (if covid ever goes away and the economy returns). One is a 7000 rpm 350. The other a 6000-6500 383. Either might benefit from a single plane intake or a spacer on the dual plane.
And of course nitrous....
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Re: 2" spacer....waste of time/$$??

Post by af2 »

6sally6 wrote: Wed May 05, 2021 6:14 pm My pardoner has a 74 Nova...3.73:1 gear....turbo 350...383 stroker...650 DP Holley...."healthy" street roller cam (hydraulic)...gear drive...the whole 9 yards.
He's thinking a 2" open spacer will make a big difference in power/torque/butt-O-meter power. I'm kinda :roll: ...no so sure.
For a street application/car show cruiser....Is it worth the trouble?
How much bigger should we jet it?
What can he expect?
6sally6
What intake???
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