[goatman-68]

Hello all,
I have a built 400 that has a Performer RPM and 850 square flange Holley. I was told a 4 hole spacer would work best verses an open hole spacer. I found an interesting divided spacer that looks like it would work much better.

Any opinions are welcome............

[chuckies76ta]

Hi: Could you share where you found the spacer. The spacer looks like it would work better on the RPM. Although I would think the RPM works fine without it.

Thanks
Charles

[68WarDog]

That spacer has a flaw I don't like,IT'S METAL, which can transfer heat to the carb and incoming charge. IMHO "the Best" for your application would be the polymer/synthetic HVH 1" super sucker clover spacer. You can fine them for around 75-85.00, or you could use a wood spacer. The HVH is said to reduce ET via increase air speed,increase throttle response and increase torque/HP.

[Cliff R]

I did some spacer testing a few years ago, back to back at the track. It took several outings to get all the needed runs in, but we managed to test 4 different spacers and compare them.

We tested a 4 hole, full divider, full open, and semi-open.

The worst of the bunch on our engine was the 4 hole. It lost ET and MPH at every point. The full open spacer wasn't much better. The full divided spacer ran quite well, picking up nearly a tenth over the first two. We tested the semi-open spacer last, and it was the best of the bunch, picking up a solid .1 seconds and nearly 2mph over the others.

Problem is, it didn't ET any better than running no spacer at all, but did run almost 2 mph faster, showing that it definetely made more power in the upper rpm range.

I didn't do any other tuning or change shift points during the testing, there just isn't enough time on a typical test and tune night to evaluate that many parts then start throwing variables into to mix.

I'm certain that we could have ended up running quicker with the semi-open spacer, as it was within .02 seconds of running no spacer at all and a solid 2mph faster......Cliff

[chuckies76ta]

Great info guys.

Thanks
Charles

[Schoust]

While we are on the subject anyone know what spacer if any that will fit under the hood of a first gen bird with an RPM manifold??

[chuckies76ta]

Originally Posted by Schoust

While we are on the subject anyone know what spacer if any that will fit under the hood of a first gen bird with an RPM manifold??

We ran an RPM on our 68 Firebird. I can't remember using any spacer or if it would fit..

Charles

[rcread]

My company manufactures Woodfiber Laminate carb spacers for a well known aftermarket manufacturer. They are kind of hit and miss as to whether you'll see an improvement in performance. Testing, like Cliff described, is the best way to go about it.

I grabbed this spacer from our warehouse the other day to use on the 400, under the Q-Jet in my LeMans. I drilled a hole and will tap it for a vacuum fitting to use as a PCV source. This is 3/4" thick, 4-hole, the only one we make for the Q-Jet.

[Cliff R]

As expected, we saw the biggest gains from using a custom made semi-open spacer, pretty much like the one pictured in Jim Hand's book on page 70.

I didn't mention it above, but each spacer was street tested as well for idle quality, throttle response, smoothness off idle, etc. Remarkably, the fully divided and 4 hole spacers "felt" very good on the street for "normal" driving, but gave up ET and MPH at every point during the track testing.

The "Jim Hand" style semi-open spacer showed good track improvements at nearly every point, but gave up just enough in 60' times with our combination that it did not run any quicker in ET than no spacer at all. Even with that said, a 2 mph improvement shows a significant HP improvment, and stronger upper mid-range and top end power production.

This testing was done quite some time ago, back when our engine was making around 494hp, and we were shifting at 5200rpm's for most track outings.

Due to hood clearance/Shaker assembly issues, we haven't done any further spacer testing. The new engine combo uses an RPM intake which just will not allow for anything else to be added above the intake flange and still keep the Shaker stuff.

I still beleive that spacers can and often do add power. This doesn't mean the vehicle will be any quicker in ET, as we found out, but as mentioned earlier, launch rpm, shift points and everything else was kept the same for the comparisons......Cliff

[goatman-68]

Thanks everyone for your input, especially Cliff for your detailed testing. I still think I may go with the one pictured in my post, and get rid of the fiber 4 hole that I have....

[440GP69]

One Thing Ive learned is the Importance of the Spacer holes to Closely match the Throttle bores of the Carb Otherwise the Carb will not have as much response, 4-hole Spacers Work on Smaller Engines Very well ie 350-400's, Semi Divided work Very well But there are things to take into consideration when Modifying them for Max gain, Similer to head Porting It takes testing and time to figure out what will be the best match, IMHO the 400 Will Not want a Spacer in Most apps, Here is a Q-jet Spacer I will be using and is an Old SS design FWIW

[68WarDog]

440 that's exactly(spacer mod) what we did with my friend's #13 headed 406 1 " HVH spacer. The car is a 78 TA with a 290B-6 solid cam 3800 stall and 456's gear. He picked up .2 in the eight mile.
I have that same spacer on my 1050 dominator/victor/468 and have a best of 6.6 @ 102mph. Since I'm running more CI than my friend's car. I may try an open spacer when the track reopens and see if I pickup. I have never ran without it or with a different spacer.

[68WarDog]

Maybe spacer can be seen

[Scott Stoneburg]

i track tested a 1" open spacer against a 1" wilson tapered spacer when i had the 850 on my car. and after several passes with both, the tapered spacer was consistently .1 sec. and .9 mph faster. well worth the $100 it cost. i didnt notice any drivability differences though.