1/2” phenolic spacer

Discussion in 'The Venerable Q-Jet' started by matt68gs400, Aug 3, 2019.

  1. matt68gs400

    matt68gs400 Well-Known Member

    curious if all quadrajet phenolic spacers will fit our “800” Buick carbs? I got a 72 455 GS quadrajet on mine.
    Last edited: Aug 3, 2019
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Bolt pattern and throttle plates on all Q-jets are the same. Yes, they will fit all Q-jets. The 800 CFM Q-jets have bigger primary venturi, not bigger throttle blades.
    matt68gs400 likes this.
  3. matt68gs400

    matt68gs400 Well-Known Member

    Thanks Larry!
  4. Cliff R

    Cliff R Well-Known Member

    Raising the carb 1/2" will require a longer link up from the divorced choke, if you are using the original set-up.

    I've done more dyno and drag strip testing with spacers than most who will read this. I've also tested every intake available for my engine that will fit under the hood. For the most part spacers are complete waste of time/funds, and many require some level of "cobbling" to use them. This includes fuel lines, throttle linkage, choke linkage, hood clearance, etc.

    My car is a LOT faster than most street cars and at the track I've back to back to back tested 4 different 1" spacers and logged all the results.

    The only spacer than ran quicker than no spacer at all was a "semi-open" design, and it was worth just under 2 MPH on top end. On the same day I tested a 4 hole spacer, fully open, fully divided and semi-divided (open between the secondaries). At the end of all the testing (and I've done this test several times at private track rentals) the quickest pass it ET was with NO SPACER AT ALL! The quickest pass in MPH was with the semi-open spacer. The slowest everyplace was 4 hole and the fully open induced a "stumble" going quickly to full throttle that would not tune out.

    I also backed up that testing on the dyno, and did a lot of street driving to see how the engine behaved there as well. The most average power was no spacer at all, and why the car ran quicker at the track. The semi-open made just under 10HP more peak HP, but less power (torque) till about 4500rpm's. So a little stronger finish and a little loss at lower RPM's.

    On the street the two spacers with fully divided primaries (4 hole and semi-open) felt just a tad better right off idle, or what I'd call "crisp" throttle response. Past about 1500-1800rpm's they showed my nothing over the others......FWIW.......Cliff
  5. matt68gs400

    matt68gs400 Well-Known Member

    Great info Cliff, thanks for posting this. It’s good to get real life answers. I’ve heard people talk about the 1/2” allowing the fuel air mix to turn easier and the carb being insulated better but who knows how many have really done extensive testing.

    I have a 4 hole 1/4” gasket on now. I think I may stick with this.

    With the semi open, between the secondaries, do you see much value in doing this with a mild or stock 455? I see above you mentioned it hurting low end torque.... probably not a good idea for a mild build.
    Last edited: Aug 4, 2019
  6. Cliff R

    Cliff R Well-Known Member

    Thanks. Keep in mind here my comments above were strictly for dual plane intakes. NEVER cut the divider way down in one, we've tried all sort of that for these stock appearing cars and it never makes more power or quicker ET/MPH.

    For single plane intakes a spacer is pretty much required. I've done a lot of testing with them as well. I've never once over all the years did a test with a carb straight on a single plane intake that made as much power as putting a spacer on it.

    Matter of fact, with a few really "high end" engines I've observed nearly 100 hp improvement adding a well blended 1" spacer vs running no spacer at all. Yes, that's not a typo, almost 100hp back to back no spacer vs a 1" spacer.

    Of course that was the extreme, most of the time it's more like 15-30hp and a good bit more mid-range power as well when we add a spacer to one.

    This brings up one more type of testing. Drop base air cleaners and air cleaners that move the lid closer to the carb. Since a single plane intake requires a 1" spacer to see it's full benefits, we often find ourselves with not enough hood clearance. So folks run out and buy a drop base air cleaner which moves the lid closer to the carb. In some cases this can really hurt power, more so than all the power you thought you were getting swapping to a single plane intake in the first place....FWIW........Cliff
  7. UNDERDOG350

    UNDERDOG350 350 Buick purestock racer

    I second the do not cut the divider out of a dual plane intake. Have tried it several times on the 350 Buick and the loss of low end power is not recovered on the top end
  8. 87GN_70GS

    87GN_70GS Well-Known Member

    I wonder how some of this changes with a 4 speed? With an auto, the rpm sweep from stall thru shift point in 1st is unavoidable. But with a manual, the clutch sets the stall rpm as high as you wish, allowing you to start a run way above the rpm where some of these mods are killing off low end torque. Of course street manners would still be affected
  9. Cliff R

    Cliff R Well-Known Member

    With all set-ups the quickest in ET will be the combination that puts the most power to the pavement in the loaded RPM range. Even though you have some control of launch RPM with manual transmission, and can slip the clutch a bit to soften the "hit", minimize or eliminate "bog", etc, you still have to at some point put the power directly to the pavement. We're also discussing set-ups that are more street oriented, so few if any leave in the good power or at really high RPM's and very narrow RPM range and quick shift points. Most of our "street" set-ups are pretty heavily loaded over a relatively broad RPM range, so more rules apply as far as power transfer from the launch to the shift point, etc.

    Auto transmission set-ups have more parasitic loss, no doubt about that, but we've made MAJOR advances in torque converter technology to provide excellent torque multiplication, flash stall, load stall, and very well coupled above the true stall speed.

    Decades ago not uncommon at all to see 400-600 (I've seen cheap "shelf" crap up around 1000RPM) slip on top end with a decent 3000-3500 stall converter. These days we are able to lock them up nearly solid above 3500rpms (for example), giving the end user the very best of both Worlds.

    The converter I use, for example flashes to 3600 rpms on full throttle starts with good traction and less than 50rpm' slip on top end. I go thru right around 119-121mph, 26" tall tires, 3.42 gears at 5300rpms if you want to run the math on it?

    Back to spacers. During my testing I've also ran into spacers, and other mods, such as cutting down dividers, that induce a "stumble" going very quickly to full throttle that can not be tuned out. Other things I've tested have done the same thing, like the K & Xtreme lid, or raising the carb up and installing a drop base air cleaner that moved the lid 1" closer to the carb.

    Some folks read about the testing and get their panties all wadded up about it, saying they've been running this set-up or that since Moby Dick thought he was a minnow, etc. I don't get caught up in all that, just trying to provide usable and accurate information as I know it to be, based on the testing we've done here, and some from helping customers, many of them running in Pure Stock and FAST Classes........Cliff

    PS: here's a clip of my car at the track, "de-tuned" to stay roll bar legal. Notice the smooth idle, rpms drop when the trans is placed in gear, you can hear the shift points, etc.

    Last edited: Aug 7, 2019
    matt68gs400 likes this.
  10. BQUICK

    BQUICK Well-Known Member

    I want one of those 100 hp spacers!!!
    No disrespect Cliff but something else must have been changed at same time or corrected.....
  11. BadBrad

    BadBrad Got 4-speed?

    I've run the Moroso open, 1/5 inch (or so) phenolic spacer for over two decades on the cast iron manifold with a stock Q-jet. Barely stretches the fuel line; really no big deal on the divorced choke. I took a little height out of the foam air cleaner seals. I went to this spacer purely to isolate the carb from so much manifold heat; I was having hot engine flood-on-start issues. Resolved all of that. There is a Mopar spreadbore spacer out there that is more like plasticky tar paper and just a little thinner than the Moroso spacer. It would also fit.
  12. Cliff R

    Cliff R Well-Known Member

    "I want one of those 100 hp spacers!!!
    No disrespect Cliff but something else must have been changed at same time or corrected....."

    No, we had the dyno rented for one day and made NO OTHER CHANGES but adding a very well made/blended 1" spacer to the intake.

    Keep in mind that with all "spread bore" carburetors mounted directly to a single plane low rise intake, like a Torker or Street Dominator that the rear secondary throttle plates stick much deeper in the plenum areas than the front plates. This causes distribution issues (obviously) as we got ALL the lost power right back adding a 1" spacer.

    We did make a couple of pulls in between with a Victor/Dominator to verify that there was a HUGE power loss with the shorter single plane intake with the Q-jet bolted directly to it.

    I would also mention that to date I haven't observed a single dyno test with a square flange carb on a single plane intake that didn't pick up some power when at least a 1" spacer was added to it......Cliff
  13. Storm1

    Storm1 Silver Level contributor

    So with TA's SP3 intake being 1-5/8" higher than stock iron manifold, and their disclaimer that 'Factory GS air cleaners may not fit', and needing a 1" spacer to get the full potential from a quadrajet, there's really no way out except for a drop base air cleaner or a custom hood.
  14. Cliff R

    Cliff R Well-Known Member

    That's the problem with many aftermarket intakes. Having a clean-slate to work from the folks designing them raise the mounting flange so they can use bigger runner and increase plenum area and provide a better "shot" at the intake runners in the heads, etc.

    For some applications, like Pontiac cars equipped with Shaker assemblies, and most factory Ram-Air set-ups moving the carb higher throws a monkey wrench into using the factory parts above the carb.

    If/when a drop base air cleaner is used to fit some intakes under the hood the lid can get too close to the carb hurting engine power. I've tested quite a few drop base air cleaner set-ups and none of them will run with my stock height Shaker base/filter/lid simply because it moves the lid too close to the carb and hurts airflow.

    Most folks don't test that deal and just assume since they have installed a better intake that they are making more power and the vehicle is now quicker at the track and will run more MPH. This may not be the case IF you have had to make changes above the carb to make things fit.

    For several years back around 1999-2005 I ran an Edelbrock RPM intake, stock Shaker base, Shaker top but no air filter and lid. I made a custom air filter for the Shaker opening and pulled all the air from the outside. I decided to go back to a stock intake as the taller intake also required other changes to effectively use it. I was also planning on racing less and street driving the car more so I put the choke flap back in the carb and E-choke back on the side of it. I replaced the 3" "turn-downs" with full length 2.5" mandrel bent tail pipes to quiet things down some.

    I figured the changes would hurt the car at the track. To my surprise I lost NOTHING at the track and it actually picked up just a tad in 60' and ran very close to the same times thru the 1/8th mile but apprx 2 mph slower! On top end I lost a little MPH in the 1/4 but it still ran nearly the same ET as the trade off in top end charge was made up with a better launch and quicker short times.

    I never even looked at running the RPM or any other high-rise intake again and have been using all the stock parts now for nearly 15 years.

    I will add here that folks over on the Pontiac Forums cry "foul" with my testing because my factory intake is "modified" and not completely stock. I guess they are trying to over shadow the fact that the stock parts are working pretty darned......FWIW.........Cliff
  15. Steve73GS

    Steve73GS 73 GEE YES

    Any thoughts or actual testing on a match ported SP1 with a Holley EFI Super Sniper set up?
  16. Cliff R

    Cliff R Well-Known Member

    Not familiar with the Holley Super Sniper set-up.

    I am not all that fond of TB type FI systems anyhow. The factory wasn't either and they disappeared pretty much for good in the early to mid-1990's replaced by far superior systems with individual injectors for each cylinder and dry intake vs a wet-flow system......Cliff
  17. Steve73GS

    Steve73GS 73 GEE YES

    Thanks for the response Cliff. Since seeing your comments and others previously on the performance loss associated with drop base, I'm curious if there is anything that can be done to offset this. Anyone using a spacer with EFI?
  18. Cliff R

    Cliff R Well-Known Member

    The loss from "drop-base" air cleaners comes from moving the lid too close to the carburetor. The incoming air needs room to make the turn into the carburetor. The higher the lid the more room is being provided for this to happen. I'd also add that if you look at many factory air cleaner lids they are raised and many even curved some to help provide an improved path for incoming air to get a better shot at the carburetor.

    I don't have any pics but my car has a factory Shaker assembly and the air cleaner lid is not only raised it has a pronounced curve to it. The engineers did things for a reason and I'd add here that the factory parts produce quicker ET and more MPH than any aftermarket air cleaner top I've tried even the K & N X-Treme lid. It also works better than running nothing at all over the carburetor.

    I could extend this discussion the intake manifolds as well. From WAY back to when I first got into this hobby I've seen folks ditch factory intakes and go aftermarket believing they were improving engine power and vehicle performance.

    A couple of years ago I had an engine on the dyno and some down time between pulls so I back to back tested three intakes on it. First test was the factory 1971 Pontiac 455 "HO" aluminum intake. The engine made 487hp. Second test was to install my factory "modified" iron intake, stock in the runners with a port match and plenum areas opened up under the carb like a Performer or Performer RPM, the engine cranked out 497HP. I removed the iron intake and installed a port matched Edelbrock RPM with I'd add here is just over 1" taller than the iron intake with noticeably larger runners........the engine made 491HP.......so it LOST 6HP vs the smaller iron intake!

    (I'd add here that the only reason I did not test the Performer intake with this engine as it LOST 15hp against my iron intake on a previous test with a 455 engine making right at 1HP/CID)

    Keep in mind that the engine being tested was 440CID with aftermarket aluminum heads and very well chose 236/242 @ .050 hydraulic roller camshaft with nearly .600" lift. Look at how many folks run out and buy Performer and Performer RPM intakes for engines makes a LOT less power thinking they are adding something someplace.......FWIW.........Cliff

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