Hey guys, I 'm currently dropping in the 455 back in the riv, but I'm waiting on an edelbrock performer intake that will be compatible with my Stage 2 q-jet from jet performance. The stock manifold will not clear the throttle linkage, So Here is the question, Will a carb spacer, 1 Inch to be exact, reduce, increase, or keep the same performance of a rebuilt 72 455? I'm curious Thanks
Difficult question, but here goes. Several years ago I wondered the same thing, so I made 4 different spacers for testing, all 1" thick. I made a 4-hole, fully open, fully divided, and semi-open (open in the rear only). Over the course of several weeks I street and track tested all of them. AT the time my car had the old 455 engine in place running mid-11's at 116-117mph. When the smoke cleared and dust settled, the best dragstrip run (ET) was with no spacer at all. I saw a solid 2mph increase with the semi-open spacer over no spacer, but lost .09 seconds in 60' and still ran .02 seconds slower on that particular run. The 4 hole spacer was the worst of the bunch, but felt very good on the street right off idle, producing smooth/strong accelleration at light throttle openings. The fully open spacers was a "turd" everyplace, and even induced a "stumble" at the track which was difficult to tune out. I'm sure if you were going for bragging rights, the sem-open spacer would have won the testing, as a solid 2mph improvment would show up with a significant improvement in HP in the upper mid-range and top end. Although not a Buick engine, I also tested every intake manifold that would fit under my hood (Shaker assembly), and the modified iron intake in the pic below was the winner at the track as well. It outran, back to back, the Holley Street Dominator, Performer, Torker I, and the new Tomahawk intake. Once again, it wasn't the fastest in MPH, getting outran by the Tomahawk intake by nearly 2mph, but still ran quicker in short times and ET. On a different subject, back to back dyno tested my stock HEI against an MSB billet distributor with locked out advance, both set at exactly 30 degrees total timing, and the HEI bested out the MSD ever so slightly clear across the loaded speed range. Got to love "stock" parts!:TU: ....Cliff
it will not make much difference.... just make it match the carb and the intake manifold holes.... so there is no disturbance of the flow..... be carefull that the center divider is kept in so you dont lose torque....do not use a open type of spacer.... if you do you will lose torque....
Actually, the spacer will make a difference, depending on the configuration, whether it is a 4-hole, open or whatever. 4 hole spacers tend to strengthen the signal to the carb, allowing one that runs slightly lean to seem stronger. Open plenum spacers tend to weaken the signal to the carb, requiring a richer mixture to overcome the weak signal. Though my testing was less intensive than Cliff's, it backs the results he got. What you gain at one end, you lose at another, and running a spacer appears to aggravate that result. For the street, I suggest a set-up with no spacer, as the Q-jet is very capable of running anything I have built, without "extra" hardware. I am, however, curious as to what you discover in your testing, should you be so inclined.
Thanks for all the replies, great stuff cliff!:TU: Now I was asking because in my case, I will have to use one temporarily since the carb I have doesn't clear the manifold with it's linkage, and the spacer I have in a box is an open one :shock: , I don;t want to lose torque! I'd rather not have a spacer at all, Anyone want to trade a Jet performance stage 2 quadrajet for a buick one:Brow: ? It'a good carb, very adjustable, but the downside is the fuel inlet is chevy style and the throttle linkage
I usually get some interference with linkage or accelerator pump on the holleys that i use all the time....so I make my own spacer out of hot rolled steel just thick enough to clear....usually 1/4'' or so....but the main reason is the 3 barrell carbs that I use... basicly what I make is just a super thick heat shield....that makes my carbs work....Dont know exactly how much power difference it makes, but by the seat of my pants:Brow: , I cant tell any difference...:laugh:
Just a note on street and "seat of the pants" testing. On my 455, the clear winner in "seat of the pants" testing is ALWAYS a single plane intake manifold with a 1" spacer and large CFM carburetor. Those intakes provide a BIG "rush" of power in the mid-range and pull very hard in the upper mid-range and top end. Since the tires typically slip some on the street (MT Drag Radials) the engine rushes right thru transition and into the power range of those parts. They "feel" very strong and any felt evaluation will quickly have the driver betting their next paycheck the car is faster at the track. The dual plane intakes, in contrast, provide a more "locomotive" power curve, strong right off idle, thru transistion onto the secondaries, and pull HARD clear across the loaded rpm range. The power curve is "boring" in contrast to the single plane intake, not big "rush" of power anyplace. (Here in lies to key as to WHY we think the other parts are faster) At the track, (and keep in mind this testing is on a car that runs nearly into the 10's) the dual plane intakes show much improved short times, usually at or near a tenth in 60'. The strong power across the entire loaded rpm range ends up with a quicker ET or at most just about a tie to the intakes that show all their colors in the upper mid-range and top end. Basically, a strong start and hard run equals a "soft" start and strong finish. Bottom line here, don't be surprised if the "go fast" parts installed do not outrun the parts replaced, even if the car "feels" stronger when street driven. Also, don't expect BIG improvements with bolt on parts. I've back to back tested as many as 8 carburetors in a single outing, couple of intakes, spacers, and combinations of all of the above. The last time we did a full track rental with a big pile of carburetors, all custom tuned exactly for the application (this included a Holley 850DP, custom HP950, Edelbrock Thunder Series 800, 5 custom Q-jets, the entire spread of ET/MPH between all of them was .18 seconds and just under 2mph. The Edelbrock 800 was the looser in all areas. The quickest ET was my own 1977 Pontiac Q-jet, the big Holley provided the highest MPH but slightly slower than the q-jet in ET. I see posts all the time where someone removes a stock distributor and runs half second quicker with an MSD, or stuffs on a big Holley carb over a stock carb and picks up 3-4 tents and 5-7mph. Just doesn't happen, IF the parts being replaced are up to par and dialed in exactly for the application......Cliff
with a 1", 4 hole wood spacer, this SBB 350 picked up and inch of vacuum at idle, cleaner spark plug burn and the same pull all the way up to 5300 rpm, no flatness up there either.
You can make four carb spacers from a single bamboo cutting board for far less than you'd pay for an aluminum one.
Hey Rivi, Why not just send your QJ back to Jet and have them install Buick linkage on it? That's what I had them do when I switched over to a later model non-Buick electric choke QJ on my stock manifold equipped Buick 350. It worked like a champ! Of course, it may be necessary for you to supply the Buick-specific primary shaft and linkage out of another carb. Give them a call and I'll bet they can fix you right up.
