Cliff's Quadrajet Parts and Rebuild Kits
General Category => Quadrajet Carb Talk and Tips => Topic started by: kelley555 on November 29, 2010, 08:23:38 AM
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Cliff,I assume all the late model carbs have this trough (1".040 X .140), on top of the tall tower that extends down to the main body well. The trough you spoke of filling with epoxy is between the primary choke flap top housing & where the smr hanger enters the main body with the smr?I noticed on my oem 1972 Q-jet didn't have this trough/slosh tower casted & my other 2 late model 1 ton carbs have it. One of the late model carbs has some kind of anti slosh shield that bolts to the 2 bolt holes in the area & the shield extends upwards to prevent gas from sloshing over to the secondary's.Just a guess,engineer's must have known they had some sloshing problems with ruff terrain vehicles.Thanks for writing such a great book that gives you enough info to "BUILD A Q-JET CARB" with right mods & receipe's, so us rookie's don't hack the carbs up & make them junkers.Without heat,this project couldn't have been done,I used the old heat gun due to not being as steady as I once was. Along with a few common sense tricks,thanks for input for the carb project.They'll be "No" Edelbrock tag installed back on this carb.They'll not get the credit for a turning this Quadrajunk to a Sleeper/Monster/Granny 72 Chevelle with a lo-po 265ci.The carb has way too many mods. different from the Edelbrock 1910.Later Leeman
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For most applications the "trough" isn't an issue. For some cars that are drag raced and launch really hard, fuel can slosh out that vent and cause a stumble. We fill in that trough for drag racing applications, and all off road applications as well.....Cliff
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Cliff,can I drill & tap 2 small screws,1 on each side of the trough,in the wider boss area for a future block-off plate? In case I have a problem,I'll make a plate that will block off the trough & never even notice the block off plate.The carb will look sorta Oem. Any passages below or is it clear? If so, how deep can I drill & tap?Later Kelley
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I just push some Marine Tex into the trough with my thumb, takes about 3 seconds to make the repair, then 24 hours to let it dry. I guess a plate and screws would be OK, provided they don't come loose and to thru the engine!.....Cliff
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Ok,I'm trying the resizing program James suggested for the pictures were too big. I'll will send a few pics I took of my engine being assembled. Kelley
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Here's a couple pics more of my engine assembly.Later kelley
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Nice pics. What is the CID, compression ratio, cam specs and type of cylinder heads? Are you using an open spacer on a dual plane intake?.....Cliff
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Cliff,it's is 415ci. ;9.5 to 1 static & around DCR 7.7 to 1 with the Crane #119691 .548/.558 lift w 1.5 ratio rockers(mine are 1.6 Int. & exh.,so .585/.595 lift ;234/242 dur maybe add 2-3 degrees with 1.6 according to Crane;advertised 296/304 dur &76 0verlap;with a normal sbc ci. (2800min.-6800 max. 7200 valve float). The heads are AFR 195 Eliminators(street pkg. with 2.05 Int,/ 1.6 exh.) they flow 280 Int./218 @.550 lift (@ 28" h2o) with 1"3/4 exh. & 4.00 bore my bore (4.125 bore & dynatech coated stepped 1"3/4 to 1."7/8 headers).The exhaust concerns me but the guy out of Kansas has 5 chevelles & swears with 2"1/2 mandrel bend exhaust it will flow as good a 3" regular bent system & without being noisey,so you can carry on a conversation or drive the wife out of the loud car. As far as the intake,I went to a head port guy & he say all the dual planes past 6000-6500 won't hang.(your's does) I was going to buy an Edel.Performer Air Gap but the older Holley Contender port volume is supposedly bigger,even an Afr guy told me that. I added the q-jet open adaptor to increase the plenum size.It may not work.The Holley intake has a divider all the way to the top,so with the open adaptor,I guess the plenum is bigger & kinda like the Edel. air gap. A lot people say the bigger motor's a intake "hogg,try to use a single plane.(you have a big motor & no single plane). A single plane intake may work better but it's a Ac car & the dual planes have the oem tapped intake/ac bracket. Lingenfelter was high on the Holley Contender(just off idle to 7200rpm)sounds like bs,pretty broad. I guess I need to have a Edel. Performer rpm air gap flowed compared to this Holley Contender/Street dominator,same part #. I have an extra Holley Intake that I could flow & compare to Edelbrock to see who's Bsing. In the old days ,I used a 2" spacer on the Holley Strip Dominator,but I had a 5500 stall & .700 lift & lauched higher. A little playing with & tuning. Do you see the q-jet adaptor could pose a problem.Later kelley
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I forgot,the piston is .005 in the hole + .038 thick gasket = .043 quench(4340 steel rods) .The Afr heads a 75cc head with a Srp inverted Dish piston, -16cc. Later kelley
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Nice engine combo. The dual plane intake will work fine. The small amount of top end power you give up clear up at 6000rpm's or so is offset by strong low and mid-range power.
I've never tested a single plane intake yet that made more "average" power in engines designed to make peak power around 5000-6000rpm's.
The single plane intakes show NOTHING below about 4500rpm's on the dyno.
Also keep in mind, that the engine spends very little time up near the shift point in a drag race.
I've done a lot of spacer testing. They can make more power, but it really takes back to back track runs to see which one works the best?
I don't like the fully open ones on dual plane intakes. We saw a LOT of torque lost in some recent dyno testing using one, even though it made a few more HP on the top end.
You can also experience some "turbulence", which shows up as hesitation/stumble/bog when you go quickly to full throttle.
The best spacer I've tested to date was semi-open. Basically divided across the front, and open between teh secondaries.
My own intake is fully divided, with about half a 50 cent piece cut out between the secondaries with no spacer. It made the quickest runs at the track over all the spacers I tested, even though it was almost 2mph slower than the semi-open spacer......Cliff
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Cliff,do they make a sq. bore to q-jet spacer like the one your talking about,semi open?Who makes it? I thought it was going to be trial & error,when it came to the installing the adapter/spacer. I have no exprience with the q-jet's installing an adapter/spacers,whether,it's open;4 hole or semi open. Which one will work for the quadrajet you've been there.Later Kelley
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A full divider can be made/inserted into any spacer or adapter. I'd start out fully divided if the intake has divider in it. Then experiment with "notching" it between the secondaries, etc.....Cliff
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Ok thanks Cliff, I'll start looking around for an adapter with a removable divider & go from their. I remember the old Weiand Excellerator intakes had a divider that you could slip the divider in the notch & tune them.I'll make a 2nd divider & start playing,start with a small radius notch & go from their. The car's pretty heavier at 3400 lbs. empty,so we need all the help getting the lead sled moving & stop the turbelence before that causes a tuning problem. Thanks for the advice.Happy holidays & merry x-mas to your family, Kelley.
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hey kelley555, how ya doin. (that sounds like i'm from Jersey or somethin) Anyway, on that divided spacer deal, there is a good readings on this subject in Jim Hand's Pontiac book. He tells ya how to make spacers and the experiments he did with them. Actually the book has some excellent info that could apply to any make of engine, not just Pontiacs. The tuning section is just worth the price of the book itself. I dont usually pimp too many books but this one has alot of info gained from alot of experience. BTW, he made his own spacer out of white pine and a roll of gasket material and some adhesives. seeya dude!!
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Omaha,I played with a lot of different spacers in the 70's & early 80's with Holley carbs with single plane high reving Sbc ,not any Q-jets though. This was a all out drag motor & car,not a street driver.I wish we had the head technology back then,we have today. To show how one can over carb an engine,I built 3 different Dp Holley's 750;800 & 850 in the 70's. I made runs on the same day with the same type car/motor/conditions & traction scienced that out & made the conclusion.If there ever was a 355 ci. that should have benefited from a larger cfm carb,it should have been that .720 lift;288/294 dur. @ .050 lift cam;high compression; 4 sp engine .The car ran more MPH & better Et. with the smaller Holley 750 dp . All 3 carbs we're setup right,not nit sh--ted,but the heads we're pretty good for the day. It's a diifferent ball; game with this engine,it will probably never see 6000 rpm with these cubes,probably 5500-5800 max. The heads just want support the cubes. I checked early this am & didn't see much for the holley sq. pat. to the q-jet adapter. I'll probably mill a slot in the open spacer. Measure how many thousandths below the carb mounting surface the intake divider is. The center divider is slightly recessed so I'll fab a divider the same width as the intake & ht. of the adapter + how far the intake is recessed. I'll probably start with a small radius notch & leave it,as per Cliff's suggestion. If the car has trouble hooking from too much tq. ,maybe decrease some power by moving the power band up slightly.Later Kelley
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Here's a slightly different style, that can be modified to suit your needs.
http://cgi.ebay.com/Carburetor-Adapter-Spread-Bore-Qjet-Square-Bore-4-Hole-/330499444454?pt=Motors_Car_Truck_Parts_Accessories&hash=item4cf34d4ee6
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77 Cruizer,thanks for the info.I believe Cliff is talking about a installing a divider down the center of the adaptor that will feed each side of the plenum of the dual plane equally. These 4 hole adaptor's may work & give more torque,but Cliff's has tested several different spacers extensively on his car/q-jet. I don't need the possible tuning/stumble problem with the new engine. I believe the 4 hole adaptor isn't exactly what Cliff was speaking about,unless I misunderstood him. So far,I've only found the Holley sq. bore to a q-jet adaptor in the 4 hole spacer or the open type. Unless their's someone out their I haven't came across,I think it will have to be a custom divider (with small radius notch) added to the adaptor,milled & retained in place by the divider of the intake,by me. So,the divider ht. is actually going to extend below the .750 adaptor by around .350 below the gasket surface. It will rest on the intake divider with a,so to speak,close to perfect match.This should seal/islolate the open plenums independently on each side of the intake. This should then prevent the turbulence Cliff spoke about & make the dual plane just a little taller. This should make the intake close to the way the it was originaly,but the small notch. Remember to say a prayer for our soldier's that are serving thru these holidays,merry x-mas. Kelley