Naw that's ok. I wonder if there's enough room to tap that area for a Holley carburetor jet? Or maybe the size of the idle fuel restrictors?
Thermoquad vs holley vs q-jets
- Thread starter ValerianMagnum
- Start date
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This method is the same as the Holley guys drilling their throttle blades for bypass air. The double booster and smaller primary of the TQ and QJ will often be tricked into thinking it’s time to flow, if you drill the throttle blades.
Definitely not a Holley jet. And the IFR jets are expensive and you don’t need the shoulder if you only tap deep enough to be flush.
How about drill and tap for a Holley air bleed or fuel jet instead?
I suppose if you want to throw money away. 5 bucks gets you 4 Holley air bleeds or 100 brass set screws.
True, but….
Sometimes you just have stuff on hand…. LOL!
Thanks
Sometimes you just have stuff on hand…. LOL!
Thanks
I'd be pretty easy to drill all the brass set screws you need with different size holes.
Ironracer
Gearhead
Pretty cool trick
MopaR&D
Nerd Member
Sounds like you'll be having to run a square-bore if that Speedmaster intake is what I'm thinking it is (Eddy Air-Gap copy).
I've messed with TQs in the past but the last one I put together from 3 cores ran kinda crappy, always had a bad off-idle stumble. I bit the bullet and bought a new 750 street demon and never looked back, somewhat similar design but you can actually buy new parts for it. I think you have a better selection of cores than I do though mine were later ones (1980s) with extra emissions junk. Some day it would be nice to get a GOOD one and make it work but dang, their sophistication is a double-edged sword it can drive you nuts. Reference material is essential for those they're like black magic lol (not really but you know what I'm saying)
I've messed with TQs in the past but the last one I put together from 3 cores ran kinda crappy, always had a bad off-idle stumble. I bit the bullet and bought a new 750 street demon and never looked back, somewhat similar design but you can actually buy new parts for it. I think you have a better selection of cores than I do though mine were later ones (1980s) with extra emissions junk. Some day it would be nice to get a GOOD one and make it work but dang, their sophistication is a double-edged sword it can drive you nuts. Reference material is essential for those they're like black magic lol (not really but you know what I'm saying)
cudavert
DARTAHOLIC
The only way I'd suggest a Holley is if you don't give a care about economy whatsoever. I love spreadbore carbs. I'm also not a fan of Holleys because of the floatbowl/accelerator pump leakage issue if your car sets up for a while (it sure happens to my Holley equipped car often).
*I'd run with the 440 TQ or Q-jet, and most likely the Q-jet.
*I'd run with the 440 TQ or Q-jet, and most likely the Q-jet.
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RRR, Dana,.
Thanks for the info.
I have that info but wondered whether your info was different to what I already had.
Couple of comments/suggestions. I have used TQs since the 1970s.
- never had to enlarge the IFR to 0.052." That is a huge increase, more than double the area of the typically stock 0.033" IFR. 0.040" is largest I have needed.
- 4 or more turns out on the mixture screws, I would be enlarging the screw discharge holes in the bore.
- the later 9000 series carbs that bypass air routed from the air horn to under the base plate was to avoid nozzle drip which could occur if the air passes down the t/bore. I have seen earlier 6000 series carbs that had the base plate drilled for bypass air; have also seen the pri blades drilled. Both methods means air is passing down the t/bore & could induce nozzle drip.
- best way to avoid n/drip if more idle air is needed is to drill the secondary blades. Engine doesn't care how it gets the air...
- have never touched the IABs & have never had a need too...
- occasionally, the idle down channel which supplies the T slot needs enlarging. Very hard to get at on the TQ. It is a brass insert in the a/horn about 1 3/8" in from the surface, so long drill bits needed.
Thanks for the info.
I have that info but wondered whether your info was different to what I already had.
Couple of comments/suggestions. I have used TQs since the 1970s.
- never had to enlarge the IFR to 0.052." That is a huge increase, more than double the area of the typically stock 0.033" IFR. 0.040" is largest I have needed.
- 4 or more turns out on the mixture screws, I would be enlarging the screw discharge holes in the bore.
- the later 9000 series carbs that bypass air routed from the air horn to under the base plate was to avoid nozzle drip which could occur if the air passes down the t/bore. I have seen earlier 6000 series carbs that had the base plate drilled for bypass air; have also seen the pri blades drilled. Both methods means air is passing down the t/bore & could induce nozzle drip.
- best way to avoid n/drip if more idle air is needed is to drill the secondary blades. Engine doesn't care how it gets the air...
- have never touched the IABs & have never had a need too...
- occasionally, the idle down channel which supplies the T slot needs enlarging. Very hard to get at on the TQ. It is a brass insert in the a/horn about 1 3/8" in from the surface, so long drill bits needed.
No drilling the rear blades is not the best way, nor was the PCV port in the rear of the baseplate the best place. Your either placing raw air or in the case of the pcv raw oil vapors into the cylinders. Put it up front where it has a chance to mix with the fuel. And if you drill the blades too large, which often happens trying to get the right tune, now you have a choice. Close up the primaries and lose transfer slot exposure or throw away your rear throttle blades.
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I gotta add this, since we are here. In mild small blocks a lot of times you’ll notice that you idle mixture screws are 3 1/2 or more turns out. That is when I plug the idle bypass and do NOT redrill, or drastically reduce the size. This renders your idle mixture screws effective again.
The said 451 still had booster drip @ .120 IBP, @ .125 it still spit fuel intermittently. @ .128 the booster drip was completely gone. At that point, in order to keep the Idle mixture screws 1 1/2 turns from bottom, the IFR’s had to be@ .052. I didn’t dream that size up. I listened to the engine and gave it what it asked for.
Dana,
Couple of comments.
- nothing wrong with drilling the sec blades for bypass air. Been doing it for years. As for 'throwing away' the blades if the holes are too big, that is why you start small...If you drilled the pri blades instead, & the holes are too big, you would have to throw those away using the same logic!! The sec blades are alum. If the holes were too big, you can solder them shut with alum solder. Haven't done that on TQs, but have done it alum blades in AVS carbs, many times.
- average V8 engine consumes about 17-21 cfm of air at idle. About 3 cfm comes from the PCV. The engine doesn't care where the air comes from, so long as it gets it. This idle air is supplied by any bypass air, PCV, the gap around the t/blades & past the t/shafts. A cumulative affect.
- not sure what the reference to the PCV port is about, I never mentioned getting BP air from it or near it. All the TQs I have seen have PCV port at the front. If you are referring to a port that might be in the baseplate at the rear of the carb, then that could be used for BP air, for reasons explained above.
- I have fitted 850 TQs to many engines, including a 468 Pontiac engine that runs 119 mph over the 1/4 mile, makes about 550 hp. Never had to go over 0.040" on the IFR. Never touched the IBP. You say you had to enlarge the IBP to 0.128". Is that a misprint? The factory hole looks to be about 040-045. 0.128" would be bigger than the brass IBP insert. With great respect, I do not think enlarging the IBP would be the best way of stopping nozzle drip. ND is caused by to much air passing through the booster at idle. The best way to stop ND is to get air to the engine from somewhere else, such as sec blades or from the airhorn as on later 9000 TQs.
Couple of comments.
- nothing wrong with drilling the sec blades for bypass air. Been doing it for years. As for 'throwing away' the blades if the holes are too big, that is why you start small...If you drilled the pri blades instead, & the holes are too big, you would have to throw those away using the same logic!! The sec blades are alum. If the holes were too big, you can solder them shut with alum solder. Haven't done that on TQs, but have done it alum blades in AVS carbs, many times.
- average V8 engine consumes about 17-21 cfm of air at idle. About 3 cfm comes from the PCV. The engine doesn't care where the air comes from, so long as it gets it. This idle air is supplied by any bypass air, PCV, the gap around the t/blades & past the t/shafts. A cumulative affect.
- not sure what the reference to the PCV port is about, I never mentioned getting BP air from it or near it. All the TQs I have seen have PCV port at the front. If you are referring to a port that might be in the baseplate at the rear of the carb, then that could be used for BP air, for reasons explained above.
- I have fitted 850 TQs to many engines, including a 468 Pontiac engine that runs 119 mph over the 1/4 mile, makes about 550 hp. Never had to go over 0.040" on the IFR. Never touched the IBP. You say you had to enlarge the IBP to 0.128". Is that a misprint? The factory hole looks to be about 040-045. 0.128" would be bigger than the brass IBP insert. With great respect, I do not think enlarging the IBP would be the best way of stopping nozzle drip. ND is caused by to much air passing through the booster at idle. The best way to stop ND is to get air to the engine from somewhere else, such as sec blades or from the airhorn as on later 9000 TQs.
I get the feeling you are not really reading everything, just skimming at best.
ValerianMagnum
the little car that could
Read on internet yesterday....that a Tquad is very hard to adjust when you have a cam with higher specs than stock, the man who wrote this in the youtube video was an expert on tquad from chrysler, dont know if its true or not.
Rat Bastid
Dunamis Metron
Dartfreak75
Restore it, Dont part it!
I bought one on here a while back. Its a cool book. Im still learning how to tune on them its harder than yall make it sound lol
Oh no Dana,
I read it. Very carefully. It was a bit confusing with your wording, but I get it now. You talked about the 'IBP' in post #39 & I thought you were talking about the IBP restriction in the air horn. All of your adjustments make sense now.
I read it. Very carefully. It was a bit confusing with your wording, but I get it now. You talked about the 'IBP' in post #39 & I thought you were talking about the IBP restriction in the air horn. All of your adjustments make sense now.
This is one of the most constructive reads on here in a very long time. Thanks to all participants.
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