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drilling TQ throttle plates? ***UPDATE***

Posted By: kilroy

drilling TQ throttle plates? ***UPDATE*** - 06/25/12 02:31 AM

Ok Im running 440 at 10.1cr, eddy heads, single plane intake, PCV hooked, choke hooked, and a purple shaft ...661 cam. (250 something @50, .557 lift), fuel pressure reg set at 5.5psi. Initial timing set at 20* total limited at 38*.

Ok with the transition slots square I have a ridiculously low idle of about 500 and usually less, which it will do but not well when running around town. Its much happier when it idles at 750 to 800 rpm. The mixture screws are set at between 1.5 to 1.25 out. after that I dont notice any other gains.

To get the idle speed I would like the transition slots are severely over exposed.

I dont want anymore initial, and I have tried it up to 30* but really was unhappy with the overall results.

I have spent the last 2hrs doing google searches trying to figure out the best method to get about 300 more rpm at idle am I at the point of drilling?

Just for the record, no vacuum leaks and NO im not switching off my tq.
Posted By: Dan Halen

Re: drilling TQ throttle plates? - 06/25/12 02:35 AM

Do you have vacuum advance hooked up?

It worked for me in a similar situation with a TQ.
Posted By: DARTH V8Я

Re: drilling TQ throttle plates? - 06/25/12 02:37 AM

try adjusting the secondaries.
Posted By: kilroy

Re: drilling TQ throttle plates? - 06/25/12 02:40 AM

Quote:

try adjusting the secondaries.



which part, the stop, the amount they open, what?

I used to do this on a holley but never heard of it on a TQ.
Posted By: kilroy

Re: drilling TQ throttle plates? - 06/25/12 02:42 AM

Quote:

Do you have vacuum advance hooked up?

It worked for me in a similar situation with a TQ.



I have the vacuum hooked up, but tuned out so it only comes in about 13hg. I dont like it dictating my idle, I know there is a lot of controversy over this but this is how I like it.

Oh and I have 7-8" vacuum at idle.
Posted By: Exit1965

Re: drilling TQ throttle plates? - 06/25/12 02:42 AM

Before drilling, or trying a different carb (like the Demons which have the adjustable idle-eze baseplate), I would suggest trying a small 4 hole spacer.

I just put one on my car and was able to close the primary butterflies quite a bit and keep the same idle speed (also adjusted the mixture).

I got mine for 14 delivered from ebay, its a 1/2" phenolic.
Posted By: kilroy

Re: drilling TQ throttle plates? - 06/25/12 02:44 AM

Quote:

Before drilling, or trying a different carb (like the Demons which have the adjustable idle-eze baseplate), I would suggest trying a small 4 hole spacer.

I just put one on my car and was able to close the primary butterflies quite a bit and keep the same idle speed (also adjusted the mixture).

I got mine for 14 delivered from ebay, its a 1/2" phenolic.



I would like to but 71-74 chargers are a bear for hood clearance. Thats partially why I run the Street Dominator intake, it has really low carb height.
Posted By: ahy

Re: drilling TQ throttle plates? - 06/25/12 03:06 AM

With a big cam they benefit from the holes... I'd go ahead and drill it.
Posted By: DaytonaTurbo

Re: drilling TQ throttle plates? - 06/25/12 04:35 AM

Is this an auto trans or standard? If standard, go ahead and drill. If auto, what is your in park/neutral idle vs in gear idle?
Posted By: kilroy

Re: drilling TQ throttle plates? - 06/25/12 04:52 AM

Quote:

Is this an auto trans or standard? If standard, go ahead and drill. If auto, what is your in park/neutral idle vs in gear idle?



Standard. now.

Ive seen a lot of stuff on line from the extra pcv to create a vacuum leak, to drilling the base plate and installing a jet, which would all work but drilling and if I had to brazing the plates seems just as easy.

Just making sure Im not missing something here.
Posted By: DaytonaTurbo

Re: drilling TQ throttle plates? - 06/25/12 06:02 AM

Worst case scenario you replace your thermoquad base plate with a donor piece if you ever need to undo it and don't want to solder, braze or jb weld the holes shut.
Posted By: superbeedave

Re: drilling TQ throttle plates? - 06/25/12 04:10 PM

I have done alot of research on this particular case and here is what I have discovered with you only running 7-8 inches of vacuum your TQ now thinks it is on a much smaller engine. Carter and Edelbrock carbs. were designed to run with 12 inches on up. The reason your idle is so low is because your not pulling in enough air and gas into the intake thru your idle circuts. The idle air bleeds are too small and you would most likely have to go to bigger jets to compensate for the low vacuum that is not pulling enough fuel thru. Also depending on which springs you have in the TQ you will have to go to probably the 3 or four inch and not the orange which is rated at 5 inches which may cause your rods to lift up some at idle and then will be bypassing the idle circuts. So drilling the plates is the most likely thing to do but your not doing anything to the fuel thing just the air thing. Does any if this make sense? And by the way, I have a 94 Chrysler Power magazine that has an article on Big Cam Blues. If I could post this entire article I would, it is very helpfull!
Posted By: MY340

Re: drilling TQ throttle plates? - 06/25/12 04:37 PM

I drilled 1/16" holes I believe on my TQ with a MP508 cammed 340-4spd and also trimmed one coil off of the metering tree spring to make it lighter. 22 intial/38 total timing advance also with no vacuum advance hooked up. These mods and adjustments do work and normally help with larger cams on street cars.
Posted By: RapidRobert

Re: drilling TQ throttle plates? - 06/25/12 04:37 PM

Quote:

Quote:

try adjusting the secondaries.



which part, the stop, the amount they open, what?

I used to do this on a holley but never heard of it on a TQ.

The amt they're open. Not saying I know that's the fix but that's what he meant
Posted By: Diplomat360

Re: drilling TQ throttle plates? - 06/25/12 05:49 PM

Look up this thread of mine.

Much smaller cam (238/244 @ 0.050") but same problem never the less.

Car has done a lot of sitting around, due to other reasons, but I'm about to re-start the work on it. Will be up and running within the next week or so, and this particular issue is near & dear to my heart! LOL

I'll be watching your thread...
Posted By: kilroy

Re: drilling TQ throttle plates? - 06/26/12 12:16 AM

Quote:

I have done alot of research on this particular case and here is what I have discovered with you only running 7-8 inches of vacuum your TQ now thinks it is on a much smaller engine. Carter and Edelbrock carbs. were designed to run with 12 inches on up. The reason your idle is so low is because your not pulling in enough air and gas into the intake thru your idle circuts. The idle air bleeds are too small and you would most likely have to go to bigger jets to compensate for the low vacuum that is not pulling enough fuel thru. Also depending on which springs you have in the TQ you will have to go to probably the 3 or four inch and not the orange which is rated at 5 inches which may cause your rods to lift up some at idle and then will be bypassing the idle circuts. So drilling the plates is the most likely thing to do but your not doing anything to the fuel thing just the air thing. Does any if this make sense? And by the way, I have a 94 Chrysler Power magazine that has an article on Big Cam Blues. If I could post this entire article I would, it is very helpfull!



The tree is not the problem it is not bouncing at idle, but anyways I dont quite think this is right. Idle circuits are Idle circuits. You maybe right about them not pulling enough fuel or air but changing the rods, springs, or main jets will not effect the idle circuit because there is no air flow pulling fuel through the main circuits and boosters. Kinda like a holley's PV circuit is active during idle but since no fuel is being pulled through the boosters it doesn't change the idle circuit richness (but as soon when fuel starts flowing through the boosters all that changes.)

I can idle, I just need some MORE idle rpms without exposing more of the transfer slots.
Posted By: kilroy

Re: drilling TQ throttle plates? - 06/26/12 12:26 AM

Quote:

Look up this thread of mine.

Much smaller cam (238/244 @ 0.050") but same problem never the less.

Car has done a lot of sitting around, due to other reasons, but I'm about to re-start the work on it. Will be up and running within the next week or so, and this particular issue is near & dear to my heart! LOL

I'll be watching your thread...



I actually saw your post when searching, though its surprisingly hard to find! Yours is a good post. Later tonight if no one comes up with a good answer ill drillem see how it idles.
Posted By: Diplomat360

Re: drilling TQ throttle plates? - 06/26/12 04:16 AM

The other option to consider would be to drill out the normal air by-pass passages even further (the ones I showed circled in RED in my photos) and then enlrage the passege in the base plate that actually feeds air into the motor as it by-passes the throttle blades.

Since I have no access to any type of drilling equipment (and boy, you have to be super careful and precise there, I'm thinking a machinist type of a job) I simply couldn't try this.

The additional problem, certainly in my setup, is the fact that I am running an open plenum spreadbore-to-squarebore adapter. Therefore, the signal, as little as there is of one with the bigger cam is bled off even further by the opposite bank. I am currently on a hunt for either a 4-hole spread-to-square bore adapter, or a Canton Racing 85-254 spacer which should preserve some of the signal. Either way, it's a crap-shoot...
Posted By: kilroy

Re: drilling TQ throttle plates? - 06/26/12 05:20 AM

Ok boys here we are. I didnt want to drill the air bleed by pass in the base plate because I wanted to be able to put the carb back to normal so I did drill the throttle blades.

I started at 1/16 which didnt do boo.

I moved up to 1/8 because when I unplugged the pcv hose and cranked out the idle mixture screws it responded with more idle speed.

What I ended up with was 9/64 holes and somewhere between 2.5 and 3.25 turns on the idle mixture with an idle of 850rpm. I also have less than .035 (give or take, its hard to hold a carb upside down and compare with a feeler gauge) of transfer slot exposed, just barely over square. The car seem to be happy, so am I.

I will take it for a long drive later this week and update more.

Again my original was 1.5 turns on mixture screw at 850rpm but with over half of the transfer slots exposed.

Im sure I could drill some tubes, but I think essentially I am doing the same thing only not messing with the other circuits or transition into those circuits by not drilling out the bleeds on the low and high speed.

No matter how you look at it, it takes a certain amount of air+fuel to equal speed.
Posted By: Dave Watt

Re: drilling TQ throttle plates? - 06/26/12 04:58 PM

I'll be curious to hear your feedback on how the part throttle cruise is when driving down the road. It may need more primary jet or, the metering rod tree may need adjusted to compensate for the additional air being brought in by the primary throttle plate holes you drilled.
Posted By: Diplomat360

Re: drilling TQ throttle plates? - 06/26/12 05:49 PM

Hmm...good to know what sizing worked for you. I haven't gone quite that big...was a little worried.

I wish there was a way to run a channel into to secondaries base plate. Sort of a controlled air leak, say, adjustable with a air-bleed type jet. The other approach would be to crack the secondary throttle plates just a tiny wee amount to let some air in, but not initiate any of the secondary fuel system....easy to say, quite a bit more difficult to actually implement.
Posted By: Rapid340

Re: drilling TQ throttle plates? - 06/26/12 06:24 PM

I played around with this problem in the past on a stroker motor with a bigger cam.

1) Drilling throttle plates may lead to booster fuel dribble.

2) Cracking open secondaries could be difficult for a number of reasons but mainly because they are so big and it would need to be done almost to perfection.

What I did was take a tee off of the PCV hose and used different orifice sizes, it seemed to work well but I did not mess with it very long. You would want to have this extra orifice take in filtered air. I tried many orifice sizes and dont remeber what I ended up with but it was not small, (I think around 3/16 inch) You would want to use a wideband A/F device to iron out your system.

Posted By: kilroy

Re: drilling TQ throttle plates? - 06/27/12 01:13 AM

Quote:

I'll be curious to hear your feedback on how the part throttle cruise is when driving down the road. It may need more primary jet or, the metering rod tree may need adjusted to compensate for the additional air being brought in by the primary throttle plate holes you drilled.



Ive already had to compensate for the extra air by opening the idle mixture screws by 1 to 1.5 turns (final tune is still out)

But I agree that the amount of fuel will probably need to be adjusted BUT I was think the opposite. More like since there is more fuel being supplied by the idle system that the rest of they system may need leaned down some, I was think by the metering rod tree. But I will definitely remember your suggestions and try them also.
Posted By: kilroy

Re: drilling TQ throttle plates? - 06/27/12 01:17 AM

Quote:

I played around with this problem in the past on a stroker motor with a bigger cam.

1) Drilling throttle plates may lead to booster fuel dribble.

2) Cracking open secondaries could be difficult for a number of reasons but mainly because they are so big and it would need to be done almost to perfection.

What I did was take a tee off of the PCV hose and used different orifice sizes, it seemed to work well but I did not mess with it very long. You would want to have this extra orifice take in filtered air. I tried many orifice sizes and dont remeber what I ended up with but it was not small, (I think around 3/16 inch) You would want to use a wideband A/F device to iron out your system.





I couldnt figure out how to crack the secondaries as they seem to come to a rest on the base plate as a stop

I thought about drilling the secondaries to counter act the possible velocity on the booster causing dribble as you suggested but what worried me, along with cracking the secondaries, was the the timing of the air velocity/ fuel/ timed vacuum open created by air bleed in the plate.
Posted By: kilroy

Re: drilling TQ throttle plates? - 06/27/12 01:22 AM

Quote:

Hmm...good to know what sizing worked for you. I haven't gone quite that big...was a little worried.

I wish there was a way to run a channel into to secondaries base plate. Sort of a controlled air leak, say, adjustable with a air-bleed type jet. The other approach would be to crack the secondary throttle plates just a tiny wee amount to let some air in, but not initiate any of the secondary fuel system....easy to say, quite a bit more difficult to actually implement.



The intriguing thing I though about doing, and I read this somewhere so I cant take any credit, was to drill below the air cleaner stud through the base plate and use some sort of adjustable orifice (jet or valve or something) this would exclude the secondary air systems and the possibility of booster drip also.

I wasnt even sure how a TQ would respond to drilling the blades so I didnt want to screw up something I could repair easy.

I think I will look more into this now.
Posted By: quickd100

Re: drilling TQ throttle plates? - 06/27/12 03:17 AM

Not trying to start any arguements but I open up the low speed jet about .003 and adjust the initial timing to cure that problem. I've run cams at 274 to 292@.050 duration with thermoquads using these fixes. I DON'T drill the butterflys. Dave
Posted By: kilroy

Re: drilling TQ throttle plates? - 06/27/12 03:43 AM

Quote:

Not trying to start any arguements but I open up the low speed jet about .003 and adjust the initial timing to cure that problem. I've run cams at 274 to [Email]292@.050[/Email] duration with thermoquads using these fixes. I DON'T drill the butterflys. Dave



On that 605? or smaller motors? Just the bleed on top or the tube? Ive tried a some to a whole lot of intial and could not get what I was looking for so I settled on 19* intial. How about your transfer slot, were they in the square to normal range? Thanks for input.
Posted By: DARTH V8Я

Re: drilling TQ throttle plates? - 06/27/12 03:52 AM

First theres a tang for the secondary stop you can bend to adjust the amount the secondaries stay open. Its in the rebuild book. Theres also a set screw on top of the tree you can adjust.. I like to do that instead of cutting the spring. Thats just butcher work when you cut the spring. I understand there might be a vacuume issue but unless your idle vac is below 10Hg.. I wouldn't cut it. Theres a couple air bleeds under the tin covers one can also drill out. Bunch of things you can do to have a crisp, bog free Thermobog. As a last resort I'd drill the throttle plates, but the above usually gets everything running peachy. Oh.. and TQ's LOVE lots of initial timing.
Posted By: kilroy

Re: drilling TQ throttle plates? - 06/27/12 11:48 PM

Quote:

First theres a tang for the secondary stop you can bend to adjust the amount the secondaries stay open. Its in the rebuild book. Theres also a set screw on top of the tree you can adjust.. I like to do that instead of cutting the spring. Thats just butcher work when you cut the spring. I understand there might be a vacuume issue but unless your idle vac is below 10Hg.. I wouldn't cut it. Theres a couple air bleeds under the tin covers one can also drill out. Bunch of things you can do to have a crisp, bog free Thermobog. As a last resort I'd drill the throttle plates, but the above usually gets everything running peachy. Oh.. and TQ's LOVE lots of initial timing.




Im pretty sure this is the part your talking about, but this is just for wide open position, there is a roll pin that runs through the shaft thats part of the stop that hits the base plate, unless Im mistaken.

Its really hot here today and Im busy with work so Ill update this weekend about the drive and tune.

Attached picture 7268063-fig2.jpg
Posted By: kilroy

Re: drilling TQ throttle plates? ***UPDATE*** - 07/02/12 12:30 AM

Ok, did some serious driving today. Im not advocating drilling blades for everyone, but as a last ditch, this worked excellent for me.

Settled on 9/64 holes drilled in both front plates on the away side of the throttle shaft from the transfer slots.

The idle is outstanding. 850rpms just over square on the transfer slots and excellent off idle movement no stumble bumble of farts while driving at any engine speed or driving attitudes and Im a stickler for stuff running without a hitch. After hot driving (its 95* and high high humidity) I was able to lean the mixture screws down to 2.5 turns, maybe able to get another 1/8 to 1/4 turn after driving some more. I have notice I think that overall Im slightly more rich (Im attributing this to the extra turn on the mixture screw) but I really dont know because I dont have an A/F meter (yet). Could just be the heat. I plan on leaning the system by a 1/4 turn on the metering rod tree and see what happens. I will let yall know more in a day or so.

Posted By: Rug_Trucker

Re: drilling TQ throttle plates? - 07/02/12 01:53 AM

Where are the air bleeds on a TQ?

Great thread!
Posted By: kilroy

Re: drilling TQ throttle plates? - 07/02/12 01:56 AM

Quote:

Where are the air bleeds on a TQ?

Great thread!



The bleeds are under the little removable plates beside the meter rods on top of the top plate.
Posted By: kilroy

Re: drilling TQ throttle plates? - 07/02/12 03:24 AM

I also forgot to mention on my earlier that I have looked at my carb during idle and have seen no booster puller over since drilling my blades.
Posted By: 440newport

Re: drilling TQ throttle plates? - 07/02/12 03:50 PM

I might need to this with mine too. I'm running nearly 20* of initial timing, but it just won't idle high enough with a "square" slot exposed.
I have to go an extra 5 or so turns on the idle screw.
It runs and drives fine, but I can tell it's a little rich on the idle.
Posted By: kilroy

Re: drilling TQ throttle plates? - 08/02/12 03:59 AM

Just thought I d update some more. Im having no drivability issues with my car after doing this. Ive leaned my carb up with the metering tree as I said a little bit and I need to mess with my vacuum adv just a bit but my carb is great idles smells cleaner now that that Im off the transfer slots so much. NO intermittent drivability issue, or top end issues. Next step getting a/f meter to get killer tune on.

Again this is not fix all, it was just my last resort to get the idle slots down to "correct" after having a very aggressive tune on the distributor and a "big" @.050 street cam.
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