Running a thermoquad on an 88 ELB conversion?

[NoCar340]

Vacuum advance does not do anything at idle. It's for part-throttle acceleration and cruise only. Under full throttle, you have mechanical advance alone.

The way you were describing where you were getting detonation, you should probably replace one of the light springs in the new distributor with the lighter-of-the-two from a stock distributor. That would slow down your rate of advance. As far as how much advance you get, that's locked into the way the distributor's built. The only way to change it is to modify the slots for the flyweights; shorten for less advance and lengthen for more. Shortening requires welding. You can also adjust the rate at which the vacuum advance pulls in by adjusting it through the vacuum port with an allen wrench; again you can't change the amount but you can change the rate. However, there were a multitude of different canisters made with a different amount of pull. The amount (in degrees of advance) is stamped right on the arm on all the factory units.

Have you tried adjusting the secondary air doors yet? It sounds like they're opening too fast. Since there's no accelerator pump on the secondary side, if you stand on it and they drop open too quickly there's not nearly enough fuel for the added air. If they're loose enough, you'll get a port stall in the carb where it will just lay down and stay down until you release the pedal. The vacuum signal goes to nil and there's no other means to pull fuel past the metering rods.

 

[8v-of-fury]

Interesting. Ok, well if you slowly rise through the rpm to where it doesn't bog (say down hill) and then you can get on it, and the secondaries can even come open and power comes on. The bog is not a secondary issue, (yet, it still may be later.. lol) it is happening with minimal throttle pedal. Past 1/4 pedal or so you get the bogging, which as you say it just kind of dies off and wont regain unless you close the throttle plates. I can watch the metering rods raise up in the carb and that is when it bogs.

So question here is, Why did it run great yesterday with GREAT off idle power, and GREAT mid throttle power, and wooooAAAAAAAHHHHHHHH secondary coming on power? Then today.. barely rev up in park, let alone get the car off the line..

 

[8v-of-fury]

This is my TQ in case you are wondering of the setup.

"9046" - 75 400 AutoTrans Federal IE Chrysler# 3830554
Primary 4099
Secondary 5143
Rods 1965
primary plates 1-1/2"

 

[NoCar340]

It definitely sounds like a vacuum leak if it's not involving the secondaries. It sounds like it's getting too much air too quickly. It's definitely not an overfueling problem. It almost never is with a ThermoQuad. In fact, I can't think of one single example in my experience where that was the problem.

 

[8v-of-fury]

Ok, thank-you. I will investigate vacuum leaks. Hope it isn't that the damn intake gaskets didn't seal properly.. lol That'd be a lot of extra work! I used like the whole tube of brush tack and rtv that came with it to seal the water and intake ports.. Maybe the intake bolts need a recheck on their torque values.

With you saying this, it makes sense! Too much air flooding the intake manifold, vacuum pressure would drop off and the metering rods would shoot up with their spring pressure because of no more vacuum holding them down.. Ahah! I have been going about this all wrong then. I was definitely thinking it was fueling.

 

[Monkeyed]

Ok, thank-you. I will investigate vacuum leaks. Hope it isn't that the damn intake gaskets didn't seal properly.. lol That'd be a lot of extra work! I used like the whole tube of brush tack and rtv that came with it to seal the water and intake ports..

You did know better than to use the RTV anywhere near the intake ports, right?

http://home.teleport.com/~cosa/vap/tech/inmanifold.htm

 

[8v-of-fury]

Yes! That is what the brush on tack was for

RTV was for the coolant ports front and back.

 

[NoCar340]

Here's a handy tip for virtually every person on the board: You know those neat-o end seals they provide with new intake gaskets? Throw them out, every time--especially if you're using an unknown intake (meaning you have no idea where it's been or what's been done to it). The end seals can actually hold the intake up too high and cause vacuum leaks from the lifter valley. Run an 1/8" bead of black silicone from intake gasket to intake gasket, both front and back, with an extra glob at the head-to-block junction point. Let it form a skin before you install the intake.

If you are having your small-block heads milled for increased compression, make sure the machinist removes .009" off the intake faces of the heads for every .010" off the deck surfaces no matter what the machinist tells you. This is a critical step in making your intake fit correctly, and if not done you will have a vacuum leak from under the intake. Guaranteed. The spec for a big block is even more extreme: .0123" off the intake face for every .010" off the deck surface. It's a lesson I learned long ago, and despite my warnings a friend just went through the "mystery vacuum leak" syndrome on his 360. Yep, it was sucking from the valley. In his case he milled the intake, but it was a somewhat special case. Always mill the intake faces of the heads, not the intake.

 

[8v-of-fury]

Hey now! That is a super great tip!

Thinking on what you are saying, then it would be running off of the Crank Case air then?? When I have the PCV valve hose to the carb disconnected and plugged at the carb. While having both valve covers with open ports, the PCV and the vapor canister dealio. There is definitely a good amount of blow-by coming out from the CCV's. Yes this is not an indicator of whether or not I have a vacuum leak.. I know. But I would think if there was a vacuum leak at the intake ports pulling from the galley then there would be minimal to no blow-by coming from the CCV's. Now this is not a fact, I know. I am not claiming you wrong and me right, text does come across weird.. so just so we are on the same page . It is an idea.

It doesn't SOUND like it has a vacuum leak, but the lean bog would point to non-metered air causing it..

I did use the cork end gaskets.. Dangit. Shoulda just done RTV. DANGIT. HMM the intake didn't look like it was milled. Also the RTV that I used to seal the water ports is all squished out the top between intake and the head.. So I feel like it has clamped down the proper amount. I know for a fact these heads have NEVER been off the engine. My Poppy (grandpa) bought this beauty new in 1988. The intake though.. I coned the carb opening with paper so my ether sprays wouldn't get sucked in.. and I sprayed around the various vacuum spots externally, no sort of rev ups. So that is good I guess.

Any thing else it may be, besides a vacuum leak??

 

[NoCar340]

The blowby out the valve covers would be either piston rings (most likely) or head gaskets. The intake wouldn't allow for that, really... although if the exhaust crossover wasn't sealed, I guess it could push pressure into the crankcase through that leak.

The bitch of the intake leaking from the valley side is that you'll never hear it. The top half of the gasket will be clamped just fine, and if all is done well you'll never know short of pulling the intake from the engine. The problem looks like this when you find it:

It's really hard to tell if an intake's been milled, because, well, they're milled when they're new... and a lot of guys will do it the wrong way, milling the intake rather than the intake side of the head, leaving them with a "matched set" that will only work with each other. That's what my friend did, but again--extenuating circumstances on a purpose-built engine. Plus, it's a factory intake.

Short of that it's gotta be something obvious. Do your testing with everything connected to the intake or carb: power brakes, PCV (in the valve cover), distributor vacuum, HVAC vacuum, etc. Make damned sure there's no open port anywhere (like the big bastard at the back of the carb). The only other thing that comes to mind is lack of fuel. Pump working well? Float levels set correctly? No obstructions in the metering circuits? Though it shouldn't matter once you open the throttle, where are your idle mixture screws set? If it's happening at such light throttle inputs obviously the secondaries aren't involved.

Here's a really obvious question and I don't mean to insult, but: is the choke working correctly?

 

[8v-of-fury]

Hmm, good pic. Great describing aid on what you mean when it doesn't clamp down right. What I meant by doesn't sound like a vacuum leak is the way the engine is running, it is not stumbling or chugging at idle (like is normally seen with a vacuum leak). Pulling off any of the lines or anything, manually inducing a real verified vacuum leak, it runs rather rough and you can tell it is not right.

Accel pump has a good shot, fuel pump seems to be just fine. IF it runs right and you can actually get the car off the line without lean bogging and a stall.. it has no problem getting up in the the higher RPM's and then idling thereafter. So I do not think it is a fuel pump issue, i guess it could be accel pump not giving enough of a shot??

I soaked and blew out every passage with shop air when i had it apart. Floats set to what the rebuild kit said, (29/32" comes to mind). Idle screws have been everywhere from 3 full turns out, to all the way turned in. The curb screw is not set to high, because the idle screws DEFINITELY are acting properly with moving the idle up or down with the smallest screw movement.

Definitely not a secondary bog, but there is a small one up there too.. but that is another day. Can't get the secondaries to open if you can't get the car off the line.. lol Likely the air door needs a small touch of love.

Uhm, i do not have the choke wired up yet! But it does not seem to affect anything. Manually holding the choke at different spots and using the throttle under the hood. Also at full operating temps with the choke wide open, it doesn't change anything.

Oh here's a thought, would the coolant ports seal if the intake was being held up? If not the coolant would have dropped and the oil risen yes?

 

[8v-of-fury]

Ok another thing.. Saturday night.. I swear the car was PERFECT.. !! PERFECT. The smallest bog when the secondaries opened (which is the coolest sound I've heard an engine make BTW). It was HOT off the line and didn't even need to downshift to pull hills, only a little more throttle needed. I was driving around tuning at various parking lot lights shining down.. Kept getting better and better, until the last tweak.. i only got like 1 km before it stalled on me and wouldn't restart.

With it running great tho, I drove around for had to be an hour. Jack rabbit starts from not moving to heavy throttle no problem. Stopped a bunch and shut it down, started no problem. I even raced a lifted duramax down the onramp and up the highway a bit (I was ahead like no problem) and I was doing 80mph in no time.

 

[NoCar340]

The coolant/oil situation was a possibility I mentioned to my friend. He dropped a little oil out of the pan (about half a quart, I think) but there was no coolant at the bottom. So it's definitely possible. However, if you used RTV around the coolant ports you probably eliminated that. You'll notice in the picture that he had not done that, but still no coolant got in the oil.

You've got to get the choke working correctly, because the car's going to do exactly what you're describing when it's not yet up to full operating temperature. I'm guessing you've gotten it fully warm, but before you start trying to figure it out it's got to be 100% to temp.

 

[8v-of-fury]

I figured the choke would cause it to be an issue when not warm, but didn't figure the issue would persist after fully at op temps. I have felt the 195F thermostat cycle (that all of the sudden burning hot air coming from the rad fan instead of cool air,, lol) so I am sure it was still causing this with choke fully open and at operating temps.

I will try holding the choke in the on, but pulled off position (like 1/2 inch i think?) and see if that changes anything.

 

[NoCar340]

If the choke is fully open at temp, then you're golden. However, once that's the case try the oldest vacuum-leak test in the book: slowly lower your hand from about the level of the top of the carb stud down over the choke tower. See what happens to the RPM. If it rises, you've got a vacuum leak.

 

[8v-of-fury]

The end goal is to cup my hand around the choke tower?

 

[NoCar340]

Pretty much. Hold your hand flat, palm down, and just slowly lower it onto the choke tower. You want to do this with the engine at temp, of course, and the choke wide open and fixed in position. At no point should the RPM increase. When your hand is flat on the choke tower, the engine should stall.

 

[Monkeyed]

brainstorming

I almost wonder if there could be a piece of crud in the carb somewhere, randomly plugging something up, or if one of the needles might be sticking.

 

[8v-of-fury]

Ok, so today I started the car and let it fast idle up to temp. In the meantime, I cut the grass. LOL Fully up to temps, choke wide open, idling in park. Lowered my hand slowly over the choke tower it never dropped or rose up. Until I fully cupped it, my hand got a splash of gas on it and the engine stalled. HOWEVER! today was the first day I put an air cleaner on it as I didn't have one that would fit. As you tightened down the stud, rpms jumped up considerably. To tune those rpm's to an acceptable running rpm the engine would stall out when you took the breather off.. wth. It didn't do it with my hand, never rose up at all.

Edelbrock cleaner from my Cougar, fit on there. Filter is probably not the best, but i can't see it being THAT RESTRICTIVE.

Couple different shots in front of cylinder #2 where the intake meets the head and block.. looks like I have a good seal there?

 

[NoCar340]

The behavior with the air cleaner still indicates a vacuum leak. Normally, installing an air cleaner will drop the idle a little if at all. Air cleaners are more restrictive than you might think. For instance, look at this Big Honkin' Air Filter's* dimensions, then look at the CFM it moves... or, rather, doesn't move.

How the intake-to-head junction looks at the ends tells you nothing about how it looks in the middle. You did follow the correct torquing sequence and specifications, right? Even if you did, that won't make up for milling or warpage. If you absolutely know 100% it's not leaking topside, it's sucking from down under.

* Yes, it's actually sold under the name Big Honkin' Air Filter. Google it... :icon_biggrin: