Thermoquad on 340 (plug photos)

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midnight340

midnight340

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So I rebuilt a '73 Industrial TQ with 1-1/2" primaries. Walker kit from O'Reilly's, choke pull-off from Mikes. Sitting on a TQ adapter on LD340. (Cc'd 9:1 compression 340, headers, Lunati solid lifter cam, MSD ignition, etc.)

I modified a set of rods to 67/52/42. Replaced .098 stock jets with Carter .101's. Drilled pump nozzles to .031" and put a slightly heavier, longer spring rod spring in. I am running no choke (tied open.) Rods are adjusted 4 turns up and air door is set at 2-1/2 turns. Idle mix at 13.5 on the A/F meter.

I get very good fuel/air #'s on the meter. Around 13.5 part throttle, 14 at cruise. WOT at 11-11.5 or so. So I should be rich enough for street driving, I'd think. But I am often told to go by the plugs, not the meter. I was running BPR8ES NGK's, and was advised here to try a hotter plug so switched to BPR6ES plugs. After 40 miles or so I'm getting no color to speak of anywhere. This includes a fair number of WOT pulls, some from a stop to over an eight mile.

Also, the base of the porcelain is pure white.

Here are the plugs:

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The question is, shouldn't I be getting more color than this? Or not enough miles to tell? Don't want to be running too lean, and have been watching the A/F meter, but wanted to check in with this. Comments?
 
midnight340 said:
The question is, shouldn't I be getting more color than this? Or not enough miles to tell? Don't want to be running too lean, and have been watching the A/F meter, but wanted to check in with this. Comments?
Click to expand...
Looks to lean to me. Should have some color by now.
 
The 440 carb should be big enough, and I've jetted up primaries, fattened secondaries by limiting the air door opening some from stock, added pre-load to the air door spring, drilled out the squirters, raised the rods to maximum recommended turns, and set the idle a bit rich. And the A/F #'s look fairly good.

Really has me scratching my head as to why the plugs look like it's lean!!!
 
It may be a skosh lean BUT, you have way too much timing on it. I'm assuming pump gas.

I had to look up that plug. Since the ding dongs at NGK can't seem to send me the correct catalog, I did a cross reference to Champion. Supposedly that plug crossed to a 9 Champion but the plug looks hotter than that to me. Hopefully, in a week or so my NGK catalog will be here and it will be easier than using a cross reference.

Ok, so it looks like you have too much total on it, and maybe a bit too much initial.

I'd deal with timing first. You should be able to see a fuel ring down at the bottom of the porcelain where it meets the shell. If you don't have a ring down there, add some main fuel.

The ground wire looks like it's getting a bit hot. It looks like the edges are getting round way too soon for the time/mileage you have on them. Those edges should still be sharp. Again, that says timing.

I'd work the timing first and then double check WOT. You need a fuel ring down there.

I can't see any cement boiling but it is a picture. So I'm not seeing anything that screams smoking lean.

Back the timing off and see what the plugs say. Then sneak back up on the timing.
 
Pretty sure the timing is at 22/34 which seems reasonable, but motors have a mind of their own!! I will check timing and back off some.
 
Might have an intake manifold leak. That will cause a lean condition too. Those tq's were notorius for being on the rich side to begin with. Just another thought. Seen that before on a 440 w 850 dbl pumper. Crappy metal gasket. Car seemed to run normal but always lean. Bought another carb thinking it was junk only to find that out later.
 
yellow rose said:
it looks like you have too much total on it, and maybe a bit too much initial.
Click to expand...

midnight340 said:
sure the timing is at 22/34 which seems reasonable
Click to expand...
Good ballpark start but now is time to get into further.
Measure the timing at various rpms from as slow rpm as you can get it, and write 'em down.
Then plot it out, or post and I will, 'cause I prefer graphs. :)
The reason is that 34* at 2000 rpm could be too much (especially if you will be using the vacuum advance), but 34* at 4000 rpm might be too little.

midnight340 said:
I get very good fuel/air #'s on the meter. Around 13.5 part throttle, 14 at cruise. WOT at 11-11.5 or so. So I should be rich enough for street driving, I'd think. But I am often told to go by the plugs, not the meter.
Click to expand...
I think both are useful. The meter's disadvantage is just an interpretation based on the left over oxygen. If the combustion changes, the resulting products can be different than assumed in the O2 - AFR relationship. Mark Whitener has pointed out that changing the timing can often change the AFR shown on a meter, and that's obviously not an actual change in the fuel air mix. Bottom line, shoot for best performance and note the AFR changes as performance improves or decreases.

In general,the fuel mixture at
idle should be somewhat rich.
off idle should slightly leaner
and with increasing load go leaner and leaner
approaching maximum load (wide open throttle) get rich
 
If it were I, a decrease of 2 degrees is where I’d start just to see what quick and easy could do. 22 initial is a lot.

PS, I think your doing a good job on this so far. Keep up the good work.
 
I installed an Autolite 63 plug in #4 (the only new plug on the bench.)

Backed off timing 2* to 20*/32* (total @3000+ where advance leveled off) and went for a drive. Some around town, a couple of WOT runs from a stop up through 2nd, the rest mostly in town but opportunities to get on it pretty good. Pulled the plug and took photos. (I'll add them in a new post.)
 
How do these look? Timing at 20/32...

Still no color, and no fuel ring at the base of the porcelain. A/F #'s very good on the meter. 15 miles of spirited driving, shouldn't I see something on the plug base or at base of porcelain?

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Ignition is all MSD, 6A box, their Ready-to Run distributor, Blaster 2 coil.

This test plug is an Autolite 63, supposed to be similar heat range to NGK BPR6ES that I’m running. (First Autolite I’d seen plated silver like the NGKs!)
 
Thanks for posting that. I had experimented with using Autolites due my perception that Champ quality had declined.
But the black coating made them hard to read. I'd give 'em a try again with the silver plate finish.

What are you using for a camara? Those are good shots for digital posting.
 
:DUsing my iPhone, zoomed in max amount. Had to take several each because it’s harder to hold steady that way...:)
 
midnight340 said:
Ignition is all MSD, 6A box, their Ready-to Run distributor, Blaster 2 coil.

This test plug is an Autolite 63, supposed to be similar heat range to NGK BPR6ES that I’m running. (First Autolite I’d seen plated silver like the NGKs!)
Click to expand...


Ok, now I can lower my panic a bit. Every plug manufacture uses a different coating on the plug and they all read a bit differently.


Now the color change on the ground wire and the heat in the shell make sense!!!

I have an Autolite book coming and hopefully it will give some data on what changes in heat will do to the shell coating.

You have plenty of ignition and it sounds like you have the tune up pretty damn close which is why there isn't much color on the upper porcelain and that's not a bad thing.

I say you are damn close, I just want to see a fuel ring down in the bottom of the plug. That WOT but it will still develop over time even if you aren't at WOT. WOT pulls will just make the ring show up sooner.

The ring should be .060-.080 wide, maybe .100 depending on what the engine wants.
 
Mattax said:
Thanks for posting that. I had experimented with using Autolites due my perception that Champ quality had declined.
But the black coating made them hard to read. I'd give 'em a try again with the silver plate finish.

What are you using for a camara? Those are good shots for digital posting.
Click to expand...

same here, changed to NGK mostly as they were easier to read, then picked up a couple of Autolites like this.
 
yellow rose said:
Ok, now I can lower my panic a bit. Every plug manufacture uses a different coating on the plug and they all read a bit differently.


Now the color change on the ground wire and the heat in the shell make sense!!!

I have an Autolite book coming and hopefully it will give some data on what changes in heat will do to the shell coating.

You have plenty of ignition and it sounds like you have the tune up pretty damn close which is why there isn't much color on the upper porcelain and that's not a bad thing.

I say you are damn close, I just want to see a fuel ring down in the bottom of the plug. That WOT but it will still develop over time even if you aren't at WOT. WOT pulls will just make the ring show up sooner.

The ring should be .060-.080 wide, maybe .100 depending on what the engine wants.
Click to expand...

I appreciate the reassurance!! Sounds like I just need to get some miles on the plugs and check again. It runs strong and clean, starts great.

One thing I really notice is that my A/F #s are MUCH more steady and consistent with the Thermoquad over the Edelbrock!!!
 
Long post, but... OK, so I was not getting any color on the porcelain and not much on the fuel ring even though the A/F #'s were pretty good. (This motor has always seemed to respond well to more fuel, more carb.)

So I decided to try the Thermoquad a while back. The first thing I noticed was how much more stable the A/F #'s were with the the TQ. And the motor liked the bigger secondaries (440 carb.) In steps I started adding more fuel to the mix. Went to .101 primary jets, drilled the pump nozzles to .031. Played with raising the tree (now at 2 turns up), and also messed with the secondary settings. Learning as I go.

(Only 9:1 but the motor has the iron X heads ported/polished by Bob Mullen in the old days. I added the .526/.546 lift solid Lunati to see if I could use the heads more.)

So, ...and here's the fun! I decided to follow old recommendations from "demonsizzler" that I found on FABO from when he was on here. Also checked the MP bible settings for "Bracket 340 with TQ and LD340 intake." And it really WOKE THIS MOTOR UP!! :D

I had removed the choke before (and it starts just fine for me.) I drilled the secondaries out to .149", kept the same .101" primaries. Drilled the pump nozzles to .038" and opened up the air door to 17/32" from the tower, and set it for very little drop when running. I checked and set the secondary throttle blades to 81* per the manual. and have the air door spring at 2-1/2 turns.

Now I FINALLY have a nice light grey around the base of the porcelain and light black on the fuel ring (flat part). Timing at 19/35. And the motor is finally sounding "happy" like never before. Pulls much harder, breaks loose when I shift to 2nd, etc. Really runs great, ...absolutely no bog or hesitation. The A/F hovers at 13.5 throughout pretty much all conditions. Amazingly consistent. Idle reads 14.5 and WOT is close to 11:1 but plugs look great. I don't know how I can add that much more fuel supply and still have about the same A/F #'s??? Anyway, I am a Thermoquad convert for sure!!!!!!!!!

Thats my report. I added all the info in case it is helpful for someone in the future.
 
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You added more fuel but not running rich? You must be burning all the fuel then.
Glad to hear the TQ is working out for you.
 
yellow rose said:
It may be a skosh lean BUT, you have way too much timing on it. I'm assuming pump gas.

I had to look up that plug. Since the ding dongs at NGK can't seem to send me the correct catalog, I did a cross reference to Champion. Supposedly that plug crossed to a 9 Champion but the plug looks hotter than that to me. Hopefully, in a week or so my NGK catalog will be here and it will be easier than using a cross reference.

Ok, so it looks like you have too much total on it, and maybe a bit too much initial.

I'd deal with timing first. You should be able to see a fuel ring down at the bottom of the porcelain where it meets the shell. If you don't have a ring down there, add some main fuel.

The ground wire looks like it's getting a bit hot. It looks like the edges are getting round way too soon for the time/mileage you have on them. Those edges should still be sharp. Again, that says timing.

I'd work the timing first and then double check WOT. You need a fuel ring down there.

I can't see any cement boiling but it is a picture. So I'm not seeing anything that screams smoking lean.

Back the timing off and see what the plugs say. Then sneak back up on the timing.
Click to expand...

Yellow Rose, I really appreciate your advice in the above post. I did play with timing first, took about 4* out of initial, and a couple out of total for now. Now that I'm getting a nice light grey at the base of the porcelain, I may add a couple of degrees back into the total and leave initial as is. Thanks again!!
 
rumblefish360 said:
You added more fuel but not running rich? You must be burning all the fuel then.
Glad to hear the TQ is working out for you.
Click to expand...

Yes, thought I was adding a lot with the .149 secondaries on top of the .101 primaries, and that the .038 nozzles would be too much for sure, but it just took it all with absolutely no sign of being too rich so far. I have done a number of drives and WOT runs, and it's just now looking good. :thumbsup:
 
midnight340 said:
So I decided to try the Thermoquad a while back. The first thing I noticed was how much more stable the was...
Click to expand...
The TQ is the Pinnacle of carburetors from Carter. It’s a very well-designed unit. Yes, a copy of the Quadra jet on a lot of fronts, but, it seems to work really well for a old archaic barbaric device. The double booster ring helps a lot.
And the motor liked the bigger secondaries (440 carb.)
Click to expand...
Errrr, that would be the primaries since all secondary sides are the same 2-1/2 inches. LOL
So, ...and here's the fun! I decided to follow old recommendations from "demonsizzler" that I found on FABO from when he was on here. Also checked the MP bible settings for "Bracket 340 with TQ and LD340 intake." And it really WOKE THIS MOTOR UP!! :D
Click to expand...
I used to have some chats with Demonsizzler before he retired and concentrated on his family. He’s a good fella.
Also, it is amazing how many people beat up the MP engines book as if it was written to screw you.
I had a 440 TQ up top my milled divider LD-340. Quite an impressive improvement for something so simple.
I had removed the choke before (and it starts just fine for me.) I drilled the secondaries out to .149", kept the same .101" primaries. Drilled the pump nozzles to .038" and opened up the air door to 17/32" from the tower, and set it for very little drop when running. I checked and set the secondary throttle blades to 81* per the manual. and have the air door spring at 2-1/2 turns.
Click to expand...
This amount of tinkering is required with carbs and more so when a stock crab is used. Getting the TQ to work great is just time and patients. For new guys, I should have suggested a lot book to keep track of things.
Anyway, I am a Thermoquad convert for sure!!!!!!!!!
Click to expand...
You and many others !!!!
When you get how they work, there a scream!
Like you mentioned, when that thing opens up and kicks in, HOLY MOLY that thing kicks hard!
Thats my report. I added all the info in case it is helpful for someone in the future.
Click to expand...
Keep everyone updated!
 
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