Offy tri-power stalls when in gear

thegreyghost

Well-known member
So I have a brand new to me 66 coupe with a 200 ci / offy tri carb setup (holley 1940's I think) and a C4. I know the engine had the cam changed, but I'm unsure what's in it. I think it may be from Clifford. Right now it will start with a little effort and run, but the instant I put it in gear the engine dies.

Here's what I've been able to check so far:

manifold vacuum is about 14 at idle - steady.
timing - who knows? When i put the light on it the mark is about an inch above the scale on the engine. Adjusting it lowers my manifold vacuum and makes the engine run worse, so I think it's close.
I "looked" all over the engine with carb cleaner for a leak and could not find one. also check the modulator on the C4 and no leaks there.

The distributor does not have vacuum advance and the ported vacuum from the carbs are plugged and leak free.

I didn't put a tach on it yet, but the idle sounds plenty fast and appears to be running only off the center carb. The screws on the two outer carbs are all the way out. I've tried turning them in a little and other than a faster idle, it didn't change anything.

Not sure where I should be looking next.

Sorry for the lack of info on the engine itself, but right now it's all I have to go on.

Any help appreciated.
 
WELCOME . anotherTri-Power, sounds like a nice ride, hope for some pics'. Stalling when put in gear is a sign of something basically wrong -typically simple but not obvious...

The Offy Tri-power will provide many hours of entertainment for a final performance tuning. For a start with an unfamiliar setup you may want to block outer carbs and try to tune for center carb only - first. You could then also swap inner-outer carbs for verifying outers' individual performance before trying to make three work right together.

... at idle typical Tri-Power setup closes off outer 2 carbs as much as possible at throttle plates so their idle-air adjust is whacky, usually shut or feathered for some 'leakage mix' from throttle shafts etc., shouldn't affect idle shift to gear unless A/F or ignition or combination is whacky.




have (three times the) fun
 
pic R great, frm pass side would B nice.

"...appears to be running only off the center carb..."
They usually run off center as 'main' or 'master' to other 2. Others come in as throttle is depressed. Look to linkage 4 ideas.
Wondering if that ctr carb needs a dash pot - 'choke pull of'- due to the C4.

Like anything new to U - trust nothing, let ear, fingers, smell, sound, sight tell U where to start 1st. Get positive ID on ALL prts/components. I''m thinkin 'slipped' HB/dampner, incorrectly rebuilt carbs/not matched to dizzy, etc as worse case scenerios AND work backwards on every system (not just motor) from there. This way driving safety and budget can coordinate. Good on ya mate! for goin to the carbs 1st as well, gotta run 1st. Then stop, steer, inspection, etc...

"...Not sure where I should be looking next. ..."
get the ctr 1 runnin right (pretend it's the only 1 at 1st, now - thru out the whole motor ie HB, ignition, etc). Then add the others. The 5 - 650 RPMs idle is good but needs higher (not sure exact #s) for the C4.

Congrats on new purchase. W E L C O M E !!! to the site, good choice on 1st stop~
 
Howdy greyghost:

First get a handle on your ignition timing and a correct mark. Verify that the timing mark on the damper is correct at top dead center and go from there. Since your ignition doesn't have vacuum advance you will likely want more initial advance, in the neighborhood of 15 degrees.

Next make sure that the outer carbs are completely closed for tuning. I'm assuming that the choke butterflys are gone and that the throttle shafts are tight. Get the center carb dialed in and then go from there. Please confirm that the carbs are Holley 1940s.

Good luck and keep us posted on your progress.

Adios, David
 
Wow. Lots of great responses and questions.

Let me follow 1st by saying I had some success this morning with it. I basically started over and got the carb cleaner back out. Once again, nothing definitive.

I fatten up the mixture by one turn on all carbs and instantly notices a big difference. Turned the idle down on the center carb to where it sounded about right, cracked the idle screw on the outer two and it appears to run fine in gear now - Awesome!

I still only have about 12" of manifold vacuum at idle, but the engine itself seems much closer to where it should be.

The center carb does have the choke pull off connected.

Not the best pic, but here's one.
SiRdPoNl.jpg
 
chad":7n44bf01 said:
pic R great, frm pass side would B nice.

"...appears to be running only off the center carb..."
They usually run off center as 'main' or 'master' to other 2. Others come in as throttle is depressed. Look to linkage 4 ideas.
Wondering if that ctr carb needs a dash pot - 'choke pull of'- due to the C4.

Like anything new to U - trust nothing, let ear, fingers, smell, sound, sight tell U where to start 1st. Get positive ID on ALL prts/components. I''m thinkin 'slipped' HB/dampner, incorrectly rebuilt carbs/not matched to dizzy, etc as worse case scenerios AND work backwards on every system (not just motor) from there. This way driving safety and budget can coordinate. Good on ya mate! for goin to the carbs 1st as well, gotta run 1st. Then stop, steer, inspection, etc...

"...Not sure where I should be looking next. ..."
get the ctr 1 runnin right (pretend it's the only 1 at 1st, now - thru out the whole motor ie HB, ignition, etc). Then add the others. The 5 - 650 RPMs idle is good but needs higher (not sure exact #s) for the C4.

Congrats on new purchase. W E L C O M E !!! to the site, good choice on 1st stop~

Pic:
izSWu7Lh.jpg
 
That "fuel rail" is a lill in the way so my antique eyes can't C much...
Do U know what dizzy it has? Looks like the hard line is back for vac signal.
Still stall when 1st moving into gear?

Like the fellas say - just wrk the ctr carb (U will do best 2 4get the 2 on the ends. Block off if possible). Get the middle perfect 1st. Wrk the HB or replace for a good 'base'. Now it seems ur off & therefore only usin a vac. gauge. Need everything U can on trips.

(later we'll ask abt the linkage to throttle connection but just assure it all operates that ONE CENTER carb correctly for now). Nuttin getting hung up, nuttin slippin, TV or kick down cable OK...
This is Y we say 'block off others' as this allows U 2 take them out of the equation but not hafta tear dwn/set up link again if they're right 4 the 'extras' now. Two ways to set the link. up - simultaneous or ctr use than outters kick in. But that's for later when U got this 1 ctr runnin. Focus on that 4 now.
Keep talkin...
 
chad":1hlroosf said:
That "fuel rail" is a lill in the way so my antique eyes can't C much...
Do U know what dizzy it has? Looks like the hard line is back for vac signal.
Still stall when 1st moving into gear?

Like the fellas say - just wrk the ctr carb (U will do best 2 4get the 2 on the ends. Block off if possible). Get the middle perfect 1st. Wrk the HB or replace for a good 'base'. Now it seems ur off & therefore only usin a vac. gauge. Need everything U can on trips.

(later we'll ask abt the linkage to throttle connection but just assure it all operates that ONE CENTER carb correctly for now). Nuttin getting hung up, nuttin slippin, TV or kick down cable OK...
This is Y we say 'block off others' as this allows U 2 take them out of the equation but not hafta tear dwn/set up link again if they're right 4 the 'extras' now. Two ways to set the link. up - simultaneous or ctr use than outters kick in. But that's for later when U got this 1 ctr runnin. Focus on that 4 now.
Keep talkin...


Yeh, I'm not a big fan of the rail, but one thing at a time...
The dizzy is a dual point mallory - no vacuum advance fed by a big fat accel coil.
The hard vac line from the manifold goes back to the modulator on the C4. Only vac line i can find on the engine - nothing coming off ported.
Once warmed up, it stays running in gear - now. adjusting the mixture has apparently helped this....I hope. Still kinda cold hearted until it's warmed up.

I noticed that the front carb is hanging up on high idle. I just kick it off and forget about it for now.
From what i can tell, they are set up to be progressive. The center carb comes on first, then is followed by the other two. It looks to be correct according to the literature from Offy. At wide open throttle, all are open fully.

Thanks so much for the help. I'm slowly learning my way around this thing....
 
The carbs are indeed the Holley 1940 type I see that the center carb has a choke unit with a line coming off it (hot air stove line). How is this line hooked up down below? Did you verify that the choke is closed when cold and opened when warmed up? The ignistion system is a good one all you need to do is check that it has the proper point Dwel settings, verify the timing mark on the Dampner is correct, and then set the base timing at 12 to 14 degrees BTDC. Good luck. (y) :nod:
 
bubba22349":38g868qt said:
The carbs are indeed the Holley 1940 type I see that the center carb has a choke unit with a line coming off it (hot air stove line). How is this line hooked up down below? Did you verify that the choke is closed when cold and opened when warmed up? The ignistion system is a good one all you need to do is check that it has the proper point Dwel settings, verify the timing mark on the Dampner is correct, and then set the base timing at 12 to 14 degrees BTDC. Good luck. (y) :nod:

Actually, the line isn't hooked to anything. It just hangs there. There's a small open tube that's welded to the headers, but into them that I think it's supposed to be in.

I have verified that the choke or chokes are one when cold and open when warm.

I haven't worked much on the ignition yet. I need to find TDC on #1 and see where the damper is. I have moved the timing so that the mark was around 14 BTDC and it ran like crap and the vacuum dropped so for now I put it back where it was.

Thanks for the help.
 
Hi, your front carb (and probably the rear carb) are set up as progressive opening. You can see the stop on the carb linkage. Make sure the front and rear carbs open and close at the same time.
You can adjust them to come in earlier or later, but probably leave them alone for now. If you play with them I would Mark the linkage with tape so you can put it back of you don't like the change.
I think the outer carbs should be adjusted fully closed, and idle only on the middle carb.
Do the idle mixture screws to get the best idle. It sounds like you figure that out.
The distributor timing should be advanced more than factory specs. Unless you have a dial advance timing light all you will see is that the mark is over the timing tab. That is good. When you advance the timing the mark should go higher, it should also go higher, up under the water pump when you give it some gas. Advance is counter clockwise.
Anyway, don't be afraid to advance the timing as long as it doesn't ping when you drive. And after you get the timing set adjust the idle.
The idle RPM will depend on the cam, but hopefully you can get it @ 800 RPM
Good luck
 
B RON CO":2m8lkgta said:
Hi, your front carb (and probably the rear carb) are set up as progressive opening. You can see the stop on the carb linkage. Make sure the front and rear carbs open and close at the same time.
You can adjust them to come in earlier or later, but probably leave them alone for now. If you play with them I would Mark the linkage with tape so you can put it back of you don't like the change.
I think the outer carbs should be adjusted fully closed, and idle only on the middle carb.
Do the idle mixture screws to get the best idle. It sounds like you figure that out.
The distributor timing should be advanced more than factory specs. Unless you have a dial advance timing light all you will see is that the mark is over the timing tab. That is good. When you advance the timing the mark should go higher, it should also go higher, up under the water pump when you give it some gas. Advance is counter clockwise.
Anyway, don't be afraid to advance the timing as long as it doesn't ping when you drive. And after you get the timing set adjust the idle.
The idle RPM will depend on the cam, but hopefully you can get it @ 800 RPM
Good luck

You're right on with where the timing mark is right now. It's probably an inch or more over the timing tab, and it does advance further with some gas.
I just dug out the old tach/dwell meter so hopefully tomorrow I can get some additional info to share.

Thanks you!
 
On that choke tube with a set of headers for good operation these lines will usally be coiled around one of the center tubes a number of turns the end of the tube is left open. The goal is for warm air to be drawn up into the choke unit to operate it. To help improve choke operation an insulating cover like is used on the OEM choke stove line also needs to be used, its slipped over the tube to help retain the heat going into the choke unit. It won't be very good if a hole is drilled in one of the header tubes and the choke line is put in it. i.e. Allowing Exhaust Gas contamination to be drawn into the choke unit. Good luck (y) :nod:
 
bubba22349":17pqmsmq said:
On that choke tube with a set of headers for good operation these lines will usally be coiled around one of the center tubes a number of turns the end of the tube is left open. The goal is for warm air to be drawn up into the choke unit to operate it. To help improve choke operation an insulating cover like is used on the OEM choke stove line also needs to be used, its slipped over the tube to help retain the heat going into the choke unit. It won't be very good if a hole is drilled in one of the header tubes and the choke line is put in it. i.e. Allowing Exhaust Gas contamination to be drawn into the choke unit. Good luck (y) :nod:

That makes sense. The tube provided on the headers is just welded on to the side of one of the tubes (circled in pic). I wouldn't think of "plumbing" it into the exhaust.

I like the idea of coiling it around a pipe.

hSUdIwG.jpg
 
1strodeo":2spormzo said:
following this thread as I like to get all the Offy 3x1 info I can! :beer:

Well, I have certainly walked into this knowing almost nothing and with help am learning as I go.

I won't get a chance to work on the beast any today, but tomorrow I will post some RPM and Dwell numbers
 
Hi, on a dual point distributor you set each set of points separately. You have to clip the + wire from the dwell meter directly to the primary post from the coil on each set of points, one at a time. Check each set of points for a nice clean contact surface, I would first check the gaps with a feeler gauge, as you know, on the high spot on the cam.
I guess you will find the gap and dwell specs somewhere.
Good luck
 
For a 6 cylinder Mallory Duel point Distribitor the basic gap setting for each point is .028. The dwell setting for each point is 29 degrees, combined dwell of both points is 34 to 37 degrees. Good luck (y) :nod:
 
So I got a little bit more info to share. I started out to check the rpm's and dwell and compare them to bubba22349 numbers. Once I hooked up the tach I notices I was around 1100 at idle. When I went to turn it down I backed all three idle screw stops out and I couldn't get it to drop below 1000. That's when I noticed that the cam on the carb is actually contacting the Offy manifold on the first two carbs and not allowing them to close completely.

Should i be running a small spacer between the carb and the manifold ?

It did quickly check the combined dwell while I had things hooked up - looked pretty steady at 36.

KhWXiYF.jpg


More to come as I get some free time.

One again, thanks for all the help.
 
...spacer may help, or time for a little forming and/or grinding ...

the aluminum Offy adapter needed clearance grinding along with forming/bending linkage where needed on the 250:







haev fun
 
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