Need help w/ 273 has issues

-
If it ever backfired up through the carb with the throttle plates closed, it could've blown out a piece of the carb gasket, so tightening wouldn't help fix a vacuum leak like that. I've seen it.

Sounds like this situation is in need of a calibrated ear!!
 
thanks, when I removed the carb, disassembled it, checked all adjustments, I put a NEW base gasket on, so huh....car has never backfired.
 
Double check the intial air gap at the choke baffle. I once had a vacuum choke pull that didn't work just right. I finally realized the breather was interfearing with its linkage.
Anyway.. When the pulloff didn't go all the way back and I mean stop a hair short of where it should go, the engine would shake. I could pop the hood and give the thing a slight finger assist and it would go on back, correct the air gap and the idle. To ignore it and wait it out resulted in a nearly flooded engine that took much longer to clear up.
 
If it misses when cold, then clears up when warm, I'd suspect choke setup. Is it manual or auto(electric) choke carb? Does the choke plate open slightly when the engine is running cold?

Solid-lifter pushrods and hydraulic-lifter pushrods are different lengths (as well as diff. appearance), and cant be mixed. If it has a juice cam, make sure you have juice pushrods, and vice-versa.
 
he said it was an edelbrock which I does not have a pull off. It should be an electric heated element or manual which can easily be adjusted by hand and eliminated as a possibility (if tried). But I do agree sounds like the air gap is not opening enough after start and loading up (set to rich) He seemed to have dismissed it as a possibility.
 
Rocky_JS said:
he said it was an edelbrock which I does not have a pull off. It should be an electric heated element or manual which can easily be adjusted by hand and eliminated as a possibility (if tried). But I do agree sounds like the air gap is not opening enough after start and loading up (set to rich) He seemed to have dismissed it as a possibility.
Click to expand...

Gotcha Rocky....I know aftermarket Eddy's don't have an external choke pull-off, but they do have one inside the electric choke housing. If that was sticking, the choke blade wouldn't open (enough) and would cause flooding and the ubiquitous black smoke out the tailpipe. Also, not sure he realizes, if its a manual choke, that you need to manually set that air gap at the choke blade to allow the engine run properly cold.
 
Tough to diagnose over the internet but the guys have come up with some good possibilities. It sounds like a choke problem to me too. Is it hard to start cold? Will it start with one pump to set the choke or do you have to pump it a few times. If the choke is set too lean the butterfly won't go completely closed and it will run rough until it warms up a bit. The plugs won't fowl because it's too lean. It won't start very easy though. When it's running rough close the choke or spray some carb spray to richen it up. If it smooths out it is too lean. If you open the butterfly manually and it smooth's out it is too rich. Where is your choke coil adjusted?
I have a 600 Edelbrock on mine and I wasn't happy with how rich it ran during warm up. It would run a bit rough until warmed up. I leaned the choke out 3 or 4 notches to the lean side of center and it starts good and runs much cleaner during warm up. tmm
 
Try turning each of your idle mixture screws out an extra 3/4 of a turn and see if that helps......just try it.
 
RedFish said:
Double check the intial air gap at the choke baffle. I once had a vacuum choke pull that didn't work just right. I finally realized the breather was interfearing with its linkage.
Anyway.. When the pulloff didn't go all the way back and I mean stop a hair short of where it should go, the engine would shake. I could pop the hood and give the thing a slight finger assist and it would go on back, correct the air gap and the idle. To ignore it and wait it out resulted in a nearly flooded engine that took much longer to clear up.
Click to expand...

I also think this is the problem. My sons 318 with a stock 273 intake, 260 duration .430 lift cam, and 1403 Edelbrock carb seemed a bit lean, more so when starting. Not as bad as Tribute SS/A 68's 273, but aggravating to be sure. I figured the Vacuum Break was set to open too far which leaned the choke mixture too much. We put a 4295s original 273 carb on and he won't give it back. Car starts and runs great. Maybe if you tried to manually close the choke plate when running or adjust the linkage to open less, you could get it to run better after start. It could take a bit of trial and error, but it would definately be worth it. Maybe get a set of smaller rods, one step richer, and try that.
 
Hi. My 273 4bbl was rebuilt the same way -- hydraulic cam & lifters, retaining the adjustable rockers. It used different pushrod lengths than the original solid stick -- I used cut-to-length pushrods. So I can confirm that this setup will run, and run well.

Bucking and rough idle doesn't sound like tight valves to me -- it sounds like cylinder imbalance, or a timing problem. I'd forget about the valvetrain and start from scratch, looking at the firing order, plug wires, compression, etc.

Or I think the carb & choke suggestions may be on the right track. I didn't realize you were running an Eddy. I'd try to find an original AFB -- once mine was rebuilt it runs so smooth, I don't see how you could improve on it. It's "like buttah..."
 
I put a hydraulic cam and lifters in my 65 273. Of course I kept the adjustable rockers as that is better. I used Rhoads "leak down" lifters for better idle and mileage. As mentioned, adj rockers require ball & cup pushrods, so can't mix up. I got ones for the 340TA engine from Summit. I adjusted w/ the intake manifold off, so I could precisely set the pre-load. Runs fine. I don't see how warming up could affect the valve-train much since all parts are steel and expand the same. If not, solid cam gaps would vary all over the place with temperature. In sum, forget about valves as the culprit.

Sounds exactly like a lean condition. Spray a little starter fluid down the throat when it is idling rough. If it smooths out, you probably have a mixture problem. Could also be spark since ether ignites easier, but unlikely. Put an in-line spark tester on a plug wire to verify a bright spark (cheap at Harbor Freight).

With a wild cam, it may never idle well. A lot of people like that, plus the throaty sound from overlapping intake and exhaust. They even like the fumes of noxious vapors and crappy mileage, all for the hot rod image.
 
OK, guys, here is the latest. First checked the carb choke setting again, with one full pedal, the choke completely sets closed, with approx 1/8" gap at butterfly. So to eliminate possible too closed I opened it an additional 1/8". then crank & gas 3 times before it would stay running. It slowly increased in rpms from 900 to 1400 in a couple of minutes, no missing just the shaking, opened butterfly with finger, did not like that, so left it closed until warm. after a few more minutes, hit the gas, idles a little rough at 850, but nothing bad. Then rpm it to 4000 no problem, smooth and good. I think the pulloff is working, I think the "new" carb may be the issue also, just do not know where else to look for it. When I had it apart, I adjusted all settings as per the rebuild kit, float, float drop, acc pump. the idle screws however have to be 2 1/2 full turns out to be fairly smooth. To Bill Grissom, when I adj the rockers, they obviously do have the ball/cup pushrod end, so are these rods all from the solid cam assm ?
 
I would like to see the choke fully closed with a cold engine. You said it had a slight gap and you leaned it out more. It sounds like it needs more choke. Tmm
 
is this an electric choke we never did clear this up?

did you need to start the car several times prior to adjusting the choke?

And with one full pedal cold does the fast idle cam set? it should not take a couple minutes to get up to the fast idle setting it should be immediate.

When you set the choke did you bent the choke rod or adjust the choke stove?
 
Electric choke, works, has power, works,,,, when full pedal given, choke cam does set. I adjusted the housing where the spring is so the butterfly opens or closes accordingly. I do however have to pedal it, 3-4 times before it will continue to run, then as stated it slowly increases rpm until about 1400-1500, and Yes I know it should me immediate, it is not, so here is a clue about the prob ?
 
when you took it apart to check and adjust the settings did you remove the choke assy from the body of the carb or was this a manual choke carb that you adapted to ele choke?

I assume since it was a new carb you didn't soak it in anything, only checked the settings, which is the smart thing to do since in shipping they get tossed and flipped all around by people who do not know better or could care less?
 
It is an electric choked, 500 cfm Edelbrock. The choke should be closed when you floor the pedal to set the choke. The choke should open slightly, called a vacuum break, when the engine starts to give the engine air. The vacuum break is known for original carbs, but for your engine you will have to do a little trial and error. You should be able to get it to start and drive off, almost like fuel injection if you get it right. The choke should be fully open when engine reaches operating temperature.
 
carb came w/electric choke, yes, just disassembled and sprayed with carb cleaner, then blew out with air, then set everything.
did not remove choke housing and the plunger/internal pull off, moves freely. Seems more now to me the carb may be the issue, just does not make sence what.....


Rocky_JS said:
when you took it apart to check and adjust the settings did you remove the choke assy from the body of the carb or was this a manual choke carb that you adapted to ele choke?

I assume since it was a new carb you didn't soak it in anything, only checked the settings, which is the smart thing to do since in shipping they get tossed and flipped all around by people who do not know better or could care less?
Click to expand...
 
seems like that where I had it set before re-trying a little less closed,
Yes i agree, but it will not do that. maybe I am missing something here on this edelbrock, as i am familiar with stock, holleys, and Quads....

66fs said:
It is an electric choked, 500 cfm Edelbrock. The choke should be closed when you floor the pedal to set the choke. The choke should open slightly, called a vacuum break, when the engine starts to give the engine air. The vacuum break is known for original carbs, but for your engine you will have to do a little trial and error. You should be able to get it to start and drive off, almost like fuel injection if you get it right.
Click to expand...
 
I'm going to toss this idea out, how about the passengers side exhaust manifold. Does it have the butterfly valve and if it does, is it sticking? It may be sticking shut until it gets hot enough to release.
 
I was thinking - the choke housing o-ring/gasket might have been omitted shifted and if manual choke conv the factory plug would need removing to allow vac to choke housing piston.

To the question above mine, the heat riser is on the passenger side exhaust manifold.




Tribute SS/A 68 said:
carb came w/electric choke, yes, just disassembled and sprayed with carb cleaner, then blew out with air, then set everything.
did not remove choke housing and the plunger/internal pull off, moves freely. Seems more now to me the carb may be the issue, just does not make sence what.....
Click to expand...
 
You stated that the carb is a NEW Edlebrock 500 cfm carb, correct? How about something simple, like the choke idle speed being set too low?
What RPM's is it idling @ when first started, cold/choke on, VS. idle speed fully warmed up/choke off?
 
The thing is, you should be able to open the choke manually, or wire it open at least long enough to determine if that seems to be related to the problem. I'm playing with EFI, but for the last couple of winters, I ran NO that is, ZERO choke. I've started the car when the temp was in the 20'sF

ALL auto chokes operate pretty much the same way, whether exhaust heated, electric, divorced, or the Holley/ Ford/ Edelbrock "round black thing."

That is, they are a simple thermostatic spring, heated by/ and/ or exhaust / electric, and some sort of pull off. They cannot close completely until you wallop the throttle to the floor once, because the mechanics of the fast idle cam prevents that.

When you start the car, either a piston (this case) or a vacuum pot "pull off" or "vacuum break" pulls the butterfly open a small amount to prevent OVER choke until the choke thermostat warms up

The type choke you have here is adjusted by loosening the screw clamps and turning the black housing. Holley has documentation at their website.

Some stuff

[ame]http://www.edelbrock.com/automotive_new/misc/tech_center/install/1000/1478.pdf[/ame]
 
You must log in or register to reply here.
-

Back
Top