Separate names with a comma.
Discussion in 'Troubleshooting & Diagnosis' started by erhan ergin, Apr 25, 2020.
I was going a say same thing, swap out the metering block
Wanted to give some update. I did make progress.
I took off the carbs and rechecked that the transfer slot is square. I opened up the secondaries a little to square them also. I increased the holes on the butterflies very slightly (I drilled 4 holes earlier). I put back the #65 iab's to the secondaries also. Now the iab's are the same on both sides.
I put the carbs back and now the car idles in Park at ~ 1100rpm with the idle screw all the way out. I think I must have opened the secondaries a little too much. I backed off on the timing a little otherwise it was idling ~ 1500rpm. I can put the car in gear and it idles at about 840 rpm. There is no stumble. Air fuel ratio is ~ 14.5 at 840rpm. It jumps to 12-13 when I step on it. It cruises at part throttle at about 13.5 so a little rich but not too bad. I think the car is driveable now. Thanks for all the suggestions and feedback.
Nice, I struggled forever till I cracked my secondaries. Then it will put your idle screw in correct position, about a turn and a half out and then your blades will be square to transition and carb works as should. Upping initial timing is key with a bigger cam and low vac. I say your ratios aren’t that far off, Id do like said , stick some tape on a/f and get it to run good . Take tape off and that’s where you run , 12.5 is great for wide open n/a. 14.5 at idle that’s nice also, the cruise drop a few on primary jet . I got down to 69/78in summer with my 780 carb due to crap humid hot air
Wanted to give an update, after about 2 years of fiddling with the carb/timing/trying to find vacuum leaks etc I caved in and took the car to an old timer mechanic close by. I did not know him earlier and someone recommended. He came thru, have not verified yet but here is what he found, Apparently my stroker engine has solid lifters and who ever did the valve adjustments before, tightened the rockers too much causing the valves to stay open. He adjusted the rockers and he says I should see 15-16 in vacuum now. The sound of the engine changed and the rough idling is gone. He said all the issues I came across like erratic cooling behavior, sluggish performance, terrible gas mileage were because of this. I did some googling to confirm if this is possible and came across several examples.
Before we found out about this, I thought of going to 1.4 ratio rockers so I could reduce the lift on what I thought was a huge cam. I probably should have at least checked the valve adjustment. I worked on motorcycle engines before and this is very common issue on them. You have to adjust the valves quite often. Never thought it would make such a difference on a pushrod engine.
Excellent update, thanks for that.
You can have hydraulic lifters lashed wrong also and kill the power and idle.
Well, just glad you finally found your issue, at least there's lots of carb information that was shared. Nothing more valuable like old hands on experience.
This was my post way back, #37, I should have included "valve" in front of leaks as I was not referring to vacuum leaks, this could of shortened your repair time frame. As the saying goes, 1st, most carb problems are ignition problems, 2nd, it's valve train/sealing problems.
"And if the AFR's are all over on idle, that could point to other issues like big cam, high overlap,reversion-pressure waves, leaks and a host of other things that sends the AFR meter in convulsions."