Hey guys, this 547 engine has a strange slight miss at cruise speed, if you squeeze the pedal and load the engine slightly it clears, also belting it it's fine and just goes. Any idea's ? It cant be spark I'm guessing.

CHEEEEEERS

Al,
may be a lean situation ?
Do you have a AFR set up ?


Tex

No Tex I don't ant don't have time to dyno before Alice trip

High vacume misfire, maybe it is a vacume leak
Ignition would be the other one I would look at

Al,
easiest thing is go up on the primary jets by 2 .Then road test .
Are you running a powervalve on primary ?
Like Cab said vacuum leak at high cruise vacuum - also show as lean

Tex

I don't have much experience on 2 4150's on a TR, but you might not be on the primary circuit yet. Sounds lean. How is the transfer slot exposure? What IFR? Maybe Mr. Thump will chime in.

Before you can properly tune ANY engine be it carbs, efi, blowers etc, you need data and w/carbs it`s a wideband. So IF you had one you could tell us the rpm/throttle range and afr`s then w/that info we could better nail the answer(s). I had a 9 second car but ran 10`s until I chassis dynoed it and found out how far off I was on my tune. As I say; it`s bad enuff to be dinosauric running carbs apparently BUT w/out data it`s a guessing game especially on street cars w/a variable of throttle positions from idle, transition, cruise and wfo.............

measure your idle mixture screws position.Now fatten up the mixture screws and see if hesitation goes away.If that doesn't help,go back to beginning position on the screws.

You migt want to try using some really thin wire(the thinnest you can get) to make up some upside down J to put in the idle bleeds, all eight That should inrichen the mixture all the way through the entire RPM range If that fixes the miss you know your on the edge of a lean misfire at part throttle operations. The next move is to get a set of the next smaller I.D. idle air bleeds, maybe.001 to .003 smaller to fix it Make sure there are no vacaume leaks also

Great quick way to test for sure and at least give you a direction to go also the ifr`s and idle bleeds have a big impact. Can you post the specs on the carbs like idles, hi`s, ifr`s, emulsion etc...........