Hey fellas, I'm running out of ideas on my 292 and I'm hoping one of you can give me some pointers.

First the idle: I think I may be running rich since today I noticed it idles better cold and then tends to surge after it warms up until it drops to far and dies. Am I on the right track? Here's where it gets tricky for me - It's not a stock carb, it's a Holley 2110 (for a 3x2 set up). Supposedly it's like 200cfm carb. I rebuilt the motor last year with a bigger cam and 1.53 lifters.

Second timing: I've read the bigger cams take a farther advanced idle. Well, I started messing with the timing and did a couple test runs with mine pushed up to about 20-23 degrees advance at 550rpm idle, no vac advance. I've always run 93 octane and figure my compression to be around only 8.5:1, but I thought I'd have ping - but no problem. I checked my damper and TDC is dead on. Didn't think to check the points - would that affect my timing light readings? My vacuum readings were still increasing as I was adjusting toward where it's set now, but I just didn't want to push it any farther. Is there something here I'm missing?

This stuff is just racking my nerves and I'm not sure where to go from here. I have a easier time tracking down electrical problems than I do with carbs.

 

Taken any vacuum readings? Using the vacuum gauge to set the idle mixture screws may also help.

 

On the initial timing, 20-23 is way too much. No more than 12 degrees. Also the use of 93 octane gas is truly a waste of money, even if you have a 8.5 to 1 CR. And it is more likely that your CR is closer to 8 to 1, both CRs being static. And then a higher performance cam drops the dynamic CR below those numbers. Therefore regular gas will be fine.

How did you check your damper TDC mark. The only way I know of doing so is with head off and piston at precise TDC.

 

First let me say I've been reading ALOT of cam, timing, carb theory the last couple weeks, but theory and practice are two different things. Actually I should have said thanks for the replies first! Anyway, I've picked up a bunch of knowledge on the subject, but don't always know how to apply it.


THX1138-Z: I reread my post, and I didn't explain my idle problem very well. I've had to have the throttle plates opened up not quite to 1/16 of an inch (when the timings set at 10 degrees) to keep the RPMs at 550. Adjusting the mix screws anywhere always seems to have the same problems except near closed. As I write this, I've decided I'm going to reset everything and go through it all again.

46Yblock:
TDC - I checked it during the rebuild, but just recently rechecked it with a dial indicator stuck in the #1 plug hole. It wasn't real easy as I had to remove the headers and took 30+ minutes to get the indicator set right, but it was worth the peace of mind.

Thanks for the tip on the gas, I wasn't sure where the problem point might be. No big loss, I've got less than 1500 miles on it right now. As for the static compression, I don't have the #'s memorized, but on the rebuild, the #'s came out to near 8.5:1 as far as I could figure. I realize the dynamic is much lower.

I guess my main concern about the timing is if its a sign something wrong, build-wise or other, that I could push it that far out.

I'm heading for the garage now and will post my findings later. Thanks again for the ideas.

 

Just a side note for you guys. You could always find TDC by using a piston stop. They are very easy to make and are fairly accurate.

I made a piston stop by taking an old spark plug (which fit the engine, of course) and smashing out all the porcelain and stuff inside and breaking the little ground electrode nub off. Then I just welded a nut on top which the bolt threads into. I took a good sized-length bolt, cut off the head, and ground it down to a smooth dome. Then I just shoved it through the spark plug case and screwed it into the nut till it was tight.









Just screw this little guy into #1 cylinder, bring the piston up by turning the crankshaft by hand until it stops when it hits the piston stop. Mark this on your damper, and then turn the engine over in the reverse direction until the piston hits the stop again. Mark this point on the damper. Finally, find the exact center between the two marks, and you now have TDC.

I used this method to find TDC recently after I realized that my damper/harmonic balancer had slipped a good bit over the years, and I couldn't rely on the marks on it to time my engine properly.

 

Well, I reset the timing to 12 degrees at 550 RPM (PCV and dist. plugged). I have around 13-14Hg. I guessing that's not bad considering the cam. As for the idle mixture, it's turned approx. 3/4 turn out with the throttle plate around 1/32 open and I have to keep it at 600-650 RPM to keep a comfortable idle. Again I'm guessing the higher idle RPM is because of the cam. I'm getting a 1Hg flutter on the vacuum gauge I need to investigate - hopefully thats not too serious. The battery was dieing off so I stopped for the night and won't be able to get back to it till Monday.

 

It all sounds pretty good. My old motor always had the same vacuum flutter you describe. What cam do you have?

Matt, very helpful and great pics! I knew the SBC guys use that type of device, but somehow I didnt transfer the info to our motors.

 

Thanks for the reassurance 46Yblock. The cam is Mummerts 265s. Again I don't know the specs off hand. I forgot to mention one of my idle mixture screws had play in it, so I replaced it with one of the soon to be secondary carb screws. I'm sure that had an effect on something, but I'm still getting a surge after it warms up. Will a vacuum leak surge on a cold engine (1 min after start - no choke) the same as a hot one or is that a sign of rich mix or even something else? It's around 300RPM and 3Hg variance at worst.

Maybe I'm getting ahead of myself, but any thoughts on degreeing the cam?

Matt:
The only thing I would add to the set up is a hook to hang the keys on so I would be sure not to hit the switch - No joke! I shot a nice ball o fire before by forgetting a plug and reconnecting the coil - a hole in a piston would top that dumb move.

 

Ok, kinda talking to myself, but the wife left and I got a chance to hit the garage for a couple hours. Started the motor cold and let it run for 2 minutes. After 2 minutes it would idle well. At warm idle, rpms would slowly drop off, but no surge. Then I realized I had not plugged two holes from where the choke plate would be mounted - seemed to help a bit. BUT one of the holes appears to go to the power valve area - hmmmm.

Another new question: The PCV valve contantly flutters at idle making an annoying sound. Rev it up and it goes away. Solutions?

 

Matt- You said you have a Holley carb. I would suggest opening up the carb and checking for distorted o-rings, cracked gaskets, etc-EVEN if the carb was new/rebuilt. Next check all mounting surfaces for the carb, manifold etc. very closely. The slightest vacuum leak can cause serious hair loss! If your PCV valve is fluttering, I would say you have a vacuum leak somewhere, and once you find it, alot of your trouble will go away with it. My experience with the older fords is that they are EXTREMELY touchy when it comes to vacuum leaks. As far as the timing is concerned, if you have determined that your balancer is accurate, points are set correctly, condenser is good (A condenser can work and still be bad) You might pull the distributor and check for bushing play-even slight bushing play can cause aggravating timing problems.