We put a comp 280h in a 352 that's been bored .040 over and also has a 4 barrel carb and an edelbrock performer rpm intake, headers too. At first we had to advance the timing a good bit to get it to run so we could drive it to the muffler shop. Now it won't idle long enough to get the timing light on it. We haven't done anything on the carb except turn up the idle screw. Help? Supposed to be in a car show Saturday!! I would also like it to idle low, as in low RPMS without stalling. It is a 4 speed manual, so no stall converter issues.
Changing the cam also changed the vacuum signal to the carb. You will have to adjust your idle MIXTURE screws to compensate for the change in cam. Unless you have a vacuum leak (ie: intake gasket or broken vacuum hose). I would also look at the other vacuum lines and fittings that had to be moved when you pulled the intake.
A vacuum leak could be possible, but as far as the mixture goes, how can I tell if it is running lean or rich? The carb is a Holley Street Avenger 570
Start turning the mixture screws. A little at a time. First, I usually turn then in see if it is running rich. Turning them out will richen the idle. You will have to go back a forth a few times to find where it will idle, then set your idle speed, recheck the mixture screws to smooth out the idle.
Alright, there are two screws, one in front and one in back. Is there one I should turn before the other? Is one for the secondaries and one for primaries?
Both idle mixture should be on the front of your carb. Check for a vac leak with some B12. Borrow a large vac guage and set the idle screws to maxium vac. People make modified lifters that will calm that can down at idle and will pump up at high RPM and preform. Posted using the Full Custom H.A.M.B. App!
This is not an avenger but an 800 double pumper, however your carb will have an idle mixture adjustment screw somewhere in the metering plate that looks like this one. It will be on the front end of the carb, one screw on each side.
If you have a vacuum advance hook it up to full vacuum on the carb or manifold. The added timing will help your idle.
Man, I hope you broke in your new cam per Comp's directions before you started all this idling and adjusting. Your comment about adjusting the timing makes one wonder if you got the cam timing right during the cam installation. Off a tooth? I hope you can get it working with carb adjustments and ignition timing. I've used Comp's 280H in several cars, it's a decent street cam if you can get the rest of your combination working together.
We didn't get it right off the bat. We tried to time it while breaking it in but we let it idle once or twice and quickly turned the distributor and brought it back up to speed. Ran it at for about 20 mins then cut it off and changed the oil. No debris that we could see, so good sign I guess. It scares me too man, I hope we can get it right. We did use break in lube, so far no signs of a wiped lobe, I hope. My dad is extremely smart when it comes to engines, but he's never had a tappet cam. He is kind of stubborn when I told him we could not let it idle, so it was pretty much forced. Don't want to point fingers, but if it's a wiped lobe it is most likely his fault.
HAMB'r down George. The guy has a fresh cam on the line, it's a FORD FE. A carb issue. Timing issue. Idle & fine tuning this monster is your forte. Do it for the team called the HAMB.
Next time you fire a car that has had the distributor removed try it this way: Rotate the crankshaft in the direction of normal engine rotation towards TDC on the compression stroke until you reach your desired initial timing as registered on the pointer/balancer and go no further. Since this is an FE it will start and run just fine at 6 degrees BTDC. Now look to see if the rotor is pointing in the vicinity of the number one plug wire. If not reposition distributor so it is. Now with the distributor hold down adjusted so you can just turn the distributor, cap on all ****oned up, turn on the ignition, not far enough to engage the starter or you will have to start all over again. With the key in the run position rotate the distributor until you hear a "POP" inside the number one plug wire where you pulled it slightly back from the plug. Tighten the hold down clamp and start the engine. In my experience if you have done as stated you will be within one degree of your initial timing and can break in the cam without having to potentially damage cam/lifters by idling the engine to time it. After the cam has been broken in you can adjust idle speed, idle mixture, timing, those three all can have an effect on idle quality so you may want to run them all several times. Just the way I do it, others may disagree, but it has worked for me for about 50 years.
You start with the primary (like in the pic) then go to the other side of the carb and adjust that one alightly to get a better idle. The ones on the rear (secondary side) you then adjust SLIGHTLY in an out to see if they change (make better) the idle.
to rule out a vacuum leak causing a bad lean condition, you can also try to manually manipulate the choke on the carb. If it perks up- you've got a vacuum leak. -rick
Comp Cams 280H model is an aggressive cam for high compression engines. Shouldn't have much bearing on idle but any idea what the compression might be?
The compression is in the 9 to 9.5 range, but the several people I have spoken to told me it wouldn't be a problem. One of them was an experienced drag racer, so I took his word for it.
Joyce's pickup runs a 280H, 10:1, and a 770 Street Avenger with an automatic, and it idles and runs fine. if you need details on my tune, shout.
If you have 4 corner idle, set all 4 to 3/4 of a turn after lightly bottoming, if its primary only, set it to 1 1/8 from bottom. Crank the primary idle way up and fire it up with the air cleaner off, just to make sure you don't have a stuck float or something making it flow out the vents causing the idle problem (not likely, but you can watch it). it'll be revving too high, but thats OK Also, its better to have the timing too far advanced than retarded, without load on it, it wont hurt a thing After its fired up, get the idle somewhere around 900, set the timing with the light, reset idle close to where you want it and adjust the a/f mixture, reset idle if required Last check, if it idles, but ported vacuum is alive on the front metering block at idle, you have way too much primary idle, and you'll have to open the secondaries to get out of the transition slot on the primaries. If that happens post back and we'll help properly set the primary throttle blades
A va*** gauge is cheap and necessary to troubleshoot idle issues. Aluminum FE intakes can be a ***** to get seated and the best way to check the install is with a va*** gauge. I had similar issues with my FE and it turned out to be Fel Pro Printoleak gaskets leaking in multiple places. I tried Edelbrock gaskets and finally got the beast sealed up with Fel Pro steel core gaskets and Gaskacinch sealer. Hopefully you can get it to idle with pulling it back apart!!
My dad called me and said he had the timing set and it was idling pretty well but then he took the points out and now we are converting to electronic ignition. I think he said it was 20 degrees with the vacuum advance
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