Let's get back to basics and see what's going on here. Chev 265PP 305 heads (58cc) Offy 360° intake Edelbrock 1404 500cfm carb 1968 distributor (2 years old) w/ Crane Cam XRi pointless ignition Only different things since I started the head swap was... 305 heads Crane Cam XRi spark plugs- different plugs set @ 35 gap I started the head swap because of a blown head gasket I found while installing the XRi. Original heads looked as if valve recession was well on it's way, so I opted for the swap. 305 heads have slightly larger intake/exhaust valves. Both 265pp & 305 heads I believe are 58cc heads. The spark plug wires are over a year old and have been moved around alot because of valve adjustments. Symptoms: rough idle rough slow accelleration WOT accelleration seems just fine seems to miss a little when just cruising at hiway speeds jerky torque converter - lurches at idle What are your thoughts as to troubleshoot this motor?
Sounds like most of the ignition stuff has been replaced. Plugs and plug wires are easy to change so start there. I would make sure you didn't over tighten the rocker arms. I had alot of the same symptoms that you had with a 283. Couple of the valves were hanging open giving it a miss at idle and cruising speeds. Also recheck your timing and make sure the ring on the balancer hasn't slipped.
times like this I miss shop cl*** and that old Sun Machine. It would point a big arrow at ignition, vacuum problems.
First - double check and triple check the firing order and rotation of the distributor to make sure that it's correct. Then check to make sure you're not hanging a valve open because you over tightened a rocker and it's bleeding off compression (essentially having a dead cylinder). You'll have to do a compression check for this one or just pull the valvecovers and double-check the preload. Start troubleshooting by pulling the plugs wires off one at a time - when pulled the idle should drop - if one cylinder makes no difference in the idle speed/quality you've found a suspect cylinder. - will likely be wire or compresison problem. If they all change idle about the same then start checking for vacuum leaks - check the gasket areas by spraying carb cleaner at them (if you don't have pretty paint on the engine - use WD40 or the like if you've got nice paint) - if the idle speed changes then you've found a leak - repair it and test again. Other things to check - distributor plugged into the proper vacuum supply - the ignition should be advanced at idle / high vacuum, then drop when the vacuum goes low until the centrifigul advance starts in, then the vacuum goes up at speed to give a total of 30-32* advance at 2500 RPM or so. Check those basics and get back to us...
if you hook up a vacuum gauge and the needle jumps around then you cuold have a tight valve. i have had a lot of lifters that pump up solid and wont bleed off and hangs the valve open.
Sounds like all the above. You would be wise to tune ,using a vacuum gauge. Adjust the valves till you get the higest reading. Then adjust the timing until the higest reading.lastly adjust the idle mixture for the higest reading. A lot of problems can be traced by using this method. Make sure all the ing. parts are top notch,and the exhaust system is adequate. Sparky
Sounds like all the above. You would be wise to tune ,using a vacuum gauge. Adjust the valves till you get the higest reading. Then adjust the timing until the higest reading.lastly adjust the idle mixture for the higest reading. A lot of problems can be traced by using this method. Make sure all the ing. parts are top notch,and the exhaust system is adequate. Sparky
Sounds like all the above. You would be wise to tune ,using a vacuum gauge. Adjust the valves till you get the higest reading. Then adjust the timing until the higest reading.lastly adjust the idle mixture for the higest reading. A lot of problems can be traced by using this method. Make sure all the ing. parts are top notch,and the exhaust system is adequate. Sparky
Reset your valves while running- back em off till they TICK- the tighten em up till clickin stops THEN 1/2-3/4 turn more to finish off. Next I'd suspect you need to examine the advance on your distributor.... test for vacuum at the distributor end and if you have vacuum fine. Next see if the advance plte moves when engine revs up. Id also suggest- a distributor swap-that may help out.
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