I've got a 283 chevy that I just rebuilt with 30 over pistons and an Erson hiflo cam. Basically stock otherwise. It's got 265 heads on it that are rebuilt to stock specs and an edelbrock c355 manifold running just 1 holley 94. I have the 265 specific intake gaskets. It's got a Mallory dual point that's got new points in it. I have maybe 100 or so miles on it now and can't get anymore than 10" of vacuum out of it ans it has an erratic idle. Otherwise it runs pretty damn good going down the road. I checked for manifold leaks with carb cleaner and around the other two blocked off carbs and I didn't find a leak. The carb isn't leaking out of the venturi while idling. My fuel pressure is set at 2.5lbs I'm pulling the rest of my hair out with this thing trying to think of what could be wrong with it. Help! Here are some pictures. Everyone likes pictures right? Sent from my SM-G935V using The H.A.M.B. mobile app
Not knowing what a Erson hiflo cam is...but if you bought this cam, totally wrong for your car. E110422-47 - Erson Cams - SBC HI FLOW 1H R/P 4/7 "Restricted intake. 9-1 to 10-1 compression.Good exhaust. Short 1/4-3/8 mile sticky tracks. Great for heavier cars. 7/4 firing order swap" If its the one you bought, did you even notice the firing order is changed? Guess we would need more info on what cam you put in.
Looks really good. How Is your vacuum gauge acting,,,what does the needle do,,,that will tell you a lot? Is the needle acting normal but low ? Is it jerking around erratically ? It will diagnose a lot of trouble for you. Get out an old manual,,,it explains what the needle actions are telling about the engine Good luck. Tommy
Hold your hand over the openings of the two outside carbs and see if it settles down, could be leaking air past the closed throttle plates
The cam had Erson HiFlo 1H stamped on it that's all. If it really was the 7/4 firing order swap wouldn't it run like crap all the time? Maybe a stupid question.
Thanks! I should have mentioned that the needle acts normal. Doesn't jerk around at all. I need to do a compression test but ran out of time today.
Where is the hose going to from the fitting tapped in under the center carburetor on the drivers side? Big one PCV and little one trans?
Looks like to me........220@050 duration and a 107* LSA is causing the......"eeratic idle".... of which you speak!! Man that's a dirt track camshaft!! It idles real snotty and have crappy vacuum. Its made for engines that don't sit at traffic lights and do bumper-to-bumper traffic. It comes alive at 2000+ RPM and hangs around til the other side of 6000RPM! This'll help it......... Put some light springs in the distrib. so the advance(36-42*total timing) is all in by 1500RPM or so. Crank in as much initial advance timing as it will stand (still crank over when the engine is warm.) Run the highest octane gas you can get. When you turn the distrib. to advance the timing.....this will increase the idle speed. Turn down the curb to about 750RPM or a little more. You DON'T want to uncover those transfer slots in the carb when idling. Adjust your carb using a vacuum guage and get the highest vacuum you can by turning the screws in /out. Play with it. Its gonna idle like a Hot Rod...not a Yugo. With a good set of rear gears you won't be under 2000rpm much at low speeds and should have goooood performance. Do this and come back and tell us what happened!! 6sally6
Is it possible to have a vacuum leak on the underside of a manifold?If the heads are surfaced could the manifold not seat well on the lower gasket? If so it would suck from the lifter valley.You have the old style oil fill tube so it can draw air in.Not sure how you would check such a problem.Do all the plugs look the same? If 1,or2 look different that might point to the problem.
Interesting.. It doesn't sound crazy at idle at all. Just a little lumpy but nothing crazy at all. I'll mess with the distributor, bump up the timing and put some 110 in it! I also ordered my linkage for the carbs so that should wake it up some. Maybe I'm just trying to set the idle too low. It runs great after idle though! Sent from my SM-G935V using The H.A.M.B. mobile app
I've thought about that too but didn't know how to check it.. All the plugs look the same Sent from my SM-G935V using The H.A.M.B. mobile app
Pieces of 1/8 plate with gaskets. I sprayed around them and no signs of a leak Sent from my SM-G935V using The H.A.M.B. mobile app
Idle 750-1000RPM what I would suggest. Light weight vehicle and lumpy cams are are gooood combo. They need LOTSA initial timing to make up for the soggy of idle manners. Hi test should be fine (not 110 octane) Change the springs in the distrib.....stick on a timing tape.....twist in 36-42 degrees total timing at aprox. 2000 RPM. Where ever the initial ends up is good. 6sally6 PS Looks like you've checked for vacuum leaks pretty close.
With that stock balancer did are you able to make true tdc? Making sure the outer didn’t rotated on the inner? Just another thought
The Jalopy Journal
