I have been having a lot of trouble with my 340. It just simply has no power and has a very inconsistent idle. Ive posted on here a few times about it but I found out some new info on it. It is a 1970 340 that has a stock bottom end. The heads were shaved just to clean them up and were mildly ported just to smooth out the ports. They are J heads with 2.02 valves. Cam is Hughes whiplash. Intake is edelbrock torker II and carb is 600 cfm edelbrock. The engine was recently honed and new rings installed. I was told that during break in, the engine got hot because they didnt put enough water in it and they had to shut it off after about a few minutes. After it cooled they filled the radiator up and fired it back up... then drove it around to break it in. Since the engine overheated is it possible the rings didnt seal good? I have put maybe 2000 miles on this engine since I have had it and it definitely hasnt improved.

a few minutes wouldnt have hurt it.

was the cam degreed when installed? it may be way off? also, whats your timing set at?

If it got too hot you would already see signs of damage, coolant leaks, blow by, oil smoke out the exhaust that doesn't go away. I think the stock bottom end and that intake are hurting you. Someone will chime in that knows more. Sounds like some carb tuning and timing adjustments are in your future. When i was a kid i fired up my 440 for the first time and i had a geyser of water shooting out the radiator(air pocket) she got up to 230 on the mechanical gauge and i shut her down quick.Beat the crap outta that motor for 6 years, never had problems.

Quote:

---

It just simply has no power and has a very inconsistent idle.

---

Unless it's about to self destruct, that sounds like a tuning issue rather than a break in issue to me. What do the spark plugs look like?

I have an eddy 600 on a stock 318 & the idle is also inconsistent. What is your timing and cranking compression and possibly a leakdown for how good the rings sealed & read this excellent info on ring breakin "breakin secrets" (takes 5 minutes). www.mototuneusa.com

You never really say what the problem is? You just say it has improved?

No, he said it "hasn't" improved.

The plugs are a tan color. I changed the plugs and it didnt really seem to make a difference though. I changed to a distributor that doesnt need the computer or ballast resistor, new plug wires and new coil... they didnt really help. As far as timing I have had it just about everywhere you can put it. Ive not adjusted the mechanical advance or the vacuum advance on this new distributor yet. I can adjust it by ear and it will sound great and run great for a while. Then suddenly it wont idle good and is back to even less power. I did get a hesitation on take off when I changed cams and adjusting the pump shot does not help so Im sure the carb does need some tuning for this cam. But still the thing just has no power and its driving me crazy. I really do not know what else to do.

Timing first then carburation is the recommended process

What type of cam (duration)

Initial timing, total timings, type of distributor (and ignition), using vacuum advance?

You'll need to provide more details so the members can help you out.

The cam is a hughes whiplas... here are the specs copied from their site:
Camshaft Technical Details
Intake Valve Lift 1.5
Exhaust Valve Lift 1.5 .512"
.518"
Intake Valve Lift 1.6
Exhaust Valve Lift 1.6 .546"
.552"
Intake Duration at .050"
Exhaust Duration at .050" 223°
236°
Lobe Separation Angle 107º
Intake Opening at .050"
Exhaust Opening at .050" 7.5° BTC
48° BBC
Intake Closing at .050"
Exhaust Closing at .050" 35.5° ABC
8° ATC
Min. Suggested Cylinder PSI
Sweet Spot RPM 2000-5300

Im unsure of the compression... its stock 1970 pistons and J heads that have been "mildly" shaved just to clean them up. I am using the thin mopar gaskets... they are .026 I think? So compression shouldnt be low.

Carb is an edelbrock Performer Series 600 cfm... its about 10 years old... works great on other engines... just not mine.

Did not degreee the cam.. just lined the dots... so maybe I should go back and degree.

All of the plugs fire if I pull them out individually to check.

Here is the distributor I just installed... white performance distributor and Im using a blaster 3 coil. Before this setup I was using a factory distributor and coil with Mopar orange box that all works great on other engines. The new setup makes it start easier but thats about it.

The initial timing I have had anywhere between 8 and 15 degrees and it doesnt run good anywhere in there. I dont know what my total timing is now. Im running vacuum advance now but it seems to idle worse and have less power with it.

Im unsure of my vacuum at idle.. im thinking I was around 15 idling at 900 rpm... I can check again tomorrow.

What else?

Good reason for firing new motors without a themostat. Break-em in and then install.

1.Put a vacuum gauge on it. 2.Clean out carb real good. 3.Check to make sure intake is not sucking oil.4.Do a compression test Good luck!

thats not a bad cam. it will idle pretty rough so set your timing at at least 15. maybe up it to 18. figure out what the timing is at 2500 rpm and make sure it doesnt go above 36 or so. see if the distrib can be adjusted to limit the timing.

the 600 carb is pretty small. but it should run if there isnt anything wrong with it. make sure the accelerator pump is pumping gas as soon as the throttle opens.

is the harmonic balancer new? was it checked to make sure the TDC mark is really TDC? something wrong and it may be the cam is not installed right or the timing may be way off or the carb is messing with you. really need to go at it one bit at a time

Do a compression test and post the results. Check for vacuum leaks and eliminate them if found. Re-curve the distributor for less mechanical advance, so you can run more initial timing and not exceed 36 degrees total.

Try swapping out the carb with a known good one if the timing adj doesn't help.

Compression tests showed about 135-145 psi per cylinder. Ive tried 3 carbs that were running fine on other engines and could not tell any difference. Should I try degreeing the cam and see if the problem lies in that?

Maybe I missed it, but what car is it in and what tranny and rear gear?

""Carb is an edelbrock Performer Series 600 cfm... its about 10 years old... works great on other engines... just not mine. ""


if this is a stock carb it wont work right at all.

I dont like them on anything but a stock engine, when you start putting bigger cams, compression ect they tend to not perform well with out changing springs,neddles jets ect and its a pain.

Find/borrow a holley and see how it does.