New engine seems to idle and run rough...

[inSANe DIEGO]

So I got Camilla running. She has a simple Recon longblock from an engine warehouse. When I first started the engine it just seemed like it was out of tune. Now (after about an hour accumulated running) the idle has gotten more "chug chug" than the straight boring hum I seem to remember from a stock chevy 350. It doesn't seem to smooth out above 2000 either. I put in a new hei distributor and of course new plugs. checked and double checked the wires and all are in the correct order. Any ideas? What are the chances of it being the carb if it has no hesitation when throttle is blipped and the engine seems kinda rough at any rpm?

TIA

[paul67]

Compression ?
paul67

[inSANe DIEGO]

Compression is somewhere around 8.5 to 8.7:1 i would guess. just a stock spec rebuild for around early 70's. I requested heads with a slightly smaller chamber to bump up compression a little, but they aren't anything outrageous. Drove it in to work today. seems to be running pretty crappy now. like a plug or two are fouled. I hate to throw new parts at the engine in hopes of the prob going away, but the wires probably could use replacing. I have an HEI dist. I seem to remember reading that it's bad to do the pulling plug wire technique to see if there is no change in idle (meaning that cyl is a problem.) Is this true? If not, can I pull the wire from the cap instead? The headers make it impossible to get most wires w/o getting burned.

[alcino]

I have had so many headaches from old plug wires. Its always good to get a new set often. I've changed the whole ignition system to find out my coil wire going to the distributor was the culprit or a few plugs weren't getting spark.

Also make sure the HEI is getting a full 12volts. I've also had issues where the engine block was not grounded well and the car would sputter at high rpms.

If you think its the carb I have an extra holley 600 4bbl. Or you could use my 600 Mighty Demon off my car for testing. Your in el cajon right?

Alcino

[inSANe DIEGO]

Yup! I'm in El Cajon...the north end too. Wintergardens and Pepper. That would be great if I could use the Holley to test with if needed...AFTER I try the new wires. I'll pick up a set on the way home. Any recommendations on wires and where to get them? Nothing super fancy- just not crap. I have a MAD enterprises New System wiring kit w/ a trunk mount helper kit on the way. Hopefully today or tomorrow it'll get here.

[inSANe DIEGO]

Ok. So I put new plug wires on the engine. BIG improvement, but it seemed like a couple of the plugs were too far gone and I should replace them. As I drove the car last week it ran worse and worse. I pulled the air cleaner off and wow. The carb was somewhat sooty on the primary side and definitely looked like it needed to be rebuilt. Did that on Sunday. Improvement noticed in driveability and smoother throttle control, but the plugs still sounded fouled. That didn't surprise me though.

I changed the plugs tonight only to find that every single plug was identical looking. They looked normal to maybe slightly lean to me. :screwy: I put in new plugs anyways and started on the oil change.

After draining the pan I proceeded to the filter. When I unscrewed the filter about a 1/4 quart of oil came out all over the floor, my arm and the engine. Even weirder, the filter only seemed half full when I flipped it over into the drain pan. Has anyone experienced this? I've done numerous oil changes on my previous engine and no spillage. WTF!!!!

After my strange oil change I started her up. The engine seemed smoother like the initial start up and also after the new plug wires. Went for a test drive and it still idles revs and cruises with a noticable chug chug to it. This is supposed to be a stock engine. What gives???? The car has good power, but it feels held back and it seems to be directly related to this chug chug pattern. 18436572... I know it well and have checked the wires several times. Any ideas??? Anyone in San Diego that wouldn't mind taking a look at my car?

[harshman]

I’m not a motor man but I’ve been trouble shooting my pos and my thought is vacuum leak or timing or bad coil (or electronics). It wouldn’t hurt to double check all the vacuum lines again and make sure all the caps are on. I do not use any vacuum on my car and had a similar problem and found that when my car backfired it popped one of the caps off. How new is your distributor/rotor/cap/coil?

[inSANe DIEGO]

brand new hei dist, plugs, plug wires. Only two vacuum lines. Trans and Vac advance. no other place for vac plugs. New carb/intake gasket. Intake gaskets installed with red spray sealer. Intake bolts sealed. Frustration building. Engine seems to idle pretty smooth, but with chug chug exhaust note. What gets me is that the plugs ALL came out exactly the same. I'm going to adjust the valves next, but the engine builder said it was spin tested and the valves were checked. I don't have much time on my hands and this friggin car is my sole transportation. I'm starting to worry that it'll have to be a warranty issue. :banghead:

[69boo307]

Is the timing right? could it be really retarded?

[inSANe DIEGO]

timing is set to stock specs. 8degree adv. checked and double checked distributor insertion (on two different days no less.) new balancer and checked that it read 0 when engine was at TDC. advanced and retarded the timing a few degrees and all it did was either slow down or speed up.

[inSANe DIEGO]

After tooling around with other things in the engine compartment I only had time to check the passenger bank b4 having to get her back together to drive the next day. Here are the numbers in psi:
#2 - 105
#4 - 115
#6 - 125
#8 - 110
Is that an acceptable variance? What should I be looking for as unacceptable?

This is a plain jane stock spec 350 circa 1970.

[streetk14]

Those compression numbers seem fine. This might be a stupid question, but did you check the timing with the vaccum advance plugged? If not, your timing is retarded. Is the big vacuum port for the pcv valve on the carb plugged? From what you are saying about the "chug chug", it sounds like a misfire. Are you saying that it runs rough at all rpms? Keep us posted,
Andy

[inSANe DIEGO]

Andy

I've set the timing with the vac adv disconnected AND connected. no noticable change in timing at idle when pulling vac adv hose.

Pcv port is hooked to a pcv valve in driver valve cover. Haven't had a chance to do any more tinkering with the engine lately. Hopefully next week I'll be able to get back on it.

Yes, it runs rough all the way up the rpm range. Gas mileage is still bad (less than 9mpg... I seem to remember getting mid to high teens at least) even after a carb rebuild. Maybe the carb is still part of the prob, but I find it really hard to believe that it's a major contributor.

[zbugger]

Two things. You did check your cap and rotor, right? Slight chance of crossfire in there. Secondly, how's your exhaust system?

[streetk14]

One other thing that I forgot to mention. You said that you set the timing to 8 degrees BTDC. Do you have access to a dial-back timing light? Make sure the mechanical advance mechanism is working & advancing the timing properly. You said that it was a new HEI, correct? Maybe you have a bad coil giving you weak spark. Just a thought.
-Andy