Engine problems

by rogal_tx Tue Sep 29, 2015 9:17 pm

Greetings,
So I got a problem with the motor on my 73 el Camino that started today.by the way its a 350 out of 86 corvette.
so I was getting on to the road and I stepped on it a little. Than I heard a knock if i recall correctly and motor started to run really rough and it died when I let my foot of the gas. It started easy but I had to put it in neutral and keep my foot on the gas while at lights trying to get back home. It seems like motor knocks a little bit and its coming from the back of the motor I think. I just adjusted the timing and it was running great.
I'm not sure where to start to identify the issue. Any help is appreciated.

by bigredlaguna Tue Sep 29, 2015 10:01 pm

I would pull the spark plugs to see the condition of them. Was it running good before the timing adjustment?

Was this the first run with the new timing?

by pila Tue Sep 29, 2015 11:18 pm

Are you sure that the distributor is clamped down tight ? If not,it may have moved...just an idea...

by REVINKEVIN / Mr. 600+HP Tue Sep 29, 2015 11:29 pm

Make sure your fuel is good. Does it smell like gas or does it smell like burning water? We were just doing this with my 1986 Silverado tonight and I had to take the carb off. All kinds of deposits in there from a 6 year project. Like Pila said make sure the distributor is tight and also check for vacuum leaks around the carb. Pull some spark plugs and check them. What kind of carb are your using? More questions on mind but these will do to start. If you vote Democrat this will never run. Just a thought.

by rogal_tx Wed Sep 30, 2015 6:27 am

It was running good with new timing (set to 36* at 2500-2700 rpm) not the first run. Spark plugs are 4 months old, they are short spark plugs because of the headers I have. Distributor is clamp down, I try to move it a little when I finally pulled to the house.fuel smells like fuel so should be good and I have 4 barrel eldebrock carb. I will check for vacuum leaks and spark plugs today and post an update.
Thx

by 77mali Wed Sep 30, 2015 5:41 pm

bigredlaguna wrote:I would pull the spark plugs to see the condition of them. Was it running good before the timing adjustment?

Was this the first run with the new timing?

x2.

This will tell you a lot about what's going on. I had my truck's 305 doing some funky stuff a while back & cleaned off the plugs from deposits accumulating on a few of them. Most likely from the POS gas we have up here in MA.

by bigredlaguna Thu Oct 01, 2015 12:03 am

You may have said in another thread, but how much time is on the engine? Is it an original 86 or an 86 vette engine that has been rebuilt to those specs?

While the plugs are out, it would be a good time to do a compression check. A bad exhaust valve would create the rough running condition.

The knock sound is difficult to diagnose over the internet, but you can try to narrow down where it is coming from by using a stethoscope. If you don't have one, you can use a broom stick to do the same thing. It looks silly, but it works.

by cutlassguy Thu Oct 01, 2015 10:16 pm

If you think its coming from the back the engine, it may be a flywheel crack. If the dizzy was tight then you could rule out the gear. Would it be possible to post a video of it cranking and then running for about 20-30sec? The chain may have jumped a tooth as well.

by pila Fri Oct 02, 2015 12:37 am

X2 on a possible cracked flex plate. Kind of a common occurrence....
Compression test is a good idea, and worth knowing that there is, or isn't, a valve problem.
Take a look under the valve/rocker arm covers. I've seen broken rocker arms, and once saw a push rod that came up through a rocker arm.

by rogal_tx Fri Oct 02, 2015 11:39 am

Its a original motor out of 86 corvette, not rebuild. And I checked Spark plugs, spark plugs wires and vacuum lines and no problem there. Car starts fine but wont stay running. I will try to get a video today.

by rogal_tx Fri Oct 02, 2015 11:41 am

I also installed new timing gears and new double chain 8 months ago.

by bracketchev1221 Fri Oct 02, 2015 3:27 pm

Check the distributor. Both the vacuum and mechanical advance. It is possible that something was hung up when you set the timing and has now released. For example if the ignition was advanced and you set the timing, it could release and become retarded at idle. Also, being that you replaced the timing set, just verify that the balancer TDC and rotor #1 still line up somewhat.

by brian74montecarlo Fri Oct 02, 2015 11:53 pm

aparently my 74 monte just developed this exact problem set. wont stay running at engine idle - have to toss it in neutral at red lights to keep from stalling out - and had to turn up the idle screw on carb to around 1100 rpm to keep it from doing a steady rpm drop to stall out.

few days ago mechanic put in new msd street hei dist. (150$ unit) said my factory unit had finaly kicked the bucket - and my tach wire ( aftermarket tach ) was grounding out somehow so he just left it unpluged for me lol.
but
he also said timing was jumping back and fourth a degree or so = timing chain stretch and im wondering if i may have jumped a tooth retarded position on timing now. car ran ok but not great when i swapped in the posi and 3.73 gear from my factory open diff and 2.73
i guess the 74 factory internals did not like 3k rpm croozing at 60s mph and finaly decided to let me kno its time for a rebuild.

im super intrested to hear what happens to be the problem on your end tho as your motor is so closley describing my symptoms also.

quick question for you - has your car backfired or recently backfired since all this has happened ? when my stock hei went out - and the tack wire grounded out at the same time aparently - the car would crank and die imediately - but if i gave no gas pedal imput it would backfire the loudest ive ever heard thru the tail pipes - wich to me indicates a later than ideal intake / exhaust opening / closing and same with timing. if indeed my engine has jumped a tooth on timing then the valve and spark events are happening too late

by pila Sat Oct 03, 2015 1:03 am

Nor likely that the engine would run with the timing chain jumping a whole tooth, but it's amazing how much the chain can stretch & get really loose, like enough to wear through the side of the timing cover, which I saw once.

by rogal_tx Sat Oct 03, 2015 8:59 am

My doesn't back fired single time. I will get the video posted today.

by cutlassguy Sat Oct 03, 2015 11:31 am

Brian, If you crank the engine with #1 plug out until the piston comes up to the top, at that point pull the distributor cap and see if the rotor if facing #1. If not you know it has jumped a tooth, therefore retarding the timing will keep it going but not for long. You can also put a socket on the balancer with the cap off and check how much stretch your chain may have by wrenching on it back and forth.
Being that its now backfiring, you may have also wiped a cam lobe. The sound of popping out the carb with throttle blips will let you know if its in need of a cam and chain.
Hope this helps
Eric

by ant7377 Sat Oct 03, 2015 3:46 pm

My friends Camaro just fid the same thing,it was the cam. We took off the valve covers and cranked it with the hei disconnected. #8 rocker didnt move. New cam. He got a Lunati voodo now,Runs good.

by cutlassguy Sun Oct 04, 2015 7:31 pm

rogal_tx, I hope it was something minor. Looking forward to an update.

by rogal_tx Sun Oct 04, 2015 8:03 pm

sorry, it took me a while to get around to it. Here it is: got carb issues.
Had a friend mechanic stop by and he listen to it. First think he said its a carb. So I have old Holley carb, swapped it today. It run fine at ideal except this carb haven't been used in a while and fuel was coming out on the tap.
Already have rebuild kit coming for my eldebrock.
Once I do that I will post another update.
Thx for all the help.

by cutlassguy Sun Oct 04, 2015 8:10 pm

That's great news, Which edelbrock carb were you running? Was it a lean condition ?

by rogal_tx Mon Oct 05, 2015 7:27 am

I've got eldebrock 4 barrel 1405.
Lean condition what it appeared to be, when we hold down the choke and not let it open too much giving some gas it was running fine.

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