Mr D.

OK, I posted in another thread that I felt my 65 327 350hp had no responce in the 750-1500 RPM range and with the help of Jerry, Berry and JohnZ to name a few I got the timing, valves etc set up correctly.

Well I drove the car again yesterday and still didn't get that warm and fuzzy feeling that it was correct, something just did not feel right about the engine. Hard to describe but I have owned and driven both small and big block Chevy's for the last 35 years and this engine is just not running right.

So today I did some more trouble shooting and discovered #1 cylinder is dead and #4 is weak. By this I mean when I pull the #1 plug wire off the cap there is ZERO difference in RPM or the sound of the engine, when I pull #4 (with #1 already off) it takes about 4-5 seconds to hear any difference in the engine RPM, I get the same results at 1000 RPM. The #1 cylinder is without a doubt DOA, dead, nada. All other cylinders drop off when the plug wire is pulled.

What I have looked at so far:

1. Pulled dist cap and looked for cracks or carbon trail, none found cap looks brand new as it should.

2. Pulled #1 plug and it looks normal, not wet or black. Swapped it with #3(plug also looked normal) and had same results.

3. Slaved in a new plug wire to #1, same results.

4. Sprayed intake rails and carb base with carb cleaner checking for a vacuum leak, none found.

5. Pulled valve cover and started engine, #1 valves open and close and are equal in operation to the rest as I can see with the naked eye.

6. Ran a compression check on #1, have 180psi.

7. Adjusted carb for the hell of it, when adjusting in the driver side air/mix screw I can turn it all the way in and not kill the engine but RPM does drop (turned it out 1 1/2 turns, than adjusted the pass side and when it is turned all the way in the engine dies. Not sure if this has anything to do with a dead #1 cylinder.

Not sure what direction to head in at this point, any ideas?????????

ghostrider20

Try a different coil. Or check the coil with a VOM or hold the coil wire to a ground, the spark should jump at least a half inch or so.

John S 1961

and they are most effective at the low rpms you are talking about. I was very surprised how smooth they make them run

wombvette

There is one thing that is for certain. If you have fuel, compression, and fire at the right time. It is going to run. It will be one of those items. So, now it is your job to check each in a logical manner and you will find the problem. I suspect a vacuum leak on the 1-4 runner making it very lean.

Mike McCoy

I may be WAY off, but have you checked the cam lift on the rocker arms. Current motor oil is no good now for old engines. You will wipe out the cam in short order (like 200 miles) unless you add zinc to your oil. If the cam lobes are worn, the engine will run, but power will be way off, especially at low RPM.

Mr D.

Goashrider - The primary and secondary coil circuits checked out good.

Vacuum readings:

750RPM - pointer wavers between 12-14"hg

1500RPM - pointer fluctuates between 18-18"hg

Dropping throttle - pointer jumps to 23"hg than drops to 13"hg and starts to waver between 12-14"hg

My Chilton manual states that if the range of the pointer decreases but wavers more rapidly with increased engine speed probably lies in an intake manifold leak.

If the pointer becomes more stable with an increase in engine speed it could point towards trouble in the carburetor.

I have another carburetor I could throw on it and see but that would be a new one for me, if that is no help than I guess it's time to pull an intake.

Anyone out there with a LT1 cam, what is your vacuum reading at idle

Mr D.

Have not done that yet but as I stated they appear to be doing their job.

jerrybramlett

Dennis, here's what you said in the last thread: "I then adjusted all valves to .023", the intake valves were in the .016-.017" range and the exhaust valves were in the .020-.025" range. I then started the car and guess what, 15" HG of steady vaccum."

Since you were happy, I kept my mouth shut. But I was thinking that's a very tight valve lash setting for an LT-1 cam.

The GM lash recommendation for your cam is .024" I / .030" E. I know some people believe super-tight lash settings will give you 10 more horsepower at 8,500 rpm. If you're a serious circle track racer, then knock yourself out. Your car will be outrun by a dump truck on the street, however, until you open up the lash to stock.

Your vacuum reading at idle now varies. It was steady right after you set the valves. Do you know what caused this change?

Mr D.

Jerry, not sure what's going on with the vacuum being steady than not or maybe it never was. I will loosen the gap up and see what this gets me but I would think #1 would fire at .023 setting.

But than what do I know at this point.

jerrybramlett

I wasn't very clear. While I think you should open up your valve lash, I don't think tight lash is causing those two cylinders to misfire.

The varying vacuum level at idle is telling us something else is wrong. I would reset the lash and then take another vacuum reading.

I'm kinda stumped on this recent problem. You've got plenty of compression. I know you've been clamping your timing light on the #1 wire, so you would have noticed an inconsistent flash at idle, right? I don't understand how your carb could short only one or two cylinders consistently, but that's all that's left if you have compression and spark.

wmf62

someone, who shall remain nameless, advocated setting the LT1 lash much tighter (i forget the exact #s) than 24 & 30, so i tried it; kids on bicycles could outrun me...
Bill

mayordaly

If your vacuum and compression checks out, along with timing and spark
you can check those cylinders with a IR heat gun, If they are running a lot hotter then rest after a long run, you may have a head gasket leaking or head warping when hot. If that checks out OK, I would think
something in valve train, worn cam lobe, spring, or lifter.
You coud also temporally bypass you fuel pump with an electric one, (low fuel preassure)
Just something else to think about?

56Heap

Have you pulled #6 and #7 plug wires while the engine is running? If so do they seem to make much of a difference?

steveair

if you use prolong additve will this be effective?

DansYellow66

I had a problem that sounded a lot like this on my car once and it turned out to be an intermittent short in the plug wire at the plug boot area. I know you said something about "slaving" in another plug wire but I would try another wire yet. Matter of fact I would put a new cap, coil, condensor, rotor and plug wires on it before I tore into it.

It also would be a good idea to get a can of choke cleaner and tube and give all your carb air bleeds and idle passages a shot of cleaner in case there is some junk in one of them.

If that doesn't work then you may need to run a leak down test, although with 180 compression it shouldn't leak enough to prevent firing.

Mr D.

Yes, when I pull 8,3,6,5,7,2, those cyl drop off line.

Jerry, that is on my list of things to do.

Good flash at idle and I have spark at the cap and assume spark at the plug.

I don't understand that myself but I do have another carb to throw on it to see if the problem stays or goes away.

New cap, coil, condensor, rotor and plug wires are an option but the ones on there are new.


I'm going to break the code on this, this will not kick my azz.

Donald #31176

A quick check using an unlit propane torch around the questionable runners might reveal a leak.

Mike McCoy

I don't know anything about prolong. Go to the Z Maxx website for comparisons of all products of this nature.

macdarren

IF you end up tearing this down to solve the problem one thing to look for....

I once has a similar problem... turned out to be a crack in the cylinder head behind the intake valve. It was hard to see even after we magnafluxed the head and I don't think it really opened up until the motor was hot. The theory goes that the the cylinder was pulling in water that kept it from firing....the car did need a little water top off now and again but nothing that seemed excessive, and I would have expected some steam out the tail pipe but again nothing. I can only conclude that the water so extingished the ignition that the water just never vaporized or that it was so little water that it could not be seen. Anyway just something to check if you can't beat without tearing into it.

As a pre-tear down last resort it might be worth pulling just the intake...I did once help with a motor where someone forgot to remove the paper towel place in the intake runner to prevent thing from falling in when while the intake was off. But I would think that kind of problem would have shown up in the compression test, but maybe not at cranking speeds.

Mr D.

Update:

I threw $100 worth of ignition parts at it, coil, points, condenser, cap and rotor with same results.

Did the unlit propane torch thing, nada.

I than swapped out the carb with one I had on the shelf but this also proved fruitless.

#1 still dead and vacuum wavers between 12-14"hg

Tomorrow I will adjust all valves to .032, do a leakdown test on #1 and put the carb back on and see what we got.

If that proves nothing than I will pull the engine back out.