Diagnosing a misfire

[Mrturner1]

Originally Posted by RichardJ

>> I set the lash too tight, and if the lash is too tight then there's no buffer between the lifter and rocker arm and that's how you get a flat cam correct?<<

Buffer? What the hell do you think you're talking about?
If the valves are too tight, you run the risk of holding the valves off the seat or not letting the springs hold the valves tight against the seat for good heat transfer. That can lead to burnt valves.
If the valves are too loose, the valve train is noisy and really loose, hammering causing excessive wear.
The most important aspect of valve lash is to allow for heat expansion and not reach either of the extremes mentioned above. Hydraulic lifters self adjust to allow for expansion, never need readjusting and are much quieter.

Stop trying to use valve lash as a tuning aid.

The cam is not causing the rich mixture. The rings are not causing the rich mixture. A flat cam lobe is not causing a rich mixture.
You don't wipe out 16 cam lobes at the same time. If all the adjuster nuts are at approximately the same height, you don't have a cam problem. You did just adjust them. I have to assume you adjusted them correctly.

Stop flitting from one wild guess to the next.

Get rid of the vacuum advance. adjust idle down to 600 and see if the idle mixture screws are responsive to adjustments in or out from the 2 turns you set them at.
I'm making the assumption that your 2 turns out is a setting and not an actual adjustment. Use your vacuum gauge and a tach.

>>36 total all in at 3000 rpm.<<
Who cares. At this point it is more important to know at what rpm mech advance begins.

Give me a break dude, were you born with all your knowledge about motors or did you learn by trying it out and making mistakes?

Solid cam lash is actually a tuning aid for those who know what they're doing, not there yet but it's not like I'm blowin it by giving it a shot to see how things change.

There's no flitting from one wild guess to another, I'm here with the truck, and know the thing inside and out so there's a good chance my hunch is correct, and that's all I was saying, it was a hunch.

You asked about all my timing and carb settings, so I told you what they were and you say it's not an adjustment it's a setting, and who cares about my timing. You asked, I assumed you wanted to know. So does my timing and mixture screws really seem that off to you??

[Mrturner1]

Originally Posted by midniteblues

Dude bro...your lash is fine .15-.18 is ok but ya gotta remember a good warm engine things will expand some and loosen up.

Its a shame somebody cant masterlock up your internals and keep you out of the innards!

VERY BIG QUESTIONS HERE.

Did you replace that oe resistor wire properly? Please tell me you did. Gotta feed it the proper 12v juice for that coil and plugs too fire properly and burn all of the cly. Fuel/air charge

Do you have more than enough clean and proper engine to frame to body grounds? If ya feed the plugs the good 12v its gotta have a good clean path to travel out of the block and back too the charge system. Believe it or not bad motor grounding can lead too weak spark and fouled plugs.

If your bowls are "half" way up the sight plug the float level is too high.

You should be able too remove the plug and have no fuel come out of the hole while its running.
Only if you gently rock the truck should it trickle out.
That is a starting point for float level.Start there and adjust the float up during test runs. After you get the plugs too stay clean.

A 750 is big but can be made too work ok.
At this point i would not be concerned with the power valve forget about it for now unless you had a serious back fire.

You need to find what your fuel pressure is. Holleys can take alot but you can still over power the needle and seat.

Can you turn mixure screws all the way in "lightly" seated will it still run without dying out?

Your getting TOO much fuel and also you could not be burning it completely.
Lets be sure you dont have dirt in the needle and seat and good fuel flow.


There is lots of little bits of very good advice in this thread its up too you on what you do with it.

Btw i would give g.o.m the key😁

I don't know what wire you're talking about. I was supposed to replace a resistor wire? I had some wiring trouble a while back but that was one of the old wires from the points system that was on it. I didn't think that needed to be replaced because I have HEI now.

[1969c10joe]

1you are running rich.2 you have wrong power valve 3your float might need adjustment i dont know holleys im not sure4 check fuel pressure 5 put the other carb on and see if it still runs rich and stops smoking

[1969c10joe]

in my limited experience weak spark usually shows up at highrpm good luck

[webfoot]

That wire needs replaced. It's designed to lower the voltage so the points don't burn up. Hei needs full 12v, I recommend a relay.

No amount of valve train adjustment is going to make those plugs look good. You need to get the carb off of there and get those floats adjusted, and inspect the needle and seat. You have 4 pages of pretty good advice so far, might be time to take some of it.
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[davepl]

Originally Posted by Mrturner1

I don't know what wire you're talking about. I was supposed to replace a resistor wire? I had some wiring trouble a while back but that was one of the old wires from the points system that was on it. I didn't think that needed to be replaced because I have HEI now.

You should search the forums on this one (resistor wire distributor) as it's fairly important.

In brief, however, in order to avoid burning the points the factory used a wire with resistance built into it. It's the white wire, normally. When you change or upgrade to an ignition that wants a full 12V, you need to get rid of the resistor wire and power your ignition with a full 12V from the fusebox.

If you keep the resistor wire you're basically trying to power a 12V unit with 6V, and the results can be unpredictable.

In your case, however, you've got a fuel issue to fix before you start chasing zebras. Fix the horses first.

[1969c10joe]

hey dave thanks i actually forgot about that now mrturner gets to use his multimeter

[1969c10joe]

Ijoined cause my drum brakes stumped mechanics and me took only one day to get a handle on them but I was all ears good luck

[webfoot]

Originally Posted by 1969c10joe

hey dave thanks i actually forgot about that now mrturner gets to use his multimeter

Did you not believe me?
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[davepl]

Remember you can't just measure voltage, you need to measure resistance.

[1969c10joe]

sorry webfoot thankyou too was making fun of my age I am suffering from early onset of oldtimers disease

[Mrturner1]

Originally Posted by webfoot

That wire needs replaced. It's designed to lower the voltage so the points don't burn up. Hei needs full 12v, I recommend a relay.

No amount of valve train adjustment is going to make those plugs look good. You need to get the carb off of there and get those floats adjusted, and inspect the needle and seat. You have 4 pages of pretty good advice so far, might be time to take some of it.
Posted via Mobile Device

I remember now, I was having issues with the resistor wire still being in the harness and it started to cook and smoke. So I pulled it out and ran a nice big fat red wire to power the ignition.

[Mrturner1]

Originally Posted by webfoot

That wire needs replaced. It's designed to lower the voltage so the points don't burn up. Hei needs full 12v, I recommend a relay.

No amount of valve train adjustment is going to make those plugs look good. You need to get the carb off of there and get those floats adjusted, and inspect the needle and seat. You have 4 pages of pretty good advice so far, might be time to take some of it.
Posted via Mobile Device

It cracks me up when people do this, I assure you I'm taking all the advice. I've bought 3 tools in the last 24 hours and started doing checks on my carb/motor that I've never done.

[Mrturner1]

Originally Posted by 1969c10joe

1you are running rich.2 you have wrong power valve 3your float might need adjustment i dont know holleys im not sure4 check fuel pressure 5 put the other carb on and see if it still runs rich and stops smoking

Ok so goin down your checklist, I jetted down on the primary from 73 to 70 because I was getting a black puff if accelerating hard from low rpm. I also measured vacuum and got 6"Hg in gear, so I put a 4.5 power valve because that's the smallest I currently have.

Now, someone mentioned float levels, and only supposed to be able to see fuel in the sight Windows if you rock the truck, but I can see fuel halfway up the sight window. So that needs adjusting still. Went through all my wiring and it's tits, I replaced everything with heavy gauge wire when I put the Powermaster alternator in.

[Mrturner1]

Well boys, it may be time to throw in the old towel and get started on my project short block.....just pulled this puppy out of the #5 cylinder.....I had a hunch

[1969c10joe]

cool jetting is important but if your floats need adjusting and or psi is too high they should be tended to first. to create that much smoke its unlikely jetting.Sides didnt you say carb ran fine at one point?

[davepl]

I still wouldn't pour money into an expensive motor project until you've SUCCESSFULLY built a budget one and it's run for a few thousand miles.

You're still new at this, as we all were at one time. And you're going to make mistakes, as we all did. But make cheaper mistakes. Make them on an old vanilla 350.

Otherwise, all of the mistakes you will inevitably make will be made on expensive parts. Don't think that just because you pay more for the parts that you will somehow rise to the occasion and do flawless work because the parts are expensive. It doesn't work that way.

Try to get your truck to go FAR before you go FAST.

[1969c10joe]

nice what do you think caused that?Btw I said powervalve not jets good idea to write down carb adjustments in a log in case you need to go back

[Mrturner1]

Originally Posted by 1969c10joe

nice what do you think caused that?Btw I said powervalve not jets good idea to write down carb adjustments in a log in case you need to go back

My rings are old and worn...it's been on its last leg for a while I'm sure. That's what happens when you throw some bigger heads and a choppy high rpm cam at an old factory short block. I did change the power alive but it needed a primary jet change as well. No matter now I suppose.

[Mrturner1]

Originally Posted by davepl

I still wouldn't pour money into an expensive motor project until you've SUCCESSFULLY built a budget one and it's run for a few thousand miles.

You're still new at this, as we all were at one time. And you're going to make mistakes, as we all did. But make cheaper mistakes. Make them on an old vanilla 350.

Otherwise, all of the mistakes you will inevitably make will be made on expensive parts. Don't think that just because you pay more for the parts that you will somehow rise to the occasion and do flawless work because the parts are expensive. It doesn't work that way.

Try to get your truck to go FAR before you go FAST.

Well there is a member from this site who lives about 15 minutes from my house, and he says he has a 350 long block that was running when he pulled it. It was running rough, but it was running. I think this will be my best choice because if you remember, back when I had my engine out on a stand I found a 5" long crack in the block. Plus it's already .040 over bore so I think a fresh start will be good. If I get a rotating assembly and use the block from the member I live near, it looks like I'll be into it for about 750$ bucks, but that's not including the work needed on the block before it's ready to build. Doesn't a block need some cleaning and mag, hone and decking? That's a couple hundred most likely plus cam beatings and install for those. Install the crank bearings and then I'd be ready to build it in my garage. I'd say at that point id have 600 into the rotating assembly, 100 for the local long block for sale, and what? another 300 for the machine shop to prep the block? So all together that's about 1000 bucks into it??

[1969c10joe]

mr turner your thread is very interesting to say the least. did you determine the problem with leak down test and or compression test?Hows your valve guides?

[Mrturner1]

I suppose the extra cheap way would be to buy the 100 dollar long block, strip it down to just the crank and rods but leave those in it. Then buy a decent set of new pistons and rings, install those and put all my top end stuff on it. I'd probably be in it for closer to 400 bucks that way, but I'd be putting a lot of faith in the crank and rods and rod bearings that are already in it.

Man what a bummer this is

[1969c10joe]

cam beatings? yeah i bet your cam gets beat!im gonna share my secret engine building technique. make friends with a good machine shop bring them coffee donuts lunch DONT DATE THEIR DAUGHTERS.

[1969c10joe]

call your local machine shop see if anyone has abandoned a block once theyget an estimate they abandon it

[1969c10joe]

ill never be offended if you dont take my ideas or advice im having fun