Diagnosing a misfire

[1969c10joe]

dont worry i can tell the guys mean well takin a week and makin a plan thats cool check fuel psi and floats use those tools you have focus on carb for a while maybe save some money

[1969c10joe]

maybe rebuild a 350 with some upgraded parts take the trick parts out of truck install your carefully rebuilt better than stock into truck drive truck while building trick motor maybe paint truck sell truck put trick motor in
a nova take your family to the track??? just an idea

[Grumpy old man]

First off NO ONE is mad at you , I think what's happening is we all get frustrated when we aren't there to help and we can only "see" what pictures you post or write so we can only give you a somewhat educated guess as to what's happening and why . You've come a long way in a few short months so be happy about that ! This is all supposed to be fun so let's try to bring some of the fun back into all of it ! All I'll say is if we were there with you , You would be buying the beer and burgers ! You have the opportunity to walk away from it for a few days and when you get back to you'll have a new look and these issues won't be so dire .you can back down some of the settings and get it to run great for a while as you work on other systems if we can just get you to keep your foot out of the pedal a bit . I'd be willing to bet you can still have a QUICK cruiser but it's just not to the race truck stage yet .check out some of the guys rides and build threads that are building their trucks along the same lines as yours and you'll see some of the do's and don'ts along the way in their builds , Remember it's all supposed to be fun and we all get frustrated in our own builds , learn from others mistakes or misfortunes and avoid some pitfalls along the way . There are a lot of guys with really high line restomods pushing serious HP that may only turn it loose 1-2 times a summer they've learned you can't do it every time you need milk and bread from the local choke and puke .

[1969c10joe]

well said

[davepl]

Originally Posted by Grumpy old man

Everyone wants to see you win this battle but I'm beginning to believe we are all getting punked ?
You'll never tune any engine if you can't read plugs correctly . Pull any plug and wipe it on a clean white rag you'll see soot not oil
smell it ? Any hint of fuel ?

Let's teach a man to fish, as it were. What's the difference between a wet black sooty plug and an oily plug? How do you tell? When you wipe it on a rag and they both leave black, which is oil and which is soot? Give him something to go on.

Now I'm not trying to give you a hard time but... your not going to build a high performance engine your first time out no matter how much $ you throw at it .

Testify! I'll be the choir...

And getting crazy over valve lash settings is overboard.

I doubt his lash is wrong but I think he does't fully grok it. I think he's probably setting them correctly but isn't confident because he doesn't really -know-. Is it fair to say that if it runs for 10 minutes without clatter the lash is OK? If it were too tight, it'd die or wipe a lobe? Tell him what he needs to know to be confident that lash isn't the problem. He's big on lash. He knows EOIC and so on but doesn't feel like he's certain he's doing it right (my guess, anyway).

Bigger and badder doesn't always work especially when dealing with carbs .

Bigger and badder is often badder, but not badder in a gooder way, just badder in a badder way like runs like crap. Keep preaching, I'm with you!

Well we know one thing none of this makes sense

What is the difference between the Master and the Beginner? The Master has failed more times than the Beginner has tried. So before the Beginner can become a Master, he has to get all his mistakes out. I, like Grumpy, probably advocate making those mistakes on cheap parts.

Unless you're secretly a trust fund baby, you can't afford to make the mistakes on trick parts and you can't afford to make the same mistake twice. Any while even animals learn from their own mistakes, a refined man learns from the mistakes of others - so ask a lot of questions and LISTEN to the advice. That doesn't mean it'll all be right, but it's probably coming from people around here that already made all those mistakes, or if not, know how to avoid them.

You can't build a Top Fuel motor until you can make a 1-cyl lawn mower run for 10 seasons. And I don't think you should build a full-roller, forged-everything screamer until you can build a wheezy old 307 that starts in -40F and purrs like it'd rather be running than not.

Start small. Make it perfect. Build on that. Repeat. Skipping steps is failure.

And Mr. Turner, no one is mad or making fun of you at all - to the contrary, I think everyone wants you to succeed. It's just that they'll give you all this well-thought out advice about taking it slow, small changes, and you'll come back with why you need a high-dollar, forged and CNC'd magic part, when all it takes is a little careful wrenching of basic parts. Some days I'd swear if your float was low we'd suggest you raise the float level and you'd be adamant that the solution is multi-port direct injection.

Case in point: a black plug. Could be oil, could be fuel. You could sort out which, you could do a compression or leakdown test to verify the rings are still good (I bet they're just fine), but you already had the catalog out with pictures of the new killer rotating assembly! You just can't throw money after that stuff until you have the ability to sort an oily plug from a fueled plug. Well you can, but not usually with great results. So you need to be able to (a) diagnose that stuff, (b) fix that stuff. Otherwise what happens when you've got a billet block and 4340 forged crank and Olliver rods and THEN your power valve fouls a plug? What then, an even better Callies crank? As you can see, it's chasing the wrong thing.

To put it more simply, we all want to see you succeed small first. Then go blow up your expensive parts, but we want you to have the success of building a mundane but RELIABLE powerplant first. Then when your projects are no longer mundane, they'll still be RELIABLE. Then you take all of those skills you acquired on the cheap motor to the expensive motor.

Trying to acquire those skills on the fly with expensive parts is a recipe for heartache that I don't think any of us looks forward to watching.

We're rooting for you. Root with us, not against us :-)

[davepl]

Here's one more for you: I was just talking with some friends yesterday, at a pro shop, where they have just rebuilt the stock 350 from a 68 Camaro. It was a totally stock motor, rated at 255hp I believe.

They bumped the compression up a bit (from 8:1 to 9.5:1 I think) and put a mild hydraulic roller cam in it. Stock iron heads, cast crank, factory rods, everything else the same.

It cranked out 370 on the dyno. That's a real deal water-brake 370hp, not a chassis dyno hero number. That may not sound like a lot in this world of 480hp LS motors, but it's pretty stout for a 1960s 350.

And all if took was a guy who's been building motors for 40+ years and some pretty cheap parts, in the big scheme of things. I mean it's still iron heads!

Knowledge is horsepower :-)

[RichardJ]

>> the carb settings were all good to go. Mixture screws were exactly where member Hugger said to put them,<<

2 turns OUT is a bench adjustment. That would be where you could set them when you rebuild a carb. It's a starting point so you can get the engine running for the first time.
You start the engine, set the timing, adjust the idle speed (hopefully down close to 600), then you make the adjustment to the mixture screws as needed. When adjusting mixture screws, turn both screws 1/4 turn and let engine settle. You use your vacuum gauge and tachometer to adjust for highest vacuum and highest rpm. With speed screw, adjust idle back down and readjust mixture screws.
Which direction from starting point? The direction that shows improvement in vacuum and rpm. 1/4 turn at a time. You stop at the point it stops showing improvement. Readjust speed screw.

Idle mixture screws meter fuel at idle, only. As your adjustment increases rpm, the idle speed screw is used to lower rpm back down.
Repeat.


Try readjusting the timing. If it will take more timing without pinging try that.

Carburetors are not plug and play.

Carburetors are not plug and play.

AS I stated and you ignored.
>> 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.<<

ARE THE MIXTURE SCREWS RESPOSIVE TO ADUSTMENT?

If not, you need to find out why.

No one is mad at you. Frustrated that you continue to pat yourself on the back about how much you have learned, but display ample evidence to the contrary.

[68is4me]

I agree with all the above guys. I enjoy reading your post and I can see that you have come along way. But sometimes it is feel like this Don't be discouraged sometimes you just have to walk away and come back at a later time.

A wise old teacher told me KISS = Keep It Simple Stupid

You have the tools, you have the resources, now you just have to execute the advice given.

When I was young and dumb I built up a 305. Yes a 305, stuck a bunch of money into cam, manifolds, carb and all the fun silly stuff. Boy was that an oil burning, shaking, underpowered, POS. But I learned by my mistakes, I also built some really nice power plants, with the help of some local racers and the local machines shop. Just hang in their we all know you can do it.

[1969c10joe]

Man you got a lot of good people pulling for you. We all learn from mistakes.So check fuel pressure inspect carb set float level and spend time with your family.Maybe ill see you on power tour if i live long enough.Good luck and have fun.

[1969c10joe]

if you screw idle screws in all the way and it doesnt stall then you are way rich. In my case my fuel psi was too high installed regulator then i calibrated carb.Smell the plugs do the smell like fuel?

[1969c10joe]

maybe review thisthread and make some notes. then you can focus on one thing like your carb

[Mrturner1]

Originally Posted by davepl

Some days I'd swear if your float was low we'd suggest you raise the float level and you'd be adamant that the solution is multi-port direct injection.

Case in point: a black plug. Could be oil, could be fuel. You could sort out which, you could do a compression or leakdown test to verify the rings are still good (I bet they're just fine), but you already had the catalog out with pictures of the new killer rotating assembly!

Now that is funny, you nailed that one right on the head. Summit package, Scat 9000 crank, forged pistons and forged H beam rods lol I guess I did jump to conclusions about the spark plug, but I really thought it was oil and probably assumed the worst. I pulled the plug at night and then went out of town to work the next morning, and didn't think to smell it. But thinking back, when I swiped my finger on it the wet black stuff was very very thin and watery, so maybe there's hope for my rings.

[Mrturner1]

Originally Posted by RichardJ

Frustrated that you continue to pat yourself on the back about how much you have learned, but display ample evidence to the contrary.

thanks Dick!








Can I call you that??

[Mrturner1]

Ok so my plan is this, first thing when I get home Thursday is gonna be to break out the new compression tester and do each cylinder. I'll write that down and then post it so you guys can tell me if its good news. I thought my floats were to high because somebody mentioned that fuel being halfway up the glass sight window on my carb is too high. I called Holley and they said that's perfect so my floats aren't the rich condition culprits. It sounds like RichardJ is pretty positive my mixture screws aren't right so I'm gonna give that a shot with the vac gauge. Power valve is brand new and the new one is a 4.5, as opposed to the 6.5 I took out. If the vac gauge is right and I'm pulling 6"Hg then even the 4.5 is too much but I'll cross that bridge when I get to it. I wouldn't be surprised if the vac really is 6"Hg because my cam is 236@.050 and its on a 106 LSA, not vacuum friendly at all. I'm also going to pull the rest of the plugs, and learn to read them so I can better diagnose the problem.

I appreciate all the help guys, this truck wouldn't even run if I didn't have everybody here to bounce stuff off and get good advice

[hops]

Man, these guys are patient.
Unless holley changed design, you need to set the float levels to the bottom of the sights. Old style you had to pull the plug to set em, as they were solid plugs. Nothing better than setting float levels on a hot engine.
Then, set the idle screws. You can use a cup of water, if necessary. When one side isn't boiling the water, hit up the other side. It's been awhile, I tossed the old p.o.s. when I rebuilt it.
And if you can't kill the engine by turning them in, your over jetted/over carbed.

Anyone close to mrturner? He needs a crash course.

**I feel for you, but you're not listening...

[1969c10joe]

and if your oil is contaminated with fuel change it ps take your family to the track maybe? its fun

[Mrturner1]

Originally Posted by hops

Man, these guys are patient.
Unless holley changed design, you need to set the float levels to the bottom of the sights. Old style you had to pull the plug to set em, as they were solid plugs. Nothing better than setting float levels on a hot engine.
Then, set the idle screws. You can use a cup of water, if necessary. When one side isn't boiling the water, hit up the other side. It's been awhile, I tossed the old p.o.s. when I rebuilt it.
And if you can't kill the engine by turning them in, your over jetted/over carbed.

Anyone close to mrturner? He needs a crash course.

**I feel for you, but you're not listening...

Are you kidding me how am I not listening?? I'm starting to think it's just amusing to tell me I don't listen and I don't know what I'm doing. Everything that's been suggested is getting looked into and put into action, give me a break man

[Mrturner1]

Originally Posted by davepl

Here's one more for you: I was just talking with some friends yesterday, at a pro shop, where they have just rebuilt the stock 350 from a 68 Camaro. It was a totally stock motor, rated at 255hp I believe.

They bumped the compression up a bit (from 8:1 to 9.5:1 I think) and put a mild hydraulic roller cam in it. Stock iron heads, cast crank, factory rods, everything else the same.

It cranked out 370 on the dyno. That's a real deal water-brake 370hp, not a chassis dyno hero number. That may not sound like a lot in this world of 480hp LS motors, but it's pretty stout for a 1960s 350.

And all if took was a guy who's been building motors for 40+ years and some pretty cheap parts, in the big scheme of things. I mean it's still iron heads!

Knowledge is horsepower :-)

370!!?? Holy cow man that's a lot for just a roller cam and a bump in compression. Is it possible mine has that much?

[hops]

Sorry if I came off harsh. I learned what I told you the hard way. I didn't have the current Internet to bounce information off of. It's nice having gigs of information at your fingertips. It's awesome really. But if you can't separate the wheat from the chaff, or apply it, it doesn't mean a thing. Get er done. Good luck.

[Grumpy old man]

Are you still dumping hot gas in your tank ?

Google "reading spark plugs " NGK has a good description with pictures

Use your senses - sight of course , but learn the correct smells associated with clean oil vs fuel fouled oil , clean trans fluid vs burnt ,, look at the plug you pictured is it wet with oil or are you really seeing black soot from unburnt fuel ? Touch it is it thick or thin ? what's it smell like ? When left on the bench for 30 minutes does it dry out ? You've mentioned strong exhaust fumes , is it the hot gas smell or is it flooding and unburnt fuel ? Burning eyes usually comes from hot fuel and mixing fuel is a science in its own right not just dumping a 5 gal can of 110 in when the gas gauge is low and constantly varying fuel quality can lead to all kinds of tuning issues . Drain the tank and just run premium gas with no additives and set up the engine that way before adding the complexities of hot fuel to your tuning ritual . And one more quick check down to the exhaust pipe and look at the color and assess what's there by inserting your finger and swiping the inside of the pipe , what's there ? Is it black and oily ? (Rings-valve guides) Black and dry smelling like fuel ?(carb -fuel issues) White/tan with Minimal residue ?(running lean ) These simple quick assessments can clue you right into what the engine is doing and how healthy it is .and should be used by anyone looking to buy their next truck before driving it .

[Mrturner1]

Originally Posted by Grumpy old man

Are you still dumping hot gas in your tank ?

Google "reading spark plugs " NGK has a good description with pictures

Use your senses - sight of course , but learn the correct smells associated with clean oil vs fuel fouled oil , clean trans fluid vs burnt ,, look at the plug you pictured is it wet with oil or are you really seeing black soot from unburnt fuel ? Touch it is it thick or thin ? what's it smell like ? When left on the bench for 30 minutes does it dry out ? You've mentioned strong exhaust fumes , is it the hot gas smell or is it flooding and unburnt fuel ? Burning eyes usually comes from hot fuel and mixing fuel is a science in its own right not just dumping a 5 gal can of 110 in when the gas gauge is low and constantly varying fuel quality can lead to all kinds of tuning issues . Drain the tank and just run premium gas with no additives and set up the engine that way before adding the complexities of hot fuel to your tuning ritual . And one more quick check down to the exhaust pipe and look at the color and assess what's there by inserting your finger and swiping the inside of the pipe , what's there ? Is it black and oily ? (Rings-valve guides) Black and dry smelling like fuel ?(carb -fuel issues) White/tan with Minimal residue ?(running lean ) These simple quick assessments can clue you right into what the engine is doing and how healthy it is .and should be used by anyone looking to buy their next truck before driving it .

Thank you for the detailed checklist I really appreciate it. I'm pretty excited to get home and check all this stuff now. I never would've thought to stick a finger in the exhaust pipe, but it makes sense.

I quit running a can a race gas when I took out that obnoxious cam I had in there. It bumped up my compression too much and almost always pinging under load. I've been filling up with premium for a couple months now and it does the job fine.

[Grumpy old man]

Well... a couple things to keep in mind are the old carbed 350's aren't today's computer driven driver friendly Ls engines with 100,000 mile plugs or multi coil ,injection so it can be trying to tune for drivebilty vs stomp it to the floor drag strip performance and achieve both !

Let's look at some old school side of the highway quick adjustments (Yes , back in the day we used to grudge race at 2:30 in the morning down the interstate , 1970's rt 287 northern NJ ) but we still had to use the trucks to get to work the next day .

Your constant pinging problem , leave the timing light in the garage and have your girl stand on the brakes(Hopefully they'll hold ) put the truck in drive and while your controlling the throttle increase engine speed to slowly apply a load to the engine when the pinging starts retard the timing until you have a steady pull with no pinging . This is the engine telling you where it wants to be not some book , tuning in FL at sea level is totally different than Nothern Ca so settings will be totally different based solely on altitude , you have multiple high perormance parts that your trying to get to work together from multiple suppliers so reading some book or tuning to bubbas numbers won't work ! Don't drive over yourself !

Your carb , while we really don't know where your floats are set once you have them correct it's been mentioned before to start at 2 turns out . This is just a starting point not the setting ! Leave the vacuum gauge in the garage , bring the engine up to fast idle and adjust the mixture by first slowly turning out until you see a rpm change then turn in slowly until you hear a stumble then slowly turn back out 1/4 to 1/2 turn the mixture settings are going to be somewhere between 11/2 to 3 turns out max . That's why you've been told to start at 2 turns out .

These old school side of the road easy , free adjustments are quick and will get you close to where THE ENGINE wants to be NOT THE BOOK .

Try it , it costs nothing ,hurts nothing ( if you don't drive over yourself ) and it's all easy to change back if you don't get the results I'm hoping you will .

Having fun yet ?

[Mrturner1]

Well I'm on day 5 after getting a vasectomy and I'm finally able to walk around without hobbling lol so it's time to start trying out all these great tips and tricks you guys have been filling me in on. I really appreciate all the help, and also you guys giving me sound advice that I can use. I'm gonna start with a compression test cylinder by cylinder and write everything down. If it doesn't have rings that seal then what's the point right? After reading all of GrumpyOldMan's thoughts I'm starting to believe it's not oil on the spark plugs, which would be great.

[Mrturner1]

Okay compression test is complete. Hopefully you all enjoy my professional diagram and chart skills lol it's easy enough to read I'm sure. It looks pretty consistent but I'm not the expert so you guys tell me what you think

[davepl]

165 vs 180 seems like a lot of variation, but I guess it's only about 10%.

Did you have the throttle blocked open when you did it? You'd imagine that forgetting to do that would reduce them all by the same proportion, but it doesn't always seem to work that way.