Got asked a question today....

[Maaso]

...that Ive never dealt with so I cant answer. Wondering if y'all could help?

Dude put a new engine in his truck, and couldnt get it to run. We've come to the conclusion his valves were too tight. Now, my question is.....could that hurt the new cam in his truck? He only cranked it on and off for a total of about 2 minutes in 5-10 second bursts. The cam was well lubed upon install, oil pump was primed seconds prior to initial start up, and it has good pressure while cranking.

 

[UR50SLO]

Re: Got asked a question today....

I doubt that anything happend. Was it a Hyd. roller cam or just a flat tappet camshaft??????

A roller won't effect anything.

A regular flat tappet camshaft needs a good 15+Min at 2000+RPM break in period or you risk having fish bowls for lifters. The lifters/lobes need to break into one another!!!!!

What exactly was the year/application?
Iv'e got a good way to set the lifter pre-load with out running the engine.
~Scott

 

[blk00z28]

Re: Got asked a question today....

How about you say it Scott. Lol

 

[UR50SLO]

Re: Got asked a question today....

I'd hate to give him a valve adjustment sequence with out knowing exactly what engine we are dealing with.
Any sbc/4.3L flat tappet or roller adjustments can be done several ways.
I prefer to go cyl. by cyl. Less confusing.
Turn the engine over with starter or breaker bar. Breaker bar tends to be slower but easier to go small moves at a time.
When your looking at the rockers turn over in normal rotation till the intake valve go's all the way down and 2/3 the way back up. (Adjust the exhaust rocker at this time)
Keep turning over slowly till the exhaust rocker just starts to go down (Adjust the intake rocker at this time)
To adjust a Hyd. camshaft turn the rocker nut down slowly till there is no play up/down of the pushrod. go a additonal 1/4 to 1/2 turn. (Pre-loads lifter)
To adjust a Mechanical roller or mechanical flat tappet turn the rocker nut down with Spec from Cam card ".18" example with a feeler gauge between rocker tip/valve stem and tighten nut.
Do this with all the cyl one at a time till completed.
This is the Crane Cam's Method.
Hope that helps if it's that kind of engine.

PS... I've found if the valve springs are weak or using old Hyd. lifters the valves can hang open if adjusted too tight. If you've got a miss back the rocker adjustment back .

 

[Bill Z]

Re: Got asked a question today....

Why are you assuming that the valves are too tight? Is it because there is backfire through the plentum? It may be because the timing is 180 degrees out. Very common mistake in a sbc.

Check out the compression stroke on #1 and then look at the rotor bug. It should be pointing to #1.

At least that issue will be eliminated if it is in, or near time.

Also, the mechanic that built the engine should of known the valves were too tight and corrected. If your friend put the engine together, he should have known they were too tight. If it slid around in assembly, it should start. After it gets warmed up, things may start happening.

Good luck.

 

[UR50SLO]

Re: Got asked a question today....

Hey Bill.... Show this picture to you Typhoon and then it'll have seen Snow

But seriously.. need to know what engine it is.

 

[Maaso]

Re: Got asked a question today....

Sorry for the slow response....its not a SyTy, but you gentlemen know your shit. And I dont have anyone else to turn to. Its a 77-78 SC 350. Thats about all I can tell you. Im assuming the vavles are too tight, and not letting the valves seat, and is leaking compression. That sound right? I dont know why else this thing wont start, its 90% new too.

I wasnt there when he done his valves, and hes kind of pissy about me wanting to takes the VCs off to check his work....

Its a Hyd. flat tappet too for who ever asked, and its even that new Voodoo series cam too if I remember right.

 

[JSM]

Re: Got asked a question today....

Do a compression check then.

Sounds like if he is pissy about removing a valve cover he isn't confident in his work in that area and doesn't want you to find it.