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New engine won't start

mr_clean

mr_clean

1/2 ton status
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Sep 21, 2003
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Location
Sacramento, CA
I need suggestions on what to check.

It is a newly rebuilt motor. Turns over fine but won't sputter. I've quadruple checked the timing TDC relation and it's dead on. Piston is up, and blows your thumb off the plug hole, harmonic balancer timing mark is on 0, distributor rotor is pointing to number 1 plug wire. Firing order is numbered 1,8,4,3,6,5,7,2.

One odd thing I noticed is when I dry adjusted the valves. I adjusted them to where the pushrods spun freely and very little play vertically in the pushrod. I also made sure the lifter was completely off the lobe when I made the adjustments. Well with the valvetrain set that way I get no compression. I back off the valve adjustment (a loose motor is a happy motor...) and I start to get compression. I get more and more the farther I back off the nuts. I mean the rockers are almost to the point where I can remove them from the pushrods and I get 100 compression.

Is 100 compression good for a motor that hasn't ever been fired after rebuild?

The heads are new GM Vortec's. I pulled stock self aligning rockers off a different 350, new pushrods, nuts and balls.

Is there something that I'm missing?

Did I not use a right part in the valvetrain?
Seems odd that I have to have so much slop in the rockers to get compression...

I have rebuilt several motors and never seen one quite like this.

Is there something I was supposed to do to new heads prior to installation?

:mad: :mad: :mad:

Thanks all!!!

Scott
 
Also I am getting spark... via timing light and pulled the plug and it fired in the dark.

I also have fresh gas pumping into the carb. I've even poured a little gas into the carb. However the plugs are never wet or even smell like gas...
 
Did you prime the engine to pump up the lifters with oil? It helps quite a bit.


Do you have spark and fuel?


I had a motor that would not fire. It took me a good month to realize the gas in the rig was two years old and varnished. I sucked out the old and put in some new fuel and it fired up...
 
sounds like a valvetrain geometry or adjustment issue...
 
I do have spark and fuel. And to correct my 2nd statement, I just pulled 7 plug and it was wet with fresh gas.

I did siphon as much old gas out as I could and dumped in 10 gallons of fresh gas.

I also primed the engine oil pump before I even tried to turn it over the first time.

I also suspect a valvetrain geometry issue, but not sure where to start checking...
 
The pushrods I bought were for a stock 86 350. I was told these were fine for my motor which is 86 with vortec heads. However that, I would think, would be the most likely area for error.

I did look over that webpage and that is pretty much how I adjusted the valves when dry. at that setting I get 0 compression (valves not closing, right?)

So I backed off 1 turn and got 25 compression, another turn got me to 50 or so... and so on and so on until I was almost all the way out and got 100 compression... does that sound like my pushrods are too long? Seems like they would be WAY too long if that was the case... Are the intake and exhaust pushrods different lengths?

I noticed that the exhaust valves have more room for adjustment on them than the intake valves. In other words if I keep an even thread count on the rocker studs, the exhaust valves will stop opening sooner than the intake valves as I back off the nuts... Make sense or is that as confusing as it sounds???

Do new heads need to have a valve grind done before they can be installed?
 
not sure what that app calls for... generally the adjusting nut will be somewhat close on thread count.. are the ones you installed the same length exh/int?
 
yes, they were all the same length. I just re-adjusted the number 1 cyl based on the instructions from that website and I get between 0 and 25 on compression...
 
Hmm, are you sure that the cam is installed properly? It sounds like it is out of time with the crankshaft. :(
 
Yeah, I'm about 99.999% sure its right. #1 exhaust goes down, then #1 Intake goes down, then TDC with rotor pointing to #1 plug wire...

I may end up checking that but I'm not ready to give up on the valvetrain issue yet. Plus I don't get any backfiring or anything... it just turns over...
 
Assuming you are not 180 degrees out of time...................
Did you degree your cam? Should Always do that so you know everythings right before final assenbly
What kind of cam? If it is a performance cam with over .450 lift you have too much lift for stock vortecs.
 
The rockers are stock self aligning so I assume they are 1.5's

Pushrod length - I don't know what the length is on them, I got them from Napa and they looked them up for me so they could have made an error...

Timing outta sync - possibly, but from what I can tell everything is right on... as per my initial post

I may try flipping it 180 out just to see if I can get a backfire or something...
or with luck it will fire up

the cam is a comp RV cam so not too high performance. I can't remember the specs off the top of my head, but I looked it up before I bought it and it worked with the vortecs.

I found the cam specs from a previous post...

it's a comp 260H

260 adv dur,
212 @ .050
440 lift
110 lobe seperation
 
did you get it fired?
if you need any hlep give me a call, well its kinda late now but the offer is there :D
 
Thanks Dale, I'm about done tinkering with it today...

It almost starts when I loosen the rocker nuts and get some compression, but the nuts are so loose that I can twist the rockers off the valve...

When I set the valve lash correctly it has no compression... Not sure what is going on, but sometimes if ya just walk away for a day or two, the answer comes to ya...

Thanks for all the suggestions all!!!

Scott
 
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