Built drag truck having issues

S

slosh

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Joined
Jun 6, 2008
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So I've built a drag truck from a bone stock Virgin 02 24 valve. Run down motor is fully built, balanced. Flycut pistons, 12v rods, etc. I just recently completed it and I was Driving my truck from my buddies shop home and my truck made a bang and started shaking real bad. Pulled over and pulled the valve cover off and all my bridges on the #5 and #6 rocker Arms came off and were laying on top of the head. So I thought the issue was my stock pushrods. I bought billet pushrods from Hamilton and installed them. Upon driving home from my buddies shop again, it did the same thing. I have enough clearance on my flycut pistons, I'm running a colt stage 5 cam with 140# single valve springs. What could be my issue. Some of my theories were ..

My theories are:

1. The valve springs are too stiff

2. The valve spring retainers are touching the valve guides

3. Valve guides and valve seats weren't cut deep enough

4. Pistons and the valves are making contact.



I'm stumped. I am looking for some more opinions and maybe I'm overlooking something
 
are your pushrods 'seated' into the tappet? you can double check that they are all the way in the tappet by pushing down on the pushrod and turning it, and then trying to pick up on it. The oil will create a little suction on the pushrod, and will create a little resistance.
 
Factory pushrods were all mushroomed. The new pushrods are extreme duty from Hamilton.
 
My rocker assemblies are tight and the further back you go with cylinders, the looser the assemblies get.
 
I have a feeling my flycuts were cut wrong. I was told I needed 70 thousandths cut out of them for my cam clearance and I had my pistons cut at 100 thousandths and I'm also running a 20 thousandths over head gasket. Colt said I had plenty of clearance, that what makes me think it's not piston valve contact. BUT I'm not ruling out the machine shop didn't mess up. I'm just looking for some explanation. My whole truck build wise is ALL BRAND NEW parts motor, head, etc
 
How would they screw it up? Cut them in the wrong location?
 
Yes it does. We have been scratching our head. We have done everything right and like I said everything is brand spanking new
 
slosh said:
Yes it does. We have been scratching our head. We have done everything right and like I said everything is brand spanking new
Click to expand...

if you didn't check PTV clearance, you didn't do everything right :lolly:
 
are you breaking the bolts to the rockers and they are laying in the tappet cover? or are the rockers breaking around the bolts?
 
The rocker bridges are laying on top of the head. Ctdiesel99, I'm kind of on the outside as I had a buddies shop help me with my truck. I hope you're right about PTV contact. That way I have the issue found and I can fix it ��
 
This is a bit of a long shot, BUT... you could have overtorqued and stretched the bridge bolts and they are popping and allowing the bridge to come off. or they are undertorqued coming loose and that is snapping them as well.
 
Nootch said:
This is a bit of a long shot, BUT... you could have overtorqued and stretched the bridge bolts and they are popping and allowing the bridge to come off. or they are undertorqued coming loose and that is snapping them as well.
Click to expand...

24v. Bridge.....not pedestal.
 
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