Help!....changed mainfold and carb and now nothing!

takehikes

Well-known member
I changed out to Offy manifold and EFI exhaust with a new Summit 4 barrel. It fired right up. Drove it around a bit and while running a bit rough it just needed adjustment to fast idle.
However it started smoking, drive it home and found it had blown the PCV valve out of the grommet so oil got on engine causing smoke. Took a while to figure out why it did that. Led me to a hose I had changed. I changed the hose on both the PCV and breather but accidentally put wrong hose on breather and it was collapsing so it was too much pressure in the engine blowing PCV out. My PCV barely went in to begin with, not a tight fit, original grommet in fact. Replaced the breather and the PCV and both their grommets and got right hose on both.
By this point I had a tired battery. It was older so changed it and starter solenoid as I had been planning on doing it. I checked my DUI and its getting plenty of volts to it, spark seems good (changed plugs while I was at it). It will crank and almost fire but not quite. I'm at my wits end as I never touched the timing, spark is good and carb is getting fuel. Only thing I touched was fast idle screw (not regular idle). Its a Summit 600cfm with electric choke (checked voltage to choke and its good). Starter is good too.
Its so baffling as it fired right up and I drove it but once i shut it off....no start. I even resorted to giving it a shot of ether and nothing.
:banghead: :banghead: :banghead:
 

pmuller9

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Either of those lines are under a vacuum not a pressure no matter where you connect them.
The only way a PVC valve can blow out is if there is excessive crankcase pressure.
I realize it is a newly rebuilt engine but do a compression test on all six cylinders anyway.
 

wallen7

Well-known member
If this was a sound good running engine before the changes I would look at the carb. Check the float level for correct setting and the choke to make sure it is not staying closed, It could have washed the cylinders down because of flooding. And by total I mean that includes the intial advanced also.
 

takehikes

Well-known member
Put in new battery as realized mine was not providing enough cranking or voltage to the DUI ignition.

The line for the breather was collapsed and sealed off and the PCV MAY have been bad too. Changed it all and PCV not popping out now while cranking. I will get to a compression test but that is bad news with a rebuilt motor (a year ago about 5k miles on it).

I highly suspect the choke and will delve in to it before a compression test. It cranks and almost fires and I keep reaching for the choke to pull it.....it sounds so much like thats all it needs.

I have plenty of voltage at DUI but may start looking at maybe the coil is going in it. I also removed cap and made sure rotor was turning while cranking.

Thanks for all the suggestions.
 

takehikes

Well-known member
:banghead: I’m screwed.
Did compression test. All bad news....front to back:
Dry- 50/140/70/80/60/40
Bit of oil in chamber-
140/no need/90/140/90/60
Pressure cane up right away so not valves. Can’t understand why this happened.
Truck ran great until that moment it didn’t.
 

wallen7

Well-known member
How much total advance did you have in it before mods and was it changed after mods were done? A 300 only likes about 28 - 30 degrees total mechanical advance and limit how much vacuum advance it has. You probably will have to pull the head to check for detonation damage on pistons and rings with those readings.
 

takehikes

Well-known member
Truck and timing spot on previous to it dying. Only items I changed were intake and exhaust. I dove it a couple times with the new setup and it was fine then suddenly it wasn’t in way home.
 
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