engine trouble

the 350 in my dad's '72 C10 is not running right, it started acting up when they were coming back from our other house which is 2.5 hrs away using the thruway. wouldn't idle, runs like crap, sounds like it's missing, smooths out when revved. and sounds like a pulsating hiss coming from the passanger side of the intake manifold, it used to constantly hiss with no pulsation. we ran a compression test on 6 of the 8 cyls, it was getting dark, so we gave up for the night but will get the other 2 tomorrow probably. all but the center 2 on the passanger side are 120, the center 2 on the passanger side are 110. any idea's? thanks. My dad thinks a couple valves burned up

Sounds like a vacumn leak to me.

A hiss would indicate a vacuum leak.

Exhaust leak that caused burnt valve/s sounds likely.

the thing about the hiss is that it has always hissed, since he bought it, checked it out for vac leaks but wasn't leaking vac, this was right after he noticed the hiss, right after he bought it. but now the hiss is pulsating, this is why my dad thought it had a burnt valve or a few.

My dad and I will have it fixed in a week or so. knowing that somthing internal in the engine went out and the fact it was tired and had a leaky rear main. my dad ordered a GM crate engine. the 260 Hp el cheapo model, but has a 3/50 warranty. the salesman actully told him it was a 3/100 warranty but 3/50 is listed in the book. should be here next week. time to break out the cherry picker.

These base crate engines are the deal of the Century. I put one in a Vette for a guy, easiest r and r I've ever done.

I think the warranty is 3/100, but it might have changed.

Don

yep and this leaves the trucks current engine as an easy repair for another project.

yup, now you can rebuild that engine into a wicked motor since you wont have to worry about time on getting it running to put it back in