6.5L running bad

[westcoasttowing]

I have a 1995 chevy 3500 hd flatbed tow truck. I just installed new heads on a used block that according to my mechanic was in good condition. It took a while to get started and then ran rough, but after following instructions from the co. that did the heads (holding the RPM's at 1500 for several minutes) it then seem to run great. Besides new heads it has a new water pump, hoses, radiator, serp. belt. all new filters etc.. I took it for a small drive and seem to run fine. The next day i did the same thing drove it for about 5 miles. I was sitting at a light and noticed the oil pressure was low and didn't increase much when revving it up. I took off from the light and started losing power. Then it stalled. I tried to start it but it didn't want to start and felt like it wasn't turning over as fast. oh BTW it has a new altenator and new batteries too. After letting it cool off for a half an hour, it started but was running terrible with lots of dark grey smoke. What first began as what I thought was blown head gaskets has turned into a nightmare. My orig. heads were shot. Then after putting new heads on my old block, come to find out the block was cracked. I am at a loss. Can someone point me in the right direction?

[Yukon6.2]

Hi West
How much do you want to spend?
That is going to dictate where you go.If $$$$$ is no object and you are planing to keep the truck for years,and it has to work and be reliable.The get a New AMG 6.5 and don't look back.Or do a conversion to a cummins.
Otherwise look for a good running doner truck,or used motor.and watch your penny's.
Thomas

[westcoasttowing]

I want to spend as little as possible to get it running and sell the p.o.s.

[trbankii]

I’d just sell it as is then. You’re going to put more money, time, and effort into it than you’d get back out of it.

[westcoasttowing]

So are you then concluding that the used block that I used is trash?
Is it the low oil pressure leading up to the stall? The oil still looks ok. No metal shavings.

[trbankii]

You said the block was cracked.

[westcoasttowing]

I'm sorry. The way I wrote it sounds confusing. My original block was cracked. Then I purchased a used block and put my new heads on it. it ran great for about 15 miles.

[trbankii]

Ok, the last line had said you found the block was cracked, you were at a loss, and wanted direction. So I figured that was where things were at this point.

Hard to say where things stand without tearing it down and taking a look at it. The 1500 rpm “break in” doesn’t sound right to me. Nor does the low oil pressure - particularly when revving it.

[Jesus]

bet it the pmd! try a new pmd or fsd mounted on a heatsink with active cooling..