brain55
Veteran Member
I have been putting off changing the intake manifold gaskets on my 8.1 for too long. I had this engine gone through over a year and 40,000 miles ago. It had 165,000 miles on it and had burned 2 quarts of oil every 3000 miles since the day I bought it new. I wanted to make sure it was sound to start towing my 14K lb mobile shop every day.
Well, nothing was easy or normal about this rebuild. First of all the 8.1 is nothing like all previous big blocks. There are next to no aftermarket parts, everything is metric and either has to come from GM or be custom built. We tried to find a core to rebuild, so we could just R&R my engine when it was done being rebuilt, but went through 3 cores and never found one that was worth rebuilding. They either needed sleeves, or had mounting ears broken off, or something that didn't make it worth while. So we went ahead and pulled my engine and rebuilt it. My motor was clean and I should have just re-ringed it and put it back together, It still had crosshatches in the cylinder walls. But, I wanted to try and do something about the oil consumption since this engine has low tension oil rings from the factory. We bought new pistons and had the oil ring grooves cut so we could use standard tension rings, nobody made standard tension rings to fit the metric grooves. Not really a big deal, just some extra down time. We sent the cam to Crower to get a custom grind done, I wanted a little more bottom end grunt out of it. You'd think that would be no big deal either, I'll get back to that. While doing all of this stuff I figured why not run some full roller rockers. Once again, sounds easy enough but it's not. You can't get valve covers to clear the tall locknuts for the roller rockers. Did I mention that the 8.1 is not like any other previous big blocks. I could have had custom valve covers made or spacers made for $700, so I decided roller rockers really wasn't worth the effort and $1000. The engine gets all reassembled with the new cam, custom pushrods, custom pistons, etc., and sent back to be installed. They got it installed and fired up but it wasn't running right. My machinist has one of those wake up in the middle of the night solving the problem moments and figures out that the cam was ground with the old GM big block firing order. Sure enough they pull the engine out and pull the cam, and it was ground wrong. Fortunately Dave Crower is a stand up guy and payed for the second R&R and the overnighting of the cams both ways and we get everything going again.
The truck ran great, well other than the transmission rebuilder having to take 3 shots at the Allison before getting it right. I had used this guy dozens of times over the previous several years without a single problem on the fleet of trucks I was in charge of. So it would figure that as soon as I took him my truck we would have problems. Anyway, once that got resolved I was happy with my truck, until it was using 4 quarts of oil every 3000 mile instead of the 2 quarts I was trying to fix. We were pretty sure it was the intake gaskets, the intake on this thing is the size of a Volkswagen and you can't put the engine in with the intake on so we figured that was likely the problem. I couldn't be without my truck at this point so I kept putting it off. Well now I am using 4 quarts every week or roughly 1000 miles and have replaced four #8 spark plugs in the last month.
So, instead of pool parties and relaxing this Labor Day weekend, I will be pulling the intake on my truck and hoping that is what is going on.
Wish me luck,
Brian
PS - Yes, I know I should have bought the Duramax.
Well, nothing was easy or normal about this rebuild. First of all the 8.1 is nothing like all previous big blocks. There are next to no aftermarket parts, everything is metric and either has to come from GM or be custom built. We tried to find a core to rebuild, so we could just R&R my engine when it was done being rebuilt, but went through 3 cores and never found one that was worth rebuilding. They either needed sleeves, or had mounting ears broken off, or something that didn't make it worth while. So we went ahead and pulled my engine and rebuilt it. My motor was clean and I should have just re-ringed it and put it back together, It still had crosshatches in the cylinder walls. But, I wanted to try and do something about the oil consumption since this engine has low tension oil rings from the factory. We bought new pistons and had the oil ring grooves cut so we could use standard tension rings, nobody made standard tension rings to fit the metric grooves. Not really a big deal, just some extra down time. We sent the cam to Crower to get a custom grind done, I wanted a little more bottom end grunt out of it. You'd think that would be no big deal either, I'll get back to that. While doing all of this stuff I figured why not run some full roller rockers. Once again, sounds easy enough but it's not. You can't get valve covers to clear the tall locknuts for the roller rockers. Did I mention that the 8.1 is not like any other previous big blocks. I could have had custom valve covers made or spacers made for $700, so I decided roller rockers really wasn't worth the effort and $1000. The engine gets all reassembled with the new cam, custom pushrods, custom pistons, etc., and sent back to be installed. They got it installed and fired up but it wasn't running right. My machinist has one of those wake up in the middle of the night solving the problem moments and figures out that the cam was ground with the old GM big block firing order. Sure enough they pull the engine out and pull the cam, and it was ground wrong. Fortunately Dave Crower is a stand up guy and payed for the second R&R and the overnighting of the cams both ways and we get everything going again.
The truck ran great, well other than the transmission rebuilder having to take 3 shots at the Allison before getting it right. I had used this guy dozens of times over the previous several years without a single problem on the fleet of trucks I was in charge of. So it would figure that as soon as I took him my truck we would have problems. Anyway, once that got resolved I was happy with my truck, until it was using 4 quarts of oil every 3000 mile instead of the 2 quarts I was trying to fix. We were pretty sure it was the intake gaskets, the intake on this thing is the size of a Volkswagen and you can't put the engine in with the intake on so we figured that was likely the problem. I couldn't be without my truck at this point so I kept putting it off. Well now I am using 4 quarts every week or roughly 1000 miles and have replaced four #8 spark plugs in the last month.
So, instead of pool parties and relaxing this Labor Day weekend, I will be pulling the intake on my truck and hoping that is what is going on.
Wish me luck,
Brian
PS - Yes, I know I should have bought the Duramax.
Another year and time to change the filter again.