1 2
dannyp84
dannyp84 New Reader
9/16/21 2:19 p.m.

In all reality I will probably put this engine back together exactly as it was with the new heads, but while it's torn apart is there anything wise to delete or modify on the 6G72 for more reliable running/better response/power? 

crankwalk (Forum Supporter)
crankwalk (Forum Supporter) SuperDork
9/16/21 11:12 p.m.
dannyp84 said:

In all reality I will probably put this engine back together exactly as it was with the new heads, but while it's torn apart is there anything wise to delete or modify on the 6G72 for more reliable running/better response/power? 

Not really beside fixing the valve stem seals and then replacing the cat if it's been in an oil burner the last 15 years. I replaced mine in my 89 and the old one was terrible 

captainawesome
captainawesome Dork
9/17/21 7:59 a.m.

Don't know if you have discussed this yet, but replace the hydraulic lifters with the updated ones while you have it apart. Can't recall the part number or which vehicle they came out of but it was inexpensive to do 10 years ago.

dannyp84
dannyp84 New Reader
9/20/21 12:15 p.m.

In reply to captainawesome :

I have replaced the lifters on one bank so far a couple years ago but they're still noisy, were the updated ones from a different vehicle?

captainawesome
captainawesome Dork
9/20/21 12:46 p.m.

In reply to dannyp84 :

I believe so. They have a different hole size if I remember correctly. 

dannyp84
dannyp84 New Reader
9/21/21 8:19 p.m.

And both heads are off! I left the plugs in so I could see which cylinders were burning oil the most, looks like just the middle one on the passenger side bank was doing the worst of it.. I didn't know how to get the cam gears off without spinning the cams so I just jammed a wrench under the lobes since the new heads have new cams and rockers anyway. The new heads arrived today and they're so clean it's a shame to put them on this crusty motor.. photos of the heads and cylinders:

 

 

dannyp84
dannyp84 New Reader
9/21/21 8:48 p.m.

Miscellaneous notes:

I've never timed a distributor before so I'll have to look up how to reinstall that properly.

the exhaust manifold looks especially crusty on that 2nd cylinder which is the one I think was burning the most oil, I wonder if part of my power loss is a clogged cat. It does not appear that any headers are available in the US for the montero and I'm skeptical that they'd make any additional power anyway, especially with all other components being stock. I will consider a replacement converter though. 

Part of me wishes I had just paid a trusted local mechanic to do this, but I know he wouldn't have time to run everything through a parts washer and I'm tired of how greasy this thing is so I'll take the time to clean most of it. This time I'll also figure out how to properly install the valve cover gaskets without getting leaks there.
 

Another part of me wonders how well the 5 cylinder Atlas motor from the 1st gen Colorado might've fit in here.. that engine makes more peak torque at a lower rpm and 5 cylinders almost always sound better than any V6.. but that's a can of worms I'm probably not prepared to open..

 

dannyp84
dannyp84 New Reader
9/26/21 4:51 p.m.

How clean does the mating surface need to be on the block to accept the new head gasket and head? I went over it with a razor blade and a green scotch pad but it still doesn't look shiny and new.. I assume a wire wheel on a drill is too abrasive but I could go get one that's made of plastic or something? 

crankwalk (Forum Supporter)
crankwalk (Forum Supporter) SuperDork
9/26/21 9:48 p.m.

400 grit emery cloth and carb cleaner. 

dannyp84
dannyp84 Reader
10/7/21 10:55 a.m.

Minor/major setback update: Yesterday I was convinced I had the block surface clean enough to accept the new gaskets and heads, but to be sure, I had a my friend from the champcar team who is a mechanical engineer come and have a look at the engine. In about 5 min he noticed dents and dings in the old cylinder head, which corresponded with damage on the #2 piston. Upon inspection of that cylinder, we found 4 grooves worn in the cylinder probably a couple thousandths deep. Something got in there and went for a ride. His opinion was that if those gouges aren't honed out, the engine will at best continue to burn oil at excessive rates. Also, hopefully it wasn't a piece of one of the rings. Right now my thought is to return the cylinder heads which were $600, and just buy a reman engine for $1500, but I'm open to other ideas. I have no experience honing or assembling a short block and the local machine shops are backed up for months when I last checked. I'll also take a quick look around for a healthy used engine, but that seems unlikely. Sometimes the bear eats you..

dannyp84
dannyp84 Reader
10/7/21 10:58 a.m.

If there's a silver lining, it's that the Montero being down has been a good excuse to drive the RX7 more, it's a real joy on the secondary roads to and from work..

dannyp84
dannyp84 Reader
10/8/21 10:24 a.m.

Also if anyone has a 6G72 in running condition, I'm interested.

1 2
Our Preferred Partners
YgKQmSqyqdZHjmztqQLdrJIwZHxDnOTbJ19XZsQXm0hcnZVjHfSwjyzCwiSVs85D