3.6 V8 Cylinder/Piston/Head Condition - Opinions Needed!!!

[Dargo]

Pulled the heads off my motor last night to see what the condition of the cylinders, etc. were. To me, everything looked ok. Meaning, no holes in pistons, no cracks, no chunks of shrapnel floating around. The closer I looked, I noticed scoring above what I assume is the exhaust and intake ports. The pictures attached are of the #6 cylinder. Looked like the worst example to me. The motor is an ‘87 3.6 275. I have owned this for many years. I have never ran it. Was trying to get it up and going this summer for my Rally Sport. After closer inspection, the electrics are pretty well shot. I’ll need all new. Before I even think about investing that kind of $$ in this motor, I need to know if this is even runnable in its current condition. Motor has good compression. 100+/- lbs on each cylinder (cold). I have no clue what kind of hours are on this powerhead. I am no motor man by any means. To me, it doesn’t look good by any means. Do I throw $2k worth of electrics at this and hope for the best or scrap/part it out and look for something else?

PS-I will update my project thread soon. Boat is pretty well wrapped up. Motor on the other hand....FML.

[Dave S]

I have seen worse...…..hone and go...….. but the main issue is the head gasket crumble...….showing it's age......their are some that can help ????????belly up...….

[Instigator]

I have an identical 3.6 V-8 I just bought, also w/one bad hole.
Cant tell from you pixs if there’s damage on piston dome at the exhaust port or reflection??

If piston is good then you lost fuel/oil to that hole same as mine.
Fuel supply line pulled off that carb on previous owner on mine.

[Dargo]

Ok! That makes sense. No fuel, no oil, makes things not slide so nice. Pistons look to be in great shape minus the black color. No holes, etc. Heads seemed decent too. Not sure what the color is about. If pistons are good, what kind of work is needed to fix the cylinders? I would imagine honing. Is that something better left to a pro shop or can a guy at home do it? Are we talking new rings if it’s honed or new pistons? Just trying to weigh the cost vs. benefit of work I may need to do. I love working on my own stuff and would love to run this motor but I don’t want to sink a ridiculous amount of cash into it. At the same time, I like the idea of knowing what I have!

[racer]

IMO it should be pulled down for a good inspection and at minimum honed as the scratches look to be bad enough that you could feel them.

[Instigator]

I’m with Al.

No telling how much debri went where.
Only one way to know.

At min, that hole needs honed, probably alum removed from bore, one piston and ring set.

If compression was good on other 7, and you’re careful, you could resassemble those 7 as is but if you have it apart, honing all 8 and rings ain’t that much more than one.
Not much additional labor either.

Honing yourself can be done but if your not experienced, it’s a good way to screw one up.
Honing is cheap at most shops too.

IMO it should be pulled down for a good inspection and at minimum honed as the scratches look to be bad enough that you could feel them.

[FUJIMO]

...what racer suggested. complete teardown to go through it properly. any & all two strokes cylinder walls & pistons should always be made perfect in my opinion, unlike what you can "get away with" on a 4-stroke car engine. they're operation/use is much different. and then, of course, you need to fix what caused the issue in the first place. motor value? have no idea.

[V-bottom]

100# compression sounds low. The 275 should be around 120-130. The XP/GT 300 motors were usually 130-140.

[Instigator]

Correct.

I missed that part.

100# compression sounds low. The 275 should be around 120-130. The XP/GT 300 motors were usually 130-140.

[Dargo]

Sounds like a plan to me. I’ll keep going with tearing it down then. For what it’s worth, I still had compression on all 8. The number 6 cylinder that I posted pictures of was just the worst out of all 8. The scoring can be felt with your finger but it is pretty light. I’ll get this thing tore down and see what else is hiding inside. Am I safe to assume best case scenario is honing and new rings on all 8? No reason not to do them all if it is apart. Thank you everyone for your input so far. Kind of uncharted territory for me so I’m apprehensive to say the very least.

[keefallan]

Yeah, that is your BEST CASE scenario. The bottom line is this.....you will have peace of mind after you tear it down and put it back together that its all new. No one mentioned this. But.....you should rebuild the carbs. If you have done the block, go thru them too to make sure the floats are good and all the orifices are clean. When you are done, it'll be all new. Besides, you have a pretty cool motor there. I would be keeping that one if it were me. Its worth it to make it like new....JMO

Take your time in the tear down. Get a factory manual. You NEED the factory manual. It will tell you how to overhaul(almost) that motor. When you remove a piston assembly, bag and tag. If you take your time, its not difficult. But its all in the details.....

Try and have fun too. This way, you will also learn your motor.........

[FUJIMO]

[FUJIMO]

[Dargo]

I was more than a little discouraged when I pulled the heads and saw the scoring. But the more I look at what needs to be done, I think it’s something I can handle. I’m sure there will be lots of questions along the way. I did rebuild the carbs over the winter hoping I wouldn’t have the issues I did with everything. Oh well, I’ll bag em and tag em with all the other parts. They were very clean already once I tore into them. I do have a factory manual already and that has made for lots of good reading. Here’s a question....if only a couple cylinders need boring, do you just do the ones needing it and oversize the piston to match or is it best to do all 8 so they are all the same? I don’t know what I would do without this site!

[keefallan]

Yeah, no hone is gonna fix that. I couldnt see those pits before.................