85/86 350X Cylinder Head ?'s

[Mondexbrute]

Are there any differences in the '85 & '86 cylinder heads on the 350x? My mechanic is rebuilding the top end on my '85 350x, the engine is an '86. He said the cam chain tensioner isnt fitting in the cylinder head. Now I got the cylinder head from Corey Sprock (400cc kit)...?

[Mondexbrute]

the cylinder head that Corey Sprock Racing sent me must have been an '85, so do I just need to get a cam chain tensioner off an '85?

[Hurricane635]

Yes, or just open up hole in the cylinder a little.

[Hurricane635]

I just remembered if you've got an 86 case the breather is different and might not fit with the 85 tensioner, I would just open up your cylinder to fit the 86 tensioner.

[Dirtcrasher]

Call me stupid, but I believe the 85 and 86 cylinder are identical; The tensioner does not go in the head, it goes in the cylinder.

Does he know how to wind it up prior to installation? (if he doesn't, RUN!!!!!!!!!!!) I don't believe the holes or bore should be off.

The 86 tensioner is longer than the 85, little design change, thats it to my knowledge.

[Hurricane635]

No, the part of the tensioner that goes in the cylinder is slightly bigger on the 86, the bolt pattern and gasket is the same. I bore all my 85 cylinders to fit 86 tensioners, that way the customer can use either tensioner.

[Dirtcrasher]

^ Please explain the same cylinder part number then?? 85/86 - same number......

[Hurricane635]

I'm not a parts guy I'm am an engine builder, all I know is what I've seen over the years. It's possible that after 20 plus years honda is only providing the 86 cylinder part #, but if you measure the different tensioners you'll see what I'm talking about.

[Mondexbrute]

Hurricane what is the best way to bore out the '85 cylinder to except an '86 tensioner? Do you have to remove the head?

[leevarnado]

babbits shows to different part numbers.12000-HA5-010 and 12000-HA5-670.its looks like one replaced the other.

[Hurricane635]

Yes you need to remove the head or tape off the opening from the inside. I use a small drum sander 3/4 inch. You only need open it up about 2mm.

[Dirtcrasher]

If it's together, I'd suggest finding a used 85 tensioner rather than drum sanding 80 thousandths out......

If it's apart, I'd ream it out 2MM larger. Just my opinion.

I still want to measure my 85 cylinders and see what the dealio is.

I may have an 85 tensioner that I'll never use............

[Hurricane635]

I'm not sure if the 85 tensioner will clear the crancase breather on the 86 case.

[Mondexbrute]

Its together, and I have both an '85 & '86 tensioner, the '85 is too short!

[Dirtcrasher]

So, it's together and working, the 85 tensioner in the 85 cylinder is too short and the 86 requires work?

Short externally but internally also?

I'm lost, my brain hurts.............