So I dropped a valve at BW and pretty much, the motor is done for. I have a friend that has a spare motor that has low compression (180-190 across the board?) that I am thinking of getting, however, here is my question:

Can I change the rings ONLY (assuming everyone thing else is fine) and be okay? If I have to hone it, I might as well get a different block and work with that since I can use some of my stuff from my motor. My concern is that the rings wont be enough to have a proper seal due to the cross hatches being worn. I am not sure how that works with the cylinder walls on F series motors.

I have experience with building engines, but that's with traditional motors that can be bored etc.

Thoughts?

 

If the compression is the same across the board the motor could be ok and the gauge is probably out? I have one gauge that reads 240psi+ and one that reads about 180psi on a healthy motor I've crossed checked it on maybe 3 engines and my own

About the rings I had a block recently that I think had ring failure but no scorring. From researching on google etc I couldn't work out whether it could be re-ringed wuthout a re-hone if the block was no scorred.

I sold it cheap to a friend who was going to do a re-ring and see how it goes since it seems like its a bit of a crapshoot

 

Were those numbers produced on a cold or warm motor?

Theres ~35psi of delta cold to hot.

 

+1 for temperature of motor affecting readings. Was it done cold? If so, that could affect the readings quite a bit. Look for consistency across.

Like one of the guys said, some gauges read different. On my motor I've seen as low as 180 on one gauge, and 225-230 on my gauge.

Yes, you can reuse the pistons and install new rings, as long as you hone the cylinders. Not bore, but hone... there's a big difference. You'll need to find a machine shop that has the right honing tool for the FRM sleeves.

Double check the motor first before digging into it.

 

Thanks guys, ill be doing a leak down test to figure this out before I proceed. I am not sure if the comp test was done when it was cold or hot, was just told low comp.

Spoke to someone that it may not be a good idea to put new rings on used piston and walls. The cross hatching is already worn and the cylinder might not be a perfect circle and could cause additional scoring.

Thoughts?

 

Thats what i read you have to rehone but the rehone for a fibre block maybe very expensive