compression test

[fordforlife]

i have a 351. i did a compression test and found out that my piston rings are bad. can i dirve it a few more days or do i need to stop right now!? Also, should i rebuild the engine, or just replace a few parts or what? one more question, should i bore the engine like 30 over, or just hone it? thx!!!!!

[GTStang]

Wether you need to bore it ove .30 or not will be decided when you spec out the cylinders top and bottom.

[Rod&Custom]

Like GTStang said, the engined needs to be miked at a shop. If the differences in the top and bottom of the cylinder are too great, then honing will not suffice, you will need it bored. You really don't want to bore it unless you know what you are getting into. You will need pricey new parts. If the specs check out ok, you can just hone it and replace your rings. Your compression should check out OK now. Hope this helps.

[351wStang]

I'd do rings, bearings, a valve job, and hope to get away with honing if I where you. Good luck.

[fordforlife]

thx for your help guys. whats a guesstimate on how much it would cost for me to buy the rings, bearings, and have the block honed (hopefully). And by valve job, you mean clean them up or replace everything? thx again!!!

[351wStang]

Originally Posted by fordforlife

thx for your help guys. whats a guesstimate on how much it would cost for me to buy the rings, bearings, and have the block honed (hopefully). And by valve job, you mean clean them up or replace everything? thx again!!!

I'd say you could get stock replacement rings for under or around $50 at most. Rod and main bearings around $20 per set and probably $15 for cam bearings if you wanna pull the cam (which wouldnt be a bad idea). To have the block honed would probably cost somewhere around $8-$10 per cylinder. While you have your block at the machine shop I would suggest having it magnafluxed, checked and possibly align bored, have your decks checked and maybe have the block decked a little. I would also suggest getting your machine shop to install new cam bearings so that you dont have to buy or make a cam bearing installer. Its easy to screw up cam bearings on install. By valve job I mean a 3 angle valve job. Hopefully you can have your valves cleaned and ground to work just fine. I'd say you could get by with your stock valve seats as well. Machine shops arent cheap but if you dont have the tools and the knowhow you can really screw your block up. Your looking at a couple hundred dollars of machine work, but you will just be rebuilding your rebuild if you try to skip that part. Also Boosted331 (I think) posted a link a while back of a good method to break new rings in. I tryed it on a sbc not to long ago and it worked just fine. I think we got better results sooner with that method. Good luck on your rebuild.

[fordforlife]

ok, i have one more question if you dont mind. would it be better to just swap in another 351w engine? I found out the other day that my uncle knows of a 351 for $400, its from a van that an old man owned, mostly highway miles. It has 65k miles, and is fuel injected. So all i have to do is swap my intake and carb and belt accesories.

[73mustang351c]

I was faced with a similiar problem with my clevland. I had repairs that would cost about $400 to do myself. I have about 3k into the engine already. I came across another clevland and c6 trans for $300. in my case I had too much into the original engine so I had to turn the engine down. If I didn't have all that money in the original then I would have scooped up the other engine (I still should have gotten it at that price and parted it out)!I guess it depends on if you haven't done much to the original and this new one cost less than fixing the problem sure buy it. just be careful that this new windsor doesn't have any problems because then you'll have 2 engines in need of work. hope this helped any.