Well, this was my first engine build. The basic objective was to swap a 305 TBI setup for a 350 TBI ... basically just wanted more street guts.

The engine is a frankenstein. The block came from a 77 Corvette (4 bolt main). Pistons and rods are GM. Clevite 77 bearings. I ripped the heads off a junkyard caprice and that seemed to work well. Had to fiddle with my Edelbrock Performer manifold but that bolts on well now.

The engine was running great ... did Comp cams recommended break in procedure and ran it for a couple of months ... then I took it on a long trip. I seemed to be going through some oil. A couple of days after my return, a weird thing happened ... the alternator/power steering bracket broke! I throw the serpetine belt, of course, and the temp guage was pegged before I notice I had an issue. I pulled over immediately and popped the hood. No steam or bad noises during this event.

Back to the junkyard. Get bracket. Install. Step son buys me a performance distributor for my birthday so we install that, too. Engine is now smoking. Smells sweet. Coolant. Bad. Replace intake manifold and head gaskets. Still smoking but no longer sweet. Get a pressure tester ... cooling system holds pressure for 60 minutes without losing a poind. Do a compression check and every cylinder is coming in at 150-160 psi except for #2 ... that one is coming in at 60. Bad. Plug wet with oil. Compression tester oily after test. More bad. Drain some oil. No coolant but reeks of gasoline.

So I pop the passenger side head ... valves on #2 look like they have been steam cleaned. No visible sign of any crack in the block or head ... so my conclusion is that the rings are fried.

Now ... why would the rings be fried? I used Speed Pro plasma moly rings. Should I have been more picky about ring gap placement? (I basically just made sure I had good angular seperation between all the gaps.) I had honed the cylinder walls ... they now feel pretty smooth. Is that normal after 4K? Did my coolant leak fry the rings? What did I do wrong?

Any comments or advice would be much appreciated. I'm planning on pulling the engine tomorrow.

 

Sounds like when the engine got hot the piston expanded and took out the rings on that one hole. It also could have cracked the piston around the ring lands.

 

are all the cylinders smooth or just the one? when you honed the cylinders you used lots of oil on the stones right? what did you set the ring endgap to? what about the rings on #2?
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Thanks for the response! Makes sense. I figure the entire short block is suspect at this point. **heavy sigh**. I'll pull the engine out tomorrow and tear it down. Yikes.

 

Hi SpitotRs305 ... thanks for the reply.

Right now I have the passenger side head off. All four cylinders are (to me) surprisingly smooth. I used lots of oil when I honed the cylinders. While I'm sure the over heating incident accelerated the problem, I suspect I was headed for trouble with the rings anyway. No leaks on this engine, but I was adding a quart of oil every 200-300 mi or so on my long trip. BTW I used regular oil during break in but then went to synthetic.

Judging from the valve appearance I think the problem is beginning to emerge on cylinder 4. Cylinders 6 and 8's valves look normal.

** On edit: Hmmm ... ring end gap ... didn't think I had to mess with that. Sounds like I might need to discover something on that subject. The book I used as a guide didn't mention anything about that. Got any hints?

 

sounds like the ring gap might not have been set correctly how did you set them? or they never sat but a quart every 200-300 isnt bad considering i have a guy at work adding a quart every couple of days and changing plugs just as fast

 

Uh ... I didn't actually do anything to set the end gap. Silly me presumed that would be correctly established by the manufacturer. I think I need to do some research on that subject. Can you give me a quick over view of the subject?

 

well the rings you bought from speed pro are called FILE-Fit which means the ring endgap needs to be set or at least checked this is done by placing the ring in the cylinder it will reside in and squaring it with a piston then inserting a feeler gauge between the ends of the ring i would set the ring gap to .022 for the top ring and .024 for the 2nd


but for the best gaps for your rings in your engine call speed pro they can give you the exact measurements

 

A quart every 300 miles is extremely bad on a fresh rebuild. I've got 180k on my truck and it doesn't leak or burn oil. I however agree with you on the ring gap.
3kelvin, what book was that from? Every engine should have the end gap checked even on pre-gapped rings that you expected these to be.

 

Thanks guys. I really appreciate the help.

It was a Haynes manual ... maybe I missed that part? I pretty much read it cover to cover.

There is NO WAY the gap was only 0.022. I'm pretty convinced it was larger than that. Clearly I need to learn a thing or two before I re-install any new piston rings.

 

Not really, it's an honest mistake made by a mis-informed mechanic . The Haynes manual is great for a stock rebuild using stock parts, or for a first timer. Get some good literature, and learn from your mistake. In fact if you use the search function, I'm confident that ring gap has been covered (if not here then somewhere).

 

Hey firstfirebird ... Feeling a little embarassed at the moment. Had been so proud of that engine. Been cranking up the search engine on this site ... yeah, this topic has been discussed a bit.

Well, good thing I don't mind gettin' greasy 'cause that engine is coming out in the morning.

 

Please update this thread, I would like to know how it goes.

 

Whoa! Am I the only one concerned that your valves were steam cleaned on that cylinder? Only on the one cylinder that now has bad rings? :hmm:

I guess pull the pistons, get new basic moly iron rings, and hone all the cylinders. Use ATF, and go at it until you see a nice crosshatch. Then squirt some oil on it, and re-assemble and go.
Be sure to work really hard at seating the rings. Heavy throttle blasts, and engine braking, during the first 50 miles.

 

think i'd have the heads tested and checked for flatness before i went too far into the short block

 

well i thought about that be he replaced the head gasket and the cooling system now holds pressure if there was still a leak on #2 it wouldnt have so it seems like there where 2 problems rings and a headgasket but i would look at the heads and block for flatness as it only happened on one cylinder

 

Updating as you suggested, firstfirebird. First, I want to thank you and the other guys for helping me out. (Embarassing admission time ... I went back to that book and checked and sure enough there is a little blurb in there about checking end gap and filing rings.)

We pulled the engine and checked the block and heads for flatness as ede recommended. That looked good. Then we popped the pistons out and checked the crank and rod bearings. No problems there, but I replaced the bearings on GP and rechecked bearing clearance with plastigage. Then I checked the ring end gap ... sure enough #2, #4 and #5 had too small a gap by .002-.004 in. The rest were accidentally within recommendations. Heh.

We saw lots of evidence of a massive oil control problem in #2 and the rings were clearly AFU. But the cylinder bore itself was fine.

We went with basic moly rings, honed carefully and used QuickSet, set end gap between .022 and 0.024 per manufacturer's recommendations and re-installed. Despite our best efforts to clean out the exhaust, there must have been a lot of crap in there because she smoked for a long time. I took one good run down the road and that was the last time we got smoke from the engine.

Been following Sonix' break in recommendations ... and having lots of fun doing it. The engine is running pretty well now. We'll just have to see how it lasts.

Thanks again, people.

 

Right on !!!