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srry 12-12-2012 11:39 AM

I'm at an impass with my 347 build
 
I'll try to be concise here (HA!), but basically I think I've worked myself into a slightly expensive situation, and I just need some advice on getting out of it... as cheaply as possible.

I've got this 347 Ford stroker I'm building and I made some rather bad decisions when it came time to get the thing machined. You see, I ordered my bottom end kit from Coast High Performance, and along with their kit, they (unknown to me at the time) sent me a rather expensive set of low tension plasma-moly rings. According to my machinist, plasma-moly rings require a much finer finish on the cylinder bore in order to live, and so I followed his recommendation, which cost me a few extra bucks. Unfortunately, in a bout of absent-mindedness, I completely forgot to ask him to use a torque plate, and my machinist never asked (he told me later he does not typically recommend this for street applications like mine... but that's under normal circumstances.) My machinist never saw my rings before he did the bore/hone, so he didn't realize they were low tension... and a while after the work had already been done, I realized what they were, did a little research on them, and realized that low tension rings really need a perfectly round bore to work correctly.

So, to sum it all up where I am at this point... I have cylinder bores that are honed specifically for these really expensive rings, but not torque plate honed, so they're not ideal. I'm worried I'm going to end up with an oil burner, especially with the already troublesome rod ratios of 347's.

At this point I can buy new plasma-moly rings that are NOT low-tension, but they are kinda big bucks (something like $140). And I already spent extra on the machining, when, if I'd known, I could have bought a set of cheapo rings from the beginning and been done with it. But does it REALLY matter? I am adamant at this point that I cannot keep throwing away money on useless parts that don't help me at all. I've run way over budget doing that kinda thing, and all the little "oh but it's only 100 bucks more" REALLY adds up. Do I just run with what I have, or drop even more money on new rings?

srry 12-12-2012 11:56 AM

Well, the block itself is of 1978 vintage, not that it really matters, with all that's being done to it.

And the rings are actually already gapped to be honest... I have been building this thing for a while now, and I was going to just run with em like you suggested, but I had second thoughts about it and came here to see if I was making a big mistake.

I was unaware that any 302's came stock with low tension rings... that makes me feel a bit safer for sure.

srry 12-12-2012 12:16 PM

Quote:

Most of the time the machine shop messes it up anyway
LOL tell me about it... having access to a high-end dial bore gauge and setting fixture at school has really made me OCD about everything. But then I just tell myself that they build tons of engines every day like that.

BogiesAnnex1 12-12-2012 12:48 PM

Quote:

Originally Posted by srry (Post 1622001)
I'll try to be concise here (HA!), but basically I think I've worked myself into a slightly expensive situation, and I just need some advice on getting out of it... as cheaply as possible.

I've got this 347 Ford stroker I'm building and I made some rather bad decisions when it came time to get the thing machined. You see, I ordered my bottom end kit from Coast High Performance, and along with their kit, they (unknown to me at the time) sent me a rather expensive set of low tension plasma-moly rings. According to my machinist, plasma-moly rings require a much finer finish on the cylinder bore in order to live, and so I followed his recommendation, which cost me a few extra bucks. Unfortunately, in a bout of absent-mindedness, I completely forgot to ask him to use a torque plate, and my machinist never asked (he told me later he does not typically recommend this for street applications like mine... but that's under normal circumstances.) My machinist never saw my rings before he did the bore/hone, so he didn't realize they were low tension... and a while after the work had already been done, I realized what they were, did a little research on them, and realized that low tension rings really need a perfectly round bore to work correctly.

So, to sum it all up where I am at this point... I have cylinder bores that are honed specifically for these really expensive rings, but not torque plate honed, so they're not ideal. I'm worried I'm going to end up with an oil burner, especially with the already troublesome rod ratios of 347's.

At this point I can buy new plasma-moly rings that are NOT low-tension, but they are kinda big bucks (something like $140). And I already spent extra on the machining, when, if I'd known, I could have bought a set of cheapo rings from the beginning and been done with it. But does it REALLY matter? I am adamant at this point that I cannot keep throwing away money on useless parts that don't help me at all. I've run way over budget doing that kinda thing, and all the little "oh but it's only 100 bucks more" REALLY adds up. Do I just run with what I have, or drop even more money on new rings?

You need to find a machinest that at least stepped into the last half of the 20th century, let alone has a knowledge base in the 21st.

As for a 100 bucks more here and there, that sounds like the line attributed to Everett Dirksen in a speach on the US Capital floor somewhere in the mid 1950's where he is said to have said "a million bucks here, a million bucks there; pretty soon you're talking real money". It is non-the-less a trueism where building engines is concerned.

I'm thinking just a plain old set of moly rings with the correct thickness for the piston ring lands will git 'er done for ya. Im not so sure the rings you have won't work, but I appriciate you're concern about the effort to fix it if they don't. If the pistons are hyper-eutectic castings or high silicon forgings and your machinest clearanced them correcctly (tight) for this material even the low tension rings should be fine. But given the torque plate error I guess there's no reason to suspect this would be correct for these high silicon, highly temperature stable, modern piston materials either. You can at least measure this to find out.

Bogie

engineczar 12-12-2012 01:00 PM

Another option is to just switch out the oil rings from a cheaper set.

Usually low tension ring sets just refer to the oil rings and not the two compression rings. Oil rings generally come anywhere from ultra low 8# to more than 20# for stock stuff. Most off the shelf low tension sets are in the 15# range.

srry 12-12-2012 01:01 PM

Thanks oldbogie, he actually did a fairly decent job on the cylinders themselves, and at the time I had access to some pretty accurate measurement tools at my school, where I affirmed that the forged pistons had around .003"-.004" clearance as was called for in the piston's instructions for my street application. Personally I do not trust ANY machinist to just "get it right" for me, and I checked and rechecked all the work that was done, and was fairly satisfied with the results, especially when I compared it to other machine work from other shops.


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