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#1
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273 tear down - Aluminum retainers junk
For the first time since 1996, I pulled the little 273 race engine out and apart to look at things. I found no bearing wear and the knurled pistons looked good also. The Iron rings made a very small ridge at the bottom of the cylinders. This was expected as there was .012" cylinder taper from top to bottom when I put the thing together. Yes, twelve thousandths taper. Cam and lifters looked good. This is the CC 292 hydrolic cam with solid lifters. Everything looked good except for the aluminum retainers. They are junk. The springs chewed away at them. The damper spring shaved and rolled aluminum into little coils.
My opinion is: Do not use aluminum valve spring retainers. Also, with the pistons loose in the top of the bore as mine were, zero deck and .039" compressed gasket thickness is the limit on tightness with closed chamber heads as the quench areas were "clean" after 8 years of racing. This only means the piston reached the head, but did not contact it "much"! This engine has seen 8000 rpm, but normally ran up to 7000 rpm. I am currently setting the 273 aside and going BIG CUBIC INCHES with a 318 ( actually 329 cid) Billy |
#2
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Billy
Go really, really big and get a 360 crank, have the mains gound to 318/340 size and with a .030 over 318 you can have a 349cuin 318 or with a 3.98 bore have a 356cuin and no one will know the difference. Food for thought I will soon have one in progress. I thankfully got talked out of using aluminum retainers for the very results you have described. |
#3
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345Dart
You are guessing close to my next project. A 360 crank in a .110" over 273 block for a whoping 313 cubic inches. The 273 block just will not open up to a 318's 3.91" bore or I would do that. I would like to stay with a 273 block as they are easily identified by the steering gear notch in the drivers side of the block. People will know that I have bore size limitations. The 1.88" intake valve will fit the bore without having to notch the cylinder for flow clearance and I could actually go to a 1.94" intake without notching. I am staying away from the 4" stroke and big cubic inches as I am not ready to go real fast yet! Billy |
#4
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Quote:
You spring for the gasket set,(I'll donate the block) and we can start to put it together in a couple weeks. I know of a 'sassy grass' green car that will probably do 12's with it. |
#5
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Valve spring harmonics will eat up any retainer; aluminum is the worst. We even inspect our titanium retainers very closely at tear downs-and some of them often need replacement.
I suspect it is a function of RPM, valve spring strength and lubrication. It seems valve spring oilers helps the life of retainers-and definitely helps the life of valve springs. |
#6
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Keep us posted, would like to see anouther 318 in the 11's. There was still one set of Mopar forged 30 over pistons in the system the last time I checked. They are light weight and won't bust your budjet.
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#7
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I have used aluminum retainers for one year too with dual springs, but I took the damper off. There was no sign of wear in them after one year, but I wouldn't count on them much longer.
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#8
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Titanium retainers start at $119.00 a set, why even mess with that Al stuff?
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#9
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I have titanium retiners in my 318. I have not ran it yet and am wondering if the dampner spring will chew them up too.
sbknut, the Mopar .030 piston is the piston in my new 318. It is a nice piston. What do you mean there is still one set in the system? Is Mopar not selling it any more? The engine goes in this weekend. I had a time finding all eight 7/16 flex plate bolts! I will then need to cobble up a new set of headers. I have the flanges made and some of the tubes ready to connect to the goilet. Billy |
#10
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Billy according to the loacal parts man there were 8 left, and no rings. These were the forged pistons, flat top with two deep valve reliefs and narrow rings. He couldn't find out if chrysler was planning another issue, but they were supposed to be a disscontinued item.
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#11
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Part number P4876968 is the piston. I think I will call and get another set tomorrow. Why would they discontinue such a good piston?
Billy |
#12
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Billy, did you get the pistons?
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#13
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12 thou taper will wear out the ring lands and/or rings themselves.
BEWARE ! |
#14
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sbknut, No, I did not get the pistons. I never got around to calling my parts guy. I hope whoever got them uses them well.
Mister Fiberglass, Yep, .012" taper is too much. It actually has less taper now than when I put it together. I guess the new rings expanded at the top of the bore and then scraped the cylinders hard while following the taper back down. That 273 was a $100 junk yard engine that I tore apart and threw back together after milling a gob off the deck. I did quite a lot of work to the heads, but the short block was "rotating junk" that surprised a lot of people. It took my 3081 pound Dart to a best of 12.36 at 109. The 318 is in the Dart. I have been building the new headers. All but the booster and collector turn outs has been completed. Billy |
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