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RicerSchnitzzzle
Join Date: Jun 2008
Posts: 385
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Chevy Pistons?
Just curious for the next rebuild..
Since chevy 350 pistons are just a hair over 100mm, what would be involved in switching over? Obviously the choices of pistons and materials would be greater at much less cost. Would just need a set of rods with porsche bottoms and chevy tops made. Seems a set of custom rods would be worth it to use better pistons for heavy boost, with out the price for custom 928 forged pistons. Pretty sure the crank can handle the power. Just thinking of how to do my DIY TT setup for high PSI. Would the pistons need to be coated to work in our blocks or is a chevy aluminium block simular?
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'81 Euro 'S' 928 5-Speed 5.0L Hybrid "Ricerschnitzzzle" Wish list: RollBar, New Helmet and driving lessons  Wishes Done: Body kit, seats, No cat, Headers, X, Afterburners, 3" exhaust, short shifter , 17" TT Rims, 250HP N2O, MSD ignition w/retard+rev limit, MSD billet distributor, Accel Coil. 5.0L block, ported heads, JE race springs + .503 "S+" cams |
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11-06-2008, 04:05 PM
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Freiherr
Join Date: Dec 2003
Location: New Orleans
Posts: 1,884
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I used 951 pistons and had them machined. A good used set can be had for around $500.
I had Pauter do my rods and those SOB's were expensive!
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11-06-2008, 04:20 PM
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Join Date: Dec 2007
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you would have to get the pistons coated, as well you would have to look at pin distance etc. I doubt that they would work all that well.
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11-06-2008, 04:21 PM
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Network Native
Join Date: Jan 2007
Location: SoCal
Posts: 10,349
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Only thing I have heard working are Porsche pistons or Nikasil and aftermarket pistons.
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11-06-2008, 05:42 PM
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Join Date: Jan 2007
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If you were to use uncoated pistons you would have to have your block Nickasil'd or use steel liners. An Alusil block is high silicon and is similar to a hyperutectic piston. Usually, the idea is to run two dis-similar materials to avoid galling. An example would be an aluminum piston w/ iron block. The stock 928 and 951 pistons are coated with an iron coating IIRC.
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1984 928's w/ 5 speed Smoked Quartz Metalic 1982 928's Turbo w/ 5 Speed Platinum Metalic 1978 Euro Widebody w/ 5 speed Guards Red Last edited by Fabio421; 11-07-2008 at 04:43 AM.. |
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11-06-2008, 05:44 PM
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Freiherr
Join Date: Dec 2003
Location: New Orleans
Posts: 1,884
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951 pistons are forged and coated.
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11-07-2008, 04:32 AM
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Posts: 652
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Yes, they are. How much were the Pauter rods? If I remember correctly they run about $1,600 a set. How much is a set of Ti rods? I would think it would be worth it to throw in an extra $800 to $1,000 and get the Ti rods. It would allow the engine to rev more freely and should reduce the risk of 2/6 bearing failure.
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1984 928's w/ 5 speed Smoked Quartz Metalic 1982 928's Turbo w/ 5 Speed Platinum Metalic 1978 Euro Widebody w/ 5 speed Guards Red |
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11-07-2008, 04:52 AM
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Network Native
Join Date: Jan 2007
Location: SoCal
Posts: 10,349
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Quote:
 How hard have you guys looked for a stock rod that could be resized to fit? I poked around a little and a small block Mopar rod was looking pretty close, just not as thick on the big end, but I have been told at least that is ok (I forget what its called, pin located or something). This one is typical I think, results of a quick search from memory and could be all wrong or terrible price etc. http://www.campbellenterprises.com/parts.php?type=search&query=K1dh6123anlba Chrysler 6.123 H-Beam (273; 318; 340; 360) connecting rod set 7/16 ARP 2000 Housing Bore 2.250" Rod Journal 2.125" wrist pin size is standard small block Chevy .927" Price: $519.95 |
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11-07-2008, 08:21 AM
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Quote:
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1984 928's w/ 5 speed Smoked Quartz Metalic 1982 928's Turbo w/ 5 Speed Platinum Metalic 1978 Euro Widebody w/ 5 speed Guards Red Last edited by Fabio421; 11-07-2008 at 05:39 PM.. |
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11-07-2008, 05:01 PM
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Network Native
Join Date: Jan 2007
Location: SoCal
Posts: 10,349
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Quote:
Totally talking out of my hat, but I still think I am right ... Oil needs to go to the bearing for cooling, flow through the bearing is the critical issue, not just presence of oil. Oil is already on the metal, and oil pressure doesn't provide more film. What is needed is flow to keep the oil from getting so hot that it breaks down and looses film strength. |
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11-07-2008, 07:39 PM
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Heavy Metal Relocator
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100mm = 3.94in
stock Chevy offerings include: LT5 350 (3.900--needs to be a .040 over piston) 366T BBC tall deck (3.935--good luck finding these) check pin height 396 BBC is close to the right bore (3.935) check pin height you can use any aftermarket piston, but you either have to nickasil (NiCom) coat the block, or sleeve it. as for rods, unless you're going to turn it towards 9000 rpms, you can use any good steel rod, as long as it's sized and the beams are polished. There are plenty of manufacturers that are producing good rods, without getting exotic. Same goes for rod bolts. 7/16 is unnecessary, as a ARP 3/8 bolt will do fine. The 7/16 just adds more weight. A $300 set of Scat steel rods will support up to 700 hp, more than plenty for what most folks are doing here. Shop eBay and you can probably get them for less...... I would offer my specs, but it would cause quite an uproar. Suffice to say, if you're going to hack up a block, you may as well put the biggest parts in it that you can. --Russ
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Absence of Evidence, is not Evidence of Absence. Bill Maher 8/4/09--- "I'll show you Obama's birth certificate, when you show me Sarah Palin's high school diploma." |
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11-08-2008, 05:33 PM
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Heavy Metal Relocator
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price is prohibitive, sizes are not quite there...... --Russ
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Absence of Evidence, is not Evidence of Absence. Bill Maher 8/4/09--- "I'll show you Obama's birth certificate, when you show me Sarah Palin's high school diploma." |
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11-08-2008, 05:37 PM
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Heavy Metal Relocator
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True, but unnecessary. price is near $1500 more for the titanium, and the question one should ask is: am I going to spin it to 9 grand? if not, just put a steel rod in it. I considered a titanium rod for the 540 BBC stroker I built for my buddy's Quick 32 car, but when we looked at the cost versus the performance gained, it wasn't worth the added expense.....This engine spins 8500 rpms all day long, has never been apart in two years, and runs a consistent 5.40 in the 1/8. Besides, it dyno-ed just over 1000hp and 850 ft lbs torque, so why spend $1500 bucks if we didn't have to? --Russ
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Absence of Evidence, is not Evidence of Absence. Bill Maher 8/4/09--- "I'll show you Obama's birth certificate, when you show me Sarah Palin's high school diploma." |
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11-08-2008, 05:57 PM
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RicerSchnitzzzle
Join Date: Jun 2008
Posts: 385
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Quote:
How much different is our aluminium block form a new corvette's? Is the silicone content lower? Trying to find a stronger piston for boost. I'm sure things can't be as easy as a slight bore, paste rub down, new rods and then chevy pistons...
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'81 Euro 'S' 928 5-Speed 5.0L Hybrid "Ricerschnitzzzle" Wish list: RollBar, New Helmet and driving lessons Wishes Done: Body kit, seats, No cat, Headers, X, Afterburners, 3" exhaust, short shifter , 17" TT Rims, 250HP N2O, MSD ignition w/retard+rev limit, MSD billet distributor, Accel Coil. 5.0L block, ported heads, JE race springs + .503 "S+" cams |
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11-08-2008, 07:16 PM
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Heavy Metal Relocator
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it's not the rings that you should measure when boring. It's the piston skirt diameter. Rings are ground to end gap measurements. You can use a GEN I 350 piston (4.000), but you would still need to do an overbore. As I said before, if you use a .040 over LT5 piston, you would match the 100mm stock bore. If you carry that out to a .060 over LT5 piston, then you would have a .020in/.51mm clean-up---an easy deal, but leading you to my next sentence----- If you are going to a non-Porsche piston, you'll need to have the block coated (USChrome will do your block---bore, coat, finish hone---for around $1300 and change). If you are going to sleeve it, then you can use any piston, up to 4.25 inch bore. (if you are going that big, it requires totally cutting out the original cylinders.) You can use an '85 block, bore and sleeve it to use a 4.125 piston (Chevy LS7) and then put a stroker crank in it. You'll get about 408 cubic inches with a 95.25mm/3.75in stroker crank. It also depends on what rod you use as well. The most common mod now is 968 pistons (104mm), a Chevy 5.85 rod, and a 95.25 stroke crank. Not quite my cup of tea, but there it is...... Just slapping in a Chevy piston doesn't really address all of the issues. I am in the process of getting the machine work done on mine.....about as big as can be done without deck plates and a longer timing belt (I wish.......  ).The silicone content is comparable to the old Chevy Vega engines.... If you are worried about piston strength, the OEM Porsche piston is pretty good for handling what everyone else has thrown at it (Kuhn, Murf, etc......). Yours may be tougher on pistons due to adding laughing gas, but if you are unsure I would recommend having the tops coated. Anyone building NOS powered pro mod engines can help. I would suggest you do just that with the pistons I sold you.....It saves you a bunch of money, unless you're looking for more cubes----- ---Russ
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Absence of Evidence, is not Evidence of Absence. Bill Maher 8/4/09--- "I'll show you Obama's birth certificate, when you show me Sarah Palin's high school diploma." Last edited by rhjames; 11-08-2008 at 08:37 PM.. |
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11-08-2008, 08:22 PM
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Network Native
Join Date: Jan 2007
Location: SoCal
Posts: 10,349
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Quote:
No need to hit 100mm exactly, thats kind of hopeless, just bore to fit anything that works up to whatever the limit of the cylinder wall is around 104mm. OTOH any indication that vette pistons would work in our blocks? Whats the Vette block made of anyway, any coatings etc.? |
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11-08-2008, 08:33 PM
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Heavy Metal Relocator
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my point was you can buy a set of sbc rods for less that $300......look at the prices on eBay and you'll get a good idea where rod prices are....some going for less than $100 for an entire set.
you could use a LS6 or LS7 rod---6.135 and resize it easier than the 6.123. of course, that would put you at a 1.9:1 rod to stroke ratio........great for winding it to the moon, but really lousy numbers for torque. all vette blocks were either cast iron, or aluminum with iron sleeves. No coatings that I am aware of, including the LT5 32V 4 cammer. as far as pistons are concerned, any thing other than Porsche OEM is going to require coating the block, unless you sleeve it. Back to square one..... ---Russ
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Absence of Evidence, is not Evidence of Absence. Bill Maher 8/4/09--- "I'll show you Obama's birth certificate, when you show me Sarah Palin's high school diploma." Last edited by rhjames; 11-08-2008 at 09:03 PM.. |
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11-08-2008, 08:55 PM
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Network Native
Join Date: Jan 2007
Location: SoCal
Posts: 10,349
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I wish I understood this better, maybe eventually.
As a layman I hear a lot of conflicting advice. Some people tell me they would never put a used piston in a new engine build, and that the only safe path is to back up the money truck. Straight up Nikasil isn't going to happen for me, good results, but not a path I care to tread. Doing a non stroker 104mm 5.4L sounds interesting to me, but only if it will fly fairly cheap, as in used pistons, no Nikasil, and a cheap modified stock rod of some kind. I'd like to put a .503 JME cam in as well as larger intake valves, but I am choking on the cam welding cost and haven't decided yet. As long as its fun I plan to keep plugging away, regardless of which way it takes me. |
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11-08-2008, 10:29 PM
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Heavy Metal Relocator
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nothing is cheap about any of this...... last price I saw on 968 pistons was $800. Crank was upwards of $1K, and then you've got to have rods and machine the block. And that's just for the basics. the difference between a 5.0 short block and a 5.4 short block is not worth the effort....or the money. --Russ
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Absence of Evidence, is not Evidence of Absence. Bill Maher 8/4/09--- "I'll show you Obama's birth certificate, when you show me Sarah Palin's high school diploma." |
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11-09-2008, 08:40 PM
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Network Native
Join Date: Jan 2007
Location: SoCal
Posts: 10,349
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Quote:
Worth the effort depends on what sort of goal you have in mind and what the alternatives are. If $5k is enough to make a hot cam 5.4L producing maybe 375 rwhp, that would be very attractive to me compared to typical Euro hybrid 290 rwhp or a $27k stroker. |
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11-09-2008, 09:41 PM
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