TurboTuna Posted February 22, 2005 Share Posted February 22, 2005 Hello, I posed this question to Adam Ginsberg earlier today. But I want to query the rest of the board. Has anyone ever used the stock cast pistons that came with their 1979, 1983-84 Mustang 5.0 motors in CMC competition? I am looking to see if they are a viable alternative for this racing series. I know they would fit within the rules but do they work for our purposes or so they just cause a motor failure. Please, anybody, chime in. Paul Quote Link to comment Share on other sites More sharing options...
King Matt1548534716 Posted February 22, 2005 Share Posted February 22, 2005 I ran the original cast-piston 302 in my 84 GT at about 6 track events last season, so I have some experience. The engine was pretty healthy when I started, making 180 rwhp with the stock carb & intake, but by the 2nd event it had about 20psi oil pressure at WOT! It never blew up, but it was close a few times. Anyway, I personally would not spend money on a rebuild using the cast pistons. If you are concerned about cost, I would recommend finding a good, used forged-piston, roller-cam short-block and building it up from there. These engines are very tough and will go many miles with reasonable maintenance. Most have very little bore wear due to high nickel content in the blocks, so you can very often get by with a bottle-brush hone and re-ring job, bolt on a set of fresh heads, and go. I wouldn't re-ring a cast piston motor either, FWIW. Alternatively, you can get a set of Speed-Pro replacement forged pistons (same as the TRWs that were OE) for about $300 or so, but they are fairly heavy. Speed-Pro and others offer lightweight flat-top versions as well. Quote Link to comment Share on other sites More sharing options...
TurboTuna Posted February 23, 2005 Author Share Posted February 23, 2005 Thanks Matt, That points me in the right direction. You wouldn't happen to know if 9.2:1 compression is legal? The 1986 Mustangs came with that ratio from the factory so I would assume it would be. Tony G. stated 9:1 maximum but that was for 87-93 cars. What did you use in building your motor as far as block, pistons, camshaft and rings? That is if you want to say or not. Paul Quote Link to comment Share on other sites More sharing options...
King Matt1548534716 Posted February 23, 2005 Share Posted February 23, 2005 I can't speak to what's "legal," but in a standard rebuild with a replacement flat-top piston, after you deck the block, mill the heads, and replace the head gasket with something like a Fel-Pro 1012-2, you are going to be in the 9.0-9.2:1 nominal compression range without really trying. I can't imagine anybody is going to break out the Whistler and quibble over a tenth or two. Quote Link to comment Share on other sites More sharing options...
TurboTuna Posted February 23, 2005 Author Share Posted February 23, 2005 Matt, My goal here is to get a quick revving engine so it can accelerate faster. Here is what I was thinking of doing... using a set of Diamond's Prolite NMRA Flat Top (402 grams) with the stock E7TE heads. The compression listed in their catalog is 9.2:1 @ 66cc combustion chamber and 9.7:1 @ 62cc's. I could just slap them together and hope I am close or really work on it so I am right on. Would opening up the combuston chamber to 66cc's be bad? I am not a cylinder head science guru and I wouldn't think that the extra cc's in the head would give any extra advantage. Would you? Boy, it sure would help if there was a specific ratio and plus or minus tolerance. Yet the opposite side of that is also true. The more rules you have the more money it costs (bad thing) and the more people can cheat (another bad thing). No wonder lawyers make so much money! Guess I should have thought my career choice out a little more. Quote Link to comment Share on other sites More sharing options...
King Matt1548534716 Posted February 23, 2005 Share Posted February 23, 2005 As I mentioned in another thread, I think ultimately the HP and Torque rules are the limiting factor. If you stick within the rules regarding stock heads and a replacement-style flat-top piston, you are going to be within a CR range that I'm sure meets the spirit and intent of the rules. You could go nuts angle milling, welding chambers, etc., but even if that got you to 10.5:1 or higher, you would still have to meet the 230/300 standard. Having talked to Tony G. about this in the past, I don't think anything in the rules precludes you from running a quality set of forged pistons. BTW, those Diamonds are super-light. IIRC, the stock replacement Speed-Pros are over 600 gms. Quote Link to comment Share on other sites More sharing options...
Members Al F. Posted February 24, 2005 Members Share Posted February 24, 2005 Matt I can think of two sections of the rules that counter what you just said. Section 8.13.1 says production engine in OEM configuration. Literally!Section 1 says if it aint specifically allowed, it aint allowed. Tuna Stick to stock stuff. At the rpms you're going to be spinning, it wont make a difference. Spend the money on tires, brake pads, and entry fees. Quote Link to comment Share on other sites More sharing options...
King Matt1548534716 Posted February 24, 2005 Share Posted February 24, 2005 Al, So are you saying that a rebuild with anything other than pistons carrying a Ford or GM part number is illegal? I think you need to explain that a little better. Your response is a non-response, because legal engine configuations include factory Ford engines that came with both cast and forged pistons, so what is "stock"? Quote Link to comment Share on other sites More sharing options...
Adam Ginsberg Posted February 24, 2005 Share Posted February 24, 2005 From ~1985 to 1992, the Mustang came from the factory with a TRW forged piston. In 1993, Ford switched to the hyper pistons. The update/backdate section of the CMC rules clearly allow Paul to replace his cast units with something more durable if he so choses. Quote Link to comment Share on other sites More sharing options...
TurboTuna Posted February 24, 2005 Author Share Posted February 24, 2005 I think the question Matt is asking is if the pistons has to be a Ford (or GM) numbered forged or hyper piston. Not an aftermarket piece made to work in the same capacity as OEM but rather are we limited to using only the OEM (Ford or GM) numbered pistons? A stock Ford forged or hyper piston straight from the factory is an upgrade from cast in my situation but are the aftermarket pistons, designed to fill that roll, legal as well per the rules? Sorry if I stepped on your toes Matt, just trying to help. Paul Quote Link to comment Share on other sites More sharing options...
Adam Ginsberg Posted February 24, 2005 Share Posted February 24, 2005 I think the question Matt is asking is if the pistons has to be a Ford (or GM) numbered forged or hyper piston. Paul - absolutely not. If you are rebuilding a motor, and wish to replace the original cast pistons with new forged units, or even replace an original set of stock forged pistons, you do not have to go to the Ford or GM dealer to buy them. If we were forced to do that, our costs would skyrocket beyond control. Provided the new units are about the same as a stock set ( weight, construction, etc ), and considered an "OEM replacement", they would be legal. I know where you're coming from - if you're replacing parts, replace them with something that will last. That makes sense, but don't get too caught up in the minutia. The reality here is we don't have a teardown rule - so long as you use OEM-style or stock parts, and make the number, you're good. Build a good, stock-type engine, go out and race. Quote Link to comment Share on other sites More sharing options...
TurboTuna Posted February 24, 2005 Author Share Posted February 24, 2005 That clears it up for me! Thanks guys! Paul Quote Link to comment Share on other sites More sharing options...
Members Al F. Posted February 24, 2005 Members Share Posted February 24, 2005 Exactly as Adam said regarding update/backdate of components. Section 5 defines "stock" as OEM or OEM equivalent specifications. That means the part does not have to have Ford stamped on it, but it better be designed to do the exact same thing, and not designed to provide any performance advantage. Quote Link to comment Share on other sites More sharing options...
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