Tell me about it. You can't be a brand guy anymore if you want to win.

Look at the NMCA Real Street or PRO Pro Stock rules. You can't find a Chevy head in there to run. There are good heads, but when I have the choice of a Victor Edlebrock Ford or a TFS R head I'm not going to use any 23deg Chevy head, for alot of reasons.

They allow you to run a 15 Deg Ford head, but not a 18 deg Chevy head. I don't see the point in that.

Winston Cup and NASCAR really need to allow the Canted Valve stuff back in for Ford. Back when Alan Kulwicki won the championship was when Ford had by far the best heads out there, and Chevy had ****. Ford basically swept the first 1/3 of that season.

Bret

 

You can run the Chevy TFS TW stuff too but it isn't as good as the Ford stuff. It's a big block class anyway the way it's worked out I guess.

 

I'm surprised that the NASCAR engines use pistons and pins that are that heavy. Lately I've dealt strictly with power cylinder components for new OE engines, but the one I'm working on now has a 430g piston in a 103mm (4.055") bore and a 52.7g piston pin (tapered ID) that is 65mm long. The engine makes 425 HP at 6000 rpm and all the components have to last through a 625 hr. durability test that cycles from peak TQ rpm to peak HP rpm at WOT. Ring mass is similar to your estimate for a NASCAR engine, which I also find surprising. We're running axial widths much greater than I expected NASCAR was down to now.

 

That engine wouldn't have a 94 mm stroke would it?

FWIW, 800 hp cycling from about torque peak to hp peak (6-9k) for 3-4 hours might compare favorably to 425 hp from 4-6k for 625 hrs!

 

I didn't even have to do the cube calcs to figure the engine you are asking about there. I thought that motor was good for 7-8K, 6K seems a little low, but still higher than the motors now. I'm not sure who else would run a 4.055 bore. That 94mm stroke could probably cut into the raw crank pretty easily too, it will be a shame if the bore on that block is really that small, I was getting excited for a stock 4.125" bore block again! 103mm bore would make sense, vs a 105mm one.

Bret

 

This is not a GM engine I'm referencing, but I can't say much more than that. Just thought it was a good data point for the mass discussion.

 

800 HP is much harder on everything. The pins have to be very strong to see 9200+ rpm and lifted throttle conditions and the pistons have immense inertial loads and heat loads going through them. I've seen plenty of low hp Late model stuff with extremely light parts. At 425 HP you could probably run 275g pistons from Wiseco or JE and a 60-75g .866 pin all day long.

 

OK, definite thread drift here, but I have to call you on this one. No way no how will a piston and pin design like that pass an OE durability series of tests. It's one thing for a Late Model or street car to use a piston like that when the aftermarket has no durability schedule they put parts like this through, but I bet I break that piston and pin combo in 100 hours, much less the 625 hours it has to pass.

I understand a NASCAR piston/pin combo has a different set of conditions it has to pass. All I was doing was throwing out another data point and saying I was surprised NASCAR pistons/pins weren't significantly lighter than the ones I've been working on. I'm especially surprised their rings are so heavy.

 

94 bird,

Who was talking about oem testing? Only you are. I don't think you've been around too much race stuff if you don't know what I'm talking about. You're also working with cast stuff most likely like the LS1 type stuff from Mahle (LS1 piston weighs 430g as well). Forged race pistons can run much lighter and don't run as hot since they tranfer heat out of the crown much better and to the cylinder walls than any cast piston.

Also a Winston Cup piston could easily go 100,000 miles under oem conditions. The rings are .043 so they would wear a little more than a 1.2 or 1.5 mm or certainly a 1/16 size ring but the pistons you are talking about couldn't make one lap at 9200 rpm in a Cup car under 800 hp load. The loads on the nascar piston are over double as high due to rpm and the heat loads and also nearly double.

You're right though the thread has drifted somewhat!

 

""BTW I don't think Dan even said that the longer stroke motor had less friction, it's actually the other way around. Yeah the same port on a larger sube motor will peak at a lower RPM, something that more camshaft will not fix very well. One of those reasons that a 383 doesn't really like LT1 heads.

Bret""

The longer stroke motor will have slightly more friction at the same rpm but less at the same piston speed. This is why if you increase stroke you will make more power even if the heads are locking up just not nearly as much as if you have better flowing heads. A 420 inch small block will eat a 377 for lunch both with 4.155 inch bores. Part of this is because the 420 runs at a lower engine speed even though the piston speed is the same or slightly higher due to the lower valvetrain speed. This enables actually MORE airflow with the same head now with more lift possible (more valvetrain intensity).

This is why you won't ever see anyone running a 400 inch Pro Stock engine even though it could turn Comp engine speeds. It would still be too far down in power due to all the cam that will have to be taken out as well as a smaller intake valve to get to this new higher 10,500 rpm limit instead of the old 500 incher's 9,500 rpm or so. Only a dumbass would even try even 450 inches. Anyone that doesn't use as much stroke as possible (I know there mechanical and piston height limits of course!) is just leaving extra power and reliability on the table for someone else to take and beat them over the head with if they both have the same stuff.

By the way Jordon Musser's original low 11 second high ten second LT1 camaro had LT1 heads and a 383 that were both done at the school and made over 400 RWHP on pump gas. I'd say that was ruinning well for a 383 with LT1 heads! We've routinely made 610-620 hp with small DART Sportsman 200s at only like 206 ccs that flow like 290 or so on a small 2.02 or 2.05 valve. I think the LT1 could easily do the same or so with a real race motor or more. We made 650hp with LT4 heads in Factory street NMCA. That was steel valves and only commercially available solid flat tappets and had to stay with chevy lifters.

 

Well no, not really. I stated up front that was what I was talking about and you stated a much lighter piston could be used. On that point we'll just have to differ.

I'm sorry. How did you get the impression I don't know what you're talking about?

Hehe, not that much lighter. BTW, the LS1 has a good bit smaller bore than the engine I'm working on. I'll put my piston's k factor up against any other big bore V8 in mass production. Sorry, a little bit of ego creeping in there. But you wouldn't know much about that would you?

It's not just about 625 hours from peak TQ to peak HP. I'm sure you know that. We are under a lot of constraints that a NASCAR piston manufacturer simply isn't. I'd love to be able to work under their simpler design criteria. However, I came from the racing side and moved to doing OE work because I really enjoy the resources I now have to work with. I still enjoy listening to some of you racer types discuss things though. I shall now go back to listening mode since my short, passing comment resulted in more of a thread drift than I originally intended.

Mike Taylor

 

Mike,

Don't go back to listening if you have something to add. Chime right in. If you are talking about "your" piston I assume you are a piston designer of which I know two. What other pistons have you designed and for what apps?

You just made the comment that you thought that 400g was heavy for a Winston Cup piston which it isn't and you were just mistaken or didn't know about that end of the piston biz. If you were just noting that OEM pistons have gotten much more advanced and lighter than accept my apologies and you're absolutely right. I marvel at some of the stock stuff you see at the core yards from Hondas to BMWs to Fords nowadays!

I just meant that your test would be a ridiculous cakewalk for a NASCAR WC piston anyday whereas the pistons you are talking about wouldn't even make a lap or two before failing under WC conditions. I know when it was legal some of the 2 ring stuff was lighter especially in the lower hp apps.

I know some piston people at Wiseco and Mahle so I love to talk about them and/or learn anything new! Also one of my old college roomates buys pistons for Ilmor and I've been around a lot of that type stuff. The OEM is where most of the development is but price is much more important than in racing so often things are much more compromised.

I have Manley restrictor pistons that weigh 325 grams in my 155,000 mile NA 363 inch small block Ford stroker but it only makes maybe 385 hp and turns 6500. They work great and are ten tear old technology for limited or restricted late models. Anyway they will probably last forever on the street since they aren't pushed very far unless I'm autocrossing or at the strip every few months. I have done several lapping events where I put entire tanks of gas through the car ar TWS in College Station Texas as well.

 

Mike,

What is the most misunderstood aspect of pistons you see people not understanding or discounting according to you yourself and from what you've seen? I know true ring land flatness and trueness under heat and load is one I can think of as well as overall piston stiffness. We've certainly had heavier pistons make more power and better vacuum because the lighter one's were simply too weak to not deflect a lot. I also see horribly out of balance domed pistons wear the skirts on the opposite side of the dome from the domes weight making the piston so heavy on one side and then the people blame it on "rod ratio" even though it's on the outside side of the block on both sides and not on the load side!

Then there's also piston pin design and rigidity as well as the pin bore's actual shape like the cnc non round when cool Mahle stuff. We see a lot of pins beat up from detonation and/or insufficient pin clearance or just too much heat for the compression height and the people blame it on the piston instead of their own bad machine work or inappropriate choice of piston for their particular application.

 

I'm emailing you since I think that's a better place for this kind of discussion.

 

I always though you bored it out and stroked it As much as the cash flow would allow.....lol