The Stovebolt Site Forums The Shop Area Engine Shop Another 292 question . . . these stinking rods are long!

Chevyman, JH, Tony, and anybody else that might know. Well after settling on 9.5:1 for a compression ratio - time to order rods to go with the pistons. One of my original rods was damaged beyond repair and I have been advised to get new rods all the way around for the boosted motor. Thus the quest for aftermarket rods. I thought I would go with Crower Sportsman rods, but I find that they dont make a rod longer than 6 inches for the bearing journal size of a 292. The stock rod is 6.760 inches long and seems like the replacement rod should be pretty close to the same. Anybody know who makes an aftermarket 292 rod?

Ken,If you're having pistons made and are going to custom made rods, get the longest ones . Talk to the piston guy, see how much you can safely move the piston pin up and get a rod to fit.As you know, the 292 has a short rod for its stroke and the rod angle at BDC is severe. Plus the piston pin is low on the piston.Of course, custom rods may be more than you want to spend on a street engine.I know there are aluminum rods available, but most guys don't recomend them for street use.

Ken: The best rod for your blown engine, would probably be a 4340 steel forging. Super tough rod! Will stand up to all the boost you can throw at them. Don't know how deep you are into your mill just yet, as far as crank, block, etc., or how much your plans/cash are into this project.

Let me recommend a shop that you should talk to, they are: www.speedomotive.com

These guy's are technical experts on all kinds of engines. Have state of the art machine shop, dyno room, balancing expertise, etc. They have super stock kits for 292 (crank, rods, pistons, in a balanced set).They even do 235/261 stuff as well. They are a top shop for NHRA, outlaw, and circle track engines also. Give these people a call, they'll help you get that 292 off the launch pad, ASAP, and done right, with quality parts that will last! Done business with them for years, and they have always done me right, and I give them a 2 thumbs up! Good Luck!

Think Chevy! :rolleyes:

Chevyman, thanks for the link - I'll give them a call . . . also, I see you are in Oregon, the engine is presently at S&H racing in Sylvan (West side of Portland) as they did another inline 292 for Walt Skoczylas '32 bantam, he manages 500+ hp at the crank with a 6-71 blower and nitromethane. S&H does great machine work and have lots of ideas, but when it comes to the 292's they are a really dependant on the owner to provide direction.

Chevyman,

I talked to Rich Sr. at Speedomotive. He asked a lot of questions about desired HP and rpm operating range. He said that they could go through a set of stock rods and guarantee them for 400+ HP / 6000 rpm operation for about half the price of aftermarket if used with a light weight Ross Piston. The OEM rods were made to withstand forces associated with a much heavier stock piston and as such do well with a little work with a lighter aftermarket piston.

They will also bush the small end and get true center-to-center distance nailed to .0005" and put in ARP bolts. Process involves 3 point balance, polishing, shot peening, heat treat and assembly to a set of Ross pistons (which they will order and sell for less than me buying direct). I think I am going to UPS my rods to him, he said he had an extra core that I could have. . . he was glad to help and seemed pretty happy to hear about a 292 getting some attention. It wont be 4340, but sounds like it will be good enough for the power I am trying to make and then some. This brings up another set of questions . . . time for a new thread

Ken: Sounds like a plan! I was not sure if stock rods would be up to the task, sounds like they are. These guys would know, as its always best to seek expert advise when in doubt, as they build racing engines for a living, and have vast knowledge and experience from years of building strokers.

Seems like you touched bases with them on your rod needs. Be sure to tell them all your needs and concerns about the blower, cam, induction, etc. I think, with there resources and knowledge, they will be able to get you going. You may want to just send them your crank and block too. And maybe have them assemble short block for you. I don't know quite where you are into all this, so I only suggest.

If you are going to pick up your piston/rod assemblies from speedo, you might want to check with them on having ceramic coating applied to piston tops/domes. This helps deter detonation and heat build up on the piston. When under high heat stresses like blower use and abuse the ceramic helps insulate heat build up, and heat transfer from the head. This is the problem that guys experience when they use cast or hyper pistons against high boost/blower pressures. The increase in dynamic compression causes fractures of the piston tops and/or ring areas. Forged pistons kinda get in a "plastic" state under very high heat or detonation, whereas cast pistons will "blow" holes in the tops. Hyper pistons have a little better tolerance than cast, but they "reflect" heat, and that causes dome/skirt expansion differential problems, and fractures. Forged pistons are sure the way to go.

On your blower set-up, are you still married to the idea of using a positive displacement unit? Or would consider a centrifical blower? What about a turbo? Maybe you might want to check with speedo on this too.

I know that to drive a PD unit like a whipple or roots on a inline, does take some ingenuity and thought. The front bearing will not hold up well. On blown inline engines that I have seen, (they were both 261's by the way) they had a support bearing, mounted on a plate that covers block front that was cut out around chain cover. I think the plates were bolted to the lower front mount holes and the water pump bolt holes. Can't remember been so long ago! Anyway, the engines were mounted off the side mounts so this freed up the use of the front of the block. The plate hung below the front of the block. There was a large piece of pipe, maybe 8 or 10 inch, welded to the plate surrounding the damper, and it had top 1/3 cut out so it kinda resembled a "horseshoe" shape. The pipe was about 7 inches long with a flatbar 3/8" by 6" welded to the outboard end. The bar had a 1 1/2" hole in center. Short flanged stub shaft (I had made the shafts for this guy), that mounted on front of HTD/Gilmer hub. Shaft plus flange was 6" OAL. Used a 4 bolt flange bearing mounted to pipe plate. This gave the additional support needed for the front main. The blower belt hub bolts directly to the damper bolt pattern. But the problem is that when mounted, the belt centerline is about 4.5 or 5 inches outward of the front main, and this causes the crankshaft snout to flex a bunch and causes terrific side load on the main. This outboard shaft arrangement, cured all that with the outer bearing taking the sideload. Anyway, if you go with a huffer, this kind of arrangement or a close variant will be what you will have to use. Talk to speedo, they will get you squared away. Glad I could be of help to you. Hope all work out well!

Think Chevy! :rolleyes: