The Stovebolt Site Forums The Shop Area Engine Shop Rod length of a 292?

Anyone know what the rod length is on a 292?
How about the compression height (piston pin centerline to piston crown).

Thanks.

The rod lenght is 6.76 and the compression height is 2.09. Sure would like to find some that were 7.00 long.

Larry

Okay. So even though the big end of a small block Chevy would fit around a 292 crank, the length is way off. The longest SBC rod I've seen for sale is 6.25". I believe Mopar has a 440 big block rod that measures 6.76" though, and is available forged. Don't know if the big end is the right size though.

And 2.09" is a little too large to find an off-the-shelf 283 forged piston to fit.

Someone's gotta make performance parts for 292's. They were race engines for years back in the day. Maybe I'm just not looking hard enough.

I was wondering why you asked. If there were any "Sportsman Rods" out there they are hiding. I've been looking myself. Leo Santucci's manual showes some pics of rods that look like they might be forged steel. I contacted Leo thru a third party and the answer was they were given to him. I spoke to Mke Kirby and all he could come up with was Alm billet. Aluminum won't cut for street because they stretch. I called Crower and got an off the wall No. There are some long rods made for BOP, but their crank end is too narrow. The crank end of the 292 is 1.045-1.050 wide. I bought a copy of AERA's connecting rod manual(1998) and went through it. There are a couple of rods that are the right lenght, but they are from low compression motors so probably not a good choice. Just in case some one asks Continetal motors found in 1962 and earlier Jeeps and Hercules motors might be the same motor.

If a 7.00 long rod could be found you couls use a 283 or the 292's little brother the 230 piston. The 230 and 283 are almost flat top pistons. Otherwise it looks like the only way you will get 10.0 or better compression will be to go with a forged piston $500-600 a set.

Another consideration is how much deck clearence you have. I have .072 on my motor. I'll lose part of that when the block is surfaced, not enough. Leo says not to take off more than .030 from the block deck. A set of forged would have what ever compression height you say. I hope to get my block to the machine shop this coming month.

I've tried finding a source on the east coast from the Internet, but haven't had any luck. There seems to be some circle tracks still running 292s. If there is anything it would on the east coast.

Larry

Here's an idea, but it means having a set of custom forged pistons made, and you're talking at least $600 for the set.

But since the small block Chevy rod is the right diameter on the big end, you can order a forged 6.25" set, which is about a half inch too short. But to make up for it, you could increase your compression height about a half inch since you have to get custom pistons anyway. That would be a compression height of 2.60" exactly.

It's just a thought, but diesel pistons are serious pieces that are made for compression ratios over 18:1, and often have a high compression height. I wonder if there's a diesel piston out there that measures 3.76" to 3.82" in diameter with something close to a 2.60" compression height. If you want higher compression, increase the compression height.
The only thing is the weight, probably would exceed 900 grams per slug.

The stock rod/stroke ratio is 1.64, which isn't bad for a motor with that much stroke. That's about the same as a 350 small block Chevy.
But the 6.25" rods would give you a rod/stroke ratio of 1.52, which is about the same as a 454 big block Chevy. So you'd still be safe to at least 6200 rpm with a good set of forged H-beam rods.

Aside from that, I wonder if any of the reputable connecting rod companies would consider making a custom set.

The SBC rod has the same problem as the BOP rods. The crank end is too narrow. Custom forged rods would be $$$$$. The exception to that might be if a forged BOP rod had enough width on the forging to do a 1.050 crank end. The idea was to run a forged rod and a cast piston, and get 10.0 plus compression. Which is about the cost of a set forged pistons. The next over bore would only require a set of cast pistons, half the cost of forged.

This is going to be a street motor. The high compression is to run E85 not set record times. The way I work it out E85 sells for 20-30% less than gas. Running E85 you loose 20-30% in mpg.. Considering consumer economics and physics the fore going will be a constant. For every 2 points you raise your compression you gain 8% in performance and 7% efficiency or is it mpg. The stock 292 is 8.0:1 raise it to 12.0:1 and gain 14% in mpg. The extra 16% performance is a freebie. :rolleyes:

There is another way to accomplish the same thing . Install a centrifugal blower, Paxton, ATI, Vortech what ever.

Larry

Hmmm. My machinist was the one that told me that small block chevy rods had the same size big end as a 292 crank. I don't personally know.
I have a set of big block rods...well, 6 out of 8. They're GM pink rods. But they're shorter than the 292 rods at 6.135". And my machinist said the big end is too large for a 292.

Okay, here's another idea. If the BOP rods are a little too small for a 292, why can't you have the 292's crank turned by a machine shop to match what your rods are? That's pretty routine actually. You can usually safely go about 0.030" undersized on a crankshaft. Would that do it for you?

Regarding the E85, it's a good idea, but runs better on either very high compression engines or with forced induction. I've got a 427 Vette with over 12:1 compression, solid roller cam, and completely maxed out. Problem is, it runs very expensive and hard to find race gas. High test isn't readily available anywhere anymore. I am thinking about converting that to E85 to take advantage of the 105 octane. It'll run cooler, cost half as much to fill up, can actually find places to fill up, and with that compression ratio, I can squeeze the power out of E85. Best thing is, I can always go back to race gas with just a 15 minute carb retune.

Good luck with your efforts on that. It's a good idea.

7 and 7.25 inch rods are out there for these engines (I have a set in one of my engines). Mike Kirby at Sissell's Automotive can help you source them. 626-331-2727

Arpee, are your rods forged steel or alumunum? I spoke with Mike, maybe I didn't ask the right question.

Hot Rod Dad, The machanist is correct the journal diameter is the same. The problem is the crank end of the rod is not wide enough and will not fill the journal side to side. If you check the BB rods on the crank end you'll also find they are too narrow. The 292 rod is 1.050 side to side. I don't remember if they were Buick or Pontiac, I think Pontiac. The journal size was good, but only .993 wide. The wrist pin dia. was too large, but that could be bushed down, maybe let the pin float and use locks in the pistons.

I've seen 2-3 figures for the octane on E85, 103, 105, and ???. I've calculated it out to 117, using an octane rating of 122 for the ethanol (found on the net) and 95 for 15% regular gas. You will have to bump the jet size on the 427 up by 25-30%. I'd like to hear how that goes when you do it. You might have to watch your fuel filter, as the ethanol may losen up residue that's happy staying put with gas. There seems to be some folks reporting that. Also there may be some parts in the fuel system that don't like alcohol another compliant reported. Once the system is flushed out your change the carb tune and go.

Larry

Right you are.

Regarding the connecting rods, My machinist said a set of ARP rod bolts will make the stock 292 rods live to higher rpms easily. He said they're stout enough, the weakness was in the rod bolt technology of the day. Then shot peen and polish for good measure.
He said get a set of custom pistons made for $100 bucks apiece, give or take.

Regarding the E85, Hot Rod magazine just answered a guy's letter asking that about his high compression 454 musclecar. They suggested a stainless steel or plated gas tank (or fuel cell) and stainless steel fuel lines. Get rid of rubber hoses and AN fittings, and finally, change out the viton needle and seat for one made for alcohol. Then rejet about 25% richer to start and tune.

I figure if I record my race gas settings, I could easily convert back to race gas for the extra power if I ever wanted or needed to. But at 12.2:1 compression, I probably won't notice a severe hit in power.

The machinist is right and I've already got the ARPs.

I think Hot Rod is CYA on the SS. The rubber hose YA, maybe re-enforced vinyl. Right on with the Viton. I need to research cirle trackers and dragsters running alcohol. I was on a JR Fuel Dragster team and we were running big Kinzerler Injectors and they had brass fittings. The return line to the fuel tank had rubber hose for couplings. We never left the alcohol (Methanol) in the system more than overnight. I never heard any specific reason for cleaning it, other than that's what was done by all. Now with your Vette I sure wouldn't take any chances.

I'm not sure you'll lose anything for power with E85. Note your timing on gas and see if you can't gain some advance with E85. If my calc is correct on the octane you might be surprised.

Larry