Inliners International Forums General Discussion Hi Performance Long rod for the 292 Chevy (New)

Here is the latest shop project in the works.

Making a 7" + long Billet 4340 steel rod for the 292. This will allow use of a 250 piston in the 292.
1. Better rod to stroke ratio
2. Lighter weight piston
3. Stronger rod option
4. Same weight as stock 292 rod yet longer.

Hope I can sell them, they are ordered.

That's something I would want for a 292 build for better ratio, happier top end and easier on the parts if you want to wind it up.
Now someone give me a core 292 to start playing with.... lol. Maybe I should finish the 230 first. Need a balancer and maybe some small parts and its done.

Great idea. When will they be available? And do you have a ball park figure for cost?

Just to guess, & to test myself. $1500 ?

MBHD

Should be done in about 2 months. Ballpark price. 600.00 for the set of 6. Price determined once I get final costs.
Yes, it is true, I try and keep the price down.

Weight will come in at 680-690 with 7/16 bolts. Length will be 7.130. These will work perfect with my current 250 pistons stocked as a flat top. My 250 has a 1.67 CH. Also having a new piston made with the 250 CH and 18CC dish. This one will put a 292 in a 9-9.5 comp range.

What would happen to the engine power or torque wise if longer rods are put in, with the right pistons of course. I know it would be easier on the parts with less piston weight. What changes is rod the rod angle. Does this change horsepower or torque? Would peak hp occur at a different rpm with this change? Just trying to learn. Jay6155

http://www.superstreetonline.com/how-to/engine/0506-ht-rod-stroke-ratio/

Short rods will drive piston speed up too high and dwell time is reduced, the pressure from the combustion has less time to push the piston down - you can't speed up the combustion, it has a duration. If your piston starts moving away from the combustion too early, the combustion pressure never gets to work very hard to push the piston down. With longer rod, you get longer dwell and slower movement after ignition, so the combustion pressure build up has more time to push the piston down (make power).

In an engine that does not need to rev high or that is not desired to rev high, short rods are fine because of how they improve the bottom end performance. Winding short rod engines to higher rpms will cause the engine to "run out of breath" and you get excessive stress loads on the rods, and may end up with failed rod bolts. Wrist pins may wear out the holes in the piston because of the violent change of direction every time it passes TDC. The piston has mass that needs to change direction. Longer rod makes this change of direction more gentle.

A 292 makes enough torque without asking, so much so that you can sacrifice a little of it to allow the engine to breathe better at higher rpms. At this point of a typical build you would have done lots of other mods to justify using higher rpms, and therefore longer rods.

My thoughts only.

Jan

Rod length also affects piston to valve clearance, ignition timing requirements and intake charge velocity. With the poor intake design of the stock 230-250-292 head, a short rod would help keep the velocity up, whereas a longer rod would slow it down. I would imagine a lump conversion would be a good companion to longer rods to compensate for the velocity drop.

That's cool Tom! I'll have to buy a set when I start my next 292.

Do the stock 292 camshaft notches provide enough clearance for the bigger rod bolts?

Good point. These rods with 7/16 bolts are designed to clear the flat spots on the 292 cam. Or , I hope they do! There were plenty of measurements taken.

Got a call. The rods are almost all done. 2 sets are done and they are sending them out to me on Friday.

Rods are in hand and I got a chance to check them.

All pics are taken with the new rod in a stock deck height block.

Deck height with stock type replacement piston is .065 down in hole. With new rod/ piston it is .030 . This block may have a taller than normal deck. It was not measured.

The rod did not touch the cam or oil pump. Some engines will need slight clearancing.

The rod weighed 10 Grams more than the stock rod shown.

Those are some sharp looking rods! Thanks, Tom.

Nice,
so what is the final price for those?

MBHD

Here you go. I try to hold the price down.

620.00 for the set. They will fit perfect with My 250 flat tops or the 18CC dished pistons I offer.
http://12bolt.com/250292_products/rod_292_long

That's a good deal and getting rid of the excessive height above the pin and the 250 pistons is an advantage. 620 bucks is a very fair price for low production high quality items.
I've heard endless discussions on rod length from tuners who spend a lot of time dyno and track testing engine changes .Almost all the discussions were V engine but the theory is the same for an inline.
They most all agreed a short rod increases low speed power and a long rod increases high speed power. The increases in power are often subtle and depend on the whole tuning package.
You can find more a lot of info on the Speed Talk forum.

I recently thought of it as a runner, take two athletes with equal muscle power, one with shorter legs is a short rod engine, he gets around quick but just can't comfortably run at high speeds. While the other guy has much longer legs, he might not be quite as nimble on a soccer field but he can run faster, with less effort Not sure this analogy works perfect, it was just a thought

Very nice set of rods Tom.

Got some weights for comparison.
This is comparing the entire assy. Rod, piston, rings, wrist pin and bearings.
Stock/ 1635 grams
Stock/replacement piston 1583 grams
Ross piston, billet rod, modern rings 1405 grams.
What will 1/2 lb do to the way a engine revs and react? Per cylinder.

It makes me think of Ron Golden's 302 with Hudson rode and custom pistons. He saved 1.25 lbs per cylinder. That's 7.5 lbs! 15 with a matching amount removed from the crank weights. I'd love to hear it run.

These 292 rods look good and I know the pistons are great.

Issue with the pistons is they are almost "Display only." I'm gonna cry when my mirror like ross pistons turn to a gas burned stain.

Hopefully you won't be seeing them for a long time.

tlowe #1716,
maybe this note should be titled "Fairly Long rod for the 292
Chevy". I'm still going down the "primrose path" to 292 bliss
with the re-machined CON, MF, etc 7.00" rod. That means a 283
piston with 1.80" CD. The R/S ratio is 1.7 as are the 327 and
350 SBC's.
my recent reading turned up a comment by a GM-Six man saying
that some attention should be paid to the skirt/thrust face of
292 pistons to help alleviate cylinder wall flex. (the list of
potential helps/fixes is long.) have you heard of generic
problems with 292 'wall flex' or is this a 'generic warning'
to take it easier on a 292 than a 4-bolt BBC?
kalvink.

The cylinder walls in most 292's are thin unless you get a Mexican block, and I have sonic checked many of those that were as thin as most non-Mexican blocks. Using a long rod in these engines for racing helps reduce cylinder wall loading. We used 7.250" length rods in ours.

Hi I have finally joined. I have purchased a set off these Rods from Tom . Also flat top pistons and other parts will dyno once engine is together .Induction is Aussie Speed intake and MSD Atomic EFI