I'm curious: what's the general consensus about shot peening connecting rods? My rebuild is a mileage and performance upgrade rebuild, not a HP or racing rebuild. Not planning on shot peening my crank. Was quoted about $80 to do all 6 original connecting rods (one will have to be replaced because of my spun bearing).

Do people think this is a no-brainer to do? Are there any drawbacks, other than spending the $?

Shot peening removes the rough surfaces and compacts the surface to make it less prone to cracking under stress....

That being said it's not really necessary if just doing a mileage and mild performance upgrade....(If I were to do this I would take a die grinder and roll sander to the casting parting lines first since they are the areas that stress cracks start first, then have the rods shot peened- of course I run more performance than you are looking for and have not needed either if you are just doing a rebuild and not looking for more than 180hp of performance...

-D.Idiot

I think shot peening anything in, on, or near a slant 6 engine is a complete waste of resources. (If I knew how to sugar coat that, I would have, sorry).

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1966 Coronet Deluxe

I asked a machine shop to shot peen something once, and they clearly did not do anything. I have made up to 260 HP NA (6000 RPM redline) and 330 HP boosted (5500 RPM redline) with totally stock rods that were just resized and had new MP bolts installed. The 330 HP, 170k mile engine has the original 1968 rod bolts, but they were resized (bolts not replaced in 1989 when rebuilt). On new builds, I will always put in new bolts and resize, but obviously this one has been fine.

Save your money for head porting or bigger valves. I would not pay to balance new pistons or crank for what you are doing either. I *might* pay to balance the rods, but you could skip that too. Resizing the rods and putting in new bolts would be a good idea though.

Lou

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Home of Slant6-powered fun machines since 1988

Thanks for the insights. Wasn't sure whether I wanted to do it or not. Now I'm clear that I won't be doing it.

If you have your own shot peener, do it....if not, don't over rev it...over 6500 rpm.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Ha! Don't think I'll be doing that. I've kept these cars pretty much bone stock. Come to think of it, do we know the operating RPM's for stock slants at various speeds? 25 MPH, 45, 65, 75, etc? Would enjoy knowing the stock figures if anyone knows. Always thought the 170 and 225 seemed really torque'd up at 65+. Sure would be nice to have a 4th or 5th gear/overdrive. They don't 'drive happy' at modern freeway speeds.

It is dependent on rear gear ratio, and tire diameter. You can play with a drive train calculator to figure out what your car’s combination will yield.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

FYI.....

Numbers for my boxy 74 Dart Swinger......
based on a 2.76 gear ratio 8 3/4" rear and 26" tall tires:
50 mph is 2000 rpm,
60 mph is 2500 rpm,
70 mph is about 2750 rpm do to a lot more wind resistance,
95 mph is almost 3800-4000 rpm. I hit this at the end of the freeway on ramp.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

If you want to do something, take a sanding roll and smooth the casting flash off the sidesof thd rods.

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Official Cookie and Mater Tormentor.