Hot Rod Forum banner

383 rods / clearancing - help?

3K views 20 replies 5 participants last post by  ddekeyser 
#1 ·
Trying to build my first engine, and taking on a 383. Used pictures as reference to save myself some cash and ground the rods myself. Have a second set if I screwed up, but hopefully someone can tell me from my pictures if I've ground too much or not enough or what. Still going to get it balanced, in case that makes a difference.
Thanks for any help.


 
See less See more
2
#2 ·
Looks like the normal amount of grinding to me for a stock type rod and bolt. I've run them above 7500 rpm in a street/strip motor looking just like that without failure or problems. They really should be ground so the direction of the "tooling marks" left by the grinder are in line with the rod beam and the rod bolt though - Vertical with the rod, not crosswise. Cross scratches can lead to strees risers and stress fractures forming, just dress them off a little more in the correct direction, a grit roll in a die grinder works well for this.

FYI, Arp makes a bolt with a smaller head the eliminates a lot of the grinding done to the bolt head. I wouldn't use any rod bolt other than ARP anyway, for strength reasons, and wouldn't trust stock rod bolts at all, with who knows how many miles on them.

You're right in the ball park, takes a trial fit with the block, crank, cam, etc to be sure.
 
#3 ·
I had read that even the clearanced bolts from ARP sometimes catch. The only reason I'm doing everything stock is because I am on a TIGHT budget. Still laid off and can't find work for the life of me.
I just ground them the same way I saw in the picture I had. Thanks for that tip.
 
#5 ·
well you should try to keep the grinding to a minimum , but preassemble it and double check both sides of the assy just to make sure spin it over by hand 3-4 times in both directions to make sure . ( use your old bearings with alot of grease as not to mess up your new ones.
 
#10 ·
ddekeyser said:
Can I even switch out the bolts now that the rods have been ground?
Yes, but the rods have to be resized any time you replace the bolts as the intererence fit of the bolt shank and the increased torque figure that the new bolts require can cause the big end of the rod to go out of round. Hopefully you haven't had them resized already because that will be money thrown away now.

Rods should be resized on any rebuild anyway. I wouldn't trust old factory bolts in a stroker.
 
#12 ·
Look at it this way, just about any motor that ends up as a core has somewhere near 100,000 miles on it, which is millions of up and down cycles trying to pull those rod bolts in half, and now you are going to put them in an engine with a longer stroke which puts even more load on them. The choice is yours, how hard do you intend to run it??. Is it a low rpm truck stroker for pulling a trailer, or a hot rod engine??

The rod bolt is the single most highly loaded fastener in the entire engine, and will be the most catastrophic if it fails.
 
#15 ·
Any new rod should still be checked for roundness by your machinist, most all in that price range are chinese made, it would be foolish to think that their quality control is very good. It has been reported by some machinist's that many of these new chinese rods have to be resized right out of the box. I haven't seen any reports of outright rod failure with chinese rods, just sizing issues.

Scat is about the only budget rod that can be counted on, Eagle and lesser names are much worse. What brand are you looking at??
 
#20 ·
A Couple Observations...

The eBay site claims: "The 4140 alloy used in these rods is far stronger than the common 5140 alloy used in most other I-beam rods. Most I-beam rods on the market that are using a 5140 alloy only have a rockwell hardness of 26 We have built up engines in the 550hp range, with ever experiencing a problem." (Was that last sentence a Freudian slip? lol)

The eBay site claims a +/- 1g weight tolerance. Procomp's site claims a +/- 2g tolerance.

Procomp's site says: "Procomp ?I? Beam Street connecting rods are manufactured from high quality 5140 chromoly steel. The rods are x-rayed and and ultrasonicly tested with all surfaces shot peened and stress relieved. Perfect for engines producing 500+ HP".

So, we have a weight tolerance discrepancy, a 50 HP 'strength' fudge along w/a completely misleading claim as to what material they're actually made of.

When I looked at 5140 steel, it's described as chromium steel- no molybdenum in it, so not chrome-moly steel. Or, the Procomp site made a big error in calling it 5140 instead of 4140- which IS chrome-moly steel.

The hardness cited on the eBay site of 34 Rockwell is for a non heat treated metal. I would have thought that rods would be heat treated?

By the appearance of those rods, they look to be a standard I beam rod slightly altered to have threads cut into them for a capscrew.

I'm always concerned when I see a 'manufacturers' site w/misspelled words and bad syntax. But in the case of Procomp, we already know they are importers, not manufacturers and any grammatical errors could be because they don't speak English as their first language, don't have much of an education and/or lack even the ability to use a spell checker.

This is a totally different thing than posting on a forum, where grammar often takes a back seat to just getting a thought across. In advertising, there's no place for errors like that, IMHO.
 
#21 ·
Ya sent an email on the material difference. Waiting to hear back. Didn't catch the weight tolerance difference.
Pretty sure the horsepower is just for advertising sake. There has to be a safety factor anyways so not to concerned about that. Don't expect to make 550 anyway.
Ya the lack of info on the pro comp site threw me off a little. But there isn't any mention of the bronze bushing on it, nor is it shown in the pictures. Have brought that question up too. Think they might be modified, whether they are Pro Comps or not.
Will let you know when I find out.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top