Ozstatman Posted March 10, 2008 Share Posted March 10, 2008 I'm posting this on behalf of Wade who is helping me with my '41 Coupe. Amongst the projects Wade has on his hands now is rebuilding Kevin's '35 1201 Standard 8. But he's stymied at the moment although he's now received the new big-end bearings, which were made in the US and took over 6 months to manufacture, he can't re-assemble the engine yet.This is because he's now found out that over the years the "Tunnel" of the big-end of the connecting rod has become elongated and to get the new bearings to fit and have the correct clearances the big-end "tunnels" will have to be re-bored to the correct size, after grinding some metal off the big-end caps.However, and this is what's stymied Wade, He doesn't know the size the tunnels should be. So I'm posting this in the belief that among our knowledgeable experts there will be someone who can give the size that an assembled, although less the 2 halves of the bearings, '35 1201 Standard 8 Big-End "Tunnel" should be?Some of my terminology or wording may not be clear as I'm grasping for the correct words to use. But bear with me and I'll try and give further explanations if clarifications are required.Thanks in anticipation. Link to comment Share on other sites More sharing options...
Guest imported_Speedster Posted March 10, 2008 Share Posted March 10, 2008 If you are Sure it's the rod-ends that are out of round and not the new bearings ???, then I'd measure the bearings and bore the rod-ends to match them. After all the end result you want is for the rods, bearings and crankshaft to all mate up with the correct tolerances. That's what is really important, not trying to match factory specs. Link to comment Share on other sites More sharing options...
Restorer32 Posted March 10, 2008 Share Posted March 10, 2008 You need to know the bearing OD and the necessary "crush" to keep the bearing where it belongs. You can't just bore the big end to the exact measurement of the bearings. Link to comment Share on other sites More sharing options...
Owen_Dyneto Posted March 10, 2008 Share Posted March 10, 2008 I gave a fairly long answer to this on another forum where you posted this, but let me just repeat that you should have a professional engine rebuilder who does this for a living every day resize and straighten your rods to get the correct "crush". Too little and the bearing will float or wiggle, get oil behind it inhibiting heat transfer, or worse, the bearing will spin. Too much crush and you'll risk waffling the shell and microcracking the bearing metal both of which will lead to fairly rapid bearing failure. The "crush" is critical! Link to comment Share on other sites More sharing options...
Guest imported_PackardV8 Posted March 13, 2008 Share Posted March 13, 2008 Oz wrote: " to get the new bearings to fit and have the correct clearances the..." It is not clear to me wheather or not the bearing shells fail to fit the rods and the caps or do they simply not plastigauge to the journals of the crank correctly???? I DOUBT that there is big-end elongation due to wear or abuse. If the shells fit the rod and cap but not the crank journal then the problem is the shells OR the cap and/or rod at one time was filed to tighten up the bearings as a make shift 'getter runnin' procedure that was common prior to the 1960's. I really need more specific info to determine what the problem is. Big end elongation due to wear or abuse i have never seen. The rod, bolts or pistons will usualy break before any permanant distortion will take place. Elongation due to shimming/filing as the procedure i mentioned above can certainly elongate or cause out-or-roundness.CHECK THE ROD cap and rod MATING surfaces to see if there are SHIMS present. Thay can be VERY THIN and nearly impossible to detect unless u know to look for them.This should get u started. Link to comment Share on other sites More sharing options...
Owen_Dyneto Posted March 13, 2008 Share Posted March 13, 2008 PackardV8, you need to spend more time in a good professional engine rebuilding shop - big ends of rods do elongate and need resizing routinely in major engine rebuilds. Check with any good shop in your area. Link to comment Share on other sites More sharing options...
Rusty_OToole Posted March 13, 2008 Share Posted March 13, 2008 I know what you are driving at. The specs for the big ends should be in any good repair manual or service data book. Unfortunately the books I have on hand don't go back that far or I would tell you.Surely someone has a manual? Link to comment Share on other sites More sharing options...
Guest imported_Speedster Posted March 13, 2008 Share Posted March 13, 2008 I think what everyone has been saying, is that you don't really need the rod-end specs from a book, but use the bearings, he has (that Are available), to get that measurement from, then reduce the diameter of the bore to compensate for the amount of crush needed. Mainly because modern bearings are Not going to be exactly like the originals. He certainly doesn't want to bore out the rod-ends and then find that there are No bearings to fit that enlarged bore, so the size of the bearings available is the controling factor. The engine rebuilder should have the crush correction data for that type bearing, correct?, or is that what he needs? Link to comment Share on other sites More sharing options...
Guest imported_PackardV8 Posted March 14, 2008 Share Posted March 14, 2008 I contend that NOT enuf information is detailed to make any determination.1. Do the inserts fit INTO the rods and caps???2. If 1. is true then does the rod assembly fit loose or tite on the journal????3. Is there any nomenclature on the inserts themselves??? Without that info no remedy can be determined. So far all we know is that they do not fit and the claim is elongation. WHICH it may NOT necessarily be. Link to comment Share on other sites More sharing options...
Owen_Dyneto Posted March 14, 2008 Share Posted March 14, 2008 Checked an old engine rebuilder's manual from the 50s. On the subject of rebuilding rods, they state that if the elongation of the big end if 0.002 or less, the rods should be resized by milling and then honing the diameter back to standard. If greater than that, the rods should be discarded and replaced. Link to comment Share on other sites More sharing options...
Guest peter packard Posted March 14, 2008 Share Posted March 14, 2008 G'day all, a very interesting thread. There IS an exact size for the resizing of the conrod tunnel. For example on a 120A and 120B the crank pin size is 2.25in and the OEM tunnel size is 2.390 inch. My books cover just about all of the engines except the 320 cu inch and 384 Cu inch. I am hoping to find out the correct info over the next few working days. Resizing is a common workshop procedure in distorted rod ends but the manufacturer is the one to set the tunnel size. Many workshops take a best estimate but it would be good to track down the correct OEM tunnel size. If we had an engineering drawing of a Packard 221631, Packard 221632 rod, this would give the Packard tunnel dimension to give the correct "crush" to the bearing shells. Do the original packard engineering drawings exist or were they thrown out during the Nance "upgrade?" of Packard? best regards Peter Toet Link to comment Share on other sites More sharing options...
Guest peter packard Posted March 15, 2008 Share Posted March 15, 2008 G'day all, I have been advised by Jim Ketchum of Egge that the tunnel size for the Standard Eight is 2.3035 inches. Egge offer a resizing service for these conrods, so they should know. Best Regards Peter Toet Link to comment Share on other sites More sharing options...
Ozstatman Posted March 15, 2008 Author Share Posted March 15, 2008 <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: peter packard</div><div class="ubbcode-body">G'day all, I have been advised by Jim Ketchum of Egge that the tunnel size for the Standard Eight is 2.3035 inches. Egge offer a resizing service for these conrods, so they should know. Best Regards Peter Toet </div></div>Peter,As always you come through for us. I'll advise Wade and on his and Kevin's behalf thank you.Based on what I've seen here and on packardinfo.com you'll be a wonderful Technical Officer for the P.A.C.A.All the bestMal Link to comment Share on other sites More sharing options...
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