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#1
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Crankshaft journals machined incorrect
I have a forged 4340 crank with 4 stroke, 3 mains and supposedly 2.25 journals. I bought this 3 months ago and left in the box. I bought 428 Icon pistons at 1.595 compression height and 5140 I beam rods with 6.625 and 2.25. After bringing to machinist the journals are cut from the factory at 2.20. All literature and documents from the company say 2.25 journals. I believe when they changed over the cranks it accidentally was cut for the Chevy journals.
What is the best way to correct it? Its a pain to return the crank and everything else on the crank checks out. But if I keep the crank I need new rods and maybe a custom piston? Do they make a thicker bearing shell so I can use my rods? |
#2
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Your FIRST action should be to contact the folks you bought the crank from.
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#3
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Yup, I did, no response yet, been a week. If they make good no problems. Looking for options.
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#4
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I bought one that was supposed to be Pontiac Js and when I got it I checked and it was BBC
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#5
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Is this one of the Speedmaster cranks?
Murf Sent from my iPhone using Tapatalk Pro |
#6
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Another option. Sell your rods. Keep the pistons and the crank. Buy BBC 6.635 length rods. Only .010 taller, will put the pistons closer to zero deck height.
Make sure to get BBC rods which have a small end bushing because you'll need to re-bush them for the .010 smaller size Pontiac pin. You'll need to buy smaller bushings. |
The Following 2 Users Say Thank You to elefantrider For This Useful Post: | ||
#7
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Yes, speedmaster for me, it’s too bad because the rest of the crankshaft checks out fine.
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#8
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Only Ohio Crankshaft ever had a 3” main 4.00 stroke crank for Pontiacs but they discontinued it some time ago. I have to agree with the suggestion of selling your 6.625 inch rods and acquiring 6.635 BBC rods.
__________________
It takes considerable knowledge just to realize the extent of your own ignorance. Dr. Thomas Sowell |
The Following User Says Thank You to hurryinhoosier62 For This Useful Post: | ||
#9
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Can the BBC rods be sized down .010 from .990 to .980? Is there enough “meat” left in the bushing, or do I need new bushings? It about a 500hp build.
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#10
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Quote:
Was your new pistons made for press or floating wrist pins? Clay |
#11
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Pistons are forged Icon for floating pins.
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#12
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All your machine shop would have to do is order the correct bushings and hone them to the correct pin size.
__________________
It takes considerable knowledge just to realize the extent of your own ignorance. Dr. Thomas Sowell |
#13
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Back in 2009 on a trip to the states I bought a 428 crank kit from star galaxy. It sat on the shelf till quite recently. I decided to assemble an engine a while ago and found I have the standard 428 pin height pistons with 6.7 rods and a 2.20 crank. As luck would have it I picked up a 428 block and crank for a good price . So now I need to buy a set of pistons to suit the 6.7 rods and crank and a set of 6.625 bushed rods. It would seem we need check our parts as soon as we get them. In my case due to the currant exchange rate its quite an expensive exercise
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#14
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I picked up a forging over here in NZ recently, was stamped 4.250", but had 2.250 journals. Got the stroke checked, yep 4.250".
Waiting to do a mock assembly in the block. With an SRP flat top my last assemby ended up about 30thou in the hole and required a cut for zero deck. Might get away with 4.25" and std 6.625 rod in this one (hopefully 🙄
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Working on going faster (and now staying dry at the same time !!) |
#15
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I will need to find those bbc bushings. Is the OD the common 1.017?
Last edited by soupman; 05-02-2020 at 08:42 PM. Reason: Wrong dimension |
#16
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Jeggs have got advertised 3 main 2.25 journal 4.210 stroke cranks by speed master(cast) does anyone know if the 2.25 journal size is correct? I was about To order a couple but this thread has got me wondering as no other company will do the cast 455 crank with 3 mains and 2.25 journals. It would be good as I have a few parts to use up.
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#17
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Mine was also a speedmaster. Based upon what is said so far in this thread seems hey are all BBC journals. Good lyck with speedmaster answer a email or phone call, no luck so far.
It’s ok for me with a bbc rods if I would have known ahead of time. |
#18
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My 4340 Star Galexy Ohio 455 Crank from 2009 had BBC Rod Journals, and was out of Spec. They remachined it. So i got a "bargain". I had it trued-up in AL, and meets PMD Main Specs, and BBC rod Specs (-020).
Confident in it, but need a 6.625" AL rod, or...a a set of >\= 455+030 slugs for 6.8" rods. |
#19
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Quote:
__________________
Will Rivera '69 Firebird 400/461, 290+ E D-Ports, HR 230/236, 4l80E, 8.5 Rear, 3.55 gears '64 LeMans 400/461, #16 Heads, HR 230/236, TKO600, 9inch Rear, 3.89 gears '69 LeMans Vert, 350, #47 heads: Non-running project |
#20
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Quote:
http://www.pppcenter.com Not sure what size you'll need, for aftermarket rods it's hard to say. I just got done doing this for a current project. Until you get one of the bushings removed from the rod, it can be very hard to measure for the new bushing OD. Due to the very thin wall, the only way I know of to get the bushing out of the rod is to bore it out on a milling machine, which is how I did it. The bushings are pressed in with a minimum .003" interference and this is very tight. There is likely some more machining to do to get the new bushings to fit properly in the rod end. The rods will have to be heated and the new bushings pressed into the rod end when the sizes are correct. The .003" interference is very important to keep the bushing from spinning. Next you will need to drill the oil hole from the rod end through the bushing, and be sure the new bushing length is exactly the same width as the rod end (which it won't be) - more machining. Then you can final hone the bushing ID to fit the pins. Probably cheaper to buy new rods.
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1964 Catalina 2+2 4sp, 421 Tri-power 1965 GTO, Roadster Shop chassis, 461, Old Faithful cam, KRE heads 305 CFM, Holley EFI, DIS ignition. 1969 GTO 467, Edelbrock 325 CFM, Terminator EFI 1969 Firebird Convertible |
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