[John Milner]

I’m building a 428 and after cleaning the block up, I noticed the rear main cap had a crack in it. It appears as if the block was dropped at one time to me and landed on the rear cap. The crack does go all the way through the rear seal groove on one side it appears. The crack does not appear to go all the way through the rear seal groove on the other crack. What are everyone’s thoughts about using this rear main cap? I’m leaning towards having a new cap or a good used cap fitted to the block.

[Gach]

I wouldn’t use that cap, definitely not. If you can find a good use cape that be the way to go, but keep in mind if you do that block would then have to be line honed with the used cap.

[Gach]

Are you same John with Ram Air 2 Firebird?

[tom s]

Get a new billet cap,you will be WAY ahead!Tom

[Goatracer1]

Can't you only buy the 3 middle caps? Definitely don't use that one.

[Gach]

Tom, last I knew you can only get the 3 middle caps unless Do you know of a sauce you can buy rear main cap also

[tom s]

Butler sells all 5,ask me how I know!Tom

[wbnapier]

https://butlerperformance.com/i-2445...ef=brand:99980

https://butlerperformance.com/i-2445...ef=brand:99980

[Gach]

WOW ! Nice!

[John Milner]

Originally Posted by Gach

Are you same John with Ram Air 2 Firebird?

No I don’t have a RA2 Firebird

[John Milner]

Thanks for the replies. I’ll look into a new cap from Butler to save this block.

[25stevem]

If the cap passes a mag test in terms of its bearing journal area and if this will be a street motor of under 550 hp I would use that cap.

I would first bolt it on and check it’s bore to confirm that’s it’s not pinched and in need of a line hone, but once mag tested and the ends of both cracks got drilled out I would use it.

The cracks are not in a major needed strength area of the cap.

Those rear main caps even if there just the plain iron non 4 bolt Armasteel ones are very strong .

Just fill the drilled holes with gasket maker.

[hurryinhoosier62]

Originally Posted by John Milner

I’m building a 428 and after cleaning the block up, I noticed the rear main cap had a crack in it. It appears as if the block was dropped at one time to me and landed on the rear cap. The crack does go all the way through the rear seal groove on one side it appears. The crack does not appear to go all the way through the rear seal groove on the other crack. What are everyone’s thoughts about using this rear main cap? I’m leaning towards having a new cap or a good used cap fitted to the block.

John, there's not a chance I would use that cap whether it passes NDT or not. The ONLY effective way to stop cracking is to "stop drill" the cracks. From the photos, it looks like those cracks are in the rear seal area. It MIGHT hold together, then again it might NOT. It's always better to be safe than sorry. Aftermarket rear main caps are available. All you will need to do is find an engine machinist who can align bore the block (not one with one of the old Kwik-Way align bore machines. They take way too much material out of the saddle.).

[tom s]

The after market caps are made so you virtually dont touch the saddle im told.Tom

[Stuart]

Originally Posted by Gach

Are you same John with Ram Air 2 Firebird?

You may be thinking of Jim Mino, he unfortunately passed away in 2020.
https://forums.maxperformanceinc.com...d.php?t=843647

[Gach]

Yes your right name John Mino, oh my god sorry to hear that. Thank you. A quick story about John I have video I bought can’t remember name of it I’ll have to dig it out. It’s a muscle car match up, race he entered. Pitting muscle cars of the era, Chevelles Camaros Mopars, Fords Pontiac’s, John clean house, with his Ram Air 11 Firebird. Tape was from 1985 . Not sure which year. Can’t remember what ET he ran. Battle of the stockers or that era. I was just getting back into Racing.

[lust4speed]

Not sure why finding a close fitting stock #5 cap wouldn't be a good alternative? Might get lucky and have a cap close enough that a line hone would be all that would be necessary. Seems like the billet caps are a challenge for some shops to work with.

[Elarson]

Life is all about understanding risk and managing it.

If the cap is used as-is and lets go someday, it will definitely break the crank. If the aft end of the crank orbits around enough, it's possible that it might do some damage to the front of the transmission.

Eric

[mgarblik]

Originally Posted by lust4speed

Not sure why finding a close fitting stock #5 cap wouldn't be a good alternative? Might get lucky and have a cap close enough that a line hone would be all that would be necessary. Seems like the billet caps are a challenge for some shops to work with.

I would not use a rear cap with the crack you have pictured. You are building a fresh 428. Semi-rare engine. Even a mostly stock one is still an investment. To buy a single #5 cap and have it properly line bored and then the entire block line honed would be around $700.00-750.00 here in Ohio. It's the right way to fix what you have here. You need to find a shop that has a Rottler F65 or similar line bore machine that can bore a single cap. An old Sunnen Machine like I have can't do this. Fitting a used cap is an option, but not a good one IMO. You are dealing with 2 different diameters on the rear cap. The bearing housing bore and the rear seal bore diameter. Finding a great fit that won't leak oil is a real crap shoot. If you go that route, I would recommend using a best rope seal for a decent shot of not having a major leaker. With a stock crank with serrated surface you stand a chance I guess. Still rolling the dice IMO. Cutting corners rarely produces the desired results. Good luck with it.

[Dragncar]

Find a good 2 bolt 455 block and run it. The larger bore won't hurt either.