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Anyone know anything about recoating bearings??
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Have a BBC with front 2 x bearings spun. I can buy a set of 20 thou oversize bearings for it but they are only in 20 thou under on the journals, they don't make STD or 010 anymore.
Idea is to close the rear 3 x caps and tunnel bore them back to standard, then tunnel bore the front two bearings to fit the 20 thou oversize bearings.
Then fit the front 2 x bearing shells and tunnel bore them to standard size, hence the need to recoat them.
This way I can run the 427 crank which is standard on the mains, with the 2 x recoated front bearings, and use standard bearings of the same Clevite type for the back 3.
I can keep the other 2 x 020 bigger shells at 020 under journals for a future rebuild to use with 020 standard type bearings in the back three.
There is no point junking this block as all BBC's need align bore or hone, and this is a standard bore 4-bolt crate engine block, so no emissions applicable in a HK. |
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i think you are getting a bit confused there is no need to do anything to the rear bearings, all bearing shells are the same outside diameter so they fit the standard block, or con rod.
the difference in size is in the thickness of the alloy (copper/lead/tin/indium) innner surface of the bearing, so a standard bearing is 20thou thinner than a 20thou over bearing.
you would be ruining the block to be boring out the rear mains.
you may be able to get the front spun surfaces rebuilt with brazing rods and rebored, or rebuilt somehow, and you might be able to buy brand new bearing caps which would be standard and only need sizing to suit the block. even second hand ones would be better than what you propose.
you could try maximum oversize just for the front ones and standard for the rear, don't know what that would be but if say 60thou they could be rebored in situ to suit the 2 front bearing housings once cleaned up, as they would be a lot thicker and have some meat in them.
but i am not an engineer so take that for what its worth good luck
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Not confused John. BBC's are reknown for spinning bearings. They normally always need at least an align hone. Clevite and King had purpose made 20 thou oversize (in the tunnel size not journal size) bearings made so the block main bearing tunnel could be overbored if the block half of the bearing tunnel was damaged. BUT, I can only now buy these 20 thou oversize bearings in 20 thou undersize on the journal. My crank is standard on the mains journals. The thought was to only bore the front 2 x main bearing tunnels to 20 thou over and put bearings in, then align hone those 2 x bearings from 20 under back to STD journal size. The undamaged bearing tunnels could remain as is and use normal bearings. |
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Byron.
Is it normal practice to overbore only just 2 of the bearing tunnels ?
I believe in keeping things simple & keep them all the same size.
Is it too costly to go 0.020" oversize on the outer of all of the bearings & machine all of the journals 0.020" under, then use a full set of the 0.020/0.020 shells ? Surely the crank suffered some slight damage when the bearings spun.
Dr Terry |
If at first you don't succeed, just call it Version 1.0 |
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thats a bit clearer, I had not heard of this practice.
the only time i had any bearings 'recoated' was on my 38 Hudson Terraplane had white metal bearings and i had them recast, spent the next week sitting underneath it with a bearing scraper and a tube of prussian blue. could have got the guy who did the rematalling to do it but they was the days when i had to run a car, drink beer, attend work, go to parties and take out girls, on a very limited income so something had to go, so never smoked couldn't afford them and couldn't go forever on OPs, money was short!
just as well the hudson had plenty of room underneath to work.
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Terry, 020/020 bearings only come with the front four 020 over, rear main bearing is standard OD. So I either have to tunnel bore four or two journals. Reason I only wanted to do two was so I could keep the other two for a possible future rebuild, then the crank could go to 020 under and just buy a set of normal 020 under, use the back three from that set and my two that I hung onto on the front.
The crank I have isn't from this block. The engine was a crate 454 engine. Crank is a 427 forged crank, and will be used with a seal adapter.
Engine combo is:
454 4 bolt block, currently STD bore but pistons I want only come in 030 and 060.
427 forged steel crank with seal adapter.
1969 L88/ZL1 TRW forged pistons.
Aftermarket rods with new bolts (probably just Eagle, or whatever Summit have on special).
1974 LS7 990 cast heads (almost exact same specs as 1969 L88/ZL1 heads except cast rather than alloy).
1969 COPO 427 (L88 also) intake manifold.
LS6/L78 solid cam (not quite as big as a 1969 L88 or ZL1 cam, but close).
Either an 850DPP Holley legacy carb (same as 1969 L88) or an 850 vac sec Holley Legacy (same as 1968 L88 or Z28), or even a 455 Olds Quadrajet I have here.
Muncie and 9" but of that breaks i'll get a Moser 12 bolt 1969 Camaro diff and get HK saddles put on.
Engine will be about 11.5:1 or thereabouts. 1969 L88/ZL1 were about 12.5:1 but these 990 heads have slightly bigger chambers due to bigger valves (LS7 had bigger valves), so it work out about 11.5:1 which will be perfect as camshaft I have states greater than 11:1 required.
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What about metal spraying back to original specs? www.duncanfoster.com.au/...20Foster%20Services.html'Metal Spray reclaiming crankshaft seal area and main bearing tunnels'
quote:
Originally posted by HK1837
Have a BBC with front 2 x bearings spun. I can buy a set of 20 thou oversize bearings for it but they are only in 20 thou under on the journals, they don't make STD or 010 anymore.
Idea is to close the rear 3 x caps and tunnel bore them back to standard, then tunnel bore the front two bearings to fit the 20 thou oversize bearings.
Then fit the front 2 x bearing shells and tunnel bore them to standard size, hence the need to recoat them.
This way I can run the 427 crank which is standard on the mains, with the 2 x recoated front bearings, and use standard bearings of the same Clevite type for the back 3.
I can keep the other 2 x 020 bigger shells at 020 under journals for a future rebuild to use with 020 standard type bearings in the back three.
There is no point junking this block as all BBC's need align bore or hone, and this is a standard bore 4-bolt crate engine block, so no emissions applicable in a HK.
Edited by user Tuesday, 7 May 2013 6:48:03 AM(UTC)
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you would want some guarantee though - many years ago i had a crankshaft for my old Plymouth metal sprayed.
after a while the crank failed and it ended up looking like a corrugated iron sheet.
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HK1837.
Mate what was the outcome of this scenario. I have found myself in the same predicament with my mk4 454 block with the middle 3 main bearings spinning.
Cheers Baz.
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Hi HK1837. I'm with johnperth. If you are planning on reusing the crank that was in it, I'd get it magnafluxed before you spend anymore money on it. That kind of failure (spun bearing) often gets you a whole lot of cracks from local journal overheating.
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quote:
Originally posted by rcfreak177
HK1837.
Mate what was the outcome of this scenario. I have found myself in the same predicament with my mk4 454 block with the middle 3 main bearings spinning.
Cheers Baz.
Outcome is block is junk, have to find another block. They won't make these bearings anymore. |
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quote:
Originally posted by gm5735
Hi HK1837. I'm with johnperth. If you are planning on reusing the crank that was in it, I'd get it magnafluxed before you spend anymore money on it. That kind of failure (spun bearing) often gets you a whole lot of cracks from local journal overheating.
Crank that was in it has gone in the scrap bin. It was a 454 crank and I can only go to 427 in a HK GTS327. |
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Oh dear. Look on the bright side though - the purist in me can urge you to make it a real HK81837 again!
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No, waste of time and money. The original engine was pulled in 1976 when it was a speedway car as it didn't have enough grunt. It is long gone. So if I can't have the original driveline i'd rather spend the $ on a decent engine! |
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Chamfered crank journals may help prevent bearings grabbing / spinning, as the oil is delivered over a greater surface area on the bearing : Crank interface |
Old holdens brought on the spot, quick decision, cash paid. |
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Spewing good blocks are hard to find. Just a little secret you may already know, the 454 Mercruiser marine engine all come out as an 010 4 bolt main block. My block is not bad and my mate reckons he will be able to save it.
I have done a fair bit of research and as RigPig mentioned metal spraying it will fix the drama.
If all else fails I know where there is a short block in Perth, MK4 std bore 4 bolt. 1500 bucks though
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blue power are doing new bbc block various bore sizes up to 4.6 and 9.8 and 10.2 deck height as well as priority main oil feed, why bother spending big bucks on rubbish.
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Anyone know anything about recoating bearings??
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