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4 bolt 6 bolt BB valve cover question
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Apollo 61
Posted 2019-08-03 12:26 PM (#585574)
Subject: 4 bolt 6 bolt BB valve cover question



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What year did they stop making 4 bolt big block valve covers and start making 6 bolt covers? Recently I've seen 6 bolts in 62s and 4 bolts in 63s?
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57chizler
Posted 2019-08-03 1:42 PM (#585577 - in reply to #585574)
Subject: RE: 4 bolt 6 bolt BB valve cover question



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The change was made midyear in the 1963 model year, 12-04-62 or thereabouts. If you saw 6-bolts on a '62 it wasn't original.
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Apollo 61
Posted 2019-08-03 2:31 PM (#585581 - in reply to #585577)
Subject: RE: 4 bolt 6 bolt BB valve cover question



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Thanks, I take it that this was done to prevent oil leaks. Is there problem using 4 bolt covers/heads with oil leaks or was just a precaution from Chrysler?
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1960fury
Posted 2019-08-03 4:36 PM (#585587 - in reply to #585581)
Subject: RE: 4 bolt 6 bolt BB valve cover question



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Apollo 61 - 2019-08-03 2:31 PM

Thanks, I take it that this was done to prevent oil leaks. Is there problem using 4 bolt covers/heads with oil leaks or was just a precaution from Chrysler?


Yes, there was a problem, that doesn't mean they all leaked, it just need some extra carefull assembly. 2 problems (not so much the number of bolts) the sealing edge isn't machined, it is a cast surface. The other: They made a major desing fault, when you shut of the engine, the oil level of the oil "sump" in the head is always a bit higher than the outer (lower) cylinder head ridge. They could have easily prevented any leaks just by rising the ridge a 3/8th of an inch or so.

Edited by 1960fury 2019-08-03 4:37 PM
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Powerflite
Posted 2022-06-15 4:10 PM (#622159 - in reply to #585581)
Subject: Re: 4 bolt 6 bolt BB valve cover question



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I wanted to see what modifications would be required if I put 4 bolt covers on a 6 bolt head. I'm curious because I imagine using aluminum heads on some of my vehicles, but I don't want to eliminate or modify my original '58 valve covers. The good news is that the extra bolts are at the same level as the rest of the sealing surface, so you could use a 4 bolt cover & gasket and it won't have any issues with sealing. It also looks like you could probably eliminate those extra bosses on the head. Can't tell for sure if there is a coolant passage nearby, but it looks to be possible, at least.



(4-6 Bolt Swap 1.jpg)



(4-6 Bolt Swap 2.jpg)



Attachments
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Attachments 4-6 Bolt Swap 1.jpg (61KB - 86 downloads)
Attachments 4-6 Bolt Swap 2.jpg (84KB - 86 downloads)
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1960fury
Posted 2022-06-15 8:51 PM (#622160 - in reply to #585574)
Subject: Re: 4 bolt 6 bolt BB valve cover question



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Even if I had a set of costly Brodix aluminum BB heads, I'd simply cut/grind these things away
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NicksGarage
Posted 2022-06-16 11:48 AM (#622165 - in reply to #585574)
Subject: Re: 4 bolt 6 bolt BB valve cover question



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My 300F has 6-bolt 1963 heads on it with the original 4-bolt valve covers. I don't have leakage problems but you have to realize that the extra bosses for the 6-bolt covers will hit the corners of the earlier ones. I use good quality Felpro cork/rubber gaskets and sealant on the valve cover side only. You don't want to over tighten the valve cover bolts or the corners will bend.

You could notch the corners of the 4-bolt covers to clear the bosses on the heads if it's causing a problem.

Eventually I'll install the correct 1960 heads on my engine.
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Powerflite
Posted 2022-06-16 12:41 PM (#622166 - in reply to #585574)
Subject: Re: 4 bolt 6 bolt BB valve cover question



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The idea is to modify the head, not the valve covers. Six bolt heads are common, '58 valve covers are not. If the gasket isn't quite thick enough to prevent the cover from hitting the surface, it looks like you could cut down that mounting surface, if you didn't want to remove it all-together.
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1960fury
Posted 2022-06-16 6:49 PM (#622178 - in reply to #622166)
Subject: Re: 4 bolt 6 bolt BB valve cover question



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Another solution, that will solve any leak issues forever, is to fabricate or have an aluminum spacer laser/water cut and permanently glue it to the head. That way the vc clears the 6 bolt ears (I'd cut them off) and the head has a perfect sealing surface. 1/16"-1/8" aluminum sheet would be thick enough I think.
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1960fury
Posted 2022-06-16 6:52 PM (#622179 - in reply to #585574)
Subject: Re: 4 bolt 6 bolt BB valve cover question



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Something like that, but not as thick and not as costly

https://www.ebay.com/itm/174917464785?hash=item28b9e4b2d1:g:jZsAAOSw...
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