Because i had scratches on my high dollar Crower crank, i opted to take the aluminum BMP block over to Chuck Lofgrens shop for a good cleaning in his power washing cabinet. It has a rotating table, multiple cleaning jets, and 150 degree heated water based cleaning solution. I am glad i did, as a couple hours of working with Chuck, and talking about race engine building can be very enlightening. Chuck runs adrag pack 392 gen 3 Hemi, and it makes 700 hp with stock rockers and lifters. We spotted cam bearings that had shifted, and were almost closed off to the oil galley on number two and three cam bearings. So a new set will be going in with locktite over at KTRE race engines in East Bethal Minnesota. Chuck also mentioned that at KTRE they found the main bearing clearance on the BMP blocks is opening up a lot when the block gets up to operating temp, enough that they are now setting main clearance at .0022 cold to compensate. I know a couple of guys that run the same BMP block that i have in thier bracket cars, and that is what they have found. So i plan to follow suit and have my crank ground accordingly. Even after having run my motor on the dyno twice, and three runs at the track, gray fine grade scotchbrite and WD40 plus paper towels brought a lot of black iron dust out of the cylinder bores. I was quite surprised at how much, and i need to go over the cylinder bores again at my shop till the paper towels come out white . I am glad I pulled that motor apart completely, as a spun cam bearing would have done serious damage.
Do you think this is because of the aluminum being a little off as far as material hardness (softer) from one run of blocks to the next or brand or the original bores being oversized to start with ? Just curious your thoughts. Doug
My KB block had roll pins in the oil passage pressed in just enough to catch the bottom edge of the cam bearing. I talked to Tim Banning about this and he told me they no longer use them. He said they loctite the bearings, I did both for insurance.
Do you think this is because of the aluminum being a little off as far as material hardness (softer) from one run of blocks to the next or brand or the original bores being oversized to start with ? Just curious your thoughts. Doug
I don't have enough experiance to make that call. My guess is it is just the right thing to do to loctite those cam bearinga in. Also there have been some issues with water weeping into the motor, and some form of cerramic sealer was run through the block and that stopped it. I will ask Chuck again about that ceramic sealer so i can do that as well as a little sealer around the water passages on headgaskets.
I ran a BM aluminum block for many years, and at least on mine you would start the run with 80 to 90 psi oil pressure and up the return road after the run it would hold 30 psi, from the block getting hot and bearing clearances getting loose I always assumed, and my main clearances usually came in at .0025 most of the time. Never had issues with cam bearings getting loose, but I was usually pretty picky about leaving the starting line at 150 degree water temp or a little less. It looked like the sleeves move around on an aluminum block as well. I used to leak test my engine regularly as part of maintenace, and the cylinders would get worse and then better sometimes, I never worried about it until they dropped below 20% leak.
Re: Loose cam bearings and other fun stuff!
[Re: gregsdart]
#3199442 12/22/2303:56 PM12/22/2303:56 PM
Because i had scratches on my high dollar Crower crank, i opted to take the aluminum BMP block over to Chuck Lofgrens shop for a good cleaning in his power washing cabinet. It has a rotating table, multiple cleaning jets, and 150 degree heated water based cleaning solution. I am glad i did, as a couple hours of working with Chuck, and talking about race engine building can be very enlightening. Chuck runs adrag pack 392 gen 3 Hemi, and it makes 700 hp with stock rockers and lifters. We spotted cam bearings that had shifted, and were almost closed off to the oil galley on number two and three cam bearings. So a new set will be going in with locktite over at KTRE race engines in East Bethal Minnesota. Chuck also mentioned that at KTRE they found the main bearing clearance on the BMP blocks is opening up a lot when the block gets up to operating temp, enough that they are now setting main clearance at .0022 cold to compensate. I know a couple of guys that run the same BMP block that i have in thier bracket cars, and that is what they have found. So i plan to follow suit and have my crank ground accordingly. Even after having run my motor on the dyno twice, and three runs at the track, gray fine grade scotchbrite and WD40 plus paper towels brought a lot of black iron dust out of the cylinder bores. I was quite surprised at how much, and i need to go over the cylinder bores again at my shop till the paper towels come out white . I am glad I pulled that motor apart completely, as a spun cam bearing would have done serious damage.
I use this from Total Seal, if it does not turn green on the cylinder it means its not clean
1968 Charger COLD A/C Hilborn EFI 512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim 2020 T/A 392 Stock 11.79 @ 114.5
Re: Loose cam bearings and other fun stuff!
[Re: CSK]
#3199448 12/22/2304:22 PM12/22/2304:22 PM
Yep, cam bearings usually need to be pinned in an aluminum block. Aluminum blocks are so much more work than cast iron blocks. Lots of little tricks like this required to keep stuff in place as the block grows.
Re: Loose cam bearings and other fun stuff!
[Re: AndyF]
#3199484 12/22/2307:19 PM12/22/2307:19 PM
Yep, cam bearings usually need to be pinned in an aluminum block. Aluminum blocks are so much more work than cast iron blocks. Lots of little tricks like this required to keep stuff in place as the block grows.
Andy, anything you care to share on prepping an aluminum block would be great!
I stay away from aluminum blocks but the guy I work with does a few every year. I know he pays a lot of attention to main bearing clearances and he pins the cam bearings. He also usually puts the block in an oven so he can verify that the sleeves have properly dropped into position. And then there is some sort of trick on surfacing the blocks to make sure the head gaskets seal on both the steel sleeves as well as the water passages. Lots of little details to watch out for and every block mfg does different things so you have to really pay attention between Indy, Dart, Brodix, etc. They all have their own little quirks. For example, some aluminum blocks require special head studs.
Re: Loose cam bearings and other fun stuff!
[Re: AndyF]
#3199547 12/23/2301:49 AM12/23/2301:49 AM
I stay away from aluminum blocks but the guy I work with does a few every year. I know he pays a lot of attention to main bearing clearances and he pins the cam bearings. He also usually puts the block in an oven so he can verify that the sleeves have properly dropped into position. And then there is some sort of trick on surfacing the blocks to make sure the head gaskets seal on both the steel sleeves as well as the water passages. Lots of little details to watch out for and every block mfg does different things so you have to really pay attention between Indy, Dart, Brodix, etc. They all have their own little quirks. For example, some aluminum blocks require special head studs.
Thanks Andy. At this point i will be running tighter main bearing clearances, and the motor will get some sort of ceramic seal treatment, along with a touch of silicone sealer around all water passages on the head gaskets. I assume my situation with the sleeves and deck surface is fine, since i had no leakage anywhere. The cam bearings will get a minimum of loctite, and maybe pinned? I found ACL makes .020 under size mains for 74 and up 440, so the crank will have to probably be cut to -.020 to get down under .0025 clearance cold, and I believe Chuck wanted .0022 as a room temp clearance. Anyone think i have missed anything?
Are these expansion issues with main/rod bearings older bmp or ALL of them? I just received mine and haven’t started any work on it yet.
The word i got was the newer blocks, being aluminum, have the same growth issues as the others, so i would check with who ever sold you the block, or whoever has been building them. I got mine from Todd at Marsh Performance.
ALL Aluminum blocks grow period. This affects rods,mains cam bearings, pistons and rods. Most error on the safe side for things like piston to head etc. The also loose heat very very quickly. Building cylinder pressure is another issue because they loose heat so fast. Most would be very surprised the compression ratios run in really good running stuff with an aluminum block. In general you need to ad compression if you are going from a steel to aluminum block.
We run a LOT of compression ratio in my stuff and the Vette. On the reverse side you can run a fair amount of compression in an aluminum block on pump gas. We have done a few in the 12.5 CR area and no issues.
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
Re: Loose cam bearings and other fun stuff!
[Re: Al_Alguire]
#3199631 12/23/2301:47 PM12/23/2301:47 PM
I know in some cases it has been an issue back in the day, My guess is millions if not billions in R&D. Same can be said for the performance of todays cars verse the cars of yesteryear.
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
Re: Loose cam bearings and other fun stuff!
[Re: hemienvy]
#3199669 12/23/2304:32 PM12/23/2304:32 PM
How is all of this not an issue with OEMs, or is it ?
Been a huge issue with OEMs starting 60 years ago with the Buick V8. The OEM guys do all sorts of weird stuff such as spraying iron on the cylinder walls rather than using sleeves.
