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questions on 4.1 production block casting 291 buildup

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jbturbov6

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Joined
Jul 14, 2004
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has anyone out there in the buick world buildup a 4.1 production block casting 291 or 484 ? is it possible to stroke one? what are the pro and cons of a peformance build of a 4.1 production block 291? I saw on RJC website he makes a deep oil pan and a girdle for the 4.1 production block and I know most of the 3.8 turbo stuff works with 4.1, so someone out there got to be building a peformance 4.1 production block. where can I get the peformance parts I would need to do this build? like what kind of pistons,cam,crank,rods,head gaskets, etc. please help,thanks
 
I believe one of the reason the production 4.1 block is not used in turbo application is due to poor lifter valley casting. if your going to build a 4.1 you might has well step up to the STAGE block. the 4.1 production block (PB) has many opening/holes around the lifter area. I know the 231 cu-in will make the same power has the 4.1 production block, but the 4.1 PB will fail in the lifter valley area due to poor support/casting.
 
plus

The deck is .125 thinner than a 109 3.8
I had 2 4.1 crack in the cyl bore --both inline with a stud.
This was a few years ago and I don't have a clue as to what casting # they were.
 
I have been running a 484 casting for years with a 4.030 bore. I have the bottom girdled and been 128 in the quarter. Me and Tom J on the board are going to start to put some power through ours. I am sure we will be posting what happens.
 
Yes

boostingbuick said:
I have been running a 484 casting for years with a 4.030 bore. I have the bottom girdled and been 128 in the quarter. Me and Tom J on the board are going to start to put some power through ours. I am sure we will be posting what happens.
Click to expand...


This is good to hear---I always kept my boost @ 22 and under.
Keep us informed. Best of luck.
 
Its not the lifter valley its the decks that seam to be the problem with the 4.1's. The valley is the same as the older hot air blocks and yes it is weaker but I don't think I've head of a person fragging one in the valley, its mostly cracking from the coolant passage to a headbolt in the deck or the deck flexing and pushing a gasket.
 
Im working on putting a #4291 4.1 block together -i guess it will be a 274 cu in. - Cat stroker crank, Carillo 6.5 rods, Ross 4.00" stage2 pistons, 3 front billet caps ,either champ irons or gn-1s, 224/224 billet roller cam, bgc intake, 70mm tb,t-70 turbo,3500 stall pats converter in a 84gn with 9" ford rear. Still Debating on a girdle or not- Dan Strezo said it should be ok to about 800hp. Arp bolts throughout including head studs.
 
My pistons are custom made by Diamond, head gaskets are parts store Fel-Pro 1000's. Everything else is 3.8 performance parts.
 
I ve been saving parts for this block for awhile now-the block from cleveland ohio , the crank and billet caps from full throttle, the pistons from billy anderson, the carrillo rods from mike booher -blownv6- on this board, the cam from billy t , heads from cal hartline , intake from bgc. im also in the process of building a stage2 motor and might consider parting out the 4291 block. the block,caps,oil pan,crank,rods,and pistons i have $2000. into them-i would sell them for that if it would help you out. the block is std and uncut,crank is new,rods reconditioned,pistons like new,oil pan like new,the program caps are new.
 
Call me ignorant for not knowing this or lazy for not doing a search, but can all those internals be used in a stage2 offcenter, crank, rods, pistons, cam. I might be interested
 
I dont see why not-the deck heights are the same. I think the only thing you would be limited to would be the bore size on the production block. im going 4.00" with mine.
 
So if I have been running 6+ years with two 4.1 484 casting with cracks from the coolant passage to the head bolt area this would be bad? I was going to have the second one welded before I put it together but figured if the first one gave me no issues then why spend the money on something that would not hurt? The only problems I have had running a 4.1 so far is detonation. It has no coolant leaks. So if anyone has any 4.1 blocks that have these cracks and are afraid to run them feel free to send them to me.
 
boostingbuick said:
So if I have been running 6+ years with two 4.1 484 casting with cracks from the coolant passage to the head bolt area this would be bad? I was going to have the second one welded before I put it together but figured if the first one gave me no issues then why spend the money on something that would not hurt? The only problems I have had running a 4.1 so far is detonation. It has no coolant leaks. So if anyone has any 4.1 blocks that have these cracks and are afraid to run them feel free to send them to me.
Click to expand...

Why is detonation a problem?
Prolly nothing to do with the block.
 
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