just another thought.
2 bolt versus 4 bolt main
Thread Starter
Melting Slicks
Joined: Feb 2007
Posts: 2,136
Likes: 62
From: West Kingston RI
2 bolt versus 4 bolt main
At what point should you think about switching to a 4 bolt main block. Am considering building 383 in the 425 to 450 horse range. If original block checks out ok would the 2 bolt block be ok, marginal or forget it for my goal? Am looking for street machine with maybe an occasional run at the strip.
Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
I wouldn't think of building a 383 with a 2-bolt block, particularly in a Corvette that'll make trips to the strip.
You're increasing the side loads on the caps due to the stroke as well as overall load due to the power increase. That's why the 400's have 2-bolt caps that are as wide as 4-bolt 350 caps - the load is spread out over a much larger area which makes it much, much more stable, similar to a big block.
I know, many, many of 'em have been built and run without issue. A lot of 'em have been built with disastrous results, too.
Find a 90's 4-bolt block. You'll have a 1-piece rear main seal and you can run factory hydraulic rollers and cams - this will save you enough to pay for the block!!! Make sure you find one with the fuel pump boss that has been drilled through for the fuel pump pushrod.
I'm sure BLOCKMAN will chime in here, and someone will jump on him for what they think is an attempt at a sale. Carl is doin' alright, he doesn't have to try to sell a machined block to everyone who asks this question. His advice is sound and based on experience with thousands of engines and blocks, not just what a few of his friends ran or what he's heard or seen on the internet.
Flame on!!!
You're increasing the side loads on the caps due to the stroke as well as overall load due to the power increase. That's why the 400's have 2-bolt caps that are as wide as 4-bolt 350 caps - the load is spread out over a much larger area which makes it much, much more stable, similar to a big block.
I know, many, many of 'em have been built and run without issue. A lot of 'em have been built with disastrous results, too.
Find a 90's 4-bolt block. You'll have a 1-piece rear main seal and you can run factory hydraulic rollers and cams - this will save you enough to pay for the block!!! Make sure you find one with the fuel pump boss that has been drilled through for the fuel pump pushrod.
I'm sure BLOCKMAN will chime in here, and someone will jump on him for what they think is an attempt at a sale. Carl is doin' alright, he doesn't have to try to sell a machined block to everyone who asks this question. His advice is sound and based on experience with thousands of engines and blocks, not just what a few of his friends ran or what he's heard or seen on the internet.
Flame on!!!
Burning Brakes
Joined: May 2009
Posts: 1,232
Likes: 6
From: Tucson AZ
St. Jude Donor '12
If you think about it, you're typical L48 making sub 200ft/lbs torque are two bolt, and truck motors making just 25-30% more torque are equipped with 4 bolt blocks.
Considering how little the cost difference is in buying a machined 4 bolt vs a 2 bolt...
For me what really justifies any added expense is having confidence that when I put my foot in it, the expensive parts will hold together. I'm ok if a ujoint snaps and messes up a shaft; I'd like the engine and trans to be the stronger links.
Considering how little the cost difference is in buying a machined 4 bolt vs a 2 bolt...
For me what really justifies any added expense is having confidence that when I put my foot in it, the expensive parts will hold together. I'm ok if a ujoint snaps and messes up a shaft; I'd like the engine and trans to be the stronger links.
Last edited by RobbSalzmann; Nov 29, 2011 at 08:11 AM.
Le Mans Master
Joined: Apr 2001
Posts: 5,941
Likes: 281
From: Was New Orleans but swam to Baton Rouge LA
Cruise-In IX Veteran
Due to wanting to go with the 383 I would recommend either getting the 2 bolt block machined and go with 4 bolt splayed caps or the 87 and newer block with the provisions for a roller setup. Both of those were mentioned earlier.
Now if you want to cheap out I would at least recommend getting arp studs for the 2 bolt block.
Now if you want to cheap out I would at least recommend getting arp studs for the 2 bolt block.
Thread Starter
Melting Slicks
Joined: Feb 2007
Posts: 2,136
Likes: 62
From: West Kingston RI
As of right now I have no money invested in this. That is why I am looking for advice. If 2 bolt was adequate I would get my original block checked out. If not I would look for 4 bolt. Don't want to waste money on the wrong thing when it could be better spent on the right. Thanks for the input thus far. All comments welcome.
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
Agree with Sigforty, if you are going to four bolt I'd use the two bolt have it set up as four bolt with billit steel splayed caps. End up with a stronger bottom end than a straight bolt four bolt.
There have been plenty of two bolt blocks from the factory not far from the HP rate your are looking for, in the 60s. They were built without the technology we have today, ie: great rods, cranks and pistons available today. You get better balancing now than was with in factory specs of then. Other than the thickness of the high dollar blocks, the billit steel splayed main caps are the big selling point. Probably the caps are more important than the thickness.
No science behind it, but the four straight bolt holes look like perforated paper holes. I have found cracks between the bolt holes on four bolt blocks now and then. I feel the splayed bolts resist lateral movement of the cap better that the vertical bolts do.
There have been plenty of two bolt blocks from the factory not far from the HP rate your are looking for, in the 60s. They were built without the technology we have today, ie: great rods, cranks and pistons available today. You get better balancing now than was with in factory specs of then. Other than the thickness of the high dollar blocks, the billit steel splayed main caps are the big selling point. Probably the caps are more important than the thickness.
No science behind it, but the four straight bolt holes look like perforated paper holes. I have found cracks between the bolt holes on four bolt blocks now and then. I feel the splayed bolts resist lateral movement of the cap better that the vertical bolts do.
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Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
450HP would be right at the bloody edge of what I'd use a 2-bolt for, even with studs. Add in the strip use and I'd say "no".
Machining a 2-bolt block for aftermarket caps is expensive, on the order of $450 or so including the caps, especially given the ready availability of late-model roller-cam 4-bolt blocks...which is all anyone should consider at this point for a GEN I build from scratch.
Machining a 2-bolt block for aftermarket caps is expensive, on the order of $450 or so including the caps, especially given the ready availability of late-model roller-cam 4-bolt blocks...which is all anyone should consider at this point for a GEN I build from scratch.
Melting Slicks
Joined: Jul 1999
Posts: 3,030
Likes: 17
From: White Pine / Dandridge TN
I've been toying with the idea of rebuilding my old 350 into a 383 for years and also contemplated 2 bolt vs 4 bolt. To that end, the most recent Summit catalog has a reconditioned 4 bolt block from between 96-2000 prepped for building a 383. It has a one piece rear main seal, compatible for factory roller or hydraulic cam and accepts mechanical fuel pump. Price is $651 plus shipping. Part # SUM-150100. I think when the times comes I'm going this route.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
The Summit blocks are shipped finish-honed - so although they look like a good deal IMHO they're not. The final bore/hone really can't be done correctly without the shop having the pistons and rings in-hand.
The other interesting aspect of getting a shortblock locally is that you also get all the roller cam hardware - spider, retainer, lifters (hydraulic roller lifters can usually be reused). GMPP and CompCams make good kits for this hardware for around $150 or so...but getting it for "free" in a shortblock is nice
The other interesting aspect of getting a shortblock locally is that you also get all the roller cam hardware - spider, retainer, lifters (hydraulic roller lifters can usually be reused). GMPP and CompCams make good kits for this hardware for around $150 or so...but getting it for "free" in a shortblock is nice
Last edited by billla; Nov 29, 2011 at 06:17 PM.
Le Mans Master
Joined: Dec 2005
Posts: 6,999
Likes: 1,685
From: Southeast TX
If you do go two bolt....and it grenades....it won't just take out the block. You have a very real chance of losing a nice crank, pistons, and rods. Maybe not all of it, but the chance is there. I've even seen one damage heads and cam in the process if the failure happens at high rpm. I think you're wise starting with a 4 bolt block.
Thread Starter
Melting Slicks
Joined: Feb 2007
Posts: 2,136
Likes: 62
From: West Kingston RI
If you do go two bolt....and it grenades....it won't just take out the block. You have a very real chance of losing a nice crank, pistons, and rods. Maybe not all of it, but the chance is there. I've even seen one damage heads and cam in the process if the failure happens at high rpm. I think you're wise starting with a 4 bolt block.
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
If you do go two bolt....and it grenades....it won't just take out the block. You have a very real chance of losing a nice crank, pistons, and rods. Maybe not all of it, but the chance is there. I've even seen one damage heads and cam in the process if the failure happens at high rpm. I think you're wise starting with a 4 bolt block.
Maybe this needs to be put back into perspective since we're not talking about an all out race engine.
Drifting
Joined: Nov 2004
Posts: 1,628
Likes: 293
2020 C3 of the Year Finalist - Modified
2 bolt 383stroker L48 here. Aluminum heads and about 10.5 : 1 compressions. I've run the mess out of this engine. It's a street car with no issues yet. I built up what I already owned. If I had the option i'd go 4bolt just for the added peace of mind.
Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
With today's CNC piston finishing, there's no reason the block can't be honed to final dimension without pistons or rings. Piston manufacturers are able to hit the dimensions spot-on every time.
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
Only time I have to have the pistons is when used or older pistons are being used. It's been a long time since I've seen a set of pistons that weren't the same size. Sometimes I add 5/10s depending on the intended use.
The lateral control and steel benefits are the reason for the splayed caps. They can be picked up used for a fair amount. Since a large number of people seem to align hone or bore any way. the cost is worth it. In my opinion.
The lateral control and steel benefits are the reason for the splayed caps. They can be picked up used for a fair amount. Since a large number of people seem to align hone or bore any way. the cost is worth it. In my opinion.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
I agree that piston tolerances these days are tight, and typically piston-to-bore clearance is designed into the piston - but the same bore for a cast, hypereutectic and forged piston? Setting piston-to-bore clearance aside, each type of ring requires a specific Ra in the bore - and that also isn't going to happen with an "off the shelf" final hone. Maybe Summit publishes the specs and a ring pack can be selected to match - but I didn't see it online.
In the end, I wouldn't do it - but everyone has to make their own decisions based on what's presented