406 SBC cracked block repairs
Thread Starter
Cruising
Joined: Dec 2001
Posts: 10
Likes: 0
From: Naperville IL
406 SBC cracked block repairs
I am a new member to the forum and this is my first post. I am tryng to save a small block 400 with 4-bolt mains that has a crack between the steam hole and the adjacent head bolt hole, 6 locations. These were picked up in a mag particle inspection. Machinest says he can repair by drilling out the bolt hole and the steam hole and replacing them with an insert that looks like a "tee" shaped helicoil. The block is drilled, tapped for the threads of the insert and counterbored for the top portion of the "tee" to fit into. The insert will provide a clamping force on the block and at the same time provide a new bolt hole. The steam hole is eliminated. Questions for the forum, do any of you have experience with this form of crack repair and has it been satisfactory? What are the ramifications of eliminating the steam holes?
Instructor
Joined: May 2001
Posts: 225
Likes: 0
From: NY
Re: 406 SBC cracked block repairs (crankarm7098)
This kind of repair would only be safe for a low performance application. You must wonder why it cracked, was it in your car when it cracked and what kind of power do you want to make? High compression, blower, nitrous?
The 4bolt 400 block can be found for $250 ready for the machine shop. I would scrap it. If you want to make plenty of power get a 2bolt and add splayed caps. It all depends on what you expect from the engine.
Good luck!
Roger
:chevy
The 4bolt 400 block can be found for $250 ready for the machine shop. I would scrap it. If you want to make plenty of power get a 2bolt and add splayed caps. It all depends on what you expect from the engine.
Good luck!
Roger
:chevy
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: 406 SBC cracked block repairs (Corvette_Z51)
Interesting question.
I'd do the math.
Figure the cost of a 2 bolt block and all the necessary machine work, plus the cost of adding Milodon or Oliver four bolt main caps to the center three positions and factor in the added durbility/peace of mind that the setup wlll give you. Compare that total cost with the repair costs and concerns you'd have with a repaired block.
Personally I'd opt for the two bolt modification way because the 2 bolt block has more meat in it than a 4 bolt version.
Just my thoughts.
Jake
I'd do the math.
Figure the cost of a 2 bolt block and all the necessary machine work, plus the cost of adding Milodon or Oliver four bolt main caps to the center three positions and factor in the added durbility/peace of mind that the setup wlll give you. Compare that total cost with the repair costs and concerns you'd have with a repaired block.
Personally I'd opt for the two bolt modification way because the 2 bolt block has more meat in it than a 4 bolt version.
Just my thoughts.
Jake
Race Director
Joined: Mar 1999
Posts: 10,258
Likes: 1
From: Calif.
Re: 406 SBC cracked block repairs (crankarm7098)
Sorry to hear about your block. The 400s are getting harder to find. If it were me I beleive I'd write off the 4-bolt 400 and go looking for a virgin 2-bolt of the '509 or '511 variety. Then I'd have it checked for cracking and machined for splayed 4-bolt main caps and align bored. Good luck to you.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: 406 SBC cracked block repairs (crankarm7098)
As stated above, the 2 bolt block is inherently stronger than the 4 bolt block. Whether a guy would "4 bolt" his 2 bolt block, would depend on it's intended usage. I bought stock 4 bolt caps to install on my 2 bolt block, but I doubt I will spend the money to have them installed, because I don't think I'll need them for what I'm doing.
"The word" is that steam holes aren't necessary for operation above 3500 rpms. I have had a set of non-steam hole heads on the 400 in my pickup for quite a few years. I haven't experienced any over heating problems. Maybe, I just got lucky. If so, that would be once in a row.
"The word" is that steam holes aren't necessary for operation above 3500 rpms. I have had a set of non-steam hole heads on the 400 in my pickup for quite a few years. I haven't experienced any over heating problems. Maybe, I just got lucky. If so, that would be once in a row.
Drifting
Joined: Jul 2001
Posts: 1,418
Likes: 1
Re: 406 SBC cracked block repairs (crankarm7098)
Quote by Jake:
"Personally I'd opt for the two bolt modification way because the 2 bolt block has more meat in it than a 4 bolt version."
Yep.A few years ago althought this was a big block some boat racers I know were busting the main webs in there 4 bolt Blown Alcohol application.They switched to a studded 2bolt block and all was fine from there on.
I believe the same would hold true to a factory casted small block.A studded two bolt should be good to 550 hp I would think.Step up from there with aftermarket blocks ect.
"Personally I'd opt for the two bolt modification way because the 2 bolt block has more meat in it than a 4 bolt version."
Yep.A few years ago althought this was a big block some boat racers I know were busting the main webs in there 4 bolt Blown Alcohol application.They switched to a studded 2bolt block and all was fine from there on.
I believe the same would hold true to a factory casted small block.A studded two bolt should be good to 550 hp I would think.Step up from there with aftermarket blocks ect.
Melting Slicks
Joined: Apr 2000
Posts: 2,793
Likes: 46
From: Elizabeth City, NC
Re: 406 SBC cracked block repairs (mountainmotor)
The 2 bolt blocks were supposed to have a higher nickel content than the 4 bolt blocks as well. So thats another plus for the 2 bolt.
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Thread Starter
Cruising
Joined: Dec 2001
Posts: 10
Likes: 0
From: Naperville IL
Re: 406 SBC cracked block repairs (LPDesRoche)
Thanks for all your quick responses. The motor was one of those rare impulsive buys at a swap meet. History is unknown. When I disassembled the motor, it had 350 style head gaskets and no steam holes in the gaskets. That may have contributed to the cracks. Goal is to have a street motor in the 375 hp range. No blower, nitrous etc. One member talked about the "511" two-bolt. Is "511" the last digits of the casting number near the bell housing mounting surface at the left rear of the block? If that is the number, this 4-bolt block has "511" as the last 3 digits. Another question on the steam holes. If the block and heads are full of water where does the steam originate and then where does it escape to?
Race Director
Joined: Mar 1999
Posts: 10,258
Likes: 1
From: Calif.
Re: 406 SBC cracked block repairs (crankarm7098)
Yup. '511 and '509 are the last three digits of the casting number. Usually the '509s and '511s are high nickel/tin alloy blocks. If you look at the front of the block under the timing cover near the camshaft you have a pretty good chance of seeing some numbers embossed there that will indicate the higher alloy content. Usually these numbers will look like a fraction with a "10" or an "010" embossed over a "20" or a "020."
What does this mean? Probably not a whole heck of a lot to the block's eventual performance in a car when it's assembled. But it's interesting to learn about this stuff and to be able to rattle it off when somebody asks about your new engine.
:cool:
What does this mean? Probably not a whole heck of a lot to the block's eventual performance in a car when it's assembled. But it's interesting to learn about this stuff and to be able to rattle it off when somebody asks about your new engine.
:cool:
Burning Brakes
Joined: Oct 2001
Posts: 1,033
Likes: 0
From: Tracy California
St. Jude Donor '05
Re: 406 SBC cracked block repairs (The Dude)
For what it's worth, My 400 SB had the same exact cracks and I ran that motor all this year in the 1/4 without any issues. I did have to use a package of stop leak at first just to stop them from seeping cooalnt.
My motor had crack's in at least two places. I worried about them for a little while, then found that they were not an issue. If you find a 400 that ain't cracked, then I assure you it will. You wont know it's cracked untill it's rebuilt.
Just my 2cent!
KM
My motor had crack's in at least two places. I worried about them for a little while, then found that they were not an issue. If you find a 400 that ain't cracked, then I assure you it will. You wont know it's cracked untill it's rebuilt.
Just my 2cent!
KM
Burning Brakes
Joined: Oct 2001
Posts: 1,033
Likes: 0
From: Tracy California
St. Jude Donor '05
Re: 406 SBC cracked block repairs (crankarm7098)
I had my valve covers off to adjust lash one day way back and I noticed the studs were seeping. I had known the cracks were there since the begining. My builder doesn't beleive they are grounds for scraping the block. He susgested the stop leak mostly because I used ARP studs wich leak anyhow. A bolt with water sealant would have worked just fine also.
KM
KM
Thread Starter
Cruising
Joined: Dec 2001
Posts: 10
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From: Naperville IL
Re: 406 SBC cracked block repairs (88-406)
KM
Are the nuts securing the head to the block holding their torque value on the studs at the holes with cracks? What has been your experience with your 400 running at a higher operating temperature than other SBC's you have owned? Most of the articles I've read on the 400 have mentioned their propensity to run hotter than other engines. Have you found this to be a problem and if so, how have you managed it?
Are the nuts securing the head to the block holding their torque value on the studs at the holes with cracks? What has been your experience with your 400 running at a higher operating temperature than other SBC's you have owned? Most of the articles I've read on the 400 have mentioned their propensity to run hotter than other engines. Have you found this to be a problem and if so, how have you managed it?
Burning Brakes
Joined: Oct 2001
Posts: 1,033
Likes: 0
From: Tracy California
St. Jude Donor '05
Re: 406 SBC cracked block repairs (crankarm7098)
The torques are staying put as far as I know. My 400 had the deck coolant hole mod, along with aftermarket heads that held alot more water including the steamholes.
I ran a big oil cooler, 160 thermostat,stock radiator and pump. My temps stayed around 180 around town and 190-200 when at the track. A bigger radiator and a better pump would helped stabilize the temps alot, but it didn't get out of hand.
My chip richened it up a little at idle and that probaly helped as well.
KM
I ran a big oil cooler, 160 thermostat,stock radiator and pump. My temps stayed around 180 around town and 190-200 when at the track. A bigger radiator and a better pump would helped stabilize the temps alot, but it didn't get out of hand.
My chip richened it up a little at idle and that probaly helped as well.
KM
Thread Starter
Cruising
Joined: Dec 2001
Posts: 10
Likes: 0
From: Naperville IL
Re: 406 SBC cracked block repairs (88-406)
KM
Sound like it is working for you. I would be happy with those running temperatures. Would you elaborate on the coolant hole mod and what was done there.
Sound like it is working for you. I would be happy with those running temperatures. Would you elaborate on the coolant hole mod and what was done there.
Burning Brakes
Joined: Oct 2001
Posts: 1,033
Likes: 0
From: Tracy California
St. Jude Donor '05
Re: 406 SBC cracked block repairs (crankarm7098)
The large coolant holes in the top row of the deck of my 400 were plugged with 3/4 inch pipe plugs, then redrilled with a smaller 3/8 hole. The pump bypass on the front of the block was also pluged but not redrilled.
KM
KM
Le Mans Master
Joined: Feb 1999
Posts: 6,172
Likes: 11
From: somers, ny
Re: 406 SBC cracked block repairs (88-406)
i would toss it and find another block. The block is cheap, relative to the expense of a complete engine. Why take the risk or worry about it after it is together. i wouldn't do it.
Thread Starter
Cruising
Joined: Dec 2001
Posts: 10
Likes: 0
From: Naperville IL
Re: 406 SBC cracked block repairs (88-406)
KM
How does the coolant mod help?
Ralph's idea of finding another block is probably the smartest thing to do, but I like exploring repair options and if there is an economical means of salvaging what I already have spent cash on, I am willing to take some risk. A great benefit of this formum is gathering opinions and then making a reasonably informed decision. This is fun!
How does the coolant mod help?
Ralph's idea of finding another block is probably the smartest thing to do, but I like exploring repair options and if there is an economical means of salvaging what I already have spent cash on, I am willing to take some risk. A great benefit of this formum is gathering opinions and then making a reasonably informed decision. This is fun!
Burning Brakes
Joined: Oct 2001
Posts: 1,033
Likes: 0
From: Tracy California
St. Jude Donor '05
Re: 406 SBC cracked block repairs (crankarm7098)
I agree, there would be some peace of mind by comming up with a block that's not craked yet. I just merely shared with you what I did and what the outcome was. Good 400 blocks are getting hard to find and if I could've afforded one, I would have gone with an after market, or a Bowtie.
Modifying the deck should yeild increased deck strength and a more efficient coolant system. By slowing the coolant down near the siameased cyl's, the coolant is able to carry away more heat.
KM
Modifying the deck should yeild increased deck strength and a more efficient coolant system. By slowing the coolant down near the siameased cyl's, the coolant is able to carry away more heat.
KM