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400 SBC build

General engine tech -- Drag Racing to Circle Track

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novafornow
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Re: 400 SBC build

Post by novafornow » Fri Jun 12, 2020 5:14 pm

Been there done that, lived to regret it. It may live and it may crack in 6 months. 383 is a better option, or a SHP block if you want the cubes.

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Re: 400 SBC build

Post by tcb3274 » Fri Jun 12, 2020 5:31 pm

The 4 bolt block measured at 4.143 with my digital calipers. The machinist used a analog calipers and said it was at .040. It seems to based on my calipers its closer to .020, but what do I know.

The 4 bolt does have some rust in the cylinders. It does need attention. I could post a pic of it.

I do have a 509 two bolt block....that he said is unusable because of what appears to be someone overtightening the oil pump stud. I have enclosed pics of it. It is a virgin bore block....he said this block is junk as well. This block measures with my calipers 4.140.
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Re: 400 SBC build

Post by tcb3274 » Fri Jun 12, 2020 5:36 pm

I do have a GM OEM roller block, but its "hencho in mexico." It is a zz4 short block with aftermarket cam and heads on it. It pushed my chevelle to 12.50's. I still have this engine in climate control. It only has like 40,000 miles on it at most, maybe more like 30,000. It has a steel crank. If I dont build a 400 cubic inch motor, I would more than likely stick with the GM steel crank and do a 355.

The 400 build would never see the strip.

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Re: 400 SBC build

Post by rfoll » Fri Jun 12, 2020 5:59 pm

tcb3274 wrote:
Fri Jun 12, 2020 12:36 pm
This is all great information.

I just got back from the machine shop and block is already .040 over....so the machinist says its junk.

Back to square one.

Looks like if I want to do this, a 400 SBC build...going to have to get a new aftermarket block.
Why is the block junk? If it has a usable .040 bore, it means the engine has already survived being run that way, and a re-hone will not likely make it fail. If the deck has not been surfaced it will need to be done. Cracking at the steam holes can make the threads weak, but if you use studs it can still be used. You mentioned street only use, making many of the aforementioned issues moot. You asked what it will take to make 475-500 hp, but if it is a street engine does it really matter? A 400+ inch sbc with decent heads and cam will spin the tires at will regardless the horsepower number. Speed pro has pistons with a 12 cc dish that will produce 10:1 compression with a 64 cc head.
So much to do, so little time...

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Re: 400 SBC build

Post by rfoll » Fri Jun 12, 2020 6:02 pm

tcb3274 wrote:
Fri Jun 12, 2020 5:31 pm
The 4 bolt block measured at 4.143 with my digital calipers. The machinist used a analog calipers and said it was at .040. It seems to based on my calipers its closer to .020, but what do I know.

The 4 bolt does have some rust in the cylinders. It does need attention. I could post a pic of it.

I do have a 509 two bolt block....that he said is unusable because of what appears to be someone overtightening the oil pump stud. I have enclosed pics of it. It is a virgin bore block....he said this block is junk as well. This block measures with my calipers 4.140.
The 2 bolt block is plenty strong enough for a street engine. The oil pump boss issue might be solved with a stud and loctite
So much to do, so little time...

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Re: 400 SBC build

Post by af2 » Fri Jun 12, 2020 6:41 pm

Find a new machinist. I ran my 400 block with studs and 2 bolt main with a 350 crank for 15 years shifting at 8500 rpm. If you are worried about the rear main cap use the good one off the 4 bolt and line bore the block. The 2 bolt block is much stronger than the 4 bolt in the webs.
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Re: 400 SBC build

Post by tcb3274 » Fri Jun 12, 2020 8:42 pm

Monza355 wrote:
Fri Jun 12, 2020 4:33 pm
If it’s useful at 4.165” bore I wouldn’t hesitate to use it as a mild street engine like you are planning. But that’s just something i would do…
It has rust in the cylinder walls...its right about that size now. Not sure how much it would need to clean up. The rust is just from sitting in the shop.

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Re: 400 SBC build

Post by tcb3274 » Fri Jun 12, 2020 8:45 pm

rfoll wrote:
Fri Jun 12, 2020 5:59 pm
tcb3274 wrote:
Fri Jun 12, 2020 12:36 pm
This is all great information.

I just got back from the machine shop and block is already .040 over....so the machinist says its junk.

Back to square one.

Looks like if I want to do this, a 400 SBC build...going to have to get a new aftermarket block.
Why is the block junk? If it has a usable .040 bore, it means the engine has already survived being run that way, and a re-hone will not likely make it fail. If the deck has not been surfaced it will need to be done. Cracking at the steam holes can make the threads weak, but if you use studs it can still be used. You mentioned street only use, making many of the aforementioned issues moot. You asked what it will take to make 475-500 hp, but if it is a street engine does it really matter? A 400+ inch sbc with decent heads and cam will spin the tires at will regardless the horsepower number. Speed pro has pistons with a 12 cc dish that will produce 10:1 compression with a 64 cc head.
I believe its .020, but it has surface style rust on the cylinder walls.

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Re: 400 SBC build

Post by tcb3274 » Fri Jun 12, 2020 8:46 pm

af2 wrote:
Fri Jun 12, 2020 6:41 pm
Find a new machinist. I ran my 400 block with studs and 2 bolt main with a 350 crank for 15 years shifting at 8500 rpm. If you are worried about the rear main cap use the good one off the 4 bolt and line bore the block. The 2 bolt block is much stronger than the 4 bolt in the webs.
In switch the main caps...is that even possible??

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Re: 400 SBC build

Post by chevyfreak » Sat Jun 13, 2020 3:11 am

[quote=tcb3274 post_id=867040 time=1592009207 user_id=30431

In switch the main caps...is that even possible??
[/quote]

Yes. It can be done. Block wil have to be line bored as to line up all main caps.. it has been done many times by many builders.
On the block thats 040, how thick is the walls? Has it been sonic tested? Sometimes there is enough wall left to go bigger.

I had a large journal 327 that was at 060 with more than enough wall thickness.

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Re: 400 SBC build

Post by tcb3274 » Sat Jun 13, 2020 7:15 am

chevyfreak wrote:
Sat Jun 13, 2020 3:11 am
[quote=tcb3274 post_id=867040 time=1592009207 user_id=30431

In switch the main caps...is that even possible??
Yes. It can be done. Block wil have to be line bored as to line up all main caps.. it has been done many times by many builders.
On the block thats 040, how thick is the walls? Has it been sonic tested? Sometimes there is enough wall left to go bigger.

I had a large journal 327 that was at 060 with more than enough wall thickness.

Chevyfreak.
[/quote]

Dont know. The machinist wouldnt even sonic test it.....

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Re: 400 SBC build

Post by tcb3274 » Sat Jun 13, 2020 7:25 am

The machinist wouldnt sonic test it.

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Re: 400 SBC build

Post by chevyfreak » Sat Jun 13, 2020 8:31 am

tcb3274 wrote:
Sat Jun 13, 2020 7:15 am
chevyfreak wrote:
Sat Jun 13, 2020 3:11 am
[quote=tcb3274 post_id=867040 time=1592009207 user_id=30431

In switch the main caps...is that even possible??
Yes. It can be done. Block wil have to be line bored as to line up all main caps.. it has been done many times by many builders.
On the block thats 040, how thick is the walls? Has it been sonic tested? Sometimes there is enough wall left to go bigger.

I had a large journal 327 that was at 060 with more than enough wall thickness.

Chevyfreak.
Dont know. The machinist wouldnt even sonic test it.....
[/quote]

Maybe he doesnt have a sonic tester or he is not interested in working on this block.
Unless there is a visible crack he cant claim its junk just because its at 040 over.
A sonic test will confirm if going to 060 is safe or not.
If it were me i would take it to another shop and that can or will sonic test it and get beter clarification on block condition.

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Re: 400 SBC build

Post by DeezNutz » Sat Jun 13, 2020 8:57 am

tcb3274 wrote:
Sat Jun 13, 2020 7:25 am
The machinist wouldnt sonic test it.
Get a new machine shop. Dont waste any more time with that one.

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Re: 400 SBC build

Post by F-BIRD'88 » Sat Jun 13, 2020 4:54 pm

[-o< The rusty bores probabily look worst than they are.
I'd consider re honing the worst looking cyylinder (with a deck plate installed) to just clean it up. Then measure it.
The kb hyper 400 sbc pistons can run nicely over a wide piston to bore clearance without much trouble.
Worst is it may be slightly noisey at idle when cold.
A slightly loose fit doesn't seem to bother things
You may find cleaned up .040 bores are fine.
Do one cylinder... First...

Use a proper cylinder bore gauge to measure the cylinders
Not calipers.
Last edited by F-BIRD'88 on Sat Jun 13, 2020 5:06 pm, edited 1 time in total.

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