Experience with 400 SBC

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Experience with 400 SBC Empty Experience with 400 SBC

Post by Iggy on Fri Sep 13, 2019 10:37 am

For a while I thought I may have to sell the Laguna to save some family property, so far I have been able to work around that and keep the Laguna. I was planning on building a 383 for the car, already have a block that is bored but needs the rest of the work - clearancing for additional stroke, honing and deburring. Then I stumbled across a very good looking early 400 block with almost no ridge and still standard bore - it is at the machine shop for cleaning and crack checking.

I have had a lot of experience with slightly over stock builds of 400 small blocks in square body trucks and have not had any issues with over heating. Because these builds were for low end torque I kept the compression around 8.5:1 and they never saw anything above 4500 RPM. I know that the 400 SBC has an unearned reputation for overheating - my experience with that was others using head gaskets that did not have steam holes.

I like the idea of putting a 400 SBC in my 1975 Laguna, I would step up to a 6" rod and flattop pistons along with most likely AFR aluminum heads and keep the compression in the low 10:1 range. this would not be a hard core performance build - I would use a big block if I wanted to go that route. I would like to know what others experience is with a 400 small block in this chassis and any mods you would recommend. Thank you.
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Post by bracketchev1221 on Fri Sep 13, 2019 7:36 pm

There is nothing wrong with mild 400” engines. I haven’t really seen a difference in 5.7 vs 6” rods in a street motor. If it was me, I would go .030 over and keep stock stroke. If your budget can support it, I would go for a scat 9000 crank. 400’s only had cast cranks anyway, but by the time and cost of refurbishing a stock crank the scat isn’t much more for new. If you can swing it, the 6” rod will allow you to go internally balanced. I do like the 2 bolts over the 4 bolts in performance builds but if you already have a 4 bolt gonfor it. For 2 bolt blocks I like to put main studs. I could go on and on, let me know what you want to know.
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Post by bracketchev1221 on Fri Sep 13, 2019 7:57 pm

I would also use an oil pan designed for longer strokes with a scraper and windage tray. Doesn’t have to be anything special, summit I think has a package pan.
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Post by jerry46765 on Sat Sep 14, 2019 12:05 pm

Hello -

I think the siamese bore 400 got a bad rap for overheating, that wasn't warranted.

I never tempted fate by always using head gaskets with steam holes and drilling steam holes in non-400 heads.

The cast crank and production short rods don't like much over 5599 rpm.

The two freeze plug blocks were always two bolt mains from mid to late 70s.

In the last 10 years, a decent 400 block is tough to find.

It's an externally balanced engine so needs unique balancer and flywheel unless you internally balance.

The rest is super bulletproof small block Chevy.

With some clearance work, a 4.00 inch stroke crank will go to 434 cubes. Try that with a 350.

Thanks -
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Post by Iggy on Sat Sep 14, 2019 10:27 pm

It is a 2-bolt block and I have the studs already - once it checks out I will have it align honed and parallel decked. A new crank is defiantly in order because I already have 6" rods and would go internally balanced. I know I am jumping ahead, the block has not even been checked out yet! I have always looked at the 400 small block as a very good truck engine and have limited experience as a performance engine. I know a few dirt track racers that quit using the 400 because they put too many rods through the side - revved too high so they went back to 350. In my case I would see 6000 RPM with a max of 6500, just want to make sure it is a reliable build that will put a smile on my face!
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Post by Iggy on Tue Oct 01, 2019 12:53 pm

Well, it looks like I will go back to my original plan of a 383 - the 400 block has a crack in the lifter valley that is not repairable!  Too bad as that was a 509 block with extra tin and nickel.

I might consider the 427 BBC I have laying around with 9.5:1 open chamber pistons, was trying to keep the weight off already front heavy Laguna so was looking at small blocks. I have a ZZ502 roller cam I could stick in it!
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Post by thatfnthing on Tue Oct 01, 2019 1:06 pm

Sorry to hear it, sounded like an interesting idea. Still, speaking from experience, the 383 won't suck. Smile
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Post by Iggy on Tue Oct 01, 2019 1:19 pm

Since I already have the block, a 350 block from a 1970 K20, I will most likely go the 383 route. The block is a 4-bolt main with extra tin and nickel - overkill! Cranks are not expensive at all and I already have 6" rods laying around so getting an internally balanced cast steel crank in a no brainer!
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Post by 73ss on Tue Oct 01, 2019 5:00 pm

Iggy wrote:Well, it looks like I will go back to my original plan of a 383 - the 400 block has a crack in the lifter valley that is not repairable!  Too bad as that was a 509 block with extra tin and nickel.

I might consider the 427 BBC I have laying around with 9.5:1 open chamber pistons, was trying to keep the weight off already front heavy Laguna so was looking at small blocks.  I have a ZZ502 roller cam I could stick in it!

Have you used the 502 cam? idle quality?
That should be a gen 6 cam, I think it is a little different set-up than a retro roller for a gen 4 block.
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Post by bracketchev1221 on Tue Oct 01, 2019 7:03 pm

Oh well. There’s nothing wrong with a 383. Just use the same approach with the longer stroke. Oil control and windage is important.
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Post by Iggy on Wed Oct 02, 2019 9:30 am

73ss wrote:
Have you used the 502 cam? idle quality?
That should be a gen 6 cam, I think it is a little different set-up than a retro roller for a gen 4 block.

The Gen VI roller cams will fit in the Mark IV or Gen V blocks using a stock type retainer plate, have to use a Gen VI timing set - blocks are already drilled and tapped, you have to use retro-fit roller lifters as the Gen VI lifters will not work.
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Post by Iggy on Wed Oct 02, 2019 9:35 am

bracketchev1221 wrote:Oh well.  There’s nothing wrong with a 383.  Just use the same approach with the longer stroke.  Oil control and windage is important.  

I have been looking at a Mildon 5 quart pan (plus filter) with baffling and windage already in the pan for a 3.75" stroke
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Post by bracketchev1221 on Wed Oct 02, 2019 10:52 am

This is for the later blocks, but something like this may work.

https://www.jegs.com/i/JEGS/555/50222/10002/-1
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Post by Iggy on Wed Oct 02, 2019 12:02 pm

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