Just picked up a STD bore sbc 400 have questions...
 

So I came accross what seemed like a deal I couldnt resist. a std bore 400 with an 817 block and what seems to be factory cast internals and dished pistons.
The dished pistons would not normally be ideal but I have these ported 190/195 64cc chinese heads that are on my 355 along with the rest of the top end of my 355 with the retro roller cam and such I want to swap over.

The guy I bought it from said his buddy owned a motorcyle shop and an employee there quite like 20 years ago leaving a lot of his stuff behind including these engine that was on a stand. When I feel for a ridge at the top on the cylinders none have anything but a little cabon buildup in spots but one cylinder, the #2 cylinder has a definite ridge I can catch my nail on but only on the outer front cylinder wall? I dont know much about this stuff as I bought my 355 block freshly bored. when I check the cylinders with my caliper it indicates 4.124-4.125 which is what I would expect for a standard bore.

I am wondering what the best way to check if I can get away with dingleball honing and re ringing the engine or if I need to have it bored out for new pistons. I havent gotten anything tore down yet as theres no room in my garage at the moment so I still need to check bearings and such.

I can see someone was in it before since they etched numbers on the rods even though the factory punched numbers were all still there. I assume it's likely someone hones and re ringed it before already.

https://cimg0.ibsrv.net/gimg/www.cor...b7e0bbbb21.jpg
https://cimg1.ibsrv.net/gimg/www.cor...6b6d803ec8.jpg
https://cimg8.ibsrv.net/gimg/www.cor...edc57c6651.jpg
https://cimg3.ibsrv.net/gimg/www.cor...81acd11a97.jpg
https://cimg6.ibsrv.net/gimg/www.cor...ae18d9f623.jpg
https://cimg9.ibsrv.net/gimg/www.cor...f861749489.jpg

It also has a double roller timing chain sprocket on the crank which tells me that has been changed also.. it looks like the guy I bought it from may have tore it all down very recently since I saw a pile of Parts sitting by one of his projects that may have come from this engine but I didn't ask. (Dhould have but got side tracked talking about his 61 impala and 70 chevelle)

Im likely going to have it checked and bored out but just weighing options here

so research is showing me that I may want to go with new pistons anyway since the deck height will likely be pretty high and the stock pistons I have are 22cc dished pistons..

https://www.motortrend.com/how-to/cc...ster-for-2500/

hmm, looks like compression wear at top?
not much but needs to be checked.
nice score anyway

Right? I mean it was $200...

:cool:

Right the 400 block are getting harder to find. Good find ,and near impossible at that price !

STD???...never-mind-

I was going to tell you to go to "the" clinic...

Doesn't the 400's take a head that has steam holes drilled in them?

Yes they do. They tend to have overheating issues otherwise.

Yes it requires a gasket for a template and a drill.. From what ive read one hole has to be drilled on a 45 degree angle to avoid any possible damage.. after porting my aluminum heads im not so nervous about doing this.

Its because the cylinders are siamesed like the LS engines and steam pockets develop otherwise..

400's can run incredibly well for small $$$.

That one has been into in the past...looks like bue headgaskets were on it etc. It's been getting some oil in the cylinders....so it depends on what you want it to do.

Me? I'd bore/hone it .020" (not uncommon size for 400's) with TQ plates and use some forged pistons. You "could" use 5.7" or longer 6.0 rods to get a lighter piston and help rod angle some...but the shorter 400 rods aren't the end of the world...especially with pump gas. Getting the piston away from TDC a little quicker can keep detonation down if you have good compression. Your heads are OK....bigger ones would be better.....but for a fun street motor on a budget, you've got a good start.


JIM

Thanks for the info,
Thats kinda where my thought process is going. Having it machined maybe 30 over simply because of the cost of the optional pistons when I do that will work with my 64cc heads. the heads I have are likely more like 200cc due to all the material I removed when porting and matching to my intake I know thats still on the smaller side for many 400 performance builds but this will be a street engine built mainly for its torque and the fact that it can produce more power with less cost and strain.

Many of the pistons I see in the -15-16cc range that would work best with my heads for pump gas are advertised for 5.7 rods... I have 2 350s I could take those rods from or I could buy refurb rods but from my research so far that will mean balancing will need to be done to the crank to account for this also correct?

Also im seeing a lot of compression ratios give with different piston and head choices but they dont say if this is with the block decked or not? I assume the numbers would only be constant if they were giving numbers for a decked block right?

I have a lot of things going on and im trying to keep costs under control with this but at the same time id like to swap blocks when swapping transmissions this summer.

I suppose I could have it bored and decked and go with these? https://www.ebay.com/itm/35305167759...Bk9SR8711LTRYw
Slightly lower static compression than I have now but with the comp 270hr cam im using that might be a good thing? I know its a mild cam for a 406 build but Its in my 355 now and id like to maybe reused it as the dyno software states modest but decent performance in the range I want it IDK im on the fence about going to a bigger cam because my engine never even sees 5,000 rpm on the street.

Also the flow numbers are from unported 190cc heads. these numbers do drop a bit when dropping the compression a bit too so IDK decision decisions. I just dont want to get carried away.
https://cimg9.ibsrv.net/gimg/www.cor...13d04be23f.jpg

Not sure why you wouldn't go over 5K on the street. If I put my foot in something....I'm going all out even if it's for a short time.

More head porting would be good.

I'm not a hypereutectic piston fan if I'm going to hammer it some. Just too many instance of detonation damage which is always a real threat on the street. Even light stuff will eventually break them. I'd save my $$ for something forged.

That's definitely a small cam. Will drive real nice though......larger heads would work even better if using something that small. Open them up some more and don't forget the intake.


JIM

They are already opened up considerably from whats in the dyno software flow numbers which was as cast.
I know this may sound lame but I dont really ever find myself flooring the pedal. At last not for long. I do like to get from light to light as quickly as possible though. Who knows that might change once I get the new suspension and steering installed and replace those 50 year old bushings.

Ive been running hyper flat tops in my 355 build now for 12 years so they are working ok for my use but thanks for the advice just the same.

What are these stock pistons? forged aluminum?

The stock pistons are cast and very heavy. I have the same engine sitting as a shortblock and it also has had a garage rebuild.

So the rod and crank bearings all have very little wear.. my guess is someone replaced them and maybe re ringed it at some point. think im going to call monday about havingit checked and maybe bored .020 not sure if I should have it decked or not. I found two possible pistons I could go with in my budget range that would work with my heads and pump gas but one required 5.7" rods and the other uses stock. The cam bearing look like they need to be replaced for sure.

https://www.ebay.com/itm/266462452952

or

https://www.ebay.com/itm/264700869106

If I used the second I would have the block decked..

I only saw the spec listed on one of them...but it said it had 5/64" rings. You can gain power and ring seal these days with thinner rings and proper honing. Those 5/64" ones are an ancient design. Lots of drag.

But if you've run hypers this long with no issues....I suppose you can replicate with this build. I just tend to build one I never have to worry about. The rods and crank don't bother me...either long or short rod version. Personally I'd install better rod bolts...but by the time you buy them, install them and rebuild the stock rods, you could buy a new set of aftermarket SCAT rods almost which are much stronger.

JIM

Buy a set of Eagle or Scat rods.....get a premium piston and have it all balanced......
Punch it .020 or .030.......the piston will probably be in the hole .020.......account for that with head gasket choice.....
I only bother to drill the lower holes on 400's now.......the upper ones can't trap air or coolant....the lower ones can......
My 406 is bottom drilled and is fine with a 100% stock cooling system...save for the thermostat....

The 406 is one of my favorite engines.....not in to anything larger now unless you have big money for pistons......

The 406 is to SBC as the 540 is to BBC......a very happy bore and stoke package.....people have been building them for a long ass time now....and still do.



Jebby