400 sbc piston advice needed - at the machine shop

I read that higher compression will give better MPG, but that too high means higher octane. Somewhere between 9.0:1 and 9.5:1 seems to be best.

I also read that quench should be between .038 and .055 with .040 being optimal.

I have also discovered that engines are really darn expensive to rebuild.

As for the machine shop, they use torque plates (aluminum for aluminum heads and steel for steel heads) They also run 180 degree oil through the block coolant passages to heat it before/while they bore/hone it. For my block, I think they will just hone it to the desired .040. They must know their stuff as other machine shops send them engines to bore/hone.

However, they did not call me today to tell me the condition and cost estimate, so I am feeling frustrated.

 

I was already looking at them, the problem is, I'm not a fan of "kits" or "crate" engines. They're both like a box of chocolates... ya' never know what yer gonna git!

But.... both kits have good points.

The Summit kit has (assuming they're quality products) Molly rings, a thicker head gasket and brass plugs.

The Northern kit has (again assuming they're quality parts) Fel Pro gaskets (Summit doesn't specify), Chain & Gears (probably Chinese) and a cam (but who knows where that came from.

To me I'd say it's a toss-up or a throw-up!

My advice...... Find a reputable machine shop, one you feel comfortable with and going to deal with. Have them first check the block and crank. Tell them what exactly you're after, what you plan on doing as well as your budget. Ask them what they can do for you on the parts they feel you need.

A good shop (not one that only sells 2600 horse engines) will work for you and with you. If he tells you he's the best there is, he's a pre-maddona..... leave! The right one will do only what you need for what you want to do. A good shop will match parts to your needs, something you won't get with a kit. A good shop will, in most cases, beat any kit price from any supply house because they're getting the whole job and they know that using the parts they are getting is better than the "pig in a poke" you could be bringing them. They will already know what cam will work with your heads and your requirements.

I can go on but I think you get my gist.

 

OK, I'll have to sit and wait to see what they can do on prices.

Oh, he can't say he is the best there is...I hold that position. HA!

 

try to shoot for the .038 quench as i said earlier you'll be happy later.

 

How far can you deck the block before the heads won't fit right?

To get that quench, I'd have to have zero deck since I have not been sucessful in finding head gaskets thinner than .039 for the .040 cylinder bore.

 

I neglected to mention that the condition of the block, per your machine shop's calculations, will dictate your next move. If the block is deemed "junk" this thread is all for not. So at this point I wouldn't be too concerned about deck height, quench, CC's, lift & lobe separation, rods or anything at this point.

Find out if the block and crank are good!

 

No, no, it is not "all for not," I've learned quite a bit. Like the fact that I've got that spare 350 4 bolt engine in the basement, and they sell a 396 rotating assembly for it, and it just takes lots of cubic dollars...see, I've learned all about engines. (grin)

 

You can deck a SBC block .020" and usually not have intake problems. Just leave out the end gaskets and use silicone, as GM did in later production. But, the price of decking ain't cheap.

The Northern kits are all quality stuff. I've been selling budget customers on them for years. Just get your "stuff" straight and order correct over/undersizes so there are no return hassles.

I never recommend hi-vol pumps on street SBC. They are more trouble than they are worth. With the government mandated oils. They cause early distrib gear and cam drive wear when used with heavier weight oils and/or colder weather. Among other things. Use a M-55 or M-55A. (higher pressure) pump. Flat tappet cams have enuff of a challange surviving these oils without adding to the problems.

 

He vaporizes me for stating a fact, and he's no man. Got that sparky?

 

If the block is junk I'd recomend looking for a 454, 427, 402, or 396. You have a heavy truck and the extra weight of a big block won't hurt you. The higher flowing heads and heavier bottom end will help a bunch in the long run. You are looking to build a 400 sb now. If you found a 402 or 396 you would have the same bore and stroke, but have 2.05 and 1.7 valves with 1.7 rocker arms. You ever have a BB Chevy? If I build a 400 sb I use 1.6 rockers and big heads just to try to get close to the big block and still have the light components in the sb.... In a 6500 lb truck I'd go for cubes and get a 454. You can get a deal on one now with gas prices crazy. Or go diesel if you really want torque and fuel mileage. To decide you need to reveiw how many miles you plan on putting on the truck.

 

MThere's a difference between a rebuild and blueprinting your block.

Be sure he's checking with torque plates to access the current condition of your block. He wouldn't hone to finished size without them, so he shouldn't be measuring current condition without them .

The wear on your bearings will effect the stacked measurements of how far the pistons are down the hole. Keep that in mind.

A lot of times its possible to hone the steel shim gaskets to the finished bore size. That keeps them out of the combustion chamber.

An RV or 4x4 cam builds cylinder pressure (COMPRESSION) at a low end RPMs. That increases your torque at the lower RPM right off idle. They won't do well at high rpms.
Velocity builds torque, at low rpms velocity comes from small intake runners, small valved heads, small tube headers. At higher RPMs you need velocity at a significantly increased volume. That's where bigger runners, valves, and headers shine at high rpms , at a cost of low end torque. The exact opposite of what you want for a heavy truck.

 

You can do what I call a cheap blueprint assemble the crank rods and pistons in the block then cut the deck turning each piston to TDC as the cutter gets to it mill untill the lowest piston is touched. Then use a .040 head gasket.

 

What ???

Deck should be parallel off of and to the crank.

Cylinder Bores squared off of both of those.

Cam parallel to the crank and deck.

What you suggest isn't going to give you any of that.

 

Ha Ha Ha!!!

I'm just going to label this thread "The Uber Dollar Ultimate Engine Build" thread.

I'm just surprised nobody suggested a Donovan block and Jessel shaft rockers by now.

 

Found a guy locally with an 817 block. It was tanked, magnaufluxed, new cam bearings, freshly bored .030, but not finished honed (that sounds weird to me). New eagle crank and 5.7 rods plus clevite bearings. No pistons. It is not decked, but was checked for square (?). He wants $650 for it. It will need to be balanced. This may be a better way to go.

I want to stay with the 400 small block since all my brackets, exhaust, etc are set up now with a 350 engine.

 

Some guys have a block prepped as you describe this one and then take it home and dry-fit everything. Then its sent back to have the decks cut and finish honed. Sounds like you found somebody half through a project, if you're lucky.

 

Finish hone to measured pistons in your hand.
no pistons >no measurement >no finish hone

 

I just talked to the machine shop. Lots of good news.

1. My Block is definitely good and usable. They are going to take it .040 over.
2. My crankshaft also looks good, the crank guy will make the actual determination if it is OK to reuse as-is with a light polish or if it needs to be reground. Thrust issue was the rear bearing. (I knew that metal in the pan had to do something bad.)
3. The stock rods are in good usable shape.

4. They said decking the block is definitely money well spent ($100)
5. Going to lightly surface cut the rebuilt 883 heads to make sure they are flat ($50 per head)

6. I decided to install the 9.1 CR speedpro pistons. The machine shop will see if they can shop around and beat Summit prices price to get the same CR. (these will work best with my smaller mileage cam)

Only bad thing is the pistons from Summit are not in stock and will take a week to get.

Things are moving forward...I might just have a new engine by the end of next

 

I wonder if the thrust bearing / wear problem was caused by the pilot bearing not being fully pressed in. It stuck out of the crankshaft about 1/8 to 3/16".

 

Those wear chunks next to the pen in the picture don't look like the "mud" wear I'd expect from the crank and main bearing thrust flange.

 

Excellent!!!

Now you're movin'!

I'm sure your machine shop will come up with pistons at a reasonable price.

As far as having an engine next week..... don't push it!

 

The chunks are magnetic. Probably Ford parts donated from another competitor.

Engine shop said they generally take the block from 9.025 to 9.000. Basically zero deck for most pistons (assuming it was 9.025 to start with). Any issue with doing that?

 

Engine shop said they generally take the block from 9.025 to 9.000. Basically zero deck for most pistons (assuming it was 9.025 to start with). Any issue with doing that?

I'm not sure that's the best approach for your build. On a performance build that's common and the head gasket thickness is your quench distance. You could do it, but if it cleaned up at 9.015 or 9.010 I'd think you'd be better off.

 

It's tricky without setting it up and checking the deck clearance. I would set up and measure the 4 corners and go .010 lower on the lowest corner and deck the other side the same. Cast pistons usually were .030 to .050 below, but you get into the kieth blacks and higher end forged pistons they tighten that clearance up some. Looks like you found a good machine shop and I would just trust them. If you want to get on there nerves just question everything they sat and say "Yeh but these guys said".

 

How important is the quench distance for an engine?

I already warned the engine shop that I am an Engineer and that I was born with that extra chromasome that makes me "need to know everything about everything".

There is bad news. I had bolted the 350 back into the COE before I knew this 400 engine would be done so quickly. Now I have to pull it apart again.

 

Performance piston manufacturers and horsepower builders have spent untold hours and many dollars coming up with .040" quench. Optimum.

Keeps down carbon build. Creates the correct flame travel/turbulance and reduces octane sensitivity.

 

Also, exposes less of the piston and cylinder to the heat of the combustion process, that translated into tolerating more compression without detonation problems. That goes along with octane sensitivity posted above.

Tighter quench or squish creates turbulence, gets more of the charge into the main part of the chamber,

Its pretty important and one of those details that really make a difference.

http://www.chevyhiperformance.com/t...shortblock/94138_piston_head_clearance_guide/

I though it was important enough to go thru the effort to get in touch with felpro to find a set of steel shim gaskets. I wound up with .042

 

Thats why we see guys in the EMC running them as tight as .027. We all know what clueless idiots THOSE guys are...

 

In my opnion the more quench area the better. When the piston comes up to TDC the mixture in the quench area has to go some where creating alot of swirl and a better mixture.