400 Refreshing

RockyPat

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Hello everyone,

I have a 1972 400 HP motor with a cast crank and 346 heads (double springs). I thought about doing a stroker (451 - with a 440 crank, or a 440 source kit, but I do not think I need to rebuild the engine).

I would like decent power - maybe 350 HP and 400 TQ. More the better, but not necessary. A nice driver engine.

It seems so far to be a low-mileage engine.

The engine turned over by hand with no issues.

I took off a cylinder head to inspect the cylinder walls and they look very good.
Still has a Chrysler gasket (gold/pink color).

Now, I am deciding what to do.

I would like to refresh the engine instead of a full rebuild to save money.

I believe the engine is standard bore.

I would like to hone the cylinders, polish the crank, replace the cam (maybe a Hughes Whiplash cam), and re-gasket the engine.

Do I have to replace the pistons? Can I get away with a re-ring? --> Do I have to rebalance the engine if I replace the pistons?

Any reservations about doing a refresh instead of a rebuild?

Another not-so-related question, I pulled off a cylinder head. I tried to do it the right way by unbolting evenly throughout the rocker assembly and heads.

Can I bolt the head and rocker assembly back on the engine now that I have taken them off? I have everything organized.

Thank you.
 

pnora

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You need to fully disassemble. Clean, inspect and measure what you have. Then decide.
 

R413

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The stock pistons won’t work with a longer stroke on the crank. They will hit the heads.

ifmyou change any piece of the crank/rod/piston it should be balanced.

yes you can put the head back on with a new gasket.

if it looks so nice just refresh what you have?

but if you just think it is standard bore then you haven’t measured anything yet. And that needs to be done to know what direction to go.
 

66Satellite47

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If the cylinders look good, why re-ring? does it have blowby symptoms? No need to rebalance a stock crank/piston combo. Doing a basic pocket port on the heads, valve job and a cam to match your car/driving application will give plenty of power/torque for the street.
 

Lefty71

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You should have started with a compression test of each cylinder before disassembly to get a baseline of potential trouble. Not much point in polishing the crank without new bearings. Any pix of what you are looking at, including the head gasket??
 

IQ52

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Hello everyone,

I have a 1972 400 HP motor with a cast crank and 346 heads (double springs). I thought about doing a stroker (451 - with a 440 crank, or a 440 source kit, but I do not think I need to rebuild the engine).

I would like decent power - maybe 350 HP and 400 TQ. More the better, but not necessary. A nice driver engine.

It seems so far to be a low-mileage engine.

The engine turned over by hand with no issues.

I took off a cylinder head to inspect the cylinder walls and they look very good.
Still has a Chrysler gasket (gold/pink color).

Now, I am deciding what to do.

I would like to refresh the engine instead of a full rebuild to save money.

I believe the engine is standard bore.

I would like to hone the cylinders, polish the crank, replace the cam (maybe a Hughes Whiplash cam), and re-gasket the engine.

Do I have to replace the pistons? Can I get away with a re-ring? --> Do I have to rebalance the engine if I replace the pistons?

Any reservations about doing a refresh instead of a rebuild?

Another not-so-related question, I pulled off a cylinder head. I tried to do it the right way by unbolting evenly throughout the rocker assembly and heads.

Can I bolt the head and rocker assembly back on the engine now that I have taken them off? I have everything organized.

Thank you.
You should do this, you should do that. What you want is completely impossible, I would just throw up my hands and walk away.

NOT.

It seems like I keep going back to this old 400 build from many years ago that qualifies as to your stated requirements.

400 w/ 350 HP/400 TQ @ less than 8:1
 

furious70

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If it was mine and I had your goals I would leave the shortblock alone. I would contemplate Stealth heads and then a cam for low CR and an Edelbrock performer intake. Job done.
 

Curiousyellow71

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If it still has 50 year old bearings and original cast rings I wouldnt hesitate to look into freshening it up. It doesn't sound like a compression test was done and its now apart..so I suggest hone it and see how it cleans up before you make ANY plans. If it looks acceptable (judgement call) clean everything up and put it back together w moly rings and new bearings and a cam. In my younger years we often did exactly that. Several had a lot of wear and with the funds we had we didn't have much choice, boring and pistons were not a option. Things have changed now and we spend more time optimizing our engine combinations. But I had a lot of fun with those old thrown together projects.
 

Jerry Hall

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I am currently going through this. A rebuild was in my mind as the 383 showed 91K on the odometer. I completely tore the engine down, measured everything and sent the block, crank and flywheel to the machine shop. The block was cleaned, sonic checked, and the cylinders honed. The crank was polished. The flywheel was surfaced .020. I purchased a rebuild kit, oil pump, file fit rings, bearings, etc. I also had the machine shop install new cam bearings and the replacement freeze plugs. I call it a rebuild, but I guess it can also be classified as a refresh. I think any time that a engine with significant miles is going to have a cam change that it should be freshened. I have seen to many original engine cars that were bought and a cam, intake, and carburetor change was made, then in less than 30 days were smoking like a tar keg.
 

Lenny459

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Hello everyone,

I have a 1972 400 HP motor with a cast crank and 346 heads (double springs). I thought about doing a stroker (451 - with a 440 crank, or a 440 source kit, but I do not think I need to rebuild the engine).

I would like decent power - maybe 350 HP and 400 TQ. More the better, but not necessary. A nice driver engine.

It seems so far to be a low-mileage engine.

The engine turned over by hand with no issues.

I took off a cylinder head to inspect the cylinder walls and they look very good.
Still has a Chrysler gasket (gold/pink color).

Now, I am deciding what to do.

I would like to refresh the engine instead of a full rebuild to save money.

I believe the engine is standard bore.

I would like to hone the cylinders, polish the crank, replace the cam (maybe a Hughes Whiplash cam), and re-gasket the engine.

Do I have to replace the pistons? Can I get away with a re-ring? --> Do I have to rebalance the engine if I replace the pistons?

Any reservations about doing a refresh instead of a rebuild?

Another not-so-related question, I pulled off a cylinder head. I tried to do it the right way by unbolting evenly throughout the rocker assembly and heads.

Can I bolt the head and rocker assembly back on the engine now that I have taken them off? I have everything organized.

Thank you.
I have the same engine and this is what I did; I have never stroked an engine though some do. Stock bore 400 I ordered keith black 10.5 to 1 pistons, added a lunati cam did a gasket match and a valve job with a good head bowl debur. Other than that just a basic bearing and gasket set with a decent intake and 750 carb. This thing is WILD!!! I have built many 440 engines and this thing will compete. I put it in a 71 Duster with a 373 gear and second gear will literally slap your head against the head rest. I am so suprised and pleased with this motor........
 

Lefty71

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I think many here would agree with the post above that the 400 is a darn fine engine....it gets a bad rap due to way is was underutilized when new, meaning the small cam smog age.....
The reality today is that if you try to work on it stock stroke, the poor piston selection makes it more like an obsolete engine, IE, 361, 413 and 426w. The stroker piston selection kinda saves it from that fate.
 

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