rebuilding Chrysler 400

[Landyacht]

Are they .030 or std?

They are .030 over flat tops with 5cc valve reliefs. These pistons will give you .020 piston to deck clearance. They are made for 400s with stock rods and stock crank. They are significantly lighter than the stock 400 pistons and have shorter skirts so I would highly recommend balancing the crank. I purchased them about 4 or 5 years ago from summit with the intention of using them on my 400 but got carried away and built a stroker motor instead.

 

[Landyacht]

Stock 1972 pistons for a 400 should raise the compression to almost 10:1.

I seriously doubt that. The 400s where pretty much all dogs with low compression and smog heads even as far back as 72. The problem is the pistons sit down too low in the bore that even with closed chamber heads you still won't get that much compression out of them

 

[Landyacht]

Just stock cast flat top pistons? I did find some 440 pistons but I'd have to bore the engine 4.350... Around $550 which isn't out of my budget but... Valve reliefs and +6.00 cc which wouldn't help compression...

You better know what the compression height is so you don't end up with a set of pistons that stick up above deck or sit too low in the bore and give you even less compression than you had before. the deck height on a 400 is 9.98 inches. The rod length is 6.38 inches. the stroke is 3.38 inches. If you divide the stroke in half and add the rod length you should get 8.07 inches. subtract 8.07 from the deck height 9.98 inches and you should get 1.91 inches.. 1.91 is the limit on what you can run for compression height before the piston rides above the deck.

 

[70bigblockdodge]

You better know what the compression height is so you don't end up with a set of pistons that stick up above deck or sit too low in the bore and give you even less compression than you had before. the deck height on a 400 is 9.98 inches. The rod length is 6.38 inches. the stroke is 3.38 inches. If you divide the stroke in half and add the rod length you should get 8.07 inches. subtract 8.07 from the deck height 9.98 inches and you should get 1.91 inches.. 1.91 is the limit on what you can run for compression height before the piston rides above the deck.

And most stock replacement pistons for a 440 are in the high 1.90s and six pack replacement piston are 2.01 IIRC.

 

[moper]

I would buy land's pistons and have the block blueprinted. Have the assembly internally balanced. Have the heads you have completely redone for performance. Add unleaded seats in the exhaust, and run 2.14/1.81 valves. Have the spring seats and guides machined. Run the thinnest head gaskets you can. Stick a cam in the 220° at .050 range cam in it and you'll have plenty of power and torque on pump gas. Might be a little more than $2K depending on your machining costs, but get good machining regardless of cost. It's well worth it in the long run.

 

[Landyacht]

I would buy land's pistons and have the block blueprinted. Have the assembly internally balanced. Have the heads you have completely redone for performance. Add unleaded seats in the exhaust, and run 2.14/1.81 valves. Have the spring seats and guides machined. Run the thinnest head gaskets you can. Stick a cam in the 220° at .050 range cam in it and you'll have plenty of power and torque on pump gas. Might be a little more than $2K depending on your machining costs, but get good machining regardless of cost. It's well worth it in the long run.

It would probably be more cost effective to just purchase a set of Stealth heads or Performer RPM heads instead of reworking an old set of cast iron heads. Performer RPM heads are now available with 79cc combustion chambers.

 

[fury1]

Buying those stealth heads would be half my budget.... Then buy a set of $500.00 pistons...$300+ for machine work... That might be reasonable!! Not looking for a high performance. Just a good driver with more power.

 

[CanCritter]

Buying those stealth heads would be half my budget.... Then buy a set of $500.00 pistons...$300+ for machine work... That might be reasonable!! Not looking for a high performance. Just a good driver with more power.

...gears....

 

[heyoldguy]

http://www.forbbodiesonly.com/mopar...3-The-slug-400-on-the-dyno&highlight=400+2bbl

Do you really need to raise the compression?

 

[olsn500]

I know it's out of budget for you in this instance. I'm also a newbie here, but 8:1 and 8.5:1 compression seem great to me. It just screams turbo. 5 to 7 psi boost that engine will jump up to around 10.5 to 1 compression, ponies will fly out the tail pipe. If you wanted to be cheap you use a carb hat instead of fuel injection and get a decent wastegate. If you have some access to fab equipment and an industrial salvage yard. You might be able to build a monster for under 5 grand.

 

[70bigblockdodge]

http://www.forbbodiesonly.com/mopar...3-The-slug-400-on-the-dyno&highlight=400+2bbl

Do you really need to raise the compression?

I agree with this, and if you have no plans to twist it to 6000+ every weekend at the track there is no need for higher compression pistons and there 400-800 dollar price tag. Spend a few bucks on a decent cam and aluminum intake and you have to put work into the heads, either you diy or pay someone to do it for you, rering and re bearing the rest if it measures okay throw some decent rod bolts in and go have fun with a rumpity rump idle running on 87 swill gasoline. Just don't race a new Challenger or Charger with the little cat heads on the fender.

 

[fury1]

Wow! That's making my wallet feel better. Might gave to base my rebuild around there's.

 

[70bigblockdodge]

Easiest way from point A to point B is to follow someone else.

 

[440_Magnum]

The slug 400 on the dyno. - General Mopar Tech Discussions

Do you really need to raise the compression?

No, you don't really have to raise the CR.... but if you're re-boring the block for new pistons due to wear, you might as well since it costs $0.00 additional. Don't make a hard-and-fast decision until you know what the block needs.

Low-compression builds can make a great driver, but it really limits your cam choice. IMO, even the Magnum/Commando reproduction grind is on the edge of being "too big" for a stock 400 compression and performance would probably be better with a more "truck/RV" style grind that keeps the actual cylinder pressure higher.

As a counter-point, don't get carried away with compression, either. If I had it all to do again, I would opt for a little lower CR on the 440 I built for my Polara nearly 10 years ago. As it is now, I have to run premium and I can't really dial in as much ignition advance as it would really like. I could go with a "bigger" cam to lower the cylinder pressure, but the ripple-down from that would be that I should then get a looser convertor and/or change the rear-end gears. Everything affects everything else, you know. :-/

 

[70bigblockdodge]

The 79cc stealth heads will not help compression much. My 400 didn't even get to 8.5:1 with fel-pro gaskets and heavily milled 516 castings measuring 73cc. I disagree with resto cam being too big, and i would never put a rv cam in anything except a actual RV most of those are smaller than a stock 1975 4 bbl cam.

 

[BigFury]

http://www.forbbodiesonly.com/mopar...3-The-slug-400-on-the-dyno&highlight=400+2bbl
The slug 400 on the dyno. - General Mopar Tech Discussions

Do you really need to raise the compression?

Funny you posted this link..I just read it today. I was pretty impressed with the dyno numbers on a 7.5:1 400. Great for a street car anyway..

 

[BigFury]

Alright guys I've decided to rebuild the 400 that's in my 75 Chrysler. I would like to pull some more power out of iti have a couple of grand in mind for a budget. I've heard that the biggest problem is compression. How can I bump up the compression without spending a bunch of money? I'm gonna go mostly stock. Aluminum intake and 4 barrel eddy and new ignition.I also heard that the stock heads flow OK. Gonna have them redone... Just want more compression.

If your going "mostly stock" then I wouldn't go wild on aluminum heads and big money pistons. Freshen the iron heads you have with a good valve job and some bowl work. Mill them .30 with a steel shim gasket. A good dual plane with 600-700 cfm carb and a cam that'll work on the low end.. best for street motoring. Sounds like your asking for a warmed up stocker. I like the smog 440 piston idea.. silvolite #1276 sell for around $300 although I've heard you may have to trim the skirts?? Can't confirm that's true..anyone?

 

[440_Magnum]

I disagree with resto cam being too big, and i would never put a rv cam in anything except a actual RV most of those are smaller than a stock 1975 4 bbl cam.

Well, "big" may not be the best word, but it will result in marginal cylinder pressures at low RPM, so it will kinda "want" a looser convertor and higher numerical rear-end gear. And its certainly a better pick than one of the MP single-pattern grinds like a .484 or .509. A more modern grind can have a better effect without going to an "RV" grind, but in all honesty a truck/RV grind is a very proven way to get usable power out of low compression. They built them that way for a reason- truck/industrial 413 engines in dump trucks or the old Harverstr 345 engines in school busses spend their lives putting out, on average, a lot more power than a 440 Magnum or Hemi in a Roadrunner. But they do it with low compression for longevity and by sacrificing a whole lot of *peak* horsepower to make the high sustained average less abusive on the engine. A high-compression engine makes huge power in short bursts, a low-compression engine can make large power continuously. In a lot of ways, that can make for a very fun-to-drive C-body, but it won't be a track star.

 

[70bigblockdodge]

Well, "big" may not be the best word, but it will result in marginal cylinder pressures at low RPM, so it will kinda "want" a looser convertor and higher numerical rear-end gear. And its certainly a better pick than one of the MP single-pattern grinds like a .484 or .509. A more modern grind can have a better effect without going to an "RV" grind, but in all honesty a truck/RV grind is a very proven way to get usable power out of low compression. They built them that way for a reason- truck/industrial 413 engines in dump trucks or the old Harverstr 345 engines in school busses spend their lives putting out, on average, a lot more power than a 440 Magnum or Hemi in a Roadrunner. But they do it with low compression for longevity and by sacrificing a whole lot of *peak* horsepower to make the high sustained average less abusive on the engine. A high-compression engine makes huge power in short bursts, a low-compression engine can make large power continuously. In a lot of ways, that can make for a very fun-to-drive C-body, but it won't be a track star.

No, everybody's car on here runs at least 2300 rpm at 65-70 mph normal speeds today. A resto cam is already coming into its own with a stock converter. Nobody has there c body grossing 12-20,000 lbs so there is no need to put a rv/lawnmower cam in anything that does not have dual wheels on the rear axel.
I currently have 2 cars with 7.8 and 8.43 both with "big hydraulics" they both run fine, yes they are temperamental around town and with power brakes, but you could not ask for cars that are more fun to drive. I do not need a torquey daily driver, oh wait I have one of those and it does not rev past 2000 rpm.