383 or 440???

Long story- I'll shorten it and get to the point.-
383 rebuilt 30 over, cam and stealth heads, sniper Efi. Car put down 300 WHP and around 400 TQ on a chassis dyno. decied to swap the cam to a good one, never been happy with the one in it. Pulled the heads to replace the springs to match and found the STEALTH heads guides are beat, the valves are hurt etc.... So now we are rebuilding the heads.

Mean while we have a 77 440 from a motor home- has been rebuilt and is low miles. But was rebuilt to go back into a motorhome. so it is low compression.

Here is the question

Do we go with the rebuilt 383 we have had in the car, it has hyperutectic pistons stock rods and crank. it is a 67 383. OR should we toss the rebuilt low compression 440 in with the stealth heads and a good cam. Will the additonal cubic inches and longer stroke compensate for the lower compression of the 440?

440. If everything was equal the 440 should give you about 60 more Hp than the 383. And there is no way the lower compression would cost that much power. Then there is the better leverage on the crank with the longer stroke 440, a better selection of intakes for the 440, etc, etc.

It's hard to beat cubic inches. Considering that the rule of thumb is 4% power per one point in compression, if you can stand the additional weight and size of the 440 versus the 383, the 440 would seem to be a good choice.

I say 440.

just make sure you calculate the hassle and potential cost of getting the correct pulleys and brackets - depending on how your 2 engines are setup and how complete. Potential exhaust fitment issues to be corrected as well. No show stoppers, just things to plan for ahead of dropping the 440 in.

Those choices - that 383 vs that 440 - sound like 2 quite different personalities.
The 383 will likely be more perky, and the 440 a bit lazy in comparison, though with more torque.
So, the better combination will depend on usage, car weight, and gearing.

What exactly are the compression ratios of the two motors? You would have had to do some creative work to acquire a decent compression ratio for the 383 considering historic piston availability.

The car, your build priorities and budget will matter as well.

Without knowing these details, maybe consider head milling and gasket choice to get back some of the 440's CR

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440 and the thinnest head gaskets you can use. Be careful about surface finish when using MLS gaskets though.

I have been in several later model motor home 440s and they all had pistons .080" or more down in the hole. In my opinion, not much is going to help that shy of new pistons. But, by keeping that in mind when choosing the rest of the combo, the low compression won't kill the power. Certainly not enough to go with the 383.

The biggest hurdle I have had with these engines, is trying to get a good timing curve in them without them pinging. They spark knock very easily. Must be because of a lack of squish.

the 383 is about 9.5 to 1. we rebuilt the motor years ago and barely ever ran it.
the 440 looks like the pistons are 1/8" down so im guessing it will be low 8 to 1 compression. Im hoping with the stealth heads we would get at least 8.5 to 1 compression.
Regardless of the motor that goes it, new headers will be coming. TTI most likely.

My vote is for the 440. You can't argue with inches. Measure how far in the hole the pistons are and get cam spec'd for what you are doing. Sd or performer intake. I had a 440 that had pistons .074 in the hole steel head gaskets 906 heads 91cc checked. The old 509 cam,Team G intake[junk] 3800 convertor 3.91 in an Abody it ran 11.91 @111. So you can make power with low compression. There are a couple good reads on for A bodies only by IQ 52 about some low compression dyno testing he did.

I'm a fan of the 383, but there's little reason to not do the 440. Cubes will win this competition. Personally I would run the 383. Have the heads shaved. 440 source says approximately 80 cc but I would have them measured and trimmed for maybe 76cs's or less. Run the .021 factory style head gasket. Pay attention to the head finish for a coated steel shim gasket. You may have to trim the sides of the intake to get it to match if you take a lot off the heads.

Assuming moving from an .039" to an .021" gasket and cutting the head to 76cc from 80cc on a .030" over 440 gets you .7 increase in compression. If the pistons are .08" in the hole and flat top you move from 9.38:1 to 10.08:1


The change of compression, with these mods, in the 383 would be lesser.

The 440 piston will be way down in the hole (.080 if stock). Shaving the heads (which might be a problem if they are used on future builds) and using a thin head gaskets are not going to have much, if any, impact. 4 CCs less in the chamber and .020 less in gasket thickness can be calculated. With the pistons that far down the hole, the difference will be small enough to probably not be worth the trouble since the OP will probably be starting with no more than 8:1 with the motor home engine.

I agree.

The pistons are probably 0.160" in the hole and and a CR of 8:1-ish. I think head milling and thin gasket to add about 0.5-ish to the CR would be worth it.

Personally, this is not the example I would use to make the case that you can make power with low compression.

This might help you, I don't know.
I am rebuilding a 383 right now. The pistons are some kind of forging, the only marking is an "80" on the underside of the crown.
Anyway, the compression height is pretty close to 1.781. Well guess what, if I use a 440 crank and the 383 rods, the pistons
will stick out of the deck about .034". With a composition gasket and 906 heads, I think I can bring it in around 9.5 ~~ 10.0 compression.
The pistons are a flattop with a small trough valve relief.
With the 3.38 crank the compression would be around 8.2.
Almost 440 inches in a low deck block.

Low deck 426 wedge.

Run which ever engine will be the most reliable while you build/rebuild the other.
I have a 440 in the car now, good motor, starts, runs, drives.
I have a 383 stroked to 438 on the stand. Big rumpty bumpty cam. Its the Road Race engine. makes all its power from 3500-6500rpms
as bad as I want the speed and power that comes with the "big motor" (the 383), I sure like the hassle free operation of the 440. But its a dog and peps out at 5000

The counter weights will need to be cut significantly to clear the pistons with 383 rods, and the piston pin bosses may need some trimming if you use 383 rods and 440 crank. Additionally, if the piston rises into the combustion chamber of a 906 you'll want clay for clearance around the edges of the chamber. I have a 383 that is .020 positive deck and a .021 gasket. I had a chamfer cut on the piston head for clearance on stock 906s. It was too close for a .06" over 383. Combustion chambers are not round, but oval. They hang over the cylinder front and rear.

The other option is to simply cut the tops of the pistons. Most forged 383 and 440 pistons have plenty of material. I've cut .170"+ off the top of TRWs and Speed Pros.

I know what you are saying. I didn't build i, but it made power. Mismatched parts and all.

Hmmmm. I would call it a good running car, but not good power. Unless the A body weighed 4200 lbs, or the DA was 10,000 ft, that motor does make good power IMO. Of course the details matter.

Ran it @ Keystone about 3600 w/me back then. I'd say around 400hp or less.

In my opinion you should move forward with the 440. I think you want to regardless anyway.

Thats kinda how it seems to be. The 383 has all the mods done to it to make more power. INtake, Cam, Headers, EFI, heads. And like I said the best we got out of it (remeber this is a street car) was 300 WHP. Ideally the 440 would be rebuilt and new pistons installed, but it has recent rebuild on it so why not just go with what it has???? Will it make less power than the 383 with the same parts on it? I doubt it.

The new setup will look more like this
low comp 440
520 ish lift cam- forgot duration
sinle plane victor intake
tti headers
sniper EFI
stealth heads
the car remains the same as

3500 stall
3.73 gears
65 b body

Will this be more of a tire shredding build than a 383 with similar engine parts and the same car setup?

Maybe you could swap out the pistons. I believe 2355 piston weighs about the same as the 1.99" and 1.91" CH replacement type pistons

The 440 will have more low end torque but if the 383 has more compression and the cam, heads, induction,etc are identical the 383 will make more HP.

I’d do some measuring & calculating before buying any parts.

I recently prepped some 75cc E Street heads for someone looking to update their stock bottom end MH 440.
The pistons were down the hole .165”

Here’s one that was tested last year:
https://www.forabodiesonly.com/mopar/threads/another-very-mild-440-build.482202/

A better manifold and a bigger cam would have woke it up a bit more.

before deciding I would do the math and work to figure out exactly how much compression the 383 atually has, mabe the same thing on the 440 motor and go from there
The Stealth heads have had two different combustion chambers sizes so if you have the smaller 80 CC versions it may make enough difference on both motors true compression ratio to help you decide
A 9.0 to 1 compression ratio on a 440 compared to a 10.5 to 1 383 may end up making the same HP with a larger increase in torque on the 440

383 and 440, 383 + .030 pop up pistons 0 deck height, 67 stock heads, a ton of compression, 509 cam, torker intake 750 DP. Ran 7.0 1/8th. 440 dead stock (74) low compression, 452 heads with a little bowl cleanup, same cam out of the 383, torker intake 750 DP best was 7.59. Same adjustable rockers on both, same stock (spacer) electronic dist and MSD 6, same coil. 3800 vert and 4.88 gears 14-32 slicks on both cars. Now 383 was in a Dart and 440 in a 64 all steel Savoy. Maybe 200 lbs different
My conclusion, you can’t beat compression.

And the differences in ET and MPH was Oops, ET was .6 in the 1/8 mile
How about 60 ft. times?
My BB 1969 Dart GTS weighed 3100 Lbs. without me in it, my lightest 1963 Plymouth Belvedere weighed was 3420 Lb, no heater, radio and with light weight Crager Super trick wheels and race tires on both cars Best ever on the Plymouth was 11.23 at 119.+ MPH, the Dart best was 11.17 at 122. +MPH
100 lbs. added on most cars equals .10 ET in the 1/4 mile
BTW , were both cars tuned to for best performance at the same track and similar weather conditions?

Didn’t have 60s when 383 was run but was within 2.5 tenths of a well built 440 in the Dart. 383 was making right at 400 hp (118 mph 1/4
in my Duster) 1.50 60 with the 440 in my 64 on 93 pump gas. I doubt it was making 350-375 hp. Both on engine stands at the moment.

No question, I'd use the 440.

Totally different applications. At that level of compression, 3-4% per point is normal (apples to apples displacement). In reality, the 440 has a big bump on power (0-5250 RPM) already on the 383 out of the gate if everything else is equal, so that's not really a good comparison.

383 will peak likely around 5,750 - 6,000 RPM.
440 will peak likely around 5,000 - 5,250 RPM.

At the end of the day, regardless, Torque x RPM / 5252 = HP. Where do you want your power curve?

383 would need more gearing and a higher stall, but HP is HP. On the street, you would - if I dare say it - be better off with LESS torque at low speed. Low speed torque is fun though, so it's a trade-off. Less likely to have problems with an engine that peaks well below 5,500 than one that needs to wind out to 6,250 - 6,500 to make power.

Also, 440 source heads - they are essentially an aluminum OE replacement. Yes, they flow marginally better OOTB (20-ish HP) but really, same cam in both, the 440 will make much more power over a 383 from 0 - 5,500 RPM.

Even after the 440's HP peak, it will still take some RPM (time) for the 383 to make up the 50-60 ft/lb deficit it has against the 440.

So, my vote - 440. Don't worry about the compression, Stealth heads - Performer RPM intake manifold - .530 to .550" lift / 230-235* duration / 110-112 LSA Hydraulic Roller. 3.55 - 3.73 gear. 3,200 - 3,800 RPM converter. Great street car with plenty of power.

Yes.