383 differences per year


New Member
Sep 2, 2023
Reaction score
Central Iowa
Just wondering what the differences are between a 1965 and 1966 383 engine. I found what appears to be a good 66 block and heads from a 66 Dodge Monaco that I would like to put into my 1965 Sport Fury while I see if the Fury's engine is salvageable. I don't think it is. At least the heads anyway. A couple of the valves were indistinguishable from the chamber it was so corroded. I haven't pulled the block from the car yet, but I'm afraid that the corrosion goes deep. But even if it is eventually saveable, can I just swap the block and heads out, add my accessories and go?
I don't have the 66 engine yet. Going to look on Saturday.

Thanks for your input.
Be aware that the '66 block has different mount on driver's side. It will not have the mounting boss on it, and the '66 mount does not work in a '65.
Well, Shucks..
So are the heads interchangable and are they worth $400 if in good condition?
Will the crank, cam, lifters, rods, pistons work in my 65?
Well, Shucks..
So are the heads interchangable and are they worth $400 if in good condition?
Will the crank, cam, lifters, rods, pistons work in my 65?
Yes, everything else is interchangeable.

Regarding the pistons... Chances are good that you'll need to bore the old block so if the pistons are standard size, you're going to end up buying pistons anyway.
Yes all the parts will swap over.

BUT, what is the bore size, are the bores worn, are the pistons worn or??? The lifters need to be kept in order and go back on the same cam lobe.

If you are asking this then you have little or no experience with this, not a good thing.

Here is the mount bracket for left front of a 1965 Cbody

Yes, I understand that I'm looking at it as a core. My biggest concern was the mounting issue which has been answered. And if the heads were any different since mine are basically trashed.
Thank you gentlemen.
To me, for core heads, that amount sounds a bit expensive. No matter what. But I'm not aware of current market value of cast iron.

No way to "shoestring" a core engine. It's going to need everything.

Be aware that the '66 block has different mount on driver's side. It will not have the mounting boss on it, and the '66 mount does not work in a '65.

This is good info, but if i were the OP I would check both blocks to confirm. Im almost certain that i have a '66 block with those bosses. Gonna have to look tho...
Fwiw I have what should be bolt on ready 906 heads that I'd sell for about what those cores are. Unclear if you meant they are ready to run or rebuildable cores. Cores have about $5 value honestly.
My 65 heads are 516's. The seller was not sure what the heads were on the 66.
Whats the difference between the 906 and 516? The valve size?
906 is a better flowing design with larger exhaust valve and better ports.
It is open chamber where 516 is closed but the actual difference in compression ratio is usually much smaller than people think
Yes. Should still have 516's. A chance that it might have small exhaust valve 915's which would be better than the 516's
Be aware that the '66 block has different mount on driver's side. It will not have the mounting boss on it, and the '66 mount does not work in a '65.
I thought they kept the bosses on later blocks and just didn't drill and tap them, due to not having to modify/replace the molds?
Last edited:
From what Uncle Tony said in one of his videos, where he detailed the particular-to-1965 lh frt mount, the new-for-1966 mount was phased-in during the first of the 1966 model run. Meaning that the boss was still there on those initial 1966 B/RB blocks, but not drilled. An interesting video on his YouTube channel. Another bit of Mopar information not generally known about.

The difference in the ports from 516 to 915/906 means nothing on a stock type driver car with a small camshaft.

And the difference in compression ratio is real and not a benefit to a 1967 and older engine with pistons from a closed chamber head.

I wouldn't switch to 906, larger exhaust valve and large combustion chamber are two negatives for the small chamber engine.
I'll politely disagree. 906's have a distinct flow advantage .300-.450" lift even in stock form.
Many 516's are over 80cc.
Some 906's can be 90cc, but some are 87-88.
The CR becomes small.
In the earlier days of emissions controls, it was felt that an open chamber, lower compression ratio was beneficial to these efforts. The exhaust temperatures between our '66 Newport 383 2bbl and our '72 Newport 400 2bbl are significant. The '66 is much cooler, by comparison. Keeping the chamber surfaces hotter and more heat in the exhaust helped "cook" the mixture better. Both engines did not have AIR pumps, just normal optimized tuning and specs.

So open chamber heads were employed, using the larger exhaust valves for better scavenging of the exhaust mixtures. Valve sizes are determined by the largest bore size the head can fit onto. Larger exhaust valves can help, BUT the flow capabilities of the ports can or cannott make that beneficial. As the size of exhaust piping relates to this too. As does the normal rpm level of the motor.

As mixture flow came to be much better researched and understood, plus combustion chamber dynamics, it was discovered that the original wedge closed chamber heads could actually produce more power and torque. "Active mixtures" were operative. On our '66 Newport 383 2bbl, its base timing spec was 12.5 degrees BTDC. Moving it to 15 degrees BTDC would increase the idle speed in direct proportion to the timing increase. My '70 Monaco 383 N, set at 5 degrees BTDC, did not have such a relationship as increasing the base timing did little to increase base idle speed, by comparison.

When I discovered NGK V-Power spark plugs (with the v-notch in their center electrode), they made the most noticeable difference in the open chambers and little in closed chambers, by observations. They still worked well, just not the same degree of improvement in throttle response, off idle and otherwise, as the open chambers had. Chrysler engines or not. When I put them in my '80 360 2bbl, it was a difference I noticed immediately upon first start, although the prior Autolites were burning well with a normal plug gap.

Remember, too, that many cyl heads were designed "by sight" and what was suspected to work, back then. Chrysler had some decent heads back then, but I also suspect they had few resources to verify that other than gauge what Chevrolet was doing with their ports and such. There were few efforts, it seems, to really maximize Chrysler heads for great low-to-mid lift flow, only focusing on max exh sizes and such. Can't forget the DC Porting Templates, either!

What I'd like to find is an aluminum cyl head for Chry 383s that has great combustion dynamics and air flow to support an easy 5500rpm and make another 50lbs-ft of torque at 3000rpm, with the most efficient combustion chamber dynamics for efficient burns with normal flat top pistons and 9.5CRs. Yet still have ports that don't "stall" until about .550" lift with great low-to-mid lift port flow and velocity. Then add some Mahle narrow-ring "MM" costed pistons to round out the combination. With Plateau Honing for good measure. That ought to make a nice motor.

Just some thoughts,