Compression ratio?

[sabre67]

1966 Chrysler 383 2bbl according to My Mopar.com website states that this engine has a 9.2:1 compression ratio. Can anybody verify this C.R. in a factory manual for me? I dont have any 1966 books. Thanks

 

[Kern Dog]

No matter what the factory service manual states, it is bullshit. They seemed to LOVE to overestimate the ratios.
My 1970 383 was rated at 8.7 to one but when I tore it down and measured everything, it came in at 8.12 to 1. It was an original piston, standard bore, UNrebuilt 383.

 

[RM23M9A]

8.12:1 be correct..
(Still a Bulletproof, healthy motor.)

 

[Kern Dog]

8.12:1 be correct..
(Still a Bulletproof, healthey motor.)

Healthy does not have an E before the Y.
Be correct yourself.

 

[RM23M9A]

C'Mon Maaaan! LoL I'm too old for these damn midget FONES.

 

[Kern Dog]

Oh, another thing.....

Magnum Force (1973)
R | 2h 4min | Action, Crime, Mystery | 25 December 1973 (USA)

 

[RM23M9A]

"A man's Got to Know his Limitations"

LoL, oops that pic's from 1971's Dirty Harry..
Briggs-

 

[yella71]

Is this the pissing contest post?

 

[66Satellite47]

My 1966 Factory Service Manual states the 383 2BBL has a 9.2 CR.
However, anyone that has actually taken a virgin engine apart has found the published number is high, compared to the ACTUAL measured values. More than likely the actual is around .5 CR lower than advertised.

 

[Don Frelier]

We had a 1966 Chrysler Newport with a 383 2barrell. That thing would surprise you, it was just one of those "good ones".

 

[66Satellite47]

My '70 Barracuda Gran Coup had a 383 2 BBL to start with. Added a DP4B & 3310-1 Holley, cheap headers. Would do pretty well on the street. Never lost to a 351 Mach 1, about even with the Chevies of different models & motors. The 340 Darts & Dusters were a major challenge. Lost to most of them. They didn't kill the tires and would run rpm. My last street race was against a '71 454 Chevelle, many rolling goes, he only went by after I lifted when my needle was well past 100. My 383 2BBL base motor was pretty good. Not so much at the track. So I bought my '65 Coronet drag car. Eventually made that a consistent winner.

 

[Don Frelier]

My cousin had a 70 Gran Coupe 383 super commando.
We redid the heads, new chain and put headers on it otherwise it was stock.
With G-60 Bias ply tires if you laid a patch and backed up up on it you could nearly pull the front wheels.
One of my favorite cars ever never saw any car stay close on the highway from 50-100 even corvettes.

 

[diesel_lv]

My '70 Barracuda Gran Coup had a 383 2 BBL to start with. Added a DP4B & 3310-1 Holley, cheap headers. Would do pretty well on the street. Never lost to a 351 Mach 1, about even with the Chevies of different models & motors. The 340 Darts & Dusters were a major challenge. Lost to most of them. They didn't kill the tires and would run rpm. My last street race was against a '71 454 Chevelle, many rolling goes, he only went by after I lifted when my needle was well past 100. My 383 2BBL base motor was pretty good. Not so much at the track. So I bought my '65 Coronet drag car. Eventually made that a consistent winner.

I love Mopar more than any other, but I've had damn near every make out there. The 351 Mach 1 was a slug off the line. It had a Cleveland which couldn't get out of it's own way unless 3.73 or steeper gears and high revs. The 2bbl heads came w 2.02 intakes and 4bbl came w 2.19's. They were for top end high rev light cars. Now the Windsor was great on the bottom end and could get a 4,200lb pig moving pretty easy.

 

[That_Tall_Dude]

1966 Chrysler 383 2bbl according to My Mopar.com website states that this engine has a 9.2:1 compression ratio. Can anybody verify this C.R. in a factory manual for me? I dont have any 1966 books. Thanks

my 69 2 barrel, was stated to be 9.2 also

but that with shim head gaskets and most folks rebuilding don’t use them

most folks use a thicker composite, felpro, that drops the compression ~ 1/2 a pt

also it’s assuming zero deck which most blocks aren’t, and varied quite a bit

Basically have measure to know

the big question; why do you want to know?

 

[sabre67]

Looking at cam choices

 

[33 IMP]

Looking at cam choices

Then, if your engine has ever had the heads off, the chances are you really have compression in the low 8's, and i would be conservative with a cam choice. ( it probably really had around 8 1/2-8 3/4, and might have lost another 1/4 to 1/2 point from a head gasket change.)

 

[Kern Dog]

The 8.12 CR that I calculated was with a .020 steel head gasket. With a Fel Pro .039 gasket, it drops to 7.85 to 1. Terrible!

 

[That_Tall_Dude]

The 8.12 CR that I calculated was with a .020 steel head gasket. With a Fel Pro .039 gasket, it drops to 7.85 to 1. Terrible!

was this on yours?

 

[That_Tall_Dude]

Looking at cam choices

Only way to make a good cam choice is to know the compression.

These blocks vary a bit, and can have the piston below the deck

I think mine are .030 with the original 2 barrel pistons that also had small dish

but I read about them being quite a way down

it really affects 383s CR due to the big bore and short stroke

Really kinda need to measure & calculate the CR

 

[Kern Dog]

It was the 383 I rebuilt for this car:

I had first planned to hone the cylinders and rebuild the 383 with the stock pistons. They sat .076 in the hole though. THis put me about a point under the goal.
I ended up going .030 over and using Speed Pro pistons that sat .025 below deck, then decked the block to get them at .014. I was aiming to be in the 9.25 CR. The heads I have were milled before I got them and when I checked the volume, they came in at either 83 or 84 ccs. My final CR was something like 9.2 or close to that....right where I was hoping to be.
I'm fuzzy on the details but I wrote about it in my build thread titled....
https://www.forbbodiesonly.com/moparforum/threads/lookie-what-5000-buys-you.178346/page-37