68 440 questions

[zerfetzen]

Hi all,
I just got an ebody with a 68 440 that has been rebuilt, but said it did not need to be bored, so it is stock bore.  He said the motor is rebuilt all stock, except for cam, intake, carb, and headers.  The previous owner said the 68 440 came out of a Chrysler Newport.  It is a non-HP motor.  He said that the stock specs were 375hp and 10.5 compression.  Is that right?

Also, didn't they report lower hp ratings, and their means of estimating hp were pretty limited.  What would the actual stock hp, torque, and compression be of that motor?

He said that the heads were milled .010.  If that's right, what would that do to compression?  In the ad, he wrote: "Heads are .010 under cut valves-double springs".  Is that the same thing?  Thanks.

[moparnut]

If it wasnt an hp motor then it wasnt 375 horse,but he may have rebuilt it to those specs.Then it wouldnt have the stock windage tray,no HP bagding and was a lesser compression and milder cam.It should be a forged crank engine with 906 heads though,i think.

[71383bee]

At this point i would have to ask what's the point of estimating HP is for your motor because it is anything but stock.  

A non HP 68 440 did not put out 375 gross horespower.  

After 71 i believe they went to a net horespower rating which was the horsepower output after accessories were installed.  The original gross ratings were run without accessories and pre 72 motors were much higher in compression with heftier cams than the post 71 motors.  

The statements made by your seller are misleading.  If he advertises that he had a 10.5:1 compression motor and then milled the heads some more that would raise the compression which would take it beyond the acceptable range for pump gas.  

You need cam and piston specs and find out what heads they are and what were done to them.  Oversize valves, hardened seats, etc.  

[zerfetzen]

Probably like anybody else, I'm just trying to learn about what I have.  Knowledge is power!  I'm trying to learn all specs about all parts I have, and thought I 'd start with the basics of the block.  I have access to a lot of Cuda specs, but a 68 block from a Newport?  No idea.

I believe the cam is a Comp Cam Xtreme Energy (Part #: 21-228-4)
Description: HYDRAULIC: This is a hot street cam recommended with 10:1 compression, lower gears, headers, and 3,000 stall.  This cam produces strong mid-range, with a rough idle.
Lift, Intake: 0.545 inches
Lift, Exhaust: 0.545 inches
Duration, Intake: 285 degrees
Duration, Exhaust: 297 degrees
Basic Operating RPM Range (listed on Summit): 2,500-6,200
Basic Operating RPM Range (quoted by previous owner): 3,500-7,300

[Follicly Challenged]

In '68 the "regular" vrs the "magnum" 440's were identical parts wise, save for the latter, got the addition of a hotter Cam, Valve Springs, Windage Tray, .001" smaller Crank sizes, exhaust manifolds, and Carb, as per application.

All '68 440's used a 2.02" Comp. Distance Piston, (.060" downhole), Flat-top, and 906 heads to yield an ACTUAL Compression Ratio around 9.8:1, even though ADVERTISED at 10:1.

Later '69 440 - 6 Pack Engines used a Flat-top Piston with 4 valve reliefs at a Comp. Distance of 2.06,(.020" downhole), for an ADVERTISED Comp. Ratio of 10.5:1, ACTUAL was more like 10.2-10.3:1.

All Engines used a "steel shim" type head gasket @ .022" thickness.

When Rebuilt, I'm guessing they used a composition style head gasket @ .042" thickness, that, and the heads being milled .010" would only offset the valves being sunk during regrinding, leads me to "GUESS" the actual compression of that engine in the 9.8:1 ballpark. Very nice street motor.
CAUTION; the actual 68-69 Piston with that Comp. Distance, lacking any Valve reliefs, doesn't accept much cam lift, be careful not to exceed .500" lift with future cam choices, lest your Valves will get "real friendly" with your Pistons !

The above, is the reason most aftermarket replacement Piston Manufacturers for years, only offered the 66-67 Piston Distance of "1.99"(.090" downhole), and 1.96"(1972-1978)(1.20" downhole), the latter being akin to a "popcorn" fart for Compression, and the 1.99 piece being inaccurately listed as the "10.1" piece, as it was, but only when using the older 66-67 closed chamber style heads.

Some Trivia;
The actual 68-69 2.06" Full Flat-Top Cast rebuilder Piston was NEVER offered by the aftermarket in oversize for rebuilding "Correct" 68-69 motors. All you guys who "THINK" you've got stock "Correct" rebuilt 10:1, 68-69 Engines using 906 heads, DON'T ! hence, why they don't perform as well as they did new, in case anyones wondering.

FC out.

[zerfetzen]

Thanks guys.  Considering this stock rebuild has an Edelbrock Victor highrise (6") intake and I think it's a Holley 750dp model 4150 (attached is a pic of the engine bay, hopefully I'm right, because I can't find a part number on the Holley), Hooker headers, and Comp Cam with .545 lift and 285/297 duration, and like FC says, probably 9.8 compression, what octane gas is best for this?

[zerfetzen]

engine bay

[zerfetzen]

Another question, if the cam is too large for these heads regarding the pistons and valves, I'm guessing my choices are either replace the cam with a milder one, or get different heads?  Recommendations?  Thanks.

[blackhood]

Basic Operating RPM Range (quoted by previous owner): 3,500-7,300

I don't know what is needed to rise the engine until there but i'm sure that it won't be good.

[71383bee]

Wow that is a hefty cam on that motor.  With stock pistons and heads i would venture a guess and say that the car is over cammed. 

With 10:1 compression of less you'll be fine with 91-92 octane gas.

[Chryco Psycho]

is anything done to the heads ? ported larger valves ? intake & cam would seem to match well

[zerfetzen]

I don't know, which is a bad answer.  To have this done right and have a working, trustworthy setup, what would you do to the heads Chryco?

[Chryco Psycho]

porting them will help get the flow inline with the cam & intake specs , larger valves & hard seats too while you are in there