Re: True 440 Compression
[Re: JohnRR]
#875457
12/09/10 12:29 PM
12/09/10 12:29 PM
|
Joined: Jan 2003
Posts: 5,784
Corpus Christi, TX
shanker
master
|
master
Joined: Jan 2003
Posts: 5,784
Corpus Christi, TX
|
I recently had the heads on my 70 Coronet R/T rebuilt due to busting an exhaust stud in one trying to change gaskets... :doh:
anyway, I was quite surprised to see that the inside of my engine had flat top pistons that sat further down in the hole than I had expected...
The Federal Government has not yet learned that you cannot legislate morality
1970 Coronet R/T FF4/FF8/V85/V1G 440/Auto/3.23
1970 Coronet R/T FK5/FK5/V8W/V1W 440/Auto/3.55
1970 Super Bee TX9/TX9/V8W/N96 383/Auto/3.91
1975 Duster 360 VS29L5 Daily Driver
|
|
|
Re: True 440 Compression
[Re: shanker]
#875458
12/09/10 01:24 PM
12/09/10 01:24 PM
|
Joined: Jan 2003
Posts: 75,047
U.S.S.A.
JohnRR
I Win
|
I Win
Joined: Jan 2003
Posts: 75,047
U.S.S.A.
|
Quote:
I recently had the heads on my 70 Coronet R/T rebuilt due to busting an exhaust stud in one trying to change gaskets... :doh:
anyway, I was quite surprised to see that the inside of my engine had flat top pistons that sat further down in the hole than I had expected...
Is the engine factory original? Did you happen to measure how far down ?
|
|
|
Re: True 440 Compression
[Re: JohnRR]
#875459
12/09/10 01:40 PM
12/09/10 01:40 PM
|
Joined: Jan 2003
Posts: 660
East Lansing, Michigan
OldHippie
super gas
|
super gas
Joined: Jan 2003
Posts: 660
East Lansing, Michigan
|
As a "for example" reply consider this. Many years ago I purchased a fresh form Chrysler 400 CI long block for a truck project I built. The advertised compression ratio for this engine, with Smog type heads (346/452 castings) was 8.2 to 1.0. The pistons were .112 (average) down the hole and actual compression computed to BARELY 7.0 to 1.0. Yes, I replaced those pistons with a milled 440 flat top piston since this was before you could buy decent pistons for a 400 and got 9.8 to 1.0 compression.
The Old Hippie Hisself
|
|
|
Re: True 440 Compression
[Re: shanker]
#875460
12/09/10 01:51 PM
12/09/10 01:51 PM
|
Joined: Feb 2005
Posts: 5,221
Branson, Mo.
joedust451
super gas
|
super gas
Joined: Feb 2005
Posts: 5,221
Branson, Mo.
|
Quote:
I recently had the heads on my 70 Coronet R/T rebuilt due to busting an exhaust stud in one trying to change gaskets... :doh:
anyway, I was quite surprised to see that the inside of my engine had flat top pistons that sat further down in the hole than I had expected...
Exactly!!! Only the 6-pack 440 came with pistons that were around .020"-.025" in the hole, there "real" compression was at 9.6-9.7, a 70 standard 440 came with pistons around .080"-.090" in the hole, there compression was around 8.7-8.8, If i'm not mistaken & i think i'm right on this, the HP & non-HP blocks had the same rotateing assembly, the only difference on these 2 engines were the HP came with a windage tray/better cam/springs, larger carter carb (not holley) & HP manifolds & dual snorkel air cleaner & different dist. (non-start retard), this was 68-70 440s.
|
|
|
Re: True 440 Compression
[Re: joedust451]
#875461
12/09/10 02:30 PM
12/09/10 02:30 PM
|
Joined: Jan 2003
Posts: 75,047
U.S.S.A.
JohnRR
I Win
|
I Win
Joined: Jan 2003
Posts: 75,047
U.S.S.A.
|
Quote:
If i'm not mistaken & i think i'm right on this, the HP & non-HP blocks had the same rotating assembly, the only difference on these 2 engines were the HP came with a windage tray/better cam/springs, larger carter carb (not holley) & HP manifolds & dual snorkel air cleaner & different dist. (non-start retard), this was 68-70 440s.
Well almost, 68/69 440's all had the same rotating assembly , 6pks were hand picked and prepped parts, same compression ratio all stated at 10.0.
1970-1973 the HP engines had the 6pk rods, external balance dampner and the 6qt pan, but the same compression rating as the non HP in 70 and 71 , no clue on 72 -73 as far as compression ratings.
|
|
|
Re: True 440 Compression
[Re: RapidRobert]
#875464
12/09/10 10:14 PM
12/09/10 10:14 PM
|
Joined: Jan 2003
Posts: 75,047
U.S.S.A.
JohnRR
I Win
|
I Win
Joined: Jan 2003
Posts: 75,047
U.S.S.A.
|
Quote:
Quote:
What is the NHRA spec for a 70 440 HP
Lookup those specs (head cc's/deck height) as the 9.7 CR is correct/actual when an eng is blueprinted down to those (minimum)NHRA specs. Actual right now will be in the low 9's or even into the 8's. If you have measured your head cc's and deck height you can plug it all into KB's calculator to see what you have
No, that is not the case with NHRA spec, at least it's not with a 68-69 383 HP , when you blueprint to NHRA spec which has a 906 at 79.5 cc (never seen a factory 906 under 90cc), and piston out of the hole .020 (factory it's .0025 below the deck), you end up somewhere between 10.5 and 11.0 depending on bore size , FACTORY ADVERTISED IS 10.0.
I used to think that was the case with the 383 and NHRA spec till I realized I had the sign wrong in the calculator I was using for the piston ABOVE the deck, there was no 383 from the factory with a positive deck height piston unless the block was machined incorrectly when it was first machined.
|
|
|
|
|
