MOPAROFFICIAL
If it has tits, it's a liabilititty.
You'll probably want more like 25 initial timing.
Low compression 340 VS high compression...
- Thread starter Kern Dog
- Start date
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You think so?
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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If we're talking 360, then here's my experience;
When I installed KB107s, they came in pretty much all of them, at .012 below deck, which at 4.045 bore is 210.5 cc per inch, and 012 below deck is thus 2.52 cc.; calculated/not measured.
My block is a 1971.
The first time I assembled this engine, I did so by cutting the block to zero deck, and I used the 028 gasket for a Squish distance of .028
At the first scheduled freshening, the following winter, I noticed that the 028 gasket was migrating towards the valley in several places. Bad news,
So I tore the engine right down, and decked it again so I could use the FelPro 039.
The new deck height was .007 pop-up, for a Squish of .032.
In subsequent freshening , the Felpro did fine and I even reused it more than once.
My heads are Edelbrock closed chambers; measured at 63cc
My KB107s are ~5cc eyebrows, per pair, not measured, stated in the catalog.
Thus my Scr with the 039 gasket, comes to;
753.5+(63+5+8.8 less 1.5 deck) divided by (75.3) = 11.01 nominal
With the 028 gasket at zero-deck the total chamber volume was
753.5+(63+5+6.8 plus 2.5 deck) divided by (77.3) = 10.75 nominal
Jus saying ........
BTW,
I own and have torn down five early 340s, and every one of them had pistons poking up above the decks. However, with those big X-head chambers, The Scr was never anywhere near the advertised 10.5, the numbers I recall were closer to 9.7.
BTW-2,
From my experience, for a streeter, cylinder pressure makes heat, makes torque, especially in the low to midrange. On the street, I would gladly sacrifice high-rpm power for ftlbs at 30/35 mph, in 1.92 Second gear.
and I ain't accepting it with rear gears, if it means that I have to scream down the hiway to get it;
and I ain't running more than 3.55s.
and, I'm not dropping it into first.
And I'm not building a bigger engine!
That just leaves pressure.
I liked 195psi;
185 is what I have today, with the bigger cam, and it's just not the same.
When I up-cammed and lost a bunch of pressure, I was almost devastated. I spent all summer looking to find the lost torque. A new lower first gear finally satisfied me.
When I installed KB107s, they came in pretty much all of them, at .012 below deck, which at 4.045 bore is 210.5 cc per inch, and 012 below deck is thus 2.52 cc.; calculated/not measured.
My block is a 1971.
The first time I assembled this engine, I did so by cutting the block to zero deck, and I used the 028 gasket for a Squish distance of .028
At the first scheduled freshening, the following winter, I noticed that the 028 gasket was migrating towards the valley in several places. Bad news,
So I tore the engine right down, and decked it again so I could use the FelPro 039.
The new deck height was .007 pop-up, for a Squish of .032.
In subsequent freshening , the Felpro did fine and I even reused it more than once.
My heads are Edelbrock closed chambers; measured at 63cc
My KB107s are ~5cc eyebrows, per pair, not measured, stated in the catalog.
Thus my Scr with the 039 gasket, comes to;
753.5+(63+5+8.8 less 1.5 deck) divided by (75.3) = 11.01 nominal
With the 028 gasket at zero-deck the total chamber volume was
753.5+(63+5+6.8 plus 2.5 deck) divided by (77.3) = 10.75 nominal
Jus saying ........
BTW,
I own and have torn down five early 340s, and every one of them had pistons poking up above the decks. However, with those big X-head chambers, The Scr was never anywhere near the advertised 10.5, the numbers I recall were closer to 9.7.
BTW-2,
From my experience, for a streeter, cylinder pressure makes heat, makes torque, especially in the low to midrange. On the street, I would gladly sacrifice high-rpm power for ftlbs at 30/35 mph, in 1.92 Second gear.
and I ain't accepting it with rear gears, if it means that I have to scream down the hiway to get it;
and I ain't running more than 3.55s.
and, I'm not dropping it into first.
And I'm not building a bigger engine!
That just leaves pressure.
I liked 195psi;
185 is what I have today, with the bigger cam, and it's just not the same.
When I up-cammed and lost a bunch of pressure, I was almost devastated. I spent all summer looking to find the lost torque. A new lower first gear finally satisfied me.
We're not talkin about 360s so we're not talkin about KB107s. We're talkin about GREG'S 340 and the pistons he has, so your whole post is completely, totally and irrefutably irrelevant. You just posted to see yourself babble. "When I did this", "When I did that". Here's a clue, sparky. THIS AIN'T ABOUT YOU. So STFU.
Agree with post #76. Best idle timing is going to be 25*...or possibly more. Low compression engines have larger chamber volumes, takes the mixture longer to complete the burn.
Those pistons with the huge valve reliefs look similar to the rebuilder pistons I used in a Pontiac 400. They took up 17cc.
Those pistons with the huge valve reliefs look similar to the rebuilder pistons I used in a Pontiac 400. They took up 17cc.
They remind me of Pontiac pistons, too. I almost said it.
Over the Spring of this year, I built a 1990 roller 360 alongside FABO member RBConvert who built a 5.9/408.
The roller is going to go into this car:
This Dart has a late 70s 360 that runs fine but I'd like to use it in this car:
I had this idea....build this 340 and use the black Dart as a mule to break in the cam, then put some miles on it until I know the cam survived. Then pull the 340 and install the roller 360 which will stay.
The roller is going to go into this car:
This Dart has a late 70s 360 that runs fine but I'd like to use it in this car:
I had this idea....build this 340 and use the black Dart as a mule to break in the cam, then put some miles on it until I know the cam survived. Then pull the 340 and install the roller 360 which will stay.
The four door will be cool. I'm kinda lookin for us a four door "something", Dart or Valiant. Preferably early Valiant like Vixen to help take some of the usage off the Escape. It just turned 200K last week.
RRR thank you for commenting on the way that members respond to posts. I believe that I am guilty of responding subjectively as well.
Being a "barnyard-builder" on a budget, it becomes easy for me to place comments into "my subjective reality" and miss the point at hand:" We're talkin about GREG'S 340 and the pistons he has."
In my case, the only weighted experience I have to offer the group comes from the projects that have worked in my favor, and the hard lessons learned from stretching my reality (a combinations of parts) beyond their intended application.
In the end, I have learned engine dynamics from both those I appreciate and those who "push the envelope" of my patience. It's a privilege to have the commentary of other gear heads at ones disposal.
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