Well to say it cannot make power with low compression pisses all over the 73 340 and the 78 and 79 360 in the Lil Red express trucks. Those engines were far from slugs. Yall been readin WAY too many magazines and suckin the forum lollipops.
LA360 compression
- Thread starter Matt68
- Start date
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Here is your 360 short block:
Here is a .030 over 360 with stock height replacement pistons:
Is being assembled with stock J Heads, and new stock size 1.88/1.60 valves.
Have the option to install the heads with the .028 ths thin head gaskets to bump the compression a tad.
Also this build has the 340 cam and stock early 340 square bore intake manifold.
Going to run out just fine as is, and won't break the bank in the process.
☆☆☆☆☆
Here is a .030 over 360 with stock height replacement pistons:
Is being assembled with stock J Heads, and new stock size 1.88/1.60 valves.
Have the option to install the heads with the .028 ths thin head gaskets to bump the compression a tad.
Also this build has the 340 cam and stock early 340 square bore intake manifold.
Going to run out just fine as is, and won't break the bank in the process.
☆☆☆☆☆
☆☆☆☆☆
From what most say even the 10.5:1 340 was only 9.5:1 cause of tolerances, read a stock copy build/dyno of 375hp 440 magnum and they said factory pistons were way down the hole to, the cr was way bellow stated. Seem like many of these 60's engines were really never high cr to begin with wonder if Ford and Chev were similar.
Dale Davies
Well-Known Member
IMHO, he does not want to finish the engine as is. Your car is at a full service shop, so they should be qualified to:
1: measure the deck height and show you the exact value.
2: they can install the intake manifold and accessories and get the engine installed.
3: I would take your short block and heads to them to finish.
IF the deck height is 0.100"+, I would be inclined to veify the stroke, piston CD and rod length. Stroke is easy once you install a degree wheel and use a piston stop to find true TDC. Rotate to BDC and measure from deck surface to the piston crown directly over the wrist pin. Then rotate to TDC and measure in the same place. The difference is the stroke.
Pull one rod and piston assembly out and measure the pin bore diameter in the piston and divide by 2. Measure from the top of the pin bore to the top of the piston crown. Add the 1/2 pin bore to get the piston CD. Now you can compare that to what the KB spec is for the piston.
Slant six run with an obscene piston below the deck surface which is definately not optimal.
The Stove Bolt Chevs were the same. You can mill 0.070"" off the deck to achieve zero deck and then 0.090" off the head to increase the CR and quench.
It is up to you if you want to go all out on this build. Don't be pushed into something you don't want or you can't afford.
Don't know what piston you are running, but if KB's as indicated and they
One thing that I don't think has been mentioned is the rods. If a story was told about the pistons, then I would want to check if new rod bolts were used and rods rebuilt. This is likely why builder mentioned stroker- buy the rods and pistons and you are most of the way to the cost of a cast crank stroker bottom end. It
If you are interested I will make you a good deal on a all new stroker kit I have.
If you are interested I will make you a good deal on a all new stroker kit I have.
Matt68
Well-Known Member
@mgoblue9798 , sent you a pm.
How is ya Karl?
Matt68
Well-Known Member
Yeah Karl, really good to see you. Its been awhile. Miss your humor! By the way, one of my all time favorite movies.
Really? Dangit. I've watched it several times trying to feel it, but I just caint get into it.
I remember great quotes like:
"Nice tie, Ty"
"This is your saliva line"
"What's a saliva line?"
(She licks his palm) "it shows how hot I can get you"
Carl is the best though!
"Cannonball, Cannonball"
"you can play 36 holes on it in the afternoon, take it home and just get stoned to the bejeezus-belt that night on this stuff."
I'll toss my2c in here as I just freshened up the 360LA last summer in my 74 Challenger. It's not high compression either, build thread here: 360 LA installing Promaxx Aluminum heads. The smaller closed chamber heads got it just over 9:1 using a stock thickness Felpro 1008 head gasket. It has .030 (dished stock pistons) that are .100 in the hole with a mild cam .480/.480 using 1.6 ratio rockers, and Promaxx 63cc aluminum heads topped with an air gap intake and Holley 625 & TTI shortys. It's not a dog... pulls my Challenger around town just fine. Unless you are chasing ET's at the track.. 400HP~400Ftlb torque is plenty fun. Run it as is and don't change a thing.
Matt68
Well-Known Member
Well, I've returned the Speedmaster 68CC Heads and I am just going with a rebuild of the late 80's swirl port 714 heads that were on my 318. Anyone know the combustion chamber size of a stock pair of 714's?
Dan the man
Well-Known Member
KB-107 pistons have a 1.675" CH. With a stock block they should be no more than 0.012" below the deck surface. Who ever figured a 0.100" is way off.
Dan the man
Well-Known Member
I used the NGK compression calculator and with kb107 pistons 0.012" below the deck and 68cc heads,0.039" thick headgasket with pistons having 5cc valve reliefs and a 4.030" bore stock stroke, I got a compression ratio of 9.90:1. I don't know how your machine shop came up with 8.0:1
Read the thread and you will know.
Matt68
Well-Known Member
@Dan the man , because it's been decided that they are not KB107's like I was told. They might be KB's, but they are a flat top piston and have no reliefs like the 107's. They are definitely sitting about .100 below deck. The above pic of the orange block is mine.
Dan the man
Well-Known Member
It's a bummer that you was miss lead about the pistons. 8.25:1-8 5:1 compression motor can be made to run good. Good luck with your project
My money says they are Silvolite stock replacement pistons.
Why would you return the heads?
QUINN FORBES
Greendemon
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