LA 318 advice
- Thread starter Baggs
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Wasn't there a guy on here that wanted to do just that? Wonder how it worked out lol
Dan the man
Well-Known Member
Why waste money going to a smaller bore?
junkyardhero
Well-Known Member
uhhh, doy. lighter pistons.
junkyardhero
Well-Known Member
Dan the man
Well-Known Member
I'd rather have the better breathing capacity of the bigger bore.
Never heard of sarcasm ?
junkyardhero
Well-Known Member
*unfurls large spread sheet*
behold daniel!
we call this "RPM"...
bask in its glory!
PRH
Here is a picture of a 1968 318 stock flat top piston with the valve reliefs, 9.2:1 cr.
See what you can make of this. Did this comparison 4 years ago, the '68 318 stock piston on the left and a '75 318 piston on the right.
As you can see the '68 piston on the left has the taller Compression Height.
Here are stock '69 pistons in a stock bore 318 block.
.040 ths down in the hole.
☆☆☆☆☆
Dan the man
Well-Known Member
Since we’ve went off the rails a few times here… I didn’t ask exactly how worn out the 318 is, but hows about this with a 48/65 (26%underdrive) pulley setup look to you. I really was wanting to pull the trigger on one during the Black Friday sale…
Chrysler Mopar SB 318 360 LA Complete 6-71 Roots Supercharger Blower Kit
Chrysler Mopar SB 318 360 LA Complete 6-71 Roots Supercharger Blower Kit
Newbomb Turk
Well-Known Member
This is another great option right here. A compression increase plus a little stroke won't hurt a thing.
PRH
Well-Known Member
Thanks for that.
Which ones have the valve pockets?
The tallest stock replacement pistons I’ve come across were the TRW forged L2329F, which are listed as having a 1.759” ch, and valve pockets worth 1.5cc.
Newbomb Turk
Well-Known Member
My issue is, and still is even if he changes the pistons he will still be down the hole. a lot. So he still needs to deck it. We can all spend as much of his money as we can but it doesn't need top be that way.
Your premise that once the block is deck and the manifold fitted it's a one off, unusable piece and that's just wrong.
I've explained this before. There are no good choices for pistons with stock stroke lengths. If the piston is .090 down the hole and you get a piston that get's you to .040 down the hole you still have to mill it. Or you should if you are in there.
If he decides down the road to go with a stroker the block was still too tall.
Saying the manifold ONLY fits that block and heads is wrong. Let's say he mills the heads (the intake face and not the manifold) then you still have the same issue. Those heads only fit that short block and manifold combo.
Making the assumption that every manifold right out of the box is going to drop right. That does not happen in the real world. That's why I asked about your experience. It matches exactly what you say it does.
If you are going to test multiple manifolds and spend the time and money to do it, a smart engine builder test fits every intake going to be tested. You'd look pretty bad if went to drop on an intake and one or more of them didn't fit.
The real world isn't like forums.
Newbomb Turk
Well-Known Member
From the tallest to the shortest we have a total of .030. When the piston is that far down the hole .030 isn't much. Then you have variations in the blocks deck height, stroke and rod length differences...which is why engines get blueprinted.
@PRH
Just measured the compression height on this original stock bore '68 318 piston.
Comes in at 1.77 ch, just as stated above for the '68 - '69 318 engines.
Free Floating Wrist Pins too.
These fit the stock bore 318 blocks.
The Sealed Power 526AP come in at 1.754 ch, and are only available in .020 and .030 overbore.
Stock Bore '74 318 block ready to go for the '68 9.2:1 cr pistons and light free floating stock rods.
Pistons will be .040 ths down in the hole.
And @66fs thanks for this too:
* * * * *
PRH
Well-Known Member
Thanks for that.
FWIW, my sealed power catalog shows the 526AP piston to have a 1.745 ch.
Obviously, for the OP’s original build to end up with pistons down the hole .100……..that’s what happens when the person ordering the parts isn’t paying attention to the details.
Out of curiosity I looked up the NHRA blueprint spec for deck clearance on a 69 318.
It’s .029” down.
FWIW, my sealed power catalog shows the 526AP piston to have a 1.745 ch.
Obviously, for the OP’s original build to end up with pistons down the hole .100……..that’s what happens when the person ordering the parts isn’t paying attention to the details.
Out of curiosity I looked up the NHRA blueprint spec for deck clearance on a 69 318.
It’s .029” down.
Kind of fun looking at side by side comparison of a '68 318 piston on the left and a '75 318 piston on the right.
Check the location of the wrist pins, and the ring land positions between the 2.
☆☆☆☆☆
Check the location of the wrist pins, and the ring land positions between the 2.
☆☆☆☆☆
I am not sure, my book does not list them. I mostly built 273's and 340's since they were high performance. Not many 318's needed rebuilding, they ran good forever. I did install 360 heads, cam, and 340 induction on more than a few 318's though. Rarely replaced pistons, as the short block was usually OK and the owner did not want to spend the coin.
Offset grinding with stock rods and undersize bearings? Any cautions when going with 2.1 or 2.0 Chevy rods with a factory crank?
Newbomb Turk
Well-Known Member
No but you need to go to 2.00 inch throws to get any real increase in stroke length.
Then you need to find a 6.125 long SBC small journal rod.
Then you need to get the pin ends to .984 diameter.
It’s not a simple operation.
PRH
Well-Known Member
At the shop I was working at in 1990 there was a disassembled, “remanned” 318 in the core pile.
It had been there since before I started, and I had no idea what the history was.
One day I decided to see what the story was.
I really couldn’t find any reason it had been disassembled.
It was already .040 on the bores, and the crank had been ground.
Stock reman job on the open chamber heads.
So I figured I’d clean it all up, get rings, bearings, gaskets, do some whittling on the heads(175-ish cfm) and put it together.
I had a used Perfect Circle brand 340 replacement cam that went in it, and I bought a std performer for it.
I never measured anything, so no idea what the actual CR was, but I seem to think the pistons weren’t near the top, and the heads just got a clean up cut.
I did run it on the dyno.
I ran a few carbs on it…..tried some spacers, moved the timing all around…….didn’t quite make 300hp.
I think the best was low 290’s with a 650DP on an open spacer.
All testing was done with 1-5/8” headers.
I sold it a guy I knew who put it in a Ramcharger, and it was a nice improvement over the stock 318 that came out.
So, it takes a pretty low effort to get close to 300hp.
It had been there since before I started, and I had no idea what the history was.
One day I decided to see what the story was.
I really couldn’t find any reason it had been disassembled.
It was already .040 on the bores, and the crank had been ground.
Stock reman job on the open chamber heads.
So I figured I’d clean it all up, get rings, bearings, gaskets, do some whittling on the heads(175-ish cfm) and put it together.
I had a used Perfect Circle brand 340 replacement cam that went in it, and I bought a std performer for it.
I never measured anything, so no idea what the actual CR was, but I seem to think the pistons weren’t near the top, and the heads just got a clean up cut.
I did run it on the dyno.
I ran a few carbs on it…..tried some spacers, moved the timing all around…….didn’t quite make 300hp.
I think the best was low 290’s with a 650DP on an open spacer.
All testing was done with 1-5/8” headers.
I sold it a guy I knew who put it in a Ramcharger, and it was a nice improvement over the stock 318 that came out.
So, it takes a pretty low effort to get close to 300hp.
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