1968 318 questions

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Justin Sykes

Justin Sykes

CrewCabDart
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I recently scored a ‘68 318 for my ‘69 Dart. I’ve heard lots of good things about the earlier 318 blocks being beefier and the ‘68 318 having 9.2-1 compression ect ect. Anything special about the crank or rods? I also noticed it has open chamber heads, so if i put my closer chamber 302 heads on what kind of compression might I be looking at there? Blocks getting torn down and rebuilt, but i’d just like to know what to expect to find. Thanks all!

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I don't remember my '68 having pistons like that, but it's probably a cast crank like mine was. You will get an increase of compression, but I would honestly be surprised if that combo had over 9:1 as is.
 
First off the blocks aren't any heavier than other 318 blocks. A 68 should have a steel crank instead of a cast crank which is good. The #302 heads will add about a half point of compression so you are looking at about 9.5/1 or so.
 
If you are going to go automatic, don't those still have the "small snout" crank?
 
My 69 318 is basically the same (9.2:1). I removed the original heads and checked the CCs, they were 69ccs. I had a set of 302 heads and checked the ccs, they were 69 ccs. I swapped them out and it gave me no great benefit except for the closed chamber. So to answer your question.....the 302s should work just fine with no loss in compression. You can easily check the CCs with a large syringe (irrigation syringe), won't cost you more than a few bucks?? CCs = ml
PS- the valve you use can also increase your compression!
PS, PS - 302 heads have hardened valve seats....A big plus if you plan to use our newer gas formulations!!!

Bard Piston Syringe with Resealable Bag 60cc

https://www.amazon.com/dp/B002JLJDQ0/?tag=fabo03-20
 
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Justin Sykes said:
I recently scored a ‘68 318 for my ‘69 Dart. I’ve heard lots of good things about the earlier 318 blocks being beefier and the ‘68 318 having 9.2-1 compression ect ect. Anything special about the crank or rods? I also noticed it has open chamber heads, so if i put my closer chamber 302 heads on what kind of compression might I be looking at there? Blocks getting torn down and rebuilt, but i’d just like to know what to expect to find. Thanks all!

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the 1968 heads are they 675 casting heads? if so I mill .025 to .030 off then and use those instead of the 302 heads and sell them to someone for 300 or 400. They are not up to open chamber heads standard without some work, chamber and intake port work. A #675 head is a superior head in terms of flow and flow potential AND durability. The 302 is like a fast burn chevy head... great idea that's destroyed by penny pinchers who wanna save $ by producing thin castings. The 302 heads problem is a multitude of things... shrouding, cracking, they came on trucks mostly if not exclusively and therefore have the non passenger car valves which are heavy and bulbous at the stem transition to head and impede flow.
They can be made good, but it's not worth It when you can't escape the cracking. If you dont have a flow bench to work with them...you're guessing and could be doing work for a 1/4 the return.

Those pistons, look like badger or sterling brand. Clean the center and look for an overbore stamp, I think it's been rebuilt.
 
Those dished pistons do not look like the '68 - '69 flat top 9 2:1 with valve reliefs.

Here are the pics of '69 Pistons below and I have another set of '68 pistons that look just like them, factory mopar 318. They sit .040 ths down in the hole at TDC, and have full floating rods.

318 3.jpg


302 Heads, 714 castings are the same head too. Work out nice, even have bigger push rod holes in them from the roller engines they came out of.
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George Jets said:
Those dished pistons do not look like the '68 - '69 flat top 9 2:1 with valve reliefs.

Here are the pics of '69 Pistons below and I have another set of '68 pistons that look just like them, factory mopar 318. They sit .040 ths down in the hole at TDC, and have full floating rods.

View attachment 1715595850

302 Heads, 714 castings are the same head too.
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My original pistons (69 318) were .030 down in the hole.
 
Actually a 69 318 being the casting date is 10-31-68 but there is nothing special about 68-69 318's...
 
Justin Sykes said:
I recently scored a ‘68 318 for my ‘69 Dart. I’ve heard lots of good things about the earlier 318 blocks being beefier and the ‘68 318 having 9.2-1 compression ect ect. Anything special about the crank or rods? I also noticed it has open chamber heads, so if i put my closer chamber 302 heads on what kind of compression might I be looking at there? Blocks getting torn down and rebuilt, but i’d just like to know what to expect to find. Thanks all!

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Click to expand...


You can use this thread to see what compression your components make:

How to Check Compression
 
Treblig said:
My original pistons (69 318) were .030 down in the hole.
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I'm thinking more like Mopar had more Nickel in them to begin with and not like any others had any more or less for the la.
I do believe that the 318 from 67 to 71 to 72 have thicker cylinder cores... unlike 302 heads which are thin pieces of **** but some people just 'Romance the stone' over anyhow due to their limited production...in which Chrysler killed them realizing that they were a piece of **** and just went to a magnum head with a little bit bigger volume intake port and better chamber.
I can about guarantee if you took an engine and swap just a heads from 675's to 302's that they wouldn't make any more power.
Maybe 4cc worth of power in squeeze...but then loses it from the shrouding and bulbous valves stem. I know of 2 sets, on running motors...n I bet they're cracked. Why bother. I could get them, port them up and no one would want them...not when it comes to spending on them, that's how not good they are.
 
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MOPAROFFICIAL said:
I'm thinking more like Mopar had more Nickel in them to begin with and not like any others had any more or less for the la.
I do believe that the 318 from 67 to 71 to 72 have thicker cylinder cores... unlike 302 heads which are thin pieces of **** but some people just 'Romance the stone' over anyhow due to their limited production...in which Chrysler killed them realizing that they were a piece of **** and just went to a magnum head with a little bit bigger volume intake port and better chamber
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Come on MOPAROFFICIAL!! Take off the gloves and tell use how you really feel about 302 heads......:rofl::poke:
 
I had a pair I stored for 15 yrs, off a running truck.... took them in, cracks off the I take seat toward the chamber/plug more in between valves. Never leaked coolant.. but it's a time bomb. And the seats can burn out with a crack across them. I stored garbage for 15 yrs. Lol. Every set since has been cracked, I can see it in the yard, dont even need to pay for them. Last one I sent through the windshield of the van I was so irritated . 714 might be a better casting
Chambers are overrated till you get to mountain tops of power making, then they can be a holy grail...but that's miles beyond what 302 head guys are doing. ..and that's the WORNG chamber shape.
 
MOPAROFFICIAL said:
I had a pair I stored for 15 yrs, off a running truck.... took them in, cracks off the I take seat toward the chamber/plug more in between valves. Never leaked coolant.. but it's a time bomb. And the seats can burn out with a crack across them. I stored garbage for 15 yrs. Lol. Every set since has been cracked, I can see it in the yard, dont even need to pay for them. Last one I sent through the windshield of the van I was so irritated . 714 might be a better casting
Chambers are overrated till you get to mountain tops of power making, then they can be a holy grail...but that's miles beyond what 302 head guys are doing. ..and that's the WORNG chamber shape.
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There, there....don't you feel better now???:lol::poke:

The set I had never cracked, guess I got lucky??
 
MOPAROFFICIAL said:
I had a pair I stored for 15 yrs, off a running truck.... took them in, cracks off the I take seat toward the chamber/plug more in between valves. Never leaked coolant.. but it's a time bomb. And the seats can burn out with a crack across them. I stored garbage for 15 yrs. Lol. Every set since has been cracked, I can see it in the yard, dont even need to pay for them. Last one I sent through the windshield of the van I was so irritated . 714 might be a better casting
Chambers are overrated till you get to mountain tops of power making, then they can be a holy grail...but that's miles beyond what 302 head guys are doing. ..and that's the WORNG chamber shape.
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Interesting that almost every performance cylinder head has chambers like all the closed chamber small block heads Mopar ever produced. Closed chamber must work.
 
toolmanmike said:
Interesting that almost every performance cylinder head has chambers like all the closed chamber small block heads Mopar ever produced. Closed chamber must work.
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If you read it again, it's the wrong shape, not ..closed is bad. If it were the right shape..it would have carried over, for lamen sake.
Magnum chamber design is better than the 302 chamber design. Most aftermarket heads that are closed..are based on the magnum chamber, not the 302.
If you think about it using that angle for an argument is putting you right there with saying that a small block Chevys closed chamber is good, just because its closed...and really the 302 chamber is better than a small block Chevy closed chamber , just not better than a magnum chamber aka the industry standard.
slippery slope :poke::popcorn:
 
MOPAROFFICIAL said:
If you read it again, it's the wrong shape, not ..closed is bad. If it were the right shape..it would have carried over, for lamen sake.
Magnum chamber design is better than the 302 chamber design. Most aftermarket heads that are closed..are based on the magnum chamber, not the 302.
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I wouldn't expect the manufacturer to design and produce the very best, optimum, chamber right out of the bucket. It's a constant improvement in design. I wonder what the 60's closed chamber heads looked like? Probably not the optimum design. (regardless of car company) There isn't too many optimum choices of Mopar small block heads with closed chambers. We're talking 318 here and not big bore 340/360 big valve/ big port heads. 920's are good, #302's are good and so are Magnums. #302's have hardened seats as do the Magnums but they take a list of parts to make them work. Just sayin'.
 
toolmanmike said:
I wouldn't expect the manufacturer to design and produce the very best, optimum, chamber right out of the bucket. It's a constant improvement in design. I wonder what the 60's closed chamber heads looked like? Probably not the optimum design. (regardless of car company) There isn't too many optimum choices of Mopar small block heads with closed chambers. We're talking 318 here and not big bore 340/360 big valve/ big port heads. 920's are good, #302's are good and so are Magnums. #302's have hardened seats as do the Magnums but they take a list of parts to make them work. Just sayin'.
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Do you have any 1964 273 heads?
 
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