Technical LA 318 and getting proper quench, possible?

I guess LA 318’s have the piston way down in the holes. Some internet talk of using KB 1.81? wrist pin height pistons for the newer Magnum engines.

Anyone have experience with this? I don’t mind spending up for the pistons, but engine might make 200-225 HP. It’s the early 70’s, 1.78 intake valves.
I’d just like a decent quench, not high compression. I suppose it has the open chamber heads as well, another reason I’m I’m not worried about going high dome pistons for compression ratio, just after a proper quench.
Thanks.

 

66-67 273's had close chambered heads.

 

That would get SCR up, but will still leave a poor quench.

 

I guess I should add, engine was rebuilt some 20+ years ago, never made it into the destined engine bay.
So it’s .030 over, heads gone through-may still need to look at hardened exhaust seats) but I need to tear it down to clean and re-lube it, so block will be apart.
Once I pull the heads off, I’ll know how deep the pistons sit. IIRC, stock wrist pin height is 1.74? But my assumption is “rebuilder” pistons were used.
So even with the KB pistons, may not have any fudge factor to square the decks.
But I guess I’m asking if it’s the right approach to take.

 

MANY...early engines had the pistons way down (.11" - .13"). Nothing new.
Good choice in different pistons (or rods), to "fix" the original design.

Mike

 

I was thinking most all the Mopar's had hardened seats. I know it was much harder to grind the seats on a Mopar than on GM or Ford heads.

 

'Proper' quench will be hard to attain when the piston is so far down.
Not too sure about the LA, but on B&RB engines the piston is quite close to the deck before quench becomes a solvable problem.
If you need a guide, consider duplicating the E58 360 parts list. Also, consider looking for/buying a copy of one of the older Mopar Engine Manuals. Complete recipes for the Mopar engines.

 

No idea on early 70’s stuff. Although I hand cut the seats on 218’s from the 40’-50’s, and you sure could tell the difference.
So, more research needed

 

That’s what the Google rabbit hole led me too. 60-80 in the hole from factory was normal. I’d have to re-search it, but I think stock wrist pin on the LA engineer is 1.74.
So the 1.81 would work fine, as long as I wasn’t a “lucky one” and at ‘060.
Then, as mentioned, have to verify what pistons were actually used. I’m just going by the shop I went to and parts they used

 

The heads I was working on at the time were late 60's to early 70's.

 

Smog era mopars had flame hardened valve seats. Not sure exactly what years.

 

Guessing you have seen this page:
https://www.forabodiesonly.com/mopar/threads/piston-choice-on-318.31498/

And
https://web.archive.org/web/2007071...rod.com/howto/113_0304_318_small_block_build/
and
https://web.archive.org/web/2008022...cles/mopar/0667em_mopar_318_engine/index.html

 

I’d have to check out the second two links, but was led to the first one many times via Google.

 

I have to pull it apart and see where I’m at right now. I’m not looking for a ground ponding engine here, if the KB pistons get me in the ball park, then I’ll see what needs to be taken off the decks. Hopefully, something that won’t involve intake milling, no clue how far a 318 block can be cut anyways. But .025-..030 should be reasonable

 

On a stock 9.6 deck height the KB pistons should end up 12 thou down the hole
1.810" compression height
6.123" rod length
1.655" crank throw

But Check the deck clearances on a L.A block , the decks are all over the place [which is why Chrysler had the pistons so far down the hole, for quick assembly line ]

 

That’s what I have been finding via Google results.

 

The original question....getting proper quench...is not going to be (easily) possible with the open chamber heads. Yes, you can get pistons to zero deck and raise compression but a proper quench distance from piston crown to cyl head deck won't be realized. For that a closed chamber with a flat quench pad is needed. Sure, a custom piston could be made with a raised area to rise above the block deck and fill the would-be quench area in the head, but it'd take a lot of work to make the fit good enough to achieve true quench. I'm talking .035-.045" quench clearance.
I sure agree on the LA engines having pistons a mile in the hole. Decks aren't square either...often look like a potato chip. I've had to mill .045" to square them up.

 

I don't have all the numbers of all the parts and their specs tumbling around in my head.
I know quench will help wake up a combo.
It sounds like this is a budget deal, not a fresh no holds build.
With all that in mind, it sounds like this is wondering if there is a magic bullet while it's apart to add and fix the quench. Just looking at this picture tells me it's not going to have an off the shelf fix.
It will probably require machining the heads, block and a custom piston that works with the current overbore and probably honing for the new rings. That may require different pushrods, intake machining and checking dist fit, along with other possible fitment. If that depth of engine mods floats your boat, go for it. But it's to the point where any answers will depend on measuring what you have as you disassemble and coming up with a plan based on hard numbers of the components you have. It is probably not going to be cheap. I dig SBMs, but the architecture is not the best for max performance.

 

Find some 80s 318, #302 heads. Closed heart shaped chamber, hard seats, larger valves, better ports. They might not get you what you want... but they will get you close. Gene.

 

I just read about using the 318 Magnum heads as well. From ‘94-‘0? 62 CC heads and closed chambers. 80’s heads may be tougher to locate. But worth a look as well.

 

If I remember right, magnum heads use different rockers, valve covers and intake and maybe? exhaust manifolds.
At least in my area, #302 heads aren't that terrible to find. I just sold a pair that was slated for a 360 build... until the guy that owns the motor said he wanted 400+ H.P. Neat heads, but not doing that with them. Gene.

 

That’s what I read as well, and push rods too.

 

Yeah, it depends on how deep you want to go.
Around here, the CL stuff is slim pickings. It would be a tossup on finding a good set of rebuilt heads as it would to grab a complete core from the U-Pik-It.

https://www.headsonly.com/product/dodge-magnum-v-8-rebuilt-cylinder-head
300 each w/shipping

https://upickitaz.com/parts-pricelist/
V8 ENGINE W/ ACC ENGINES 400.00 core 95.00
V8 ENGINE W/O ACC ENGINES 295.00

At that point, you have a rebuilt short block that needs to be QA'ed and a pair of heads that need extra parts, or a roller bottom end and a complete matching top end that all need some reconditioning. Mounts could be another issue if going full engine.

 

If I get them from the Pick and Pull initial out lay is less. Then to a shop for rebuild, be a wash $$ wise probably, but can see what I have ahead of time. Plus take the VCs and rocket arms as well.

 

I just picked up a 318 with 904 for my Dart project. I’ve been doing a little research. The engine has good compression and runs ok. I’ll be adding a 4 bbl intake and carb. With some help and guidance from @carbking i’ll be running a 500 cfm AFB. Also will run a Mopar electronic ignition with vacuum advance and a spring kit. Sometime down the road I’ll add a performance cam.
My understanding in talking with and reading stuff from other 318 owners is that original smog heads are ok. The 302 heads are better but usually by the time you get done buying, rebuilding, porting etc, you might as well buy an aftermarket head which will outperform the 302 heads. The stock heads will support 250+ hp. Pistons anre indeed down the hole you either have to deck the block and/ or use different pistons.
I understand the desire to get a good quench area but is it needed or justified. I guess that depends on the intended use. I believe 250 or more HP is attainable with simple performance upgrades 4 bbl, headers, ignition and cam and should work well on pump gas and be reliable. There are some thin head gaskets available to help a little. If you want 400 Hp just follow the recipes posted above. I’m signed up on thread and interested in your results.
Dan

 

Well, block was machined, to what depth, don’t know yet. Has to come apart for clean and lube. Sitting for 25 or so years.
Once heads are off, I can get an idea (rough) of deck squareness, I see the standard 318 magnum pistons have a .020 taller pin height. So that gets some back, but the deck will tell the reset of the story.
It’s not about the most I can get out of it, but I like efficiency, 200/225 HP would be fine. Truck only weighs 2400? have to look at the data plate again, so not pushing a lot of weight around.
And too danged old to street race

 

If it is really strictly a street car, chasing quench is a waste of time and money for the benefit you receive.
I've had a lot of 318s that put a lot of hurt on much larger displacement motors with a 4bbl carb, dual exhaust, a good timing chain, the correct cam, a good tune up, and a rear gear ratio better then a 2:76. Knowing how to drive without smoking the tires also helps.

The stuff required when you race a clock and another car for a 1/4 mile isn't the same as the stuff you need on the street.

But, according to some of the experts here, all those 318 I ran must have been the rare good ones Chrysler built.

 

Another article on pistons and quench
https://www.forabodiesonly.com/mopar/threads/318-pistons-and-quench.302610/
Dan

 

Does that include fuel economy? Because to me it sounds like that's what he's aiming for, and while being faster than other cars may be fun you aren't allowed to go very fast on public roads anyway.
Spending some time and money on optimizing an engine for fuel economy when it has to come apart anyway may make very good sense - and fuel won't be getting cheaper in the future.

 

Yes this is true, however optimizing the quench may likely get the engine into a pretty high static compression ratio maybe 10:1 or higher which will likely cause detonation and require more expensive higher octane gasoline. It’s really a balancing act in my opinion. A stock 8.5:1 compression 318 can get decent fuel economy especially if the fuel system, cam and ignition are picked for fuel economy. Both power and economy should better with some well thought out performance upgrades. Even the stock smog heads work pretty well as the small ports and valves keep the flow velocity high. Chasing the quench area which I believe is in the 0.040 to 0.050 range is something that only @Budget36 can determine if
he wants to pursue or not.
Dan