340 the hard way; Stroked 318

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bschubarg

bschubarg

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Bored one night surfing E-bay for good deals when....

I saw a RV grind camshaft ( 204@.050/.420(int)214@0.050/.442(ex) ) from General Dynamics for $25.00... new. Hmmmm.... bought it and stabbed it in my '85 LA 318 4BBl. Nice improvement and sounds really nice. Even has a lope with the unported, small valved '302 heads; I can almost lay rubber with my 2.45 open rear.

Bored one night surfing E-bay for good deals when....

I came across a set of Magnum heads from a 2002 Durango. Hmmm... $200 for a complete set....okay... I bought em and slightly ported them and put 'em on my fore mentioned LA 318. Also a nice improvement. Still can't light up the tires at will but with a power brake, I get a good launch.

Bored one night surfing E-bay for good deals when....

I came across a set of 1 5/8" Headman headers, new for $50 if you use the "Buy it now" button. Hmmm... so I "bought it then", installed them with a set of (2" in/out)header glass packs(Cherry Bombs) that bolt directly to the collectors...bought the glass packs... ready for it... on E-bay, $20.00 each.
The car is definitely louder and pulls a bit harder, but still...can't light the tires at will. Getting a little annoyed...

Bored one night surfing e-bay for good deals when....

An E-bayer is selling his new Professional Products Air Gap Aluminium intake for the LA/Magnum engine. Hmmmm... $140, sounds like a deal. Week later I installed it along with a 600 cfm Holley Vacuum 4BBL. The car is not as efficient when it comes to gas mileage as it was with the previous Rochester QJet(new intake only accepts square bore carbs), but it does look much nicer... but still can't light the tires at will, almost, but not quite...

Bored(and annoyed) one night surfing e-bay for good deals when....

I came across a forged stroker crank for a 318/340(P4529710) with a 3.51" swing. This makes a .030 318 a 342....Even though the crank is a 8 bolt flange, for $300...hmmm...bought it!

Now that I have most of the components for a nice street machine, I can, with the proper cam and compression get my 3800 lb w/ driver Magnum headed(slightly ported) 342" Mopar with headers down the track in the low 13's.

Yes, there is a question here. Since this really isn't a 340 due to the unique stroke(3.51" vs 3.31") and the rod ratio has changed(for the better I understand) and I will be using Magnum heads with the fore mentioned intake manifold and carb, how would you build the rest of the engine to achieve the goal of low 13's in the 1/4 with a 3.55 geared porker(3800 lbs).
 
bschubarg said:
Bored one night surfing E-bay for good deals when....

I saw a RV grind camshaft ( 204@.050/.420(int)214@0.050/.442(ex) ) from General Dynamics for $25.00... new. Hmmmm.... bought it and stabbed it in my '85 LA 318 4BBl. Nice improvement and sounds really nice. Even has a lope with the unported, small valved '302 heads; I can almost lay rubber with my 2.45 open rear.

Bored one night surfing E-bay for good deals when....

I came across a set of Magnum heads from a 2002 Durango. Hmmm... $200 for a complete set....okay... I bought em and slightly ported them and put 'em on my fore mentioned LA 318. Also a nice improvement. Still can't light up the tires at will but with a power brake, I get a good launch.

Bored one night surfing E-bay for good deals when....

I came across a set of 1 5/8" Headman headers, new for $50 if you use the "Buy it now" button. Hmmm... so I "bought it then", installed them with a set of (2" in/out)header glass packs(Cherry Bombs) that bolt directly to the collectors...bought the glass packs... ready for it... on E-bay, $20.00 each.
The car is definitely louder and pulls a bit harder, but still...can't light the tires at will. Getting a little annoyed...

Bored one night surfing e-bay for good deals when....

An E-bayer is selling his new Professional Products Air Gap Aluminium intake for the LA/Magnum engine. Hmmmm... $140, sounds like a deal. Week later I installed it along with a 600 cfm Holley Vacuum 4BBL. The car is not as efficient when it comes to gas mileage as it was with the previous Rochester QJet(new intake only accepts square bore carbs), but it does look much nicer... but still can't light the tires at will, almost, but not quite...

Bored(and annoyed) one night surfing e-bay for good deals when....

I came across a forged stroker crank for a 318/340(P4529710) with a 3.51" swing. This makes a .030 318 a 342....Even though the crank is a 8 bolt flange, for $300...hmmm...bought it!

Now that I have most of the components for a nice street machine, I can, with the proper cam and compression get my 3800 lb w/ driver Magnum headed(slightly ported) 342" Mopar with headers down the track in the low 13's.

Yes, there is a question here. Since this really isn't a 340 due to the unique stroke(3.51" vs 3.31") and the rod ratio has changed(for the better I understand) and I will be using Magnum heads with the fore mentioned intake manifold and carb, how would you build the rest of the engine to achieve the goal of low 13's in the 1/4 with a 3.55 geared porker(3800 lbs).
Click to expand...

Im not too much of a cam expert. but you do know you cannot use replacement 318 pistons, you'll need to find some stroker 318 pistons to work with that crank. low 13s for a 3.55 geared 3,800lbs is asking a lot out of a 318. Anything can be done if you put enough money into it, i'd look into edelbrock heads, a GOOD torque converter, and whatever cam comes recommended from the crowd. just my 2cents
 
GoodysGotaCuda said:
Im not too much of a cam expert. but you do know you cannot use replacement 318 pistons, you'll need to find some stroker 318 pistons to work with that crank. low 13s for a 3.55 geared 3,800lbs is asking a lot out of a 318. Anything can be done if you put enough money into it, i'd look into edelbrock heads, a GOOD torque converter, and whatever cam comes recommended from the crowd. just my 2cents
Click to expand...


It is going to be a 342, not a 318 with a longer stroke for more torque down low and thru out the power band.

I realize I am going to need different pistons with a different compression height. The new stroker crank is going to put the piston 0.100 further up the bore...

I am interested in compliments to the existing components from those who are familiar with camshaft theory and this fairly unique stroke for a 318. Specifically, piston C.P. and compression ratio along with Hypers or Forged.
Camshaft specs with what LSA and duration for the Magnum heads and new stroke.

I guess.. just what other parts would you add to get this 342... moving....?
 
Since you asked about it, here are the full specs on my cam if your interested.

Comp
#20-311-4
CRS 270AH-10

Cam Specs - Int - Exh
Adv Duration 270 - 280
Dur @ .050 224 - 230
Lobe Sep 110
Valve Lift .470 - .480

:D
 
So you basically have a short stroke small bore 360 ;) . The cam will need to be bigger. I wouldnt look too far. Anything in the 220-230° @ .050 will run nice, but the 230 ones may be too lumpy for power brakes and stock convertor. I dont see the Magnum in the 13s wiothout some better help. Help like gearing, help like stall speed. BTW, the 8 bolt flange means the $75 SFI approved flex plate too if you have to buy one. Just look under "Hemi", and I dont know if you'll find one with the small attaching bolts for the convertor, so the bolts you have will not be "right". They will work, but should be upgraded with a better convertor. IIRC the real reason for that crank is to make the 340s clear the 365" rule for dirt tracks.
 
I used a comp 280H cam in my 370 and it ran a high 13 leaving in 2nd gear with no posi and street tires. I think that that would get you close to what you are looking for. If not I would try to go up a little but no higher than a .510in lift cam if you are going to do much driving on the street with it. By the way that was with a stock slant six converter and it worked great.
 
The MP P4529710 Forged crank was indeed designed to clear the 365" rule and better compete with the small block bow ties. I did a "Google" and came up with some interesting blogs behind the P4529710.

I also did purchase the SFI Flex Plate, but didn't realize that it requires a larger bolt to secure the converter.....damn....

I have also decided to regrind my existing roller camshaft for my '85 Block that came originally with a roller.

Cam Specs - Int - Exh

Dur @ .050 226 - 230
Lobe Sep 111
Valve Lift .474 - .474(@1.5)
valve Lift .502 - .502(@1.6)

I have the stock Magnum rockers @ 1.6 and purchased the matching springs(P4876062) for the above cam.

I kept the same lift but a bit more duration on the exhaust side. I have performed a mild port on the intake, but a more aggressive port on the exhaust. So I think the intake to exhaust ratio is more equal requiring less lift and duration otherwise.

Now on to the pistons....

I plan on zero decking with the 3.51" crank and moper was kind enough to offer some suggestions. Measurements on a stock block with a 9.599 block height indicate that a compression height for the piston should be 1.721. There are ready available pistons that are 1.741. Is it possible to shave 0.020 off the top of the pistons or am I playing russian roulette? I don't plan on revving it past 6K and everything will be balanced.

BJS Racing has lit a fire under my butt with his post. 13 second car with a 370cu in. with a 280H. Tell me that wasn't with a 2900 lb car and and 4.56 gears....!

Thanks again guys for your input....
 
When you had this 318 apart did you happen to measure the distance the slugs are down in the hole? you may be able to use the ones you have.
The last 318 I measured they were .110 in the hole, so the thought was to use a 360 crank - take .025 off the top of the 318 pistons and end up with a 10.0CR motor with open chamber heads.
As you have closed chamber heads you may have a CR problem -too high.

IMO you need to do some carefull measuring of components to get some data on what you have before you purchase pistons etc.
block deck height? (not all small blocks ended up 9.599 - I had one that was stock 9.582)
top of piston to top of deck?
cumbustion chamber CC?
Altitude at your location? I'm at 3200ft so a calculated 10.4CR still runs fine on pump gas.
Idealy you wouls want to end up with a zero deck motor so a ,040 gasket gives you the proper quench, The same can be obtained for example with a piston sticking .014" above deck and a .054"th head gasket. Food for thought.
 
Excellent post 388dart.

Currently the piston i have now sits 0.085 in the hole.
Combustion chamber is 59cc.

I live at sea level here in Miami Florida.

I was planning on using a 0.040 head gasket with my zero deck. Never thought of possibly going with a thicker gasket should the piston be + zero deck.

I figure, if I can get close with a off the shelf piston, I could make up for the zero deck goal by decking the block or using thicker gaskets.

Finally, I don't plan on using the pistons I currently have in the 318 now. I have to freshen up the bores and I want to use moly rings.

Thanks again 388dart....
 
I would think a small fly cut on top of the pistons will be all thats needed not a biggie - if at all. Measure your deck heights like someone else suggested on the pistons in your block you may not need to do anything ! Use the felpro thick gaskets which are .038 when compressed, and you should be close to a perfect quench.
 
66dartgt said:
I would think a small fly cut on top of the pistons will be all thats needed not a biggie - if at all. Measure your deck heights like someone else suggested on the pistons in your block you may not need to do anything ! Use the felpro thick gaskets which are .038 when compressed, and you should be close to a perfect quench.
Click to expand...

I was thinking the same thing should the pistons come aove the deck. I plan on pulling the engine soon to get it cleaned, and bored 0.030. I will check the dimensions, even takes pics if you like, and then send the block back for the final hone and decking if necessary.

Do you think I can get away with measuring the deck clearance on a block without a final hone with pistons without rings on them, but hung on the rods and get a pretty decent(read accurate) measurement reading? I don't like the idea of having the block machined and final prepped for assembly when I still have to take some readings only to have the block possibly decked.

BTW.. you guys are gonna laugh when I tell you what car this engine is going to....I'll keep this secret for now....

Thanks again for all your help. I'de be interested in hearing your advice on the above situation.

Best Regards
 
I would definetly measure every pistons deck height, along with every other critical dimension in the motor as you disassemble it. Theres a wealth of information to be had by doing this. It tells you what kind of piece you are working with and what will need attention.

Getting back to the deck heights, if you reuse and recondition your rods the actual piston deck height will be slightly shorter (further down in the hole). Why ? Because when you recondition rods you take material off the mating surfaces of the rod cap and the bottom of the rod and then machine the bearing bore back to the stock dimension, this effectively makes the rod a tad shorter, not much but some. Save your old pistons to use as a guide for deck height estimations with the new pistons, you can mic from the top of the rod pin to the top of the piston and get a very good idea how tall and where your new pistons will end up.

If you use new rods then you'll need to mock the engine together with the pistons and measure your deck height.

Keep in mind you'll want to balance the whole mess too. It'll be a lot of screwing around, but I like detailed stuff like this...
 
Guitar Jones said:
You would have been miles ahead if you bought a used 360 for $200 and had it bored with new pistons.
Click to expand...

I get that alot.... but as Robert Frost has said once in "The Road Not Taken", I will take the one that is less travelled by...

Sure the 360 is an easier route,,, but the parts I have acquired so far pretty much fallen on my lap. And of equal importance, with the help of Moper, 66DartGT , RumbleFish , 388Dart , GoodysGotaCuda, and BJS Racing I am willing to bet that this stroked 318 will run like a scalded pussy cat....

The funny thing is... I haven't told anyone yet as to what car is going to get the ticked off puddy cat.....
 
BSCHUBARG i have a simple solution -buy my 360 motor that already runs low 13`s high 12`s im building a 408 as we speak i only ran my dart 1 time it was the 1st time also on a drag strip before it was tuned on a dyno and rejetted it ran 13.3 after the jet change it gained 17 HP and 36 more torque -J-heas ported and polished -air gap intake -to the rear tires was 272 and 403 ft lbs of torque i have dyno sheet . Just a thought and i live in Ft lauderdale.
 
j heads with alot of work done on them- 509 lift cam 9.5.1 compression , edelbrock airgap intake with a moroso carb spacer 410 posi, caltracs with mono leafsprings -10" 3500 stall (holley HP750 DP)headers ,built 904 with cheetah valvebody and hurst prostick shifter
 
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