318 build

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moparyoungin

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I am building a semi-budget 318. I just bought a set of speed-pro .30 over forged pistons on ebay for 200$. I have a 68 318 motor that I hope has a forged crank in it. I think I'm going to use a set of 73 318 rods with pioneer rod bolts and have it balanced. I'm using magnum heads. I have two sets of sealed power .30 over rings(e178x30) that I might use but I am planing on using nitrous. I figured I would need file fit rings. I'm wondering if I will have enough piston to valve clearance to use a .500ish lift cam? I am not decking the block. I bought a a-833 for 200$ and it came with a flywheel. I'm not sure how to tell if its a forged or cast crank flywheel. This is going in a 1976 Plymouth Scamp.
 
Do the pistons have valve notches? What is the piston part #?

Do you have a casting number off of the flywheel?


Chuck
 
I'm not sure how to tell if its a forged or cast crank flywheel.
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B&S I think this is the question. And I say the factory OE unit is preety good, but the wheel itself is cast. (I believe so)

Theres is nothing to worry about when bolting on the flywheel to any crank. Just weather or not it is internal or extrnal balanced. The extrenal balanced unit comes off a 360 or the one year only 340 that is extrenally balanced.

The crank must have a poilt hole to accept the tranny snout. Use with bushing.
 
BoredandStroked said:
No offense but what are you asking pal?
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Umm sorry....that'll teach me to not proof read :) I thought there was a difference between cast and forged crank flywheels. I was wondering if I should spend the extra money for file fit rings if I'm going to be using nitrous. I also wondering if I could use around a .500 lift cam. I don't want to buy a cam that won't work. :blob:


http://store.summitracing.com/partdetail.asp?part=TRW-L2329F30&autoview=sku
 
Umm sorry....that'll teach me to not proof read
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Ha ha ha ha! I gotta tel ya, I was seriously laffin at B&S's reply.


I'm not to sure about file fit rings being better for N02. To tight a fit and the rings will heat up and touch, bind up and cause all soughts of ugly marks on the cylinder wall.
But on the cam, a .500 should fit most any piston. Now, on the piston, what is the number for them.
 
rumblefish360 said:
Ha ha ha ha! I gotta tel ya, I was seriously laffin at B&S's reply.


I'm not to sure about file fit rings being better for N02. To tight a fit and the rings will heat up and touch, bind up and cause all soughts of ugly marks on the cylinder wall.
But on the cam, a .500 should fit most any piston. Now, on the piston, what is the number for them.
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The pistons are L2329F30.
 
Yea and I was too when I wrote it. I see some questions now just didnt at the time, just thought he was telling us about his combo.

One thing about Magnum heads and their parts is the limit on cam lift. The guide to retainer clearance limits the cam lift to .530 ish. If you go over it will hit and cause major problems. So unless you send the heads out to get guides machined down, you would have to limit the lift. Also, some cam companys only list their products with 1.5 ratio rockers, however the magnums are 1.6, so you have to take that into consideration. For example a cam lift of .490 with 1.5 rocker arms would be roughly .522 lift with the magnums 1.6 rockers.

As to the rings, I wouldnt really go with file fit for the simple fact I am not a nitrous guy and know just a little bit about it. I will know more once I start on my friends 318 but that wont be for a couple weeks to even months. But anyways I digress, I would use the rings you have and limit the jet setting to 100, no more then 125 though.

A few notes in my opinion is this would be a killer combo if you got the correct machine work done to it and blueprinted every aspect of it. Like I said before I am not a nitrous guy and just started on researching some ideas once I found my friend a car. But this could be a very streetable combo while also being a very race ready combo.

One thing to look at is the pistons, what would your final compression ratio be once you lets say square deck the block and heads and such. One thing I do know is depending on camshaft selection a good ratio to limit the compression is 8.5 to 1 with 9.5 being the max.
 
Don't forget to check for retainer to guide clearance as well as spring bind. You should purchase valve springs that match the cam too. With the 1.6 magnum rockers your lift will be a bit higher than what the cam manufacturer lists.

Also, get some high quality adjustable rockers too so you can adjust lifter preload.
 
Good advise so far.Im planning a magnum swap with my 83 cop 318.It has all the usual cop stuff,windage tray,360 heads,4 bbl intake,dismal 7.5/1 compression.

I needed to get hydraulic lifters for an amc,correct length pushrods from mopar,magnum heads.I just picked up an M1 for use with magnums on ebay.Was either buy the intake,build a jig to drill em or pay some one to do it.Figure I came out ahead getting the M1 (for what I paid).

Also have magnum head porting templates.These should? be reusable when Im done with em...

Anyways,your compression will be somewhere around 9 to 9.3 to 1.Perfect for the street.Might be a bit higher depending on how thick your head gasket is and how muck material is removed to deck and square the block.

I wonder if perfect seal rings would work for nitrous?
 
I think valve to piston clearance will be an issue but your going to be low on compression. It will be in the high 8s if your lucky.
 
Your not gonna have an issure with piston to valve clearence.....those things will be at least .050 in the hole.....if you are gonna spray it you'll want the rings opened up a little more. Put the end gap in the middle of the stock specs and you'll be fine up to a 150 shot...any more than that any your gonna wanna open em up more but be warned you'll have blow-by when just cruising. Don't go cheap on the rods and bolts if you are spraying. Get too ARP bolts. Stock rods that have been prepped will be okay but don't go over a 150 shot or you'll be pushing your luck. Make sure you do your homework on fuel system requirments when using the laughing gas as well.....it's fun stuff but if you don't know what you are doing you'll destroy a motor real quick.
 
Thanks guys. I went and picked up my motor yesterday. Took the pan off and the crank isn't forged. The motor turns real nice though. I made up my mind and I'm going to get forged rods and filefit rings. The pistons that are in it are flat tops and probally .10 in the hole which surprised me. It's a '68 block.
 
I think for reasons of budget I'd change a little. First, Running NOS means a bit more than simple build. second, the forged pistons are heavy compared to factory. third, Magnum heads allow for the designing in of quench. Now, the NOS you want to use is not that much. And, it's only a help when you have a supply of it, and when the engine is tuned for it. You can run out, and the tune you normall drive on is not the one NOS likes the best. I dont recommend ever running NOS on hypereutectic pistons unless you are staying very mild. Like a 75hp kit. Once you reach 100hp, there are timing changes and stuff that should be done to stay safe under boost. Witht the heavy pistons, you can run more juice. But, to internally balance the engine, you will need to add heavy metal (Mallory) to the crank. Because the crank isnt heavy enough to counterweight the pistons. That metal is very expensive, and billed by the ounce. A typical build would require two slugs, at a cost of about $50-$75 er slug to balance, above the cost of the balancing work. Plus, the pistons you have, are not expensive, They are factory type replacements. In your block, that means they end up somewhere around .070 down in the bore from the deck. So static compression even using the "smallish" Magnum type chambers, wont be over 8.5:1. If you raised the static to 10:1, using a tight quench, you would get back a lot of the power the NOS is getting you, and you'd have it all the time, on pump fuel. I would go this way: Sell the heavy forged pistons. Buy some zero deck flat top hypers. The KB167s are $250 a set, weight less than the factory stock cast, and will give you a static of close to 10:1 with a typical Magnum chamber of 62-3cc. Plus, they give a .043 quench with the cheaper Fel Pro blue gaskets. You can add a slightly better cam, and end up with a 318 on pump gas that will easliy make 350-380hp all the time on pump fuel. The forged piston version might make 300-330 at 8:1, andd you'll want the juice for the rest. I think mine's cheaper with NOS at $50/10-15 seconds of use (with a typical 10lbs bottle and 100hp kit). Probably cheaper with the machining costs too.
 
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