Why are 318's low HP and torque?

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streetmachine said:
I haven't confirmed but, I believe he is talking about advertised compression and not "static" compression. Even the earlier 67-69 blocks should be about 8.2.1 to 8.5.1 static? The later they the worse the compression height became and then after 72 was all downhill.
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I don't think any 318 has ever blueprinted 8.5....advertised maybe. They suck. lol
 
YY1 said:
For the record my 67 FSM says 9.2:1, and my 1969 Motor's manual also says 9.2:1 for 1969 and older LA 318s. I have a 72 FSM somewhere, but can't locate it.
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I believe you. I'm just saying actual measurement. Sorry..I shouldda been more clear.
 
Mopar typically rated the engines higher in compression then they actually were. Like '68-'70 340s rated at 10.5:1 compression but were really more like 9.5:1 compression.
 
So my 1980's 318 block has even lower compression than the late 60's to early 70's? If so, that sucks! More work for me....
 
So if you can't swing swapping in some zero deck pistons you will want to stay with a mild cam and small chamber heads. I largish cam will bleed off cylinder pressure which is something you don't want to do.
 
Can you give me a couple recomendations for cams?
Also would it help my hp to get an electronic igniion like msd?
 
COMP Cams 20-223-3 - COMP Cams Xtreme Energy Camshafts is a good one. Had it on one of my setups works well with stock stamp rockers to.
 
here is one reason

2012-06-14-053.jpg


340 gasket on a 318 head,you get the idea.
 
On the 318 heads I opened up the runners to match the gaskit on a 4barrel. Also changed the springs and retainers and locks to go with the cam. Ran super strong to 6500. oh and thay were 70's heads
 
StrokerScamp said:
Stock compression height is 1.720. You can get some stock replacement 4 eyebrow type pistons with a 1.741 compression height. That might not sound like much, but it makes a difference.
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Do you have a part number for said pistons StrokerScamp?
The standard answer when somene starts a thread abaout building a 'teen is to fit the KB pistons. Some of us builders of 'teens are doing so for finacial reasons. So pistons like the ones mentioned above, would be of great help to folks like me. (Plus the $3-400 360 junkyard core you guys can find anywhere is more like $1200+ here. IF you can even find one)
 
I'd like that part # as well.

That xe256 cam also has a nice torque curve.
 
Valvebounce said:
Do you have a part number for said pistons StrokerScamp?
The standard answer when somene starts a thread abaout building a 'teen is to fit the KB pistons. Some of us builders of 'teens are doing so for finacial reasons. So pistons like the ones mentioned above, would be of great help to folks like me. (Plus the $3-400 360 junkyard core you guys can find anywhere is more like $1200+ here. IF you can even find one)
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Same problem here, a 360 rebuilder hard to find and expensive.
 
KB has an online catalog:

[ame]http://www.kb-silvolite.com/assets/automotive_catalog.pdf[/ame]

I see 2 318 stock stroke pistons listed:

KB167 KB167 KTM 2-5/64, 1-3/16 FT 5cc 2V 10.4 10.1 9.6 9.2 507/132 .275 .280-2.160" .280-2.160"

OR

KB399 KB399 KTM 2-5/64, 1-3/16 .140” SD -6cc 2V 12.2 11.7 11.0 10.4 541/132 .275 .286-2.200" .286-2.200"
 
I have a street master intake, headman headers, 273 valve covers, 650 avs Carter carburetor, crane cam from summit racing, stock lower end.... Thanks y'all.
 
340sFastback said:
KB has an online catalog:

http://www.kb-silvolite.com/assets/automotive_catalog.pdf

I see 2 318 stock stroke pistons listed:

KB167 KB167 KTM 2-5/64, 1-3/16 FT 5cc 2V 10.4 10.1 9.6 9.2 507/132 .275 .280-2.160" .280-2.160"

OR

KB399 KB399 KTM 2-5/64, 1-3/16 .140” SD -6cc 2V 12.2 11.7 11.0 10.4 541/132 .275 .286-2.200" .286-2.200"
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StrokerScamp said:
Stock compression height is 1.720. You can get some stock replacement 4 eyebrow type pistons with a 1.741 compression height. That might not sound like much, but it makes a difference. Get some Magnum heads or 302 heads and get them down to 55cc, have the block bluprinted to 9.6 (which is the factory spec, they're always high) use the .021 thickness head gasket and you have a 9.1 motor. Just right for idling around stuck in traffic in the summer and will never spark knock. Cheaper than setting up a quench motor. Those pistons only cost about 100-125 bucks, whereas the KB167 quench type pistons are around 400. Even if you choose to save money and not blueprint the block deck, you're still gonna have respectable compression considering the stock 318 blueprints in the 7s compression wise. You'll have enough to support a 325 HP 318 with smart parts choices.
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I was actually refering to the cheapie replacement pistons.
 
I am going to ask a very simple question because of All the talk about pistons.....what is the difference between forged and stock pistons? Why do people get new ones other than the normal wear and tear? Thanks guys.
 
Forged are lot stronger good for high RPM, HP and Power Assisted engine but are heavier and greater piston to wall clearance. Cast are alot more fragile but are cheaper lighter and can run tighter clearances but are mostly in low compression. Hypereutectic piston are light, can run tight clearances, come in higher compression, inbetween the cost of forged/cast, can handle more power and RPM's than cast but not as much as forged.
 
Bore size IMO doesn't come that much into play. The LS1 has a smaller bore than the 318 and the LS1 can make plenty of power (but LS1 magic is in the heads)...
LS1=3.89
318=3.91

Small (under carbed with a 2bbl), log exhaust manifolds with single exhaust, tiny 1.78/1.58 valves, pistons way below the deck= low compression, and if I can recall, the factory cam is under .400 lift.

Correct these problems (mainly compression) and the 318 will run like a bat outta he//....
 
Chryslerkid said:
Why do people get new ones other than the normal wear and tear? Thanks guys.
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If the cylinders need to be bored then you will need larger pistons. The other reason is to go with higher compression pistons, especially in a 318.
 
I see. Cool thanks for the info. I see why people who are trying to make a lot of HP want forged pistons now.

Since I have been told several times now that my street master intake manifold is crap....what are some good intake manifolds that I could use in place of it?

Remember I have a near stock 318 engine build going on. Nothin too radical....
 
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