What kind of heads do I have?

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Greenmachine225

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Hey guys so I have a 318 I’m gonna build and I was going to use a set of 360 heads and put some work into them but I was thinking I might as well spend some money on the stock 71 318 heads cause I heard they have a smaller combustion chamber. When I actually took a look at the heads it looks like they have 1.88 and 1.60 valves like the 360 heads and the valves match up perfectly to the 360 ones so have no idea what heads they are or which of the two I should use. The casting number is 3769974.
 
'76 360 heads. They should have around 69cc chambers which would be the same as a factory stock '69 318 with the higher compression (9.1:1).

treblig
 
You are correct I misread my book. Depending on the year....... My "How to hot rod small block Mopar engines" book shows the 71-76 360 head to be between 65-73 CCs, then the 77-89 to be 66 to 72.5 and 90-92 to be 68 to 74.5 CCs.
 
From my experience the numbers are usually on the high end compared to the book
 
Those heads (360) would work well with some pop up pistons to compensate for the CCs?? Since he's building the engine anyway it won't cost much more to get high compression pistons?? The highest compression 318 heads are '69 and older.

treblig
 
Hey guys so I have a 318 I’m gonna build and I was going to use a set of 360 heads and put some work into them but I was thinking I might as well spend some money on the stock 71 318 heads cause I heard they have a smaller combustion chamber. When I actually took a look at the heads it looks like they have 1.88 and 1.60 valves like the 360 heads and the valves match up perfectly to the 360 ones so have no idea what heads they are or which of the two I should use. The casting number is 3769974.

If you put in a set of 10.5 compression pistons in the 318, with the 360 heads, you will end up around 9.2 compression...
 
I'm building a 318 right now as well and have done alot of research on pistons and if you have the money then yes you can boost compression with pistons kb has a piston with a compression height of 1.810 which would put you about .01 below the deck without machine work assuming everything is stock. For a price tag of around 450 with rings!
 
I'm building a 318 right now as well and have done alot of research on pistons and if you have the money then yes you can boost compression with pistons kb has a piston with a compression height of 1.810 which would put you about .01 below the deck without machine work assuming everything is stock. For a price tag of around 450 with rings!
If the OP is not building a race motor I'm sure he could get some custom piston made for less than $450??
 
Those pistons have a +5 cc relief so with 73cc heads. 01 under the deck and a .028 head gasket you would be at about 8.7 cr. Which is better than a stock 318 and the benefit of the 360 heads id say it would be a real runner! I'd like to do that myself.
 
If the OP is not building a race motor I'm sure he could get some custom piston made for less than $450??
I agree I'm just telling how much pistons are im going thru the same thing I can't afford to put that much in pistons but in order to raise cr with pistons that's the price tag! There are other options out there like the 526s and 814 but they only raise the compression height around. 030 that's not gonna be alot of gain but they have a price tag of about 136 plus paying someone to install them.
 
I agree I'm just telling how much pistons are im going thru the same thing I can't afford to put that much in pistons but in order to raise cr with pistons that's the price tag! There are other options out there like the 526s and 814 but they only raise the compression height around. 030 that's not gonna be alot of gain but they have a price tag of about 136 plus paying someone to install them.
360 heads have bigger intake/exhaust ports in comparison to 318 heads, so if you looking for power at higher RPMs the 360 heads would flow more. You could also shave the 360 heads a little (that doesn't cost too much). But if money is tight then you're more limited on options?/

Treblig
 
Yea absolutely you could mill the heads and deck the block but that's more money! I guess it comes down to what the OP wants and how much he wants to spend!
 
I'm building a 318 right now as well and have done alot of research on pistons and if you have the money then yes you can boost compression with pistons kb has a piston with a compression height of 1.810 which would put you about .01 below the deck without machine work assuming everything is stock. For a price tag of around 450 with rings!
I’m planning to get the KB167 pistons, are those the ones you’re talking about?
 
Yes that's them they have a compression height of 1.810 that will really help with compression you could also mill the heads and deck the block and bring it up more. But with milling you have watch your push rod length and rocker geometry.
 
Yes that's them they have a compression height of 1.810 that will really help with compression you could also mill the heads and deck the block and bring it up more. But with milling you have watch your push rod length and rocker geometry.
You should take this advice and use it on everything, stock or modified, cut or uncut.
You are correct I misread my book. Depending on the year....... My "How to hot rod small block Mopar engines" book shows the 71-76 360 head to be between 65-73 CCs, then the 77-89 to be 66 to 72.5 and 90-92 to be 68 to 74.5 CCs.
The book shows the low cc amounts as a min chamber size.

Those heads (360) would work well with some pop up pistons to compensate for the CCs?? Since he's building the engine anyway it won't cost much more to get high compression pistons??

treblig
Custom slugs? They can be expensive. Or VERY expensive. A domed high compression 318 slug is hard to find at best.
Killing the heads for a better ratio is a catch 22 as you know because of the fitment issues created.
Between the flat top KB’s, HyperU’s or forged, decked block & milled heads, you can do pretty good. But it is a PIA.

Being a little light on the ratio isn’t a bad thing. Being light a 1/2 point off the recommendation of the cams suggested ratio is OK. 1 point down is approaching crummy. The closer you are to the recommended ratio for the cam is for efficiency. I would not want to run a cam like, oh let’s say, 240@.050 in a 8.0-1 engine. It would be way happier in a 10-1.

Just remember IQ52’s threads on compression and cylinder head flow. Flow will trump compression every time. LMAO, and people trashed the MoPar advice of 360 heads on a 318 even though Jim backed up the MP advice with his dyno tests.
 
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