What cam to use in a 318

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with that rear ratio and stall speed, I think an XE268 would be a little big. personally, I'd probably stick with something that has a duration more like and XE256 or XE262. I ran a hydraulic roller in my '85 block with magnum heads that had .320" lobe lift (.512 calculated valve lift with 1.6 rockers) without issue. I had my stock roller cam reground by bullet cams. in their flat tappet lobes, I'd look at something like their HC260/296 lobe on the intake and their HC270/312on the exhaust....I am not a fan of lumpy idles, so I'd probably do it on a 112ish LSA, but install it at 106 ICL. Bullet Cams Master List
 
The old comp High Energy 268 is also another good choice here. Or even a regrind on an old 360 cam core and lifters. An Oregon 1369 ground onto 108 LSA is as good as it can get here. It’s doable because most stock 360 cores are ground close to a 109 to start with.
Hydraulic Camshaft Specifications
 
I think I am going to go with Oregon cams, we discussed a few different options including re-grinding my vintage 318 cam that is good shape and made of better material. I like the idea of something not mass produced from who knows where.
 
Someone asked how you get to 9.2 compression, .030 overbore, magnum heads, and you can use 318 magnum pistons that have a taller compression height in a LA motor they work fine, as 5.2 and LA engines have basically the same rod You would want to re-balance but that's always a good idea when changing pistons anyway. They are not as tall as the KB's but will get you a nice boost in compression for replacement piston prices.
 
Re-grinding a stock cam to get more lift will leave the lobe physically much smaller..... You may need longer prods. Not the best solution.
 
Garrett Ellison said:
The old comp High Energy 268 is also another good choice here. Or even a regrind on an old 360 cam core and lifters. An Oregon 1369 ground onto 108 LSA is as good as it can get here. It’s doable because most stock 360 cores are ground close to a 109 to start with.
Hydraulic Camshaft Specifications
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I would also endorse the Comp DEH275 here. IF you can find one. A better idea would be to let Oregon grind whatever their closest is.
 
furz4 said:
Someone asked how you get to 9.2 compression, .030 overbore, magnum heads, and you can use 318 magnum pistons that have a taller compression height in a LA motor they work fine, as 5.2 and LA engines have basically the same rod You would want to re-balance but that's always a good idea when changing pistons anyway. They are not as tall as the KB's but will get you a nice boost in compression for replacement piston prices.
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Do you have a part # for those 5.2 magnum pistons? I asking because the last time I looked those up they were the same thing as the LA pistons.
 
I've often wondered what exactly the difference was in the 67-69 9.2:1 318 and the 84-ish to 91 9.2:1 318 to differentiate them from the 8.8:1 318's from 1970 to 1983.

The piston part numbers are different, and the heads are different, but I've never been able to compile exactly what portion is attributable to what part.
 
YY1 said:
I've often wondered what exactly the difference was in the 67-69 9.2:1 318 and the 84-ish to 91 9.2:1 318 to differentiate them from the 8.8:1 318's from 1970 to 1983.

The piston part numbers are different, and the heads are different, but I've never been able to compile exactly what portion is attributable to what part.
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The stroke and the rods didn't change dimensions but the heads did so the compression height of the pistons had to change.
 
YY1 said:
I've often wondered what exactly the difference was in the 67-69 9.2:1 318 and the 84-ish to 91 9.2:1 318 to differentiate them from the 8.8:1 318's from 1970 to 1983.

The piston part numbers are different, and the heads are different, but I've never been able to compile exactly what portion is attributable to what part.
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probably compression height of the pistons and open chamber heads

ETA: tree'd by TMM!
 
Those are fairly obvious observations.

If you use 1967 pistons (and change nothing else) on an 8.8 engine, what is the new compression ratio?
If you use 1986 pistons (and change nothing else) on an 8.8 engine, what is the new compression ratio?
If you use 5.2 Magnum pistons (and change nothing else) on an 8.8 engine, what is the new compression ratio?

If you use 1967 (920) heads (and change nothing else) on an 8.8 engine, what is the new compression ratio?
If you use "302" heads (and change nothing else) on an 8.8 engine, what is the new compression ratio?
If you use Magnum heads (and change nothing else) on an 8.8 engine, what is the new compression ratio?

...and the several other potential combinations.
 
YY1 said:
Those are fairly obvious observations.

If you use 1967 pistons (and change nothing else) on an 8.8 engine, what is the new compression ratio?
If you use 1986 pistons (and change nothing else) on an 8.8 engine, what is the new compression ratio?
If you use 5.2 Magnum pistons (and change nothing else) on an 8.8 engine, what is the new compression ratio?

If you use 1967 (920) heads (and change nothing else) on an 8.8 engine, what is the new compression ratio?
If you use "302" heads (and change nothing else) on an 8.8 engine, what is the new compression ratio?
If you use Magnum heads (and change nothing else) on an 8.8 engine, what is the new compression ratio?

...and the several other potential combinations.
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I love it!!!! A thinking man.


Dartswinger70 said:
What do the heads flow (cfm) that would give you something to go on for cam selection.
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Just what I’d like to know before a cam is selected along with a bit more information of course….. but cylinder head flow is really good to know.


Dan the man said:
No valve reliefs, would that cause piston to valve clearance problems?
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That depends on a slew of things. How far the piston is down the hole, how big the valves are & how much lift the cam has, or actually the actual valve lift. Head gaskets selection also has a play on this.
 
rumblefish360 said:
That depends on a slew of things. How far the piston is down the hole, how big the valves are & how much lift the cam has, or actually the actual valve lift. Head gaskets selection also has a play on this
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Lift (or max lift) has almost nothing to do with P to V. It’s not how far the valve opens, it’s when and how long it opens. Duration has the biggest impact on P to V clearance.

@Dan the man watch this video

 
toolmanmike said:
The stroke and the rods didn't change dimensions but the heads did so the compression height of the pistons had to change.
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Don't forget head gaskets. They went from .020" steel shim gaskets to the much thicker composite head gaskets too. So there's some more difference.
 
TT5.9mag said:
Lift (or max lift) has almost nothing to do with P to V. It’s not how far the valve opens, it’s when and how long it opens. Duration has the biggest impact on P to V clearance.

@Dan the man watch this video

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Yup and no matter what, you sometimes cannot get it through to people. lol
 
Bewy said:
Re-grinding a stock cam to get more lift will leave the lobe physically much smaller..... You may need longer prods. Not the best solution.
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Can you explain why it's a bad idea? Other than your opinion? As long as the valve train geometry is correct with the correct length pushrod, it hurts nothing. So from an actual engineering standpoint, please tell us why it's not a good idea.
 
YY1 said:
I've often wondered what exactly the difference was in the 67-69 9.2:1 318 and the 84-ish to 91 9.2:1 318 to differentiate them from the 8.8:1 318's from 1970 to 1983.

The piston part numbers are different, and the heads are different, but I've never been able to compile exactly what portion is attributable to what part.
Click to expand...
All my old Chilton manuals said the 70s and earlier 80s 318s were 8.6:1 and 360s were "advertised" as 8.2- 8.4 but then in the 80s some of the 360s were advertised as actually being below 8:1, the heavy duty ones in 1 ton trucks and such being listed amongst the lowest.
I wonder then if the ones advertised as below 8:1 were really in the low 7s.... My experience with engines from that era is as built they are all less than "advertised" CR.... Pitiful. No wonder some of these engines were such wheezing gas sucking slugs..... Not just talking Mopar either ...
 
volaredon said:
All my old Chilton manuals said the 70s and earlier 80s 318s were 8.6:1 and 360s were "advertised" as 8.2- 8.4 but then in the 80s some of the 360s were advertised as actually being below 8:1, the heavy duty ones in 1 ton trucks and such being listed amongst the lowest.
I wonder then if the ones advertised as below 8:1 were really in the low 7s.... My experience with engines from that era is as built they are all less than "advertised" CR.... Pitiful. No wonder some of these engines were such wheezing gas sucking slugs..... Not just talking Mopar either ...
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The Early Hemis from 53-59 were all advertised at 7.5:1 if they were in trucks.
 
Newbomb Turk said:
And they probably were lower than that. I’ve pulled several of the early hemi’s apart and I checked one. It was 6.7:1.
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I would not be surprised. Why would you want higher? If you had a Dodge D500 dump truck fully loaded with dirt and a 354 Power Giant under the hood, you sure as heck wouldn't want 10:1.
 
RustyRatRod said:
I would not be surprised. Why would you want higher? If you had a Dodge D500 dump truck fully loaded with dirt and a 354 Power Giant under the hood, you sure as heck wouldn't want 10:1.
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Especially back then. Fuel was really questionable and much more than that and you’d be in the poo poo.
 
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