Cam swap without pulling motor

-
Personally I would pull the engine. It might sound like more work, but in the end it's a lot easier.

Tom
 
I found this to be odd from the get-go. With the low CR and long, retarded cam, how could I get 152 psi?

ABC8FD23-A0F3-4683-82E7-30125ABE49DB.jpeg
 
If I pull that motor, I’ll want to put it back as a 408. That’s part of the reason it’s still in there. I’m removing temptation from my path.
 
I've asked this question for years and still don't have an answer (any answer good or bad)/ and the reason why I've never really liked a 360 and get really pissed when I see SO MANY 318 posts reduced to "ditch it for a 360"...
Why in the HELL did every 360 made come from the factory castrated with DISHED pistons?
Being down in the hole is one thing/ but then they dish them? I know even in the 80s the "heavy duty" 360s in like the heavier gvw 3/4 ton and 1 ton were even advertised as 7.x compression. Does that mean they were really 6.x? That would be the absolute last thing you'd want for a workhorse.
I don't know any better way to reduce power on an engine by dished pistons ,
other than to pop off a couple of plug wires .. yes the longer stroke of the 360 is usually an advantage. Usually. But then you put dishes pistons in to more than counteract that advantage?
The only thing any 360 (I have had) has done better than any 318 I have had was to pad the pockets of the gas station owners. I've never had one from new but I've also noticed that if I have to pull them apart the 360 has been more likely to be sludged up
Id really like to take a 360 and build up, see what I can do with one, but as built stock, there wasn't much to write home about with them
 
volaredon said:
I've asked this question for years and still don't have an answer (any answer good or bad)/ and the reason why I've never really liked a 360 and get really pissed when I see SO MANY 318 posts reduced to "ditch it for a 360"...
Why in the HELL did every 360 made come from the factory castrated with DISHED pistons?
Being down in the hole is one thing/ but then they dish them? I know even in the 80s the "heavy duty" 360s in like the heavier gvw 3/4 ton and 1 ton were even advertised as 7.x compression. Does that mean they were really 6.x?
I don't know any better way to reduce power on an engine other than to pop off a couple of plug wires .. yes the longer stroke of the 360 is usually an advantage. Usually. But then you put dishes pistons in to more than counteract that advantage?
The only thing any 360 (I have had) has done better than any 318 I have had was to pad the pockets of the gas station owners. I've never had one from new but I've also noticed that if I have to pull them apart the 360 has been more likely to be sludged up
Id really like to take a 360 and build up, see what I can do with one, but as built stock, there wasn't much to write home about with them
Click to expand...
Actually, the first year 360s were equipped with actual flat top, non dished pistons. And 1.88 valve J heads
 
volaredon said:
I've asked this question for years and still don't have an answer (any answer good or bad)/ and the reason why I've never really liked a 360 and get really pissed when I see SO MANY 318 posts reduced to "ditch it for a 360"...
Why in the HELL did every 360 made come from the factory castrated with DISHED pistons?
Being down in the hole is one thing/ but then they dish them? I know even in the 80s the "heavy duty" 360s in like the heavier gvw 3/4 ton and 1 ton were even advertised as 7.x compression. Does that mean they were really 6.x? That would be the absolute last thing you'd want for a workhorse.
I don't know any better way to reduce power on an engine by dished pistons ,
other than to pop off a couple of plug wires .. yes the longer stroke of the 360 is usually an advantage. Usually. But then you put dishes pistons in to more than counteract that advantage?
The only thing any 360 (I have had) has done better than any 318 I have had was to pad the pockets of the gas station owners. I've never had one from new but I've also noticed that if I have to pull them apart the 360 has been more likely to be sludged up
Id really like to take a 360 and build up, see what I can do with one, but as built stock, there wasn't much to write home about with them
Click to expand...
The answer is this: Smog era emissions restrictions were put in place and the engineers at the time didn't have tech/budget to work with to meet the rules. They reduced emissions by reducing compression. They in turn increased displacement to regain some of the lost torque.
 
Reinstalling valves and installed height of springs is a little on the high side by 0.030" or so. I have some 0.031" shims, so the spring height is easy to fix. The previous valve job left the valves about 0.040" uneven. I got them within 0.010"-0.012" with the new valve job. I would imagine that the valves are now around 0.050"-0.060" deeper than original. At what point does this start becoming a problem with stock rocker arm geometry? At a minimum I may need shorter pushrods. Should I consider grinding a little off the tops of the valve stems?
 
Valves that have hardened tips(not all do), often don’t have the hardening extend below the tip very much, so I wouldn’t be grinding enough off to try and improve the rocker geometry.

I’d set the rockers/shafts on the heads while they’re on the bench so you can easily see what the rocker to valve tip situation is like, and get a game plan in your mind of how that will need to be(if it needs to be) addressed.
 
With the cam I’m using, Lunati recommends a spring pressure of 115 lbs on the seat. To get there, I have to install two shims - 0.062 + 0.031. That gets my installed height right around 1.600” and the seat pressure at 110-115. Any problem with stacking two shims?
 
Lunati recommends about 350 lbs over the nose for this cam @ 0.454/0.475 intake/exhaust lift. What is the danger zone for stock stamped steel rockers? I was talking with a Mopar performance parts supplier today and he suggested that 250 lbs was about the max for stock rockers. What say y'all? I have punched a pushrod through a rocker on one occasion.

Now that I think about it, 350 may be a little high. I know it's more than 250 though. I need to go back and check the specs, but the question remains - what is max for stock rocker?

I found the specs. Looks like 300-305 over the nose.
 
Last edited:
My .02 is…….
It’s not a race car………..so it doesn’t need the max rpm capability.
I’d shoot for 290-320 over the nose.
 
PRH said:
Valves that have hardened tips(not all do), often don’t have the hardening extend below the tip very much, so I wouldn’t be grinding enough off to try and improve the rocker geometry.
Click to expand...
Just use lash caps.
 
JunkyJimmy said:
If you have a John Deere dealership close go get some caps for a 4440 tractor. 3/8 stem can buy 1 or 2 to try, they use to be like 2 bucks each.
Click to expand...
Do they sell them in 11/32?

Any oem head I do gets 11/32s. Seems crazy to use 3/8 valves today unless you already have them
 
Last edited:
Earlie A said:
Lunati recommends about 350 lbs over the nose for this cam @ 0.454/0.475 intake/exhaust lift. What is the danger zone for stock stamped steel rockers? I was talking with a Mopar performance parts supplier today and he suggested that 250 lbs was about the max for stock rockers. What say y'all? I have punched a pushrod through a rocker on one occasion.

Now that I think about it, 350 may be a little high. I know it's more than 250 though. I need to go back and check the specs, but the question remains - what is max for stock rocker?

I found the specs. Looks like 300-305 over the nose.
Click to expand...
What are you calling a "stock rocker"? I always thought the 340 rockers were a little stronger, due to their hotter cams than the other LA motor rockers, except for maybe the 273 or 6 pack adjustables.
 
Swinger 340 said:
What are you calling a "stock rocker"? I always thought the 340 rockers were a little stronger, due to their hotter cams than the other LA motor rockers, except for maybe the 273 or 6 pack adjustables.
Click to expand...
I’ve never noticed any differences between any of the stamped steel 340/360 factory rockers as far as dimensions or material thickness. It would not surprise me if the older factory stamped rockers were made of better quality steel than the new replacement rockers.
 
Since the heads were off and the compression is low, I had the heads milled 0.070" as seen in the picture below. I realize that changing pistons is the best way to go about upping the compression. You guys told me that and you are correct. This is just something I wanted to try. A previous refresh already had milled the heads 0.008" so the total off the deck face is 0.078". The intake face of the head was also milled 95% of the 0.078".

The factory 1.88/1.60 valves are shown on the right. I have a set of 2.02/1.60 nail head valves that I would like to install (as seen on the left), but I'll probably have to sink the intake valve a little to get some top angle. If I install the 2.02 valve the valve job would be 38/45/60/75.

What is the minimum top cut width I should try to get by with? Milling the heads removed the ridge in the chamber on the short side of the intake valve. I bet removing this ridge has increased high lift reversion flow.

IMG_3038.jpg
 
We all have our own way we like to do things.

In a mild application like this, I’m not going to get overly concerned with having a steep top angle.
So, I’d run a shallower angle, which would give me more top angle length with less lowering of the seat depth.
 
You must log in or register to reply here.
-

Back
Top