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dodgerammit View Drop Down
AMC Apprentice
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Joined: Apr/26/2019
Location: TN
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Points: 151 		Post Options Post Options   Thanks (0) Thanks(0)   Quote dodgerammit Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2019 at 10:44am
I agree to match cam and compression.

At 9.0:1 compression with my cam choice (Engle 5052), 21cc dish wiseco forged, zero decking my block, and .040" head gasket thickness (quench) should put me at 7.5:1 DCR which should allow 87 octane usage.

That said, the guy at Engle said my cam would be fine at 8.5:1 as well.  He specifically said much above 9:1 would not be ideal.

If you read SC397's builds, you will see he used a calculator to figure compression ratio. I used that thing extensively, plugging differing values into it to see what changed. Great learning experience seeing what made a big difference and what didn't. Helped me dial in what I needed done to get where I wanted.
84 Grand Wagoneer Garnet Red (mine)360/727/229 44/20
84 AMC Eagle Wagon (Wife's) Deep blue 258/mushbox/129 30/15
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ghcoe View Drop Down
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Joined: Sep/29/2018
Location: SW Idaho
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Points: 72 		Post Options Post Options   Thanks (0) Thanks(0)   Quote ghcoe Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2019 at 10:57am
Originally posted by BassBoat BassBoat wrote:

I am a strong proponent of matching cam and compression to give good effective compression.  Two things that have been recommended in this thread are the Comp 268H, a good all around performance cam as suggested by SC397, and bumping the compression to 9.5 as recommended by Trader.  I agree 100%  At 9.5 to one static compression your effective compression is about 8.35, and that should be fine for pump gas.  I run 8.6 and 8.75 in my 390s on premium
 
Thanks BassBoat, I probably know enough about engines to be dangerous to myself. I tend to over think things, so I have to turn to people who know more about this than I do before I go crazy...
 
So with that said is there a way to increase compression if I only have the heads rebuilt? I was thinking that valve choice could increase compression without having the heads shaved, which I really don't want to do, plus I have no idea if they were in the first place so there may not be much to play with. I know cam choice does change dynamic compression so that is why I was asking for a good choice. I would at this point assume that I would notice a improvement with the 268H whether with static compression of stock (lowish 8), 9.5 or anything in between, from what people are saying?
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dodgerammit View Drop Down
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Points: 151 		Post Options Post Options   Thanks (0) Thanks(0)   Quote dodgerammit Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2019 at 11:26am
Greyhoundsamx has a cam spreadsheet you can use to plug variables in. It will show DCR.

There is a thread on FSJnetwork concerning what a bump in CR does. Basically gives a solid increase in performance across the operating range.
84 Grand Wagoneer Garnet Red (mine)360/727/229 44/20
84 AMC Eagle Wagon (Wife's) Deep blue 258/mushbox/129 30/15
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ghcoe View Drop Down
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Joined: Sep/29/2018
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Points: 72 		Post Options Post Options   Thanks (0) Thanks(0)   Quote ghcoe Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2019 at 3:10pm
Originally posted by dodgerammit dodgerammit wrote:

Greyhoundsamx has a cam spreadsheet you can use to plug variables in. It will show DCR.

There is a thread on FSJnetwork concerning what a bump in CR does. Basically gives a solid increase in performance across the operating range.


 
Thanks for the links. Very helpful. George
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SC397 View Drop Down
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Points: 5476 		Post Options Post Options   Thanks (0) Thanks(0)   Quote SC397 Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2019 at 4:41pm
This was a 8.5:1 360 cheapie re-ring build that we put together with the 268H cam and he seems to really like it. 
The nice thing about that cam is that you can use your stock length push rods. It is basically the same lift as a stock 401 cam with a little more duration.
Stock 401 Cam: 208/210 @ .050" .458" valve lift and 114 LSA
CompCam 268H: 218/218 @ .050" .456" valve lift and 110 LSA
Stock 360 Cam: 196/196 @ .050 .426" valve lift and 110.5 LSA


Edited by SC397 - Dec/13/2019 at 9:36am
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ghcoe View Drop Down
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Joined: Sep/29/2018
Location: SW Idaho
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Points: 72 		Post Options Post Options   Thanks (0) Thanks(0)   Quote ghcoe Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2019 at 5:32pm
Originally posted by SC397 SC397 wrote:

This was a 8.5:1 360 cheapie re-ring build that we put together with the 268H cam and he seems to really like it. 
The nice thing about that cam is that you can use your stock length push rods. It is basically the same lift as a stock 401 cam with a little more duration.
Stock 401 Cam: 208/210 @ .050" .458" valve lift and 114 LSA
ComCam 268H: 214/214 @ .050" .456" valve lift and 110 LSA
Stock 360 Cam: 196/196 @ .050 .426" valve lift and 110.5 LSA
 
Thanks for that!
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Sonic Silver View Drop Down
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Joined: Nov/23/2011
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Points: 7949 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic Silver Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2019 at 6:05pm
Originally posted by SC397 SC397 wrote:

This was a 8.5:1 360 cheapie re-ring build that we put together with the 268H cam and he seems to really like it. 
The nice thing about that cam is that you can use your stock length push rods. It is basically the same lift as a stock 401 cam with a little more duration.
Stock 401 Cam: 208/210 @ .050" .458" valve lift and 114 LSA

ComCam 268H: 214/214 @ .050" .456" valve lift and 110 LSA

Stock 360 Cam: 196/196 @ .050 .426" valve lift and 110.5 LSA

The factory 401 cam that I had measured 20 years ago by the Cam Doctor machine at Cam Motion showed 207/208 .456 lift. The Comp 268 H is 218* at .050.
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SC397 View Drop Down
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Points: 5476 		Post Options Post Options   Thanks (0) Thanks(0)   Quote SC397 Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2019 at 7:30pm
My mistake.  The 268H is 218/218.  
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Sonic Silver View Drop Down
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Points: 7949 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic Silver Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2019 at 7:55pm
Originally posted by SC397 SC397 wrote:

My mistake.  The 268H is 218/218.  
Where did you get your 208/210 duration for the 401 cam? Just wondered if there was ever a change or why the one I got measured is different. Mine came from an AMC dealer and was new.


Also, not only is there 10 degrees difference in duration at .050 between the 401 and Comp 268, there is a 18 degrees less overlap in the AMC 401, due both to the duration and wider 4 degree lobe centers. Big difference.

Edited by Sonic Silver - Dec/07/2019 at 8:02pm
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Trader View Drop Down
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Points: 6881 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2019 at 8:26pm
As on a 8.5:1 pump gas I have used these for the maximum street, horse trailer/off road crowd, Howards CL312481-11.
Just from experience, Jeeps and cars 360 and 401 seem to like the 111 degree separation angle, and 0.475" is the maximum lift to get the low end torque.
The thing to remember on a towing/work vehicle vs a car is you need to have the engine torque come in well before the torque converter specification on the bottom end. Not so critical on a street vehicle, especially if it's lite.
If you match RPM's, then the torque converter is putting maximum load to the engine when the engine is just developing it's torque. Under heavy load, in this circumstance, the engine tends to bog down regardless of what accessories you add.  
I have avoided Comps, but they did replace a couple, that had less then 0.900" lobe widths. They may be better now. If you buy any cam, measure the lobe widths! Return anything with GM lobe widths!
Also Howard's lifters are nominally 0.9035" vs Comps 0.0903" which is closer to factory specification.
This is a maximum and maybe not what you are looking for. As SC397 has recommended other options I would defer to more experience. Just though I would put out the maximum cam, from my experience, for your application.
  
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