318, max cam size for stock pistons

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Well had a friend that has built quite a few Hemi's degree my thumper cam. Well it was spot on. Well is now. It saw just a hair off. The problem as he tells me is the intake centerline is only 102, which has the intake valve opining way to soon for my non valve relief pistons. Thus causing my clearance issues. I guess that is how they get that wild sound out of them. Looks like I need to shelve, or sell this cam for now and get something a little tamer, and with a normal center line for this engine.

Thanks to every one for all the help!
 
I just had a 318 built and had a motorhome cam upgrade. A longer carry for bottom end power and it works well. Needs no adjustment or special add ons and supplys quiet a bit more power.
 
Well after much discussion with deferent friends I have decided to go with the Mopar Performance P4452992AE cam shaft

http://www.summitracing.com/parts/DCC-4452992AE/

If any one wants a thumpr cam to try I will give them one heck of a deal. LOL Looks like it would work fine with pistons that have valve reliefs. I will be listing it for sale.

Thanks again to every one for all the help!
 
Stock? The only thing stock is the pistons, rods, and crank.

71 318 short block, (pistons are not 0 deck but come up a lot closer than the later 318's I have had)

66 273 heads 1.88 1.60 valves. Milled and ported
273 rockers
Thin head gaskets
Edy LD4B intake
windage tray, deep sump pan

2500 stall converter
full manual reverse valve body
3.55 gears

TTI 2.5in exhaust
Soon to have Doug's headers

Why would this cam be a dog? Every one I have talked to seems to think it would be a good fit.


I agree that 238 is a bit steeper than I would like on duration, but I also do not want a cam that is not much over stock. This car is not a driver it is a play toy. The other cam I found that is right in there with a little less duration is this summit one.
http://www.summitracing.com/parts/SUM-1798/
Thanks
 
too much duration for a SMALL motor...but if it makes you happy...be happy...

and if you want honest answers...post the combo that you are going to build...your original post is about how big of cam with stock pistons...you dont post anything about heads...intake..converter...
 
I think you'll be fine. More compression would help the bottom end some but your running small ports with bigger valves and should have some good velocity, that will bring back some bottom end anyway. If you heads are ported well they will have quite a bit extra flow. I will pull pretty hard to 6000 RPM I would bet. Make sure you optomize the ignition timing, it will probably like 16-18 degrees inital. Should run fine on cheap gas too.
 
70aarcuda said:
too much duration for a SMALL motor...but if it makes you happy...be happy...

and if you want honest answers...post the combo that you are going to build...your original post is about how big of cam with stock pistons...you dont post anything about heads...intake..converter...
Click to expand...


Actually if you look at my second post in the thread I did list every thing in my combo at that time. Yes I have changed a few things since then, but I did map it out pretty well. So I do not see what the problem is. I am not trying to be a smart you know what, just trying to understand the tone.
 
furz4 said:
I think you'll be fine. More compression would help the bottom end some but your running small ports with bigger valves and should have some good velocity, that will bring back some bottom end anyway. If you heads are ported well they will have quite a bit extra flow. I will pull pretty hard to 6000 RPM I would bet. Make sure you optomize the ignition timing, it will probably like 16-18 degrees inital. Should run fine on cheap gas too.
Click to expand...


Thanks,
That is about what I was thinking. And thanks for the timing tip!
 
70aar is correct. That cam has far too much duration for a small displacement, stock compression engine. A good cam for a stock comp 318 would be no more than about 228 deg at .050 on the intake side and something in the 224 range would be even better.

Handicapping it with small port heads is just a mismatch. To use that cam to it's potential you'd need to bump the CR to about 10:1, get a single plane manifold and use some quality closed chamber alum heads with porting and 2.02 valves, change your TC to a 3500rpm stall and get steeper gears. that's a 6500 rpm cam in a 318 and it'll drive you nuts under 3000 rpm.
 
ramcharger said:
70aar is correct. That cam has far too much duration for a small displacement, stock compression engine. A good cam for a stock comp 318 would be no more than about 228 deg at .050 on the intake side and something in the 224 range would be even better.

Handicapping it with small port heads is just a mismatch. To use that cam to it's potential you'd need to bump the CR to about 10:1, get a single plane manifold and use some quality closed chamber alum heads with porting and 2.02 valves, change your TC to a 3500rpm stall and get steeper gears. that's a 6500 rpm cam in a 318 and it'll drive you nuts under 3000 rpm.
Click to expand...

Thanks for the info.
It should be about 9 to 9.5 to one compression. I really do not see how it would be that bad, but you must know something I do not. I am no cam expert. That is how I got roped in two this dam thumpr cam on the recommendation of comp cams. I ran a MP 484 in a 318 in high school in a charger. Drove it every day, and loved it. This is a much liter car, with more converter, and more gear. I sure am not going to go to this trouble of building an engine just to put a little smooth idling cam back in. If I was going to do that I would just leave the engine in the car that is in there. I just do not see how it is to big. But I am open to ideas.

What about this cam?
http://www.yearone.com/serverfiles/fbshopmain2.asp?input=fd1416&SM=1&SC=
Would it be noticeable in a 318?
 
604 said:
Thanks for the info.
It should be about 9 to 9.5 to one compression. I really do not see how it would be that bad, but you must know something I do not. I am no cam expert. That is how I got roped in two this dam thumpr cam on the recommendation of comp cams. I ran a MP 484 in a 318 in high school in a charger. Drove it every day, and loved it. This is a much liter car, with more converter, and more gear. I sure am not going to go to this trouble of building an engine just to put a little smooth idling cam back in. If I was going to do that I would just leave the engine in the car that is in there. I just do not see how it is to big. But I am open to ideas.

What about this cam?
http://www.yearone.com/serverfiles/fbshopmain2.asp?input=fd1416&SM=1&SC=
Would it be noticeable in a 318?
Click to expand...

i had 9.2:1 on my slant on the first go around... and with the 246 @ .050 cam it was pretty lazy all around... it would bleed off alot of compression...

so i bumped it up to 10:1 and now the thing idles better, runs like a raped ape, and still get 20mpg with 3.91's while going to mats...
 
805moparkid said:
i had 9.2:1 on my slant on the first go around... and with the 246 @ .050 cam it was pretty lazy all around... it would bleed off alot of compression...

so i bumped it up to 10:1 and now the thing idles better, runs like a raped ape, and still get 20mpg with 3.91's while going to mats...
Click to expand...


Hay thanks!
And off subject but man I love your 65 Plymouth!!!!! I have always wanted an altered mopar. Thinking about doing it to my other 65 dart some day. But I have to ask. How bad is it driving one set up like that??

Thanks!
Kevin
 
604 said:
Hay thanks!
And off subject but man I love your 65 Plymouth!!!!! I have always wanted an altered mopar. Thinking about doing it to my other 65 dart some day. But I have to ask. How bad is it driving one set up like that??

Thanks!
Kevin
Click to expand...

i dont know yet its not done BUT... my boss had one he built and he said its BETTER than a normal car... becasue it turns on a dime... as long as you get the front suspension square its gonna go straight...

P.S. mine is torsion bar not Straight axle...
 
Cool! I looked at your video and saw the front suspension. Should be one nice ride!
 
604 said:
Well talked to another guy at comp cams and he seemed to really know his stuff. He could not understand whey some one else had recommended the thumpr. Well any way this is the cam he recommended. From the input on hear it looks to fit the bill

http://www.summitracing.com/parts/CCA-20-223-3/
Click to expand...

And there you go, a cam with intake duration in the mid 20's. :) That should fit the bill nicely.
 
Cam line techs are all different.I like Crower.I called three different times,(to find out)what cam for a 408 SBM.All three answers were different.I was given a name by a ex employer,I called him last.He picked the cam that made sense.I did this as a experiment to see how this would happen.
 
Abodybomber said:
Cam line techs are all different.I like Crower.I called three different times,(to find out)what cam for a 408 SBM.All three answers were different.I was given a name by a ex employer,I called him last.He picked the cam that made sense.I did this as a experiment to see how this would happen.
Click to expand...

well whats good about that is your getting experienced quotes, not computer printouts....
 
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