the pistons are Keith Black KB 107-040, but yeah not 100% sure on the compression.
360cu Engine Upgrades
- Thread starter Trivium91
- Start date
the pistons are Keith Black KB 107-040, but yeah not 100% sure on the compression.
Ok so i think the compression ratio im being told is not accurate. I checked out a few sites and they are all saying with 72CC heads compression ratio should be right around 9.8. so with Stock heads around 9.7: 1 im thinking? Source is here:
KB Mopar 360 Pistons Hypereutectic Chrysler Plymouth Dodge 360 Pistons
the pistons are the KB107 40
At any rate im thinking to go with either the Comp Cam XE 274 or XE 268, im leaning towards the XE274 as ive read a few other forums with 10 year old posts that were recommending them with my keith black pistons. I would love to go with the thumpr series since i already have a high stall, however it sounds like thumpr wont work work with my heads without machining them to fit the springs.
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The XE-274 doesn't require any machine work to heads that I'm aware of. You might be thinking Magnum heads that have a max valve lift of .525" and require machining of the spring seat for more. This cam can be used with factory style rockers - you don't need to spend $800 on a set of adjustable rockers. Mopar used to sell a slightly heavier version of the factory stamped steel rockers. I used those for years with that cam.
You'll like it. A 3k stall and 3.90 gears will compliment it well. You didn't say what you have for exhaust, but headers are a must.
You'll like it. A 3k stall and 3.90 gears will compliment it well. You didn't say what you have for exhaust, but headers are a must.
Right i cant remember the brand (headman maybe) but they are long tubes headers out of dual 2.5" Magnaflows.
Basically i've narrowed my cam choices down to the following:
XE-274
XE-268
Thumpr 279TH7
the 268 was an option case the 274 will cause problems for me with the 587 J heads (367587-12). I really wanted the thumpr as i have a high stall already but it sounds like it needs dual valve spring's and otherwise modifications to make it work as its not really designed for stock heads.
Oldiron440
Well-Known Member
If your planning on using parts or part of your currant combination you should pull it apart and not make assumption's. because they bite me in the butt every time.
Well I’m 100% sure at this point that the compression is only 9.7:1 based on the fact that I have stock heads which I’m told is 73 CC so I Don’t think I’m assuming anything at the moment, unless I’m missing something else? And of course the headers I’m not sure of the brand, no way to tell at this point.
M_Body_Coupe
Well-Known Member
The Thumpr grinds produce that sound due to the match larger exhaust duration...take a close look at the specs.
Depending on the exhaust valve open/close events (timing) this may impact the behaviour of the cam more than just the sound of course, hard to tell w/o looking at the numbers.
If you want that sound make sure you stick closely to the cam recommendations as far as your combo goes, anything else is just shooting in the dark!
Depending on the exhaust valve open/close events (timing) this may impact the behaviour of the cam more than just the sound of course, hard to tell w/o looking at the numbers.
If you want that sound make sure you stick closely to the cam recommendations as far as your combo goes, anything else is just shooting in the dark!
Alright well I got someone more knowl
alright well I got someone more knowledgeable that knows the engine as well to look at the xe274 cam, sounds like this is the one I’m getting. That being said, I should probably look at getting some adjustable rocker arms. Any suggestions that don’t cost $600?
alright well I got someone more knowledgeable that knows the engine as well to look at the xe274 cam, sounds like this is the one I’m getting. That being said, I should probably look at getting some adjustable rocker arms. Any suggestions that don’t cost $600?
SuicideRider
Active Member
I had good luck with the 268 cam in an otherwise stock 360 in an 83 ramcharger. Woke the big heavy truck right up.
jasperjacko
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I would never build for a sound. Set a performance goal, do your research, and use proven combos of parts. You will be happy.
AJ/FormS
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What elevation are you at?
You would likely be 100% wrong, because you cannot be sure, until you know, and you cannot know until you measure it.
You could say;you are 100% sure the ratio is NOT 15:1, that would be pretty safe. But the difference between 9.7 and 10.7, is 8.9cc, or ~.042 in deck height, or about the difference between a flat-top piston and a dished piston.
You say you have KB107-40s in there, but did you put them there?
You say the heads are such and such, but did you measure them?
The reason I'm being a dick is because if your Scr is not high enough,for the cam you want to run,then your off-idle power will take a dump and then you will need a Big TC. But your midrange to 3000/3500 will also be poor. Again requiring a bigger TC to bandaid.
And there is no good reason to put up with that in your application.
You would likely be 100% wrong, because you cannot be sure, until you know, and you cannot know until you measure it.
You could say;you are 100% sure the ratio is NOT 15:1, that would be pretty safe. But the difference between 9.7 and 10.7, is 8.9cc, or ~.042 in deck height, or about the difference between a flat-top piston and a dished piston.
You say you have KB107-40s in there, but did you put them there?
You say the heads are such and such, but did you measure them?
The reason I'm being a dick is because if your Scr is not high enough,for the cam you want to run,then your off-idle power will take a dump and then you will need a Big TC. But your midrange to 3000/3500 will also be poor. Again requiring a bigger TC to bandaid.
And there is no good reason to put up with that in your application.
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Well sounds like i will buying the 274 Cam and measuring out those things while its all apart to properly measure compression, hopefully i dont have to return the Cam. I did read some other forums where guys were using the 274 cam with the same pistons and stock heads. They even used OEM rocker arms but claimed they wore out in 8000 miles. Does anyone have a recommendation of rocker arms for stock 587 J heads?
I used these: Mancini Racing Steel Rocker Arms w/Shafts, 1.5 Ratio
Factory style. Racked up a shit ton of miles on the motor the decade I ran it.
Factory style. Racked up a shit ton of miles on the motor the decade I ran it.
Awesome thanks! Great price aswell. Are these adjustable? Or did you not need them to be adjustable when you had your 274 cam?
On a side note im thinking I will also be pulling one of the heads off to check deck height as that's the only unknown to get an exact value for the compression. Im pretty certain its just shy of 10:1 at this point, but yes i agree with everyone that it does not hurt to double check and that im not 100% sure. I believe they make a special tool for checking the deck height.
M_Body_Coupe
Well-Known Member
Static CR is only one of several metrics, something a little more precise, perhaps more relevant would be to do a cranking pressure test on what you currently have.
Make sure the battery is up to charge, go WOT (but of course make sure the ignition does not actually carry through to the plugs), give it a good 3-4 turns (engine spins) per each cylinder and see where the pressure gauge goes.
Here is why this is the only way to tell what your current combo gives you: the statis CR combined with the cam timing events will either give you a decent cranking pressure, or not.
Case in point, this is what I had gone through with a Hughes HE3844AL hydraulic flat tappet cam (286/290 advertised dur, 238/244 dur @0.050, .535/.540 lift, 108 LSA):
1) blueprinted static CR of 9.7:1, cranking pressure of 165 PSI
...followed by:
2) blueprinted static CR of 10.5:1, cranking pressure of 185 PSI
Now in my case I had actually planned to do some porting work on the heads and since they were off already I literally decided to run a little experiment to see first-hand what a point of compression bump would do to this motor. This required a cut to the heads, stuff was of coursed measure out, and the appropriate adjustment made on the intake side as well.
End result (keep in mind I run this thing on 91 octane premium with a loose converter), motor of course sounded a tad different (was actually surprised about the amount of extra 'crispness' in the exhaust note), the off idle was better but given that there was already plenty of power up-top I couldn't really tell much difference.
Now at the track I went 2mph faster in the 1/4 mile, but my 60' times just sucked shit, even more so following the changes...I went from a best of 1.87 to 2.09. But I had sort of expected that dismal performance given that the car is not set up at all for 1/4 mile racing (no weight transfer).
Anyways, the fact that I gained mph means the motor made more power. Hard to tell what's due to the increased static CR and what was due to increased head air-flow.
Make sure the battery is up to charge, go WOT (but of course make sure the ignition does not actually carry through to the plugs), give it a good 3-4 turns (engine spins) per each cylinder and see where the pressure gauge goes.
Here is why this is the only way to tell what your current combo gives you: the statis CR combined with the cam timing events will either give you a decent cranking pressure, or not.
Case in point, this is what I had gone through with a Hughes HE3844AL hydraulic flat tappet cam (286/290 advertised dur, 238/244 dur @0.050, .535/.540 lift, 108 LSA):
1) blueprinted static CR of 9.7:1, cranking pressure of 165 PSI
...followed by:
2) blueprinted static CR of 10.5:1, cranking pressure of 185 PSI
Now in my case I had actually planned to do some porting work on the heads and since they were off already I literally decided to run a little experiment to see first-hand what a point of compression bump would do to this motor. This required a cut to the heads, stuff was of coursed measure out, and the appropriate adjustment made on the intake side as well.
End result (keep in mind I run this thing on 91 octane premium with a loose converter), motor of course sounded a tad different (was actually surprised about the amount of extra 'crispness' in the exhaust note), the off idle was better but given that there was already plenty of power up-top I couldn't really tell much difference.
Now at the track I went 2mph faster in the 1/4 mile, but my 60' times just sucked shit, even more so following the changes...I went from a best of 1.87 to 2.09. But I had sort of expected that dismal performance given that the car is not set up at all for 1/4 mile racing (no weight transfer).
Anyways, the fact that I gained mph means the motor made more power. Hard to tell what's due to the increased static CR and what was due to increased head air-flow.
MBDale
Well-Known Member
On the topic of heads, with a stock 2.02 J head using stainless steel,swirl polished nail head valves, would that raise compression over stock steel valves?
So what would have to be done exactly to the heads, when you say port for 2.02 this is machining the intake ports from 1.88 to 2.02? What other port work would i need to do? Just polishing?
Provided i skip all that head work for now and assuming the following, what sort of power could i expect?
-9.8:1 Compression Ratio, stock stroke @3.580" Bored .040 Over.
-RPM Performer intake
-750CFM performer carb
-Headers
-XE274 Cam
-Stock 1.88 J heads
I might look into a different electronic ignition after all this aswell, im not convinced that it will add anything for power but might make things more responsive.
If i can get at least 350HP i would be happy, anything over 400HP is going to yield me tickets with the 3.91 rear end, so im trying to keep it under that.
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barbee6043
Well-Known Member
What is the rear end gear?, that is the first thing in seat of the pants feel!! Then TC, and don't forget a good tune.
The heads are your bottleneck. They flow around 185 CFM in stock form. I would put the motor in the low 300's for horse power.
I would take the heads to a shop and have them open the intake valves up from 1.88 to 2.02. Minor port and bowl work to get rid of casting slag and gasket match the intake ports. Don't go nuts. You'll have a solid 350 HP when all is said and done.
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