360 & high lift cam

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MR4V

MR4V

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Just about to buy the parts to rebuild my 360. This is what I'm looking at.
360 + 30thou, balanced.
Flat top pistons with fly cut or valve relief
Zero deck with 10.1 comp
J port heads with pocket port, 2.02 & 1.60
Roller rockers 1.5 ratio
Air gap with 750 hp Holley
130 GPH fuel pump
This is the first time this 360 will be milled & the heads have plenty of meat left in them.

Now I want to run mechanical flat tappet cam & the cam I have been looking at is a Comp Cam part number 20-247-4 with .495/.495 lift & duration @ 050 of 236/236.

What I want to know is if I increase the lift to one of the following what problems am I going to have?

Comp Cam number 20-248-4, lift .525/.525, duration @ 50 248
Comp cam number 20-230-4, lift .502/.511, duration @ 50 242
Comp cam number 20-231-4, lift .520/.540, duration @ 50 252

I will be running an auto & 3.7 rear

Thanks
 
I am currently doing the exact same build with KB107's and I am using the comp 20-248-4 cam. So far the short block is assembled, but heads are waiting to be ported. I am interested too. Subscribed.
 
I got a 360 .020 with kb107 pistons...it has a Engle 253 @.050 duration cam with .600 lift with 1.6 rockers... I have a quench around.....adding in my heads....041 thousands...

it has eddy magnum aluminum heads...
 
SB Mopars generally have a lot of valve to piston clearance so .600 lift is not uncommon. The only problem I can think of is the retainers hitting the guides if the guides aren't cut down for more clearance. In stock form they usually won't handle over .500 lift before the retainer hits the guide. Sometimes even less than that. I had a set of J heads once that were stock and wouldn't handle over .460 lift.
 
yes..the heads will need to have the guides shorten..and narrowed if running dual valve springs along with the correct valve spring and retainer to work with the cam you choose..
 
As this is a street engine with a rev limit of 6500, a stall that is matched to the cam & very tight to suit the street the pistons are Speed Pro Z8KH116PC30 Hypereutectics.

So if I mill down the the valve guildes I should be ok to run .540 to .580, will I need the mill the spring seats to suit heaver springs?
 
I would recommend this one:

Comp cam number 20-230-4, lift .502/.511, duration @ 50 242

Even with pocket porting, the "J" heads will waste a camshaft with much over .500" lift. They are just not made to flow that much. right at or below .500" lift, they really shine. It's not always about flow. With the "J" and "X" heads it was more about velocity. The duration figures on the other two camshafts is really too much for what you have. That cam's duartion above is almost too much. 242 degrees is a heap. You have enough gear to compensate for it, though. I would stick with that smaller grind. You'll be much happier when you stab the gas. Just my opinion.
 
StrokerScamp said:
I would recommend this one:

Comp cam number 20-230-4, lift .502/.511, duration @ 50 242

Even with pocket porting, the "J" heads will waste a camshaft with much over .500" lift. They are just not made to flow that much. right at or below .500" lift, they really shine. It's not always about flow. With the "J" and "X" heads it was more about velocity. The duration figures on the other two camshafts is really too much for what you have. That cam's duartion above is almost too much. 242 degrees is a heap. You have enough gear to compensate for it, though. I would stick with that smaller grind. You'll be much happier when you stab the gas. Just my opinion.
Click to expand...

Thanks for that. The engine builder has recommended a duration of between 242 & 248 @ 50.
With the Comp cam above ( 20-230-4 ) is it still recommended to mill down the guilde?
 
Any modern cam you want to run will need the guides and spring seats cut for dual springs and the positive seals... I have this done on every head I get done now. Doesn't make sense not to anymore.

StrokerScamp said:
Even with pocket porting, the "J" heads will waste a camshaft with much over .500" lift. They are just not made to flow that much. right at or below .500" lift, they really shine. It's not always about flow. With the "J" and "X" heads it was more about velocity. The duration figures on the other two camshafts is really too much for what you have.
Click to expand...


I would say you've got the right idea, but I don't agree with this statement 100%. There are a couple things I see that I'd consider off. The general idea of "smaller is better when choosing a cam for a street car" I agree 100% with. If you blueprint the engine and really get a true 10:1 out of it, I don't think 230-240° will be "too much". If you don't get the compression, I wouldn't go more than about 225°@.050 because bolting the parts together will give you around 9.3:1 depending on the parts, and that's going to be sluggish below 2500.

The issue with LA mopars that applies to these heads as described is the pushrod angle. With any Mopar head, stock 273 to W2 and a 58° (factory) block, you will lose around .016-.022" lift on both intake and exh just because of the poor angles of the pushrod. Some engines will lose more, depending. So when you are looking to choose a flat tappet, you have to take off the lash figure, plus the loss thru the pushrod right off the bat. That leaves us with .480 out of the gate with the XE282S.
In addition to that, the statement that the heads don't flow so don't bother is not really accurate either. You want to give the heads the best chance to get the mix in... That means being open for the longest period of degrees as you can. If the heads peak between .350 and .450, and you run a cam that is really only .480 at the valve, and 245°@.050 , it's only spending about 100° actually above the .350 mark where the heads want to flow. You want to get the best lift under the curve for your heads, which usually means lifting about .050 beyond the highest flow rate (which is a guess if the heads weren't flowed) and keep the duration at .050 decent enough to keep the valve open where the heads will make good use of it. This would be especially true with ehads that are mildly or home ported because the low lift may not have been drastically improved by the work. I think I might suggest something like the XS268S with 1.6 rockers or up the compression slightly and use the 1.5s on the Lunati 60442 which would be rather hairy in this build but I think a bit better than the Magnum 292 solid.
 
I think the 236 .495 cam would be a very nice street cam. Not too big and real torquey. I am all for low end torque and response.
 
Moper, nice reply. Good read! Good job!
 
rumblefish360 said:
Moper, nice reply. Good read! Good job!
Click to expand...

I will second that.
The 360 will be blueprinted so 10.1 is achieved, the heads will also be flowed & porting keeped to a minium & I want to stay with 1.5 ratio rockers.
The target is to get 330-350RWPH for a Dart & mid 12s.
I'm I aimming to high I do not think so.
 
I've read in EngineMasters that you can run a higher duration cam with high compression such as yours, otherwise you risk detonation with pump gas unless you plan on getting higher octane fuel. The latest issue had a comparison of different CompCam lift/durations and the best all around with a nice torque curve was the XE268H. Its got .477/.480 lift and 268/280 advertised duration. They considered it one of the best grinds for the street. The Chevy engine they were using had a compression ratio of just under 11:1. Here's the link for the Chrysler part #:

http://www.compperformancegroupstor...en=CTGY&Store_Code=CC&Category_Code=LACAMHFHE
 
MR4V said:
The target is to get 330-350RWPH for a Dart & mid 12s.
I'm I aimming to high I do not think so.
Click to expand...

I think your doing good.

rick360 said:
I've read in EngineMasters that you can run a higher duration cam with high compression such as yours, otherwise you risk detonation with pump gas unless you plan on getting higher octane fuel. The latest issue had a comparison of different CompCam lift/durations and the best all around with a nice torque curve was the XE268H. Its got .477/.480 lift and 268/280 advertised duration. They considered it one of the best grinds for the street. The Chevy engine they were using had a compression ratio of just under 11:1. Here's the link for the Chrysler part #:

http://www.compperformancegroupstor...en=CTGY&Store_Code=CC&Category_Code=LACAMHFHE
Click to expand...

He shouldn't have a detionation issue with the build. If there was to be one, iot would come with a smaller cam. Avoiding detonation with a smaller cam, a retarding of timing would solve that issue but limit max HP output. "The cave eat" of improper parts selection.
 
MR4V said:
I will second that.
The 360 will be blueprinted so 10.1 is achieved, the heads will also be flowed & porting keeped to a minium & I want to stay with 1.5 ratio rockers.
The target is to get 330-350RWPH for a Dart & mid 12s.
I'm I aimming to high I do not think so.
Click to expand...

As long as the heads are done right that's achievable. Air flow is key. If you don't mind running a solid cam you'd meet your goal much easier. A buddy of mine ran a comp 20-231-4 in a 9.7 to 1 compression 340 with minimal porting on X heads and ran 12.30's in a full street 67 Cuda. It's kinda nasty idling but super responsive. It also requires a 3000+ stall converter but most all the others you are looking at also require a converter of similar size.

Oh yeah, I can attest to Moper's comment on the lift loss. I played with a couple cams in an old engine I had measuring actual valve lift at the cam and found that with geometry as perfect as you can get you still loose at least .015 lift. If the geometry is off lift loss can go considerably higher than that.
 
Running a solid cam is the aim & the stall will be very tight so it is easyer to drive on the street.
The valve geometry loss is interesting, this is my first Mopar so reading up on them I decidered to treated it like a Ford street engine thats how I came up with the above combination & RWHP.
 
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