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Overkill Cam?

Bedwards

Bedwards

New member
Anyone ever heard anything about the cam from Overkill? I have a guy wanting to trade it for my 1.9 rockers, since he doesn't want to install it. He bought like 3 years ago, but he can't remember the name, and doesn't have the specs on it.
 
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Will emailed me back and thinks it is the SBC cam. It measures 210/220 @.050" with 116LSA and .507 lift with 1.6 rocker arms. He said:

The cam lobes it uses are the same CompCam lobes*as ZZP's naturally aspired camshafts; they have a very fast opening rate, so while the duration and max lift may seem ho-hum, the lobe is very fat at mid-opening, so the valves stay open at and above .300" lift longer than the specs would suggest.
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What do you guys know about this cam?
 
I say just go to a S1X or XP...tired and true...both awesome cam choices. That is a pretty small cam, about the size of a VS...and honestly...you won't see MUCH more gains over a good 1.9 rocker setup. Granted, a cam is better than rockers...but a VS vs. 1.9's...probably not worth the work IMO. If you do get it...get 1.7 rockers to make the lift even more...that, I could see being worth it.
 
^^^^

You're only judging it on the size of its max lift. I sent the gentleman originaling posting a detailed email on the whats and whys of the cam's design.
 


I think I'm going to go with this cam (after I learn some tuning skills), assuming the cam the guy has is the same one Will gave me information for. Thanks Will!
 
matt5112 said:
the duration places it above a VS, but still not up to XP or S1X levels.
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Don't be so sure. Assuming the IS1x cam has the same ramp rates (opening rates) as their IS3 cam, the .200 duration on the S1x would be 126/137. This compares to 126/136 for the VS cam, 131/138 for the Overkill cam in question, 133/145 for the XP cam.

.200" duration is very important yet rarely given in a cam's spec sheet. Look at any flow numbers for a cylinder head and you'll see the head flows very poorly until above .300" lift. Combine .200" cam lift with a typical 1.5 rocker arm ratio and you get .300" valve lift. The duration at .200" spec will show how long the camshaft will keep the valves open at lifts where the heads really start to flow, gives you an idea of the potential flow of the cam.

Max lift may be a spec that sells to consumers but in reality the difference between .500" lift and .550" on stock 3800 heads is about 1% gain in flow and the time spent at max lift is very minimal. The VS and Overkill cam could be enhanced with 1.7 rocker arm ratios even on stock heads and the extra lift gained is not the real benefit; because the rocker arm ratio amplifies every movement the cam makes, it makes the ramp rates even quicker, so .300" valve lift is achieved ever quicker.

That's just a quick point of view on the whats and whys of the cam design. It doesn't take into other considerations such as duration below .050" lift (which is what most cams are rated at) and how that effects idle and emissions and overlap, doesn't take into effect intake centreline or intake closing points and how that effects cylinder fill etc.

I don't sell the cam anymore, I have no vested interest other than I did custom design it for my beta tester, he had very good success with it (300+whp non-IC GenIII about 5 years ago which was very rare at the time), there are quite a few locals with the cam and very happy with it, but it was difficult to market, to educate the whats and whys, and as I still see people see the modest duration and lift who say its a small cam buy something else, I just wanted to put in a detailed reply.
 
Good call Will. Hope to see some good results from his car then. I always suggested a cam sitting at a lower lift rate to utilize a higher ratio set of rockers...as 1.7's compared to the stock 1.6's...But your convincing statement on duration has me wondering. I know my cam MAKES more power than my XP...I noticed the for sure difference...as I also know its a higher RPM performer...and I can feel it pull harder up top than my XP did. But...is it really worth all the lift? Sitting at .574/.566 @ 114 LSA and at .050" I'm at 224 across the board.

Thoughts?
 
bluegtp91 said:
Good call Will. Hope to see some good results from his car then. I always suggested a cam sitting at a lower lift rate to utilize a higher ratio set of rockers...as 1.7's compared to the stock 1.6's...But your convincing statement on duration has me wondering. I know my cam MAKES more power than my XP...I noticed the for sure difference...as I also know its a higher RPM performer...and I can feel it pull harder up top than my XP did. But...is it really worth all the lift? Sitting at .574/.566 @ 114 LSA and at .050" I'm at 224 across the board.

Thoughts?
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Sounds like you have XFI lobes? If so you have 149/147 .200" lift I/E which is very good. IS3 is 138/144 with similar duration so you're far ahead.

With a 112 intake centreline you'd have +48 exhaust opening and -44 intake closing which are good numbers. I did an XFI cam with 224/236 duration, similar intake closing, had great top end, shook welds loose on the exhaust system but I'd reduce the exhaust duration doing it over again as the exhaust opening was very early and I lost some mid-range torque.

If your head flow ratio is 80% intake:exhaust, the cam need not be so exhaust biased. Your single pattern cam isn't such a bad idea.
 
will, the cam nick bought is a TEP. the TEP from what i remember having was .566/.566 at peak lift on 1.6s, but for some reason they changed the grind and are still selling it under the same name.
 


our full spec sheet
gross lift .574/.566
duration @.006 tappet lift 274/276
valve timing @.050 Int:1 BTDC 43 ABDC
exh:49 BBDC -5ATDC
duration @.050 224 224
Lobe lift .359/.354
lobe separation 114
 
^^^

I remember the TEP originally being 222/222 duration and .566 lift as well. They've changed to the XFI lobes from CompCams based on those specs. It'll have a little blowthrough on the exhaust by the boost at mid-rpm but the exhaust doesn't open and release the energy too early and the intake closes fairly late to help cylinder filling at higher rpm. Probably losing mid-range torque but can see it being a very good high rpm cam.
 
Overkill said:
^^^

I remember the TEP originally being 222/222 duration and .566 lift as well. They've changed to the XFI lobes from CompCams based on those specs. It'll have a little blowthrough on the exhaust by the boost at mid-rpm but the exhaust doesn't open and release the energy too early and the intake closes fairly late to help cylinder filling at higher rpm. Probably losing mid-range torque but can see it being a very good high rpm cam.
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Thanks Will.

I never went that deep into researching for a cam choice. I just heard Chris Green went low 12's on it with just heads, IC, pulley, TEP Cam, injectors, and a custom tune...stock everything else...even transmission/all season tires. I have a Triple Edge Transmission...and slicks...and P&P'd custom heads. I figured low 12's on a COLD day with awesome track prep...but from my speedo video people tell me its an 11's car no problem...and I find that hard to believe.
 
Overkill said:
Sounds like you have XFI lobes? If so you have 149/147 .200" lift I/E which is very good. IS3 is 138/144 with similar duration so you're far ahead.

With a 112 intake centreline you'd have +48 exhaust opening and -44 intake closing which are good numbers. I did an XFI cam with 224/236 duration, similar intake closing, had great top end, shook welds loose on the exhaust system but I'd reduce the exhaust duration doing it over again as the exhaust opening was very early and I lost some mid-range torque.
Click to expand...

Sounds like the specs off of the cam I bought from you a couple of years ago that you called the BBC Prototype....and, it wins all around. Although, I've tamed the idle, the power band is amazing IMO and I couldn't be happier with my choice.
224/236 duration, 573/571 lift, 115 * LSA
 


Reptile said:
Sounds like the specs off of the cam I bought from you a couple of years ago that you called the BBC Prototype....and, it wins all around. Although, I've tamed the idle, the power band is amazing IMO and I couldn't be happier with my choice.
224/236 duration, 573/571 lift, 115 * LSA
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That's the one. Glad to hear you're enjoying it. I ran a 3000 stall converter and 3.69s when I ran it, so torque wasn't a high priority, I just wanted it to run like hell above 4500rpm. I wish I still had a video of it idling, had to take the car to a better exhaust shop, redo most of the welds!
 
Bah, Solid mounts keep the idle in check, although driving down the road makes her sing in the ol' floorboard pretty good. LOL

I've yet to take it to the track unfortunately, but it's probably a little on the stupid side. the 245/45/17's don't stand a chance with even 3.29 gears.
 
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