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Difference in performance between these two camshafts?
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Timmo
Posted 2016-01-27 1:05 PM (#502480)
Subject: Difference in performance between these two camshafts?



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Location: Egg Harbor Township, NJ
Currently running a PAW camshaft P/N 11361 advanced 4 degrees

Lobe Lift---Valve lift---Adv. Dur.---.050 Dur.---Lobe Sep.
---.293------.440----------270---------218----------110

This is the cam that came with the motor when I purchased it years ago. It has always been run 4 degrees advanced (cuz that's how it was when I bought it).


I was considering switching to a Hot Heads cam P/N 23002.392

270@111 (.465 lift, 221 Dur .050, 111 ls) 392


Is there any benefit switching out the cams? Any increase in performance? Should the current cam be run with 4 degrees advance? Or, should I just leave well enough alone?

Car description is in the signature. Recently added a hot heads single 4-barrel intake. This is the same car run in the dyno video a few posts down:

http://www.forwardlook.net/forums/forums/thread-view.asp?tid=60250&...

Edited by Timmo 2016-01-27 1:08 PM
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Shep
Posted 2016-01-27 5:16 PM (#502504 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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That cam will make slightly more power at the upper levels, that said modern cams have different lobe profiles than old style ones, even if the specs are close or the same, so there is some guess work involved.
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Timmo
Posted 2016-01-27 6:11 PM (#502505 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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Both the cams seem to me as though they are pretty close. It's really getting down to the setup of the engine combined with the platform the motor is in. In this case, it's a forward look car, with an early hemi engine and some simple performance upgrades. I'm hoping there is a guru that knows what would be the right choice for this particular chassis and motor combo. (considering vehicle weight, gear ratios, carburation, intended use, and so on)



Edited by Timmo 2016-01-27 6:14 PM
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Shep
Posted 2016-01-27 9:40 PM (#502525 - in reply to #502505)
Subject: Re: Difference in performance between these two camshafts?



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Gotta be on the conservative side with a heavy car, with a stock convertor , the 3.91 gears give you little margin for more duration, but not much.

Edited by Shep 2016-01-27 9:42 PM
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wayfarer
Posted 2016-01-28 11:23 AM (#502559 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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If the engine runs well and the car has adequate power for your needs then why screw with it? The two profiles are very similar so you would gain little in performance and as noted, a bigger cam in a heavy car needs a deeper gear.
If for no other reason, the $500-600 outlay would discourage me.
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57chizler
Posted 2016-01-28 2:50 PM (#502579 - in reply to #502559)
Subject: Re: Difference in performance between these two camshafts?



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I agree, any performance gain won't be felt by the old "buttmeter" and would minimal on a dyno.
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Timmo
Posted 2016-01-28 4:01 PM (#502591 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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Ok. Good enough for me. Thanks for the input guys.
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Chrispy
Posted 2016-02-23 1:58 PM (#504970 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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Im in deep on my cam selection and you are quite right, these are very very similar in my modeling, the paw is slightly stronger down low, but the HH cam is a little stronger up at 4500 to 6k. Not a huge diff and not worth it.
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Powerflite
Posted 2016-02-24 1:50 AM (#505021 - in reply to #504970)
Subject: Re: Difference in performance between these two camshafts?



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If you would like a little more high end performance, you can take your current cam and remove the 4 degree advance on it. Most likely that was done to work better with a stock converter. But you might be able to live with it or else increase the stall speed of your converter a little.
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Timmo
Posted 2016-02-24 7:09 AM (#505039 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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I don't want to lose any down low power. I was considering the Hot Heads cam only if it would give me at least the same low end power, and a bit more up top. If I can't feel it in the butt-dyno, than it isn't worth it to me to spend the extra money on a different cam anyway.
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Powerflite
Posted 2016-02-24 10:11 AM (#505046 - in reply to #505039)
Subject: Re: Difference in performance between these two camshafts?



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A friend of mine had a '68 Mustang that we dropped a 351 motor into. We also put a performance cam with around 270 degrees total duration, so very similar to what you have. Initially, we put a 4 degree advance on it thinking that it would give us a lot of low end torque, but the car ran like a dog. It just seemed anemic and gave worse performance than the 289 that he originally had in the car. He was really disappointed with it and was even thinking of putting the old motor back into it. But on a whim, we decided to set the cam back to 0 degrees and it was like night and day. The motor really woke up and performed great - not as great as the 392 hemi in my Barracuda though as I HAD to prove to him. That's my only experience with advanced cams so that's why I suggested it.

Edited by Powerflite 2016-02-24 10:26 AM
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Shep
Posted 2016-02-24 10:34 AM (#505048 - in reply to #505046)
Subject: Re: Difference in performance between these two camshafts?



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Advancing or regarding the cam can be guess work at times, duration at .050, LSA, and intake centerline all are part of equation, some cams are already designed with maybe 4 degrees advance, the cam manufacturers should always be consulted here. Of course, weight, gearing and compression are also in the mix. Very easy to over cam a combination, and as discussed already, torque in mid range is the target for street cars.
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Chrispy
Posted 2016-02-24 1:23 PM (#505062 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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Retarding to 0 might not be a bad idea, you'll trade a very small amount of low end for a little bit of top end. Do you plan to dyno again once you get the serp belt setup? i'd love to see what your changes have done since the last dyno pull.
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Timmo
Posted 2016-02-24 4:15 PM (#505076 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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I may do another dyno run at some point, but probably not for at least a few months or even longer. I would like to try adjusting the cam timing but I don't want to have to pull off the timing cover right now. I only just got the car back on the road for the first time in 8 years a few months ago.
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Powerflite
Posted 2019-08-01 10:44 PM (#585510 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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I am thinking of putting this hot heads cam into my 331 hemi with the same specs as above. I am a little concerned about it because this motor has low 8.5:1 compression. But the intake and exhaust flow great. What do you think? Will the 8.5 compression make this 270 cam a problem to run?
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wayfarer
Posted 2019-08-09 11:16 AM (#585820 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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The 221@050 is tolerable in 8½ c/r engines, just not ideal...but then nothing is I guess... I'd be asking about the amount of overlap as this will definately affect performance.
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Powerflite
Posted 2019-08-11 11:48 PM (#585884 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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Thanks Wayfarer. What amount of overlap would be acceptable and how does that affect the way it runs?
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wayfarer
Posted 2019-08-12 11:50 AM (#585904 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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First, consider that the advertised c/r was very optimistic and 8½ may actually be 8. Then mix in a 3500+ lb car.....

'Positive' Overlap is the period of time when both the intake and exhaust valves are open/off-the-seat. (And yes, there are many
profiles with 'negative' overlap where both valves are on-the-seat/closed for a couples degrees.)
The longer that the valves are both open the more cylinder pressure you will lose through the open exhaust valve and, essentially,
lower the effective c/r. For the average, stock, 331 I would probably keep the overlap to a max of about 4°, and '0' would be better.
This is my personal opinion only, others will have differing experiences.
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1960fury
Posted 2019-08-12 3:30 PM (#585915 - in reply to #585904)
Subject: Re: Difference in performance between these two camshafts?



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wayfarer - 2019-08-12 11:50 AM

First, consider that the advertised c/r was very optimistic and 8½ may actually be 8. Then mix in a 3500+ lb car.....

'Positive' Overlap is the period of time when both the intake and exhaust valves are open/off-the-seat.


I know that you know what overlap is, but the correct way to describe it is, it is the time when both the intake and exhaust valves are off the seat at the same time.
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Powerflite
Posted 2019-08-20 12:22 PM (#586285 - in reply to #502480)
Subject: RE: Difference in performance between these two camshafts?



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Got a response from Hot Heads. Looks like they are selling an Isky cam. I am confused by the card though, it says "48 degrees overlap", but if you look at when the exhaust opens and the intake closes, there is -1 degree of overlap or 0 overlap. I assume that's the right number since 48 would be obnoxiously large. But what is that 48 degree number referring to?

Also, I don't see how overlap would affect the compression because the exhaust is open, letting the spent gases out, and then the intake opens to let the new fuel in. Overlap occurs between these. Both valves are well closed during the compression stroke so it seems that the overlap will just affect how much exhaust gas will blow back up your intake during low rpm and affect how much fuel is able to get into the motor during that time - a low rpm driveability issue, not a compression issue. Do you agree? Anyway, I think that 0 degree of overlap should work out well for me.

Edited by Powerflite 2019-08-20 12:26 PM




(270 cam card.jpg)



Attachments
----------------
Attachments 270 cam card.jpg (162KB - 36 downloads)
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1960fury
Posted 2019-08-20 4:17 PM (#586298 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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in open 24° before TDC, ex close 24° after TDC
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Powerflite
Posted 2019-08-20 6:31 PM (#586302 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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I see that those are the total overlap, including very small movement, but the -1 degree number is the amount before .05" of lift. I am thinking that the number at .05" is the one that matters more.
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wayfarer
Posted 2019-08-25 1:57 PM (#586546 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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Yup, 48° is a big number.
You do know that you can call Isky and buy direct....? They will help you choose a better profile.
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Powerflite
Posted 2019-08-25 5:26 PM (#586552 - in reply to #502480)
Subject: Re: Difference in performance between these two camshafts?



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Hotheads didn't know the answers to my questions so he called Isky. He said this cam is what they recommend to maintain good low speed compression while still giving a performance boost with a stock converter. So I bought it from them. I will install it when it arrives, but I need to build some custom headers for the car first.
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