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post #16 of 53 (permalink) Old 10-14-2015, 09:08 AM
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Re: 393W not running up to expectations

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Change the heads and let it breathe
That is my gut feeling as well but some people do seem to run pretty darn quick with them.


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post #17 of 53 (permalink) Old 10-14-2015, 08:32 PM Thread Starter
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Re: 393W not running up to expectations

There is a fuel pressure gauge that remained constant at 6 -7 PSI during the entire pass and the throttle plates do open fully.

I think I may have answered my own question by stating it rev'ed higher and with no problems when they were on the 351W and with same with the cam. I'm now wondering if the heads and/or cam may not flow/big enough. But, it that is the case, it should have far more bottom end and then die off as the RPMs increase. I'm still hoping for a relatively inexpensive solution.

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post #18 of 53 (permalink) Old 10-15-2015, 03:00 PM
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Re: 393W not running up to expectations

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Originally Posted by k718cougar View Post
I'm still hoping for a relatively inexpensive solution.
a custom cam as i mentioned.

did you set the timing curve so it is optimal for this setup.

you can plug the vacuum advance if you have one then rev the engine to between 1/3rd and 1/2 throttle, then advance the timing 4 degrees and if the rpm increases noticeably and it still runs smooth, this is closer to where it wants to be.

leave the vac adv plugged and test drive it and listen for it to ping when you accelerate.

jetting may also help.
.

Last edited by barnett468; 10-15-2015 at 03:05 PM.
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post #19 of 53 (permalink) Old 10-17-2015, 09:10 PM Thread Starter
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Re: 393W not running up to expectations

On a whim, I contacted Comp Cams for a possible cam recommendation. Needless to say, I was a bit shocked when they recommended we switch to the XR286R, but with a 108* lobe separation instead of the off-the-shelf 110*. Seems a little shorter than what I have, but they also knew the specs of what is currently being used. If anything, I thought the recommendation would go the other way and be a bit larger.

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post #20 of 53 (permalink) Old 10-18-2015, 06:58 AM
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Re: 393W not running up to expectations

I just looked over your build again, the one thing I need to clarify is are you advancing your cam 4 degrees now?

If true this will kill power over 5500 or so, with 4000 rpm stall, 4.30 gears and 393 cid. you don't need the lower rpm help that advancing the cam does and 4 degrees on a 108 CL seems like a lot.

Over 5000 rpm is were your combination spends most of time so before making a cam change I would put your cam strait up and go from there.

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post #21 of 53 (permalink) Old 10-18-2015, 09:18 AM
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Re: 393W not running up to expectations

half to wounder if the port work dropped the air flow. Have had quite a few heads with home port work and some supposedly reputable shops on my bench that were compromised. Some could be helped but were just ok others I can clean up but cant guarantee anything. Knowing the flow and at what lift point the flow starts to drop is very important to selecting a cam.
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post #22 of 53 (permalink) Old 10-18-2015, 09:35 AM
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Re: 393W not running up to expectations

You might scroll down through here to see flow #s for World heads

Stan Weiss' - Cylinder Head Flow Data at 28 Inches of Water -- DFW / FLW Flow Files for use with Engine Simulation Software

Also there were several changes to them over the years
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post #23 of 53 (permalink) Old 10-18-2015, 08:09 PM Thread Starter
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Re: 393W not running up to expectations

Iowan, the cam advancing makes sense. I'll see if we can change that for the next evaluation runs.

Regarding the "porting", they weren't ported, I have discovered they were cleaned up, not opened up. I don't know how much just cleaning them would hurt flow that much.

We are also going to tighten the valve clearance a bit to see if that improves or degrades anything. Hopefully, it improves showing a larger cam is needed.

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post #24 of 53 (permalink) Old 10-19-2015, 12:42 AM
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Re: 393W not running up to expectations

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Originally Posted by k718cougar View Post
We are also going to tighten the valve clearance a bit to see if that improves or degrades anything. Hopefully, it improves showing a larger cam is needed.
Although you might gain some power with a "bigger" cam, you will likely gain power with a cam that is better matched to your heads and combo as i previously suggested, but you can simply keep that cam and get better heads.
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post #25 of 53 (permalink) Old 10-19-2015, 03:30 AM
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Re: 393W not running up to expectations

The "right" cam for your car may change the characteristics of what you have and is probably worth 15-20 HP more than you have now (with those heads.) You will always be constrained because of the flow limitations of the unported heads.

Is that really worth the effort to experiment with? Find an AFR 195 or better yet due to your drag racing preference an AFR 205 (both inline heads that might match you current pistons valve reliefs) and you will be "worlds" faster. Pun intended. There are certainly other good heads out there but for an"out of the box" type head its pretty hard to beat the AFR's. You could recoup some of the cost by selling your current heads.

I might have mentioned it earlier but a swap from the ProComps to the AFR 205's was worth 1/2 a second using the same basic combination including the custom cam that was spec'ed specifically for the ProComps. That is what I consider real world results that was well worth the effort . . . . .

Dennis

65' Stang Street/Strip. Dart 434W NA, Victor heads, G101A 4 Spd, 4:56 rear gear, on 93 octane pushing 3550lbs. [email protected]

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post #26 of 53 (permalink) Old 10-19-2015, 06:13 AM
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Re: 393W not running up to expectations

rEMOVING PARTING LINE line imperfections and a 80ish grit finish all over is good for maybe 5 CFM at best.
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post #27 of 53 (permalink) Old 10-19-2015, 07:41 PM Thread Starter
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Re: 393W not running up to expectations

Barnett468, you are correct. What I was trying to say was changing valve lash may give me an indicator as to where the cam may be. I do realize there are waaaaay more variables with this.

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post #28 of 53 (permalink) Old 10-19-2015, 09:12 PM
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Re: 393W not running up to expectations

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Originally Posted by k718cougar View Post
Barnett468, you are correct. What I was trying to say was changing valve lash may give me an indicator as to where the cam may be. I do realize there are waaaaay more variables with this.
yes, i understand and its certainly wont cost you anything to do that but the only real way to tell if it makes a difference is by putting it on a dyno and making a couple runs then changing the lash and running it again.

there are too many variables at a track to really tell.
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post #29 of 53 (permalink) Old 11-05-2015, 06:29 PM Thread Starter
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Re: 393W not running up to expectations

dennis111, regarding your reply, "I might have mentioned it earlier but a swap from the ProComps to the AFR 205's was worth 1/2 a second using the same basic combination including the custom cam that was spec'ed specifically for the ProComps. That is what I consider real world results that was well worth the effort . . . . .", was there a significant difference from one cam profile to another to better match the AFR heads vs the ProComps?

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post #30 of 53 (permalink) Old 11-06-2015, 04:12 AM
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Re: 393W not running up to expectations

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Originally Posted by k718cougar View Post
dennis111, regarding your reply, "I might have mentioned it earlier but a swap from the ProComps to the AFR 205's was worth 1/2 a second using the same basic combination including the custom cam that was spec'ed specifically for the ProComps. That is what I consider real world results that was well worth the effort . . . . .", was there a significant difference from one cam profile to another to better match the AFR heads vs the ProComps?
It was the same cam that was custom spec'ed for the Procomp heads-I just simply reinstalled it. It was all in the heads (and the Procomps had some porting done.)

What really made the 393 run even better was a custom SR roller cam that I later installed (and what put the car into the 11.20's.) I don't know the specs on it anymore but it had at least 10 degrees duration. I like experimenting with different cams so details are fuzzy. If you are interested in my experiences, they were all fully detailed here on FM from my drag racing infancy beginning in 2007.

Dennis

65' Stang Street/Strip. Dart 434W NA, Victor heads, G101A 4 Spd, 4:56 rear gear, on 93 octane pushing 3550lbs. [email protected]
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