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P79 Cam in Turbo engine with stock ECU


Ben's Z

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I have been shafted once and it appears I am on the verge of being hosed again by two different forum members on used P90 Cam. First member "Francisco" sold me a cam with a smashed dowel pin and a crack from the dowel pin hole to the edge. I will update this tomorrow if member #2 does not reimburse me in 24 hours. His cam was supposed to be here Thursday, problem is his USPS tracking number has never been valid.

 

Given that, a member I trust said he would give me a P79 cam for my turbo engine swap. I have read both good and bad about doing this when I intend to run the OE ECU. The cam does need to be sent of to be polished. Should I tell Delta Cam to do anything else to it while they have it? What does having a cam cleaned up usually cost? As mentioned before in previous theads here are my intended mods.

Bell RRFPR

FMIC

Manual Boost Adjuster

3" Exhaust

 

I think I would have had this motor back in 4 weeks ago if I had gotten some honesty out of our fellow members. Getting real hard to trust people.

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I've got one of those cams with the dowel pin smashed into it, but my machinist thinks it can be fixed...for a price.

 

Is your cylinder head a hydraulic lifter P90 or a solid lifter? If it's a solid lifter, then the cam will *run*, but may not run that well, might run just fine, might run better than stock. I dunno how the ECU would handle it.

 

Basically, under 4000RPM, and not at WOT, the ecu uses the AFM to calculate fueling. Over 4000RPM, or at WOT, the ecu enters a pre-programmed fuel curve. It can't make any kind of adjustment at that point, and is just going to follow that curve till it's under 4000RPM and less than WOT.

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The dowel pin might be just for location. Clamping force from the bolt would hold the sprocket. The crack might be irrelavant since it's "pinned" by the dowel hole. Just a proposal worth thinking about.

 

Edit - I got curious, did a search and found an old Hybridz thread on the same topic - http://forums.hybrid...-issues-beware/

 

And another - http://www.the510realm.com/viewtopic.php?f=2&t=11001&view=next

Edited by NewZed
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Actually.....it's 3500rpm where the stock zxt fuel system goes into open loop.

 

With 108 ft. pounds of torque, the dowel does nothing but properly index the gear as you install it.

 

The cracking is from the sprocket beating back and forth on the dowel because the bolt isn't tight enough.

 

I would simply get a used p79 head, bolt it on, and now you have a running car while you can sort out the p90 and cam options.

 

I'm about to put a p79 back on in place of a P90 and notice no difference in the performance between the two.

Edited by HowlerMonkey
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Actually.....it's 3500rpm where the stock zxt fuel system goes into open loop.

 

With 108 ft. pounds of torque, the dowel does nothing but properly index the gear as you install it.

 

The cracking is from the sprocket beating back and forth on the dowel because the bolt isn't tight enough.

 

I would simply get a used p79 head, bolt it on, and now you have a running car while you can sort out the p90 and cam options.

 

I'm about to put a p79 back on in place of a P90 and notice no difference in the performance between the two.

 

I don't have a P79 head to put on and I have a rebuilt P90 on the bench minus the cam.

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I think I am going to go with my 77 280z cam and be done with it. Should I use my cam towers from that head or my rebuilt P90? Should I use the rockers arms from the 280 or my resurfaced ones? I was thinking about keeping my resurfaced ones off to the side for now in case I have any errors in my first rebuild attempt.

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I would take a breather, study what's been suggested, and put a sensible plan together. I have this vision of you throwing everything together, getting it running, then revving the crap out of it until it blows up just to vent some frustration.

 

Seriously, you have several paths to get a good cam in the engine and get things working. The whole cam, cam tower and rocker arm things have been discussed to death on the various forums. The most recommended suggestion seems to be to take the cam, towers and rocker arms out as a complete assembly, with every part in the same order and orientation and swap them over to the other head. Tap on the cam towers as you slowly tghten the bolts to make sure the cam spins freely befoe you torque the bolts down. "Blue" up all of the rubbing parts afterward, spin the engine over a few times, then check for high spots and/or odd wear patterns.

 

This is what I've learned. I've never had a cam off though.

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I would take a breather, study what's been suggested, and put a sensible plan together. I have this vision of you throwing everything together, getting it running, then revving the crap out of it until it blows up just to vent some frustration.

 

Seriously, you have several paths to get a good cam in the engine and get things working. The whole cam, cam tower and rocker arm things have been discussed to death on the various forums. The most recommended suggestion seems to be to take the cam, towers and rocker arms out as a complete assembly, with every part in the same order and orientation and swap them over to the other head. Tap on the cam towers as you slowly tghten the bolts to make sure the cam spins freely befoe you torque the bolts down. "Blue" up all of the rubbing parts afterward, spin the engine over a few times, then check for high spots and/or odd wear patterns.

 

This is what I've learned. I've never had a cam off though.

 

I agree, don't half-ass your project you will be sorry. It may take a little while longer but at least you will have the desired results..

 

I'm actually swapping a cam myself and doing what NewZed stated, because I had read multiple times that's what you had to do...

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I am not doing anything half assed. I have just made the determination to use my 77 280z Cam, because input from the crowd for or against was never answered. I also think it is erroneous to use the cam towers from the 280z head and not the cam tower from my P90. The P90 has been shaved and I am certain my N47 has never left the block. Everything, rockers, lash pads, and cam will be used from my 280z engine. No one (still) has answered what adverse affects if any what my "A" cam will have in this turbo motor using the stock ECU. My 77 engine has less than 94k on it and the cam looks like brand new. I will put permanent marker on all of it and roll it over to check for wear.

 

I took my f'ed P90 cam (that "Francisco" sold me) last night, oiled the P90 towers and the cam spun over in the journals, it was a little tight but I also wasn't done tapping and tightening.

Edited by Ben's Z
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