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Sent My N47 Head to The Machine Shop.....


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I sent my N47 of to a local machine shop for a cam regrind (out sourced), valve seals and cut/seats, new lash, rockers, lash pads etc. Told the guy not to removed the cam retainer caps...well I guess the caps were removed. Every manual, forum I have read states DO NOT REMOVE CAPS. They are still working on the head at this point and it has yet to be installed. From what I understand there can be alignment issues with the bearings, thus big time failure. This work is being done on my donor head, and I have my perfectly working stock head still on the car. Any input would be greatly appreciated.

1978 280Z all stock.

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Most people call them cam towers.  If he marked them they should go back on just fine.  Search "cam tower alignment" and you'll probably find some threads about tapping on the towers while bolting them in place.  The towers are the bearings.

 

Interesting work you're having done since lash pads are hard to come by, along with new rocker arms.  Plus the issues with cam break-in.  Details on what parts he uses and how he sets them up would be worth posting.

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Thanks for the reply NewZed.

Lash pads are from the ZStore out of Cali, and the rockers are being resurfaced. I found some ITM rockers online, but couldn't find much info on them so I thought I'll try the regrind. The head is off a car that hasn't been started for over 25 years and sat after being ditched 4-5 years before that. The previous owner could not get it running, but I got it running last Spring so there is very little to no wear on the rockers according to the shop.

 I'm heading down to the shop this Tuesday, I'll get as much info as I can and post. Also the machine shop has done local early Z work as well and have a good rep. They do return all old parts and a complete itemized list of all parts is supplied when the work is complete. I will be port matching the intake/exhaust and confirm all clearances and specs. I have been reading How to Modify Your Nissan & Datsun OHC Engine by Frank Honsowetz, but I am not going to the extreme spec listed in the book, but has been a great source of info.

 

The wife and ran the car last September down to Portland, had a great time. Ran like a champ stock....but a little faster is always better ;)

Edited by FrappNasty
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 I have been reading How to Modify Your Nissan & Datsun OHC Engine by Frank Honsowetz, but I am not going to the extreme spec listed in the book, but has been a great source of info.

Check page 89, it describes the tap and turn procedure.  Be careful on the torque values for the bolts, one of the books, either Monroe's or Honsowetz's, has a mistake.  Your shop will probably get it all done right though, if they've worked on them before.

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Cam towers are marked from the factory, they have little indicators on the side with squares noting the number they are.

 

I have heard the same thing everywhere, but I've also heard evidence to the opposite. As long as the cam rotates nicely without grabbing anything and you make an effort to put them in where they were you should be ok.

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Got the head back from the shop. with the regrind cam installed, they shaved .004 off, so no shims, so when I was comparing the old gasket with the rebuilt head, the old gasket would have blocked coolant passages, but never has a issue with the old head/gasket set up. But I overlay the new gasket in the rebuilt head and this head (all passages line up) but I'm guessing the head has been shaved before these guys got their hands on it. The rebuilt head is a N47 head with a oiling bar, it has exhaust liners, but has a block off plate for a carbed fuel pump. The combustion chamber is smaller due to shaving and a caliper check confirms this. So the fire ring on the new gasket with the rebuilt head combustion chamber are not close to being flush. So a few questions, move to number 2 on the cam sprocket, Pull the front cover and mod the chain tensioner  and also did the cam lobe oiling bar have gaskets?

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Only one question was identifiable.  Yes.  Not much to it though, thin paper.

My bad NewZed with the poorly worded questions. The rebuilt head has been shaved to the point where the fire ring on the new gasket sits outside the combustion circumference on the head. I know this will happen with a shaved head, it just seems a little excessive. Thanks for the oiling bar answer, there was a couple of homemade gaskets used before on the bar so I wasn't sure if they were necessary . Here is a list of the head work done.

 

New valve guides

Replaced all exhaust valves

3 angle grind with lapping

New lash pads

Rockers refaced

Head shaved 0.004

Cam regrind. Misplaced the specs, will call the guy and post later.

Exhaust liners left in...too much of a PITA to remove.

 

I port matched the exhaust/intake gasket. The exhaust side of the gasket (Felpro) was partially blocking output to the stock manifold. Replaced fuel/coolant lines. OEM injectors serviced and flow tested. Need to set up valve lash. I'll try to post pix later as well ( always have issues with file size issues in these forums)

Edited by FrappNasty
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Hi all, finished installing the rebuilt head, all went fairly smooth with no major issues. Did a cold valve adjustment, twice and rotated the crank numerous times to ensure no interference issues. The shop had applied copious moly assembly grease to the rockers and I added a zinc additive to the oil as per the cam shop. The resurfaced rockers were lining up nicely with the cam lobes also. The car fired up with no issues, some quick timing adjustments were done. I should note the the throttle body was carbed up bad, and I cleaned it out when everything was apart at the time, so some idle air issue were addressed also during initial start up. The cam is right lumpy at cold idle, and once it warms becomes  more civilized. ran the car up to temp in the garage and did a hot valve adjustment twice, and checked the cam and rockers and lobes all seems good at this point. The engine seems to have a faster throttle response than with the stock setup in the garage. I cannot drive right now due to my drivers license suspended due to a heart issue 3 weeks ago...one more week to go before I can drive like a maniac again! I got some cam specs from the cam regrind. 335 lift, 110LSA 248@050.This was a pattern they copy years ago, from what I do not know and neither do they, but have done this pattern before for the 240Z guys.  But since this was a extra head I had sitting around I thought, what the hell lets do it.

1-Oem cam and head setup

2-Lumpy time. (low res, sound is alright)

 

 

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