Barefootdan's 280z Build

[Dave WM]

you should make sure you have a VERY clean head surface, then use a good quality straight edge, go from one end of the head to the other with feeler gage. you should go diagonal as well.

IF you need to get head work I would suggest you ask around, you want some one that has worked on L type heads. there is a lot to take into consideration. I looked into it some, there is not only surfacing the mating surface, but also you have to make sure the cam tower surface is not bowed. If so you end up having cam issues. I have read the correct thing to do is surface both sides and then shim the cam towers to keep the geometry correct and the chain length correct. You may want to contact someone like Datsun Sprit in VA, they seem to have a pretty good rep.

[Zed Head]

They can be straightened then skimmed.  Just one more item on your costs calculation.

You should get this book. Your project has expanded.  It has all of the details of things that we're talking about.

https://www.amazon.com/Rebuild-Your-Nissan-Datsun-Engine-ebook/dp/B006VUICHG

The head looks like it is probably unskimmed.  Here's a shot of one that looks "factory" fresh, from eBay.   You can see the slight casting flash.

https://www.ebay.com/itm/Datsun-280z-1975-N42-Cylinder-head-With-Valve-Cover/174620730333?hash=item28a834e3dd:g:nMcAAOSwXGxgGChK

 

[Barefootdan]

Hmm, time to decide now which route might be best. Picking up the longblock with unknown psi (it does spin freely) or rebuild mine. I've got some thinking to do!

[siteunseen]

I don't think that head's been cut. It can be measured from the bottom to the top edge to be certain.

Does it have bronze valve seats? A spray oiling bar? 

If you find an older machinist they can make that one like new for pretty cheap. They're good heads with square exhaust ports. You need an oiling cam but that'd be easy to find, probably from someone on here? I may have one in storage on an n47? Can't remember if I used it as a core to the cam guys? I can look though.

[Barefootdan]

3 hours ago, siteunseen said:

I don't think that head's been cut. It can be measured from the bottom to the top edge to be certain.

Does it have bronze valve seats? A spray oiling bar? 

If you find an older machinist they can make that one like new for pretty cheap. They're good heads with square exhaust ports. You need an oiling cam but that'd be easy to find, probably from someone on here? I may have one in storage on an n47? Can't remember if I used it as a core to the cam guys? I can look though.

I'll get out there and measure to be sure. I think 107.9mm is the spec. I dont recall if it had bronze valve seats, but it did have the spray oiling bar for sure. I am leaning towards a valve job on mine. Buying a different motor seems like the easy way out 🙂 

Would it be worth the time to have the head shaved to increase compression? Then shim the cam towers of course. I wouldnt run flat top pistons if I went this route for cost savings.

[S30Driver]

The AAR and its coolant heating block can be removed, but at the cost of no increased idle speed during warmup.  You will have to keep your foot on the gas pedal for a few minutes until there is some heat in the engine before it will idle without dying.   In your part of the country, should not be a big problem.

The AAR is a hard to find part in good working condition if your is bad, so you may be ahead of the game by eliminating it.

I had one of the steel coolant lines that feed the heater block under the AAR fail without warning coming home late one night (form Dave Irwin's house) years ago.   One of the few times I came close to overheating.   Noticed steam coming off the hood before I saw the temp gauge.  Made for a longggg ride home those last 8 or 10 miles....

[siteunseen]

16 hours ago, Barefootdan said:

I'll get out there and measure to be sure. I think 107.9mm is the spec. I dont recall if it had bronze valve seats, but it did have the spray oiling bar for sure. I am leaning towards a valve job on mine. Buying a different motor seems like the easy way out 🙂 

Would it be worth the time to have the head shaved to increase compression? Then shim the cam towers of course. I wouldnt run flat top pistons if I went this route for cost savings.

I measured my original N47 off my 280, I'm sure it's never been touched and it measured 4.25 inches which is 107.95mm. Probably measured some grease too.

I would just do the basics and have a good solid car you won't have to worry about. I jumped out of the gate at first on my 2.8 build but was talked down by some guys that have "been there done that" people. I know I'll get scorned for this but I read a long time ago, before ethanol was added to our gas, flat tops in an N42 block with an N42 head was as easy and about as cheap a good running combo you could do. I have the flat tops out of a ZX motor I took apart but the car runs fines and I don't have the energy to tear it apart just to add those. They're fun cars to drive as is and you won't out run any of the new cars so just put a good motor together, add a header and 2.5" exhaust and drive it like you stole it. I beat the hell out my 280 on 87 pump gas and it begs to be driven every time I go downstairs but I'd rather work around my house and drink beer. The car's value is going up so I let it sit most of the time. Too many idiots on the roads around here. Double for the 240. It ain't going nowhere. 

[Barefootdan]

On 4/2/2021 at 11:11 AM, siteunseen said:

I measured my original N47 off my 280, I'm sure it's never been touched and it measured 4.25 inches which is 107.95mm. Probably measured some grease too.

I would just do the basics and have a good solid car you won't have to worry about. I jumped out of the gate at first on my 2.8 build but was talked down by some guys that have "been there done that" people. I know I'll get scorned for this but I read a long time ago, before ethanol was added to our gas, flat tops in an N42 block with an N42 head was as easy and about as cheap a good running combo you could do. I have the flat tops out of a ZX motor I took apart but the car runs fines and I don't have the energy to tear it apart just to add those. They're fun cars to drive as is and you won't out run any of the new cars so just put a good motor together, add a header and 2.5" exhaust and drive it like you stole it. I beat the hell out my 280 on 87 pump gas and it begs to be driven every time I go downstairs but I'd rather work around my house and drink beer. The car's value is going up so I let it sit most of the time. Too many idiots on the roads around here. Double for the 240. It ain't going nowhere. 

Thats a good point. I almost wonder if I should just toss the head back on after fixing the bent valve to see where it puts me. 

[Barefootdan]

Small project update. I was able to finally decide the direction of the build. I'll be rebuilding the current head (if the machine shop approves) and use the stock cam for now. I figure it is not worth the money for a stage 1 cam and the original EFI. Later on I can decide on megasquirt or carbs and worry about power then. I'll slap on some 6-2 headers and some twice pipes out the rear. 

I was debating in my post above to not worry about the rings, but I did a quick test by pouring some gas into the cylinders to see how bad they are. Welp, good thing I checked. Within 15 minutes there was a noticeable drop in 4 of the 6. Maybe 30 minutes later they were empty except for Cylinder #6 which held great. SO out they will come. Next debate is pulling the pistons with the block in the car or finding a hoist and stand. Not so much a money issue, rather the space of the two is annoying. Has anyone had experience pulling pistons without pulling the block?

Lastly, I made some progress in the engine bay while everything was out. I pulled the wiring harnesses back to the firewall and re-wrapped them. Cleaned it up the best I could and was planning to do a quick paint. But I am just not happy with how unclean I got it. I'll need to push it out front for a pressure wash before I go painting. I wish I took photos of this...there was dirt thick enough to match the brake lines on the frame rails! 

[Mark Maras]

I have a H.F. engine hoist that folds up and doesn't take up much space. Years ago I pulled and reinstalled my 240 engine using two 2x4x8s, garage rafters, a one ton cable jack, jack stands and the Z jack. I unbolted everything under the car, lowered it, hooked up the cable jack to the engine, finished unbolting the topside, lifted the engine a bit and rolled the car back as I lifted the engine. It sounds like a PITA but it all went well.

[Barefootdan]

Yea I may resort to buying one...I should look at it like I am able to get a deeper clean in and replace the clutch if needed too. I'm this far in already!

[siteunseen]

5 hours ago, Mark Maras said:

I have a H.F. engine hoist that folds up and doesn't take up much space. Years ago I pulled and reinstalled my 240 engine using two 2x4x8s, garage rafters, a one ton cable jack, jack stands and the Z jack. I unbolted everything under the car, lowered it, hooked up the cable jack to the engine, finished unbolting the topside, lifted the engine a bit and rolled the car back as I lifted the engine. It sounds like a PITA but it all went well.

You have that good "figuring out sense" that's so prevalent on classiczcars.com. I've been blessed with it also but once I got involved with this forum I realized I'm barely touched with it.