Stock engine rebuild advice - what to ask machine shop, etc.

[1 tuff z]

Nearly completed the disassembly of the L24 that came in the Fairlady Z I picked up last spring.  Weak compression, wouldn't rev, etc. Figured since the original L20 was long gone I don't have to stay stock.  I have an L28 [from 1978 280z with 100k miles on it] sitting on an engine stand so my brain says marry the E31 head with L28 block = greater displacement, a bit more HP & TQ without much fuss.

 

I plan to assemble the engine & head myself and feel confident in doing so [done this 3 times successfully in the past for L's].  So I want to take the L28 block & E31 head to a machine shop and have them check to ensure that all is well but am uncertain precisely what questions to ask but have an idea, so here goes.

 

L28 block

Aside from the following [assuming I'm close] what else should I ask?

 

Hot tank block then;

• Check crankshaft for any defects, spec main all journals to ensure within stock tolerances
• Check rods & pistons for same as above
• Check the bores for any irregularities & within tolerances
• Check deck is straight

Assume all is ok, take home, install new main bearings, rod bearings & piston rings.

 

Do or should I consider new wrist pins?

Any other internal parts that should be replaced?

 

 

E31 head

• Have pressure tested
• Notice that the top of 1 valve guide was broken off [where valve stem seal attaches]
• Replace just 1 valve guide or all 12?
• Check all the valves, valve seats, guides, spring seats
• Check cam [i believe it is aftermarket but no markings or way for me to properly ID] and specs if able
• Check rocker arms
• Check springs [believe there is a way to measure both tension & proper length]
• Check if straight, length & width

Do I need to keep each valve in their respective 'holes'?

 

You can either reply to this thread or email me directly [palermodavid13@gmail]

 

Both myself & my Fairlady Z thank you in advance!

 

David

Edited March 28, 2015 by 1 tuff z

[NewZed]

Is the E31 head modified with bigger valves?  Seems like the stock N47 head would be the way to go.

 

100,000 on an L28 doesn't seem like a lot.  Is there even a reason to take it apart?  Not an expert, just asking.

[1 tuff z]

NewZed, I haven't measured the E31 valves but do believe the head had some port-polish work done.  The L28 had a head gasket issue and suspected the head had subsequently warped but I have not confirmed that [PO told me this when I purchased the 280z a few years ago as a parts Z] and I didn't want a head with the steel exhaust liners.

 

I'm not building a high performance engine, just close to stock and reliable.  

[Tony D]

Bottom End:

Adding a lot of cost with no appreciable benefit using replacement parts that are almost positively of lesser quality than what you removed.

 

Farthest I would go in this situation would be to replace the rod bolts with ARP's, clean and MAYBE replace the oil control rings, with a deglaze and run it with a new water pump.

 

Top End:

E31 Mythology...sell it to a racer that needs it to remain in class, buy another head and mildly cam it accordingly.

 

Worry about the bottom end in another 200,000 miles...

[1 tuff z]

Tony, thanks for chiming in.  Suggestions for head & cam?  I'm not knowledgeable in the cam area and would like to purchase a complete kit [cam, springs & lash pads] that i know would all work together.

[Tony D]

I don't have Bryan Blakes stock head flow data... A cam that peaks flow around that as a stock port and 470 lift. Talking quickly with Ron at Isky (after 2PM PST) should get you a "Kit" that should maximize what you have. Stock Pistons power peak between 6000-6500...

 

The cam you get will give the same rev-characteristics as the original L20A...make sure you tell Ron what gear you have in the differential. Most ZS Fairlady Z's have a 3.7, but the GL may have 3.9 or even a 4.11, that can be a big factor in cam selection. You will be running 3,500 on the freeways in an early five speed...which I find just FINE in my 260Z, you are RIGHT THERE for passing in top gear, pulling as fast as possible to redline.

 

Gear it according to capabilities...a four speed car with a 3.70 would be 6,350... Meaning a cam that peaked in that range would be well matched. My standard for stock performance was my old 75 FLZ S-Model, it plain had the best overall all around performance I found. I've tried emulating that and found an L28 cammed like that matched with the 3.7 or 3.9 really makes for the same driving experience as that car had....but with a bit more traction difficulties. Good tires fix that! LOL

 

Really, the money you planned on spending doing the bottom end...ship your E31 head off to Slover's Porting in LA (ONLY IF YOU KNOW THAT E31 IS NOT CORRODED!!!) and have him install the valves, port it properly to give you the optimal flow for your cam. The power is in the head, so is the fun in driving. Money spent in the head is easily transferred to multiple blocks if something goes wrong down below.

 

At least, that's the way I'd go about it. Having dished Pistons may be an advantage as Ron will AK's "do you want to cut your Pistons?" Well, dished domes are "precut" a few mm, so you can tolerate a bit more lift....since you are doing springs anyway, take all the lift you can for all the cylinder filling you can.

 

I digress...

[z-ya]

Dave,

 

Looks like a cool project.

 

Questions: what is your budget? What induction (SUs?)

 

I agree with Tony, putting a lot of money into the bottom end for a street NA is probably not a good use of funds. Use that on the head.

 

An L28 with dished pistons, and E31, and a Felpro gasket will get you around 8.75:1. Good for pump gas. There is a cam grind I used on a build from Schnieder (regrind), that worked really well on a 9:1 L28 and used the stock springs. I can look that up if you are interested. Power tops out around 6500RPM. I'd say it makes around 200HP at the crank. Plenty of get up and go for the street in a 2400lb car.

 

Here is what I would do:

 

- Pull head off, and if there is little to no ridge on the cylinders, leave the short block alone.

- Take the valves from the N47 head, buy new L28 seats, and have them installed into the E31 head (make sure the assembled height is the same for intake and exhaust, long story).

- Have the L28 cam reground and use the N47 cam towers so that you can run without a spray bar.

- Have some basic headwork done (unshroud the valves, and some intake port work)

 

For the headwork, give the machinist a budget to work within. I didn't on one of my E31 heads, and $2900 later I have a beautiful, and expensive head.

 

If you want to chat about it, you got my number.

 

Pete

[NewZed]

 

- Take the valves from the N47 head, buy new L28 seats, and have them installed into the E31 head (make sure the assembled height is the same for intake and exhaust, long story).

- Have the L28 cam reground and use the N47 cam towers so that you can run without a spray bar.

- Have some basic headwork done (unshroud the valves, and some intake port work)

 

 

He said that he thought the E31 head was worked on.  The N47 already has the bigger valves.  Why not just have the N47 head worked on?  The exhaust liners?  Is it exhaust or intake where the L heads are restrictive?  Tony D mentions E31 mythology, is there much to be gained with the E31?

 

I would assume he will use carbs so my brain says drop the L28 in, unmolested, and spend the time and money on getting the carbs tuned right, if they're even the right carbs for a bigger engine.  17% more displacement, with an engine that should be good for another 100K miles.  The Nissan factory really seemed to do a great job on putting these engines together.  Thank Deming.

[1 tuff z]

Many thanks for all the great advice guys!  Per Tony D, I called yesterday both ISKY cams and Slover porting.  Michael at Slover was very patient with my questions and gave me an estimate for the following: street [nothing too radical] port job, replace & hone valve guides, replace intake seats, enlarge exhaust seats, install larger intake & exhaust valves.  I then spoke with Ron at ISKY, heard some great stories [we spoke a bit about his dad Ed after I figured out who he was.  I had read a great 1 page article in Car & Driver last year-their 1 page interview they do each month inside the back page].  Ron's dad Ed is 94, still drives!  Ron suggested [after he guided me about cam ID a bit of crude measuring of the unknown grind that came on the E31 head] I send the stock 280 cam for him to regrind.  Also suggested I get matching valve springs & lash pads but he thought I might be able to use either set of lash pads I have from either the E31 or N47 heads.  Ron thinks the FLZ cam may have been a BRE spec grind [based on the firewall end stamping].  Likely I'll send it to him to get specs measured.

 

Pete, I let both Michael & Ron know I did NOT want or need to spend excessively on this nor did I need too much power [already have my LSx powered Z for that] and needed to keep this very reasonable.  My estimate, based on what they both told me is I'll have everything [after shipping round trip NY to CA & back] for just under $2k.  I'll assemble everything myself as well as checking wipe patterns on rocker arms, etc.  Tomorrow I'm at Jimmy Z's shop [he's the billet machinest guy who makes Z parts] where we work on & store our ChumpCar [2002 Nissan Sentra] and can check the 280 block to see if there's a ridge top of the cylinders.  Thanks for that heads up!

 

Need to get back into my Frank H. "How to hot rod...Datsun" book again!

 

Tonight I'll measure the E31 valves vs. N47 valves then ask Michael at Slover if the N47's will work.  

 

NewZed, I'm running Mikuni 44's [came on the FLZ], which I rebuilt after purchasing needed parts from Todd at Wolfcreek Racing.  The venturis are smaller, I think Todd told me they're about a 42mm equivalent now.  FLZ also came with a 6-2 header with 2-1 collector.  Header appears to be in good condition and planning to use it.

[Tony D]

Ex-cellent!

[z-ya]

Dave,

 

When you send him the E31 head and N47 cam, send the N47 cam towers too. He can mount and then align hone them on the E31 head. 

 

All regrinds require lash caps of a different thickness than stock. Isky should be able to at least provide the thickness you will need with the reground cam. If you think the E31 has a regrind in it, then you might be able to use those lash pads. It's worth a shot.

 

This is the cam I used on a recent street car build. Very drivable on the street, and will work fine with stock springs.

[1 tuff z]

Pete, this may be a dumb question but...since the head is going to Slover and cam to ISKY [2 separate businesses], do I send the cam towers along with the head to the 'porter'?  Or, do I have the cam ground first then send it along with the head & towers to the porter?

Dave,

 

When you send him the E31 head and N47 cam, send the N47 cam towers too. He can mount and then align hone them on the E31 head. 

 

All regrinds require lash caps of a different thickness than stock. Isky should be able to at least provide the thickness you will need with the reground cam. If you think the E31 has a regrind in it, then you might be able to use those lash pads. It's worth a shot.

 

This is the cam I used on a recent street car build. Very drivable on the street, and will work fine with stock springs.

[z-ya]

Hi Dave,

 

Slover will just need the cam towers. They should be able to align hone them if needed. You can send them the E31 cam so they can check for any binding and or fit. Or, you can check that before to send it out. Just torque the N47 cam towers on the E31 head, and make sure the cam spins freely. If it binds, then it will need to be align honed.

[1 tuff z]

Got it, thanks Pete.  I'll grab the n47 cam [at Jimmy Z's shop] tomorrow, swap cam towers and check how it spins.  Pete, pardon my ignorance but why not keep the E31 cam towers and spray bar?

 

Measured the E31 and N47 valves using my HF digital vernier calipers on the widest part of the valve face.  Measurements below first in mm then inches.  Checking with Frank Honsowetz's book, pg 136 it lists stock valve sizes.  So, it would appear both heads have their stock valves.

 

         Intake               Exhaust

E31  42.11 / 1.657      33.05 / 1.302

 

N47  44.08 / 1.735     35.06 / 1.380

[z-ya]

Since the N47 cam is internally oiled, you don't need the spray bar. Can you still run it? Yes. My concern with running both on a street engine is that you are sending the same volume of oil, at the stock pressure, to both the cam and the spray bar. You can play around with enlarging the oil restrictors in the block. I don't recommend this because now less oil will be going to the bottom end. Nissan engineers are really smart , and designed these heads to use one or the other.

 

On the L28 race motor I run both a drilled cam and spray bar. I have had no issues with cam wear. But...., I am running over 80psi of oil pressure, at a much higher volume. 

 

So you can use the E31 towers, and an make some little block off plates for where the spray bar mounts. Or, you can just use the N47 towers. Personally I don't like having the spray bar there because it gets in the way when adjusting the valve lash.

 

Yup, looks like the E31 is stock from a valve size perspective.

 

Pete

[NewZed]

 

         Intake               Exhaust

E31  42.11 / 1.657      33.05 / 1.302

 

N47  44.08 / 1.735     35.06 / 1.380

So, basically, you're going to spend a lot of money to avoid having liners in the exhaust ports?  I'd source an N42 head, send it to Slover and be lots of money ahead.  Same end result, much cheaper.

 

If you have the pile of parts, piecing together valves and castings with machine work might make sense.  But the N42 is already there.

[z-ya]

No one is saying the N47 head is bad. I ran one on my track car for 3 years, and the motor made good power. The E31 will give you a bit more CR, and it already has square exhaust ports in case Dave wants to use the stock 240Z manifold, or he has a square port header (Dave, if your header is a round port, then use the N47 for sure).

 

The cost to install new seats is minimal as compared to the overall cost of rebuilding a head. So for the smaller combustion chamber I would always pick the E31. 99.9% of all racers do the same. The fact that he already has one makes the choice easy.

[NewZed]

 

The cost to install new seats is minimal as compared to the overall cost of rebuilding a head. So for the smaller combustion chamber I would always pick the E31. 99.9% of all racers do the same. The fact that he already has one makes the choice easy.

But you're leaving out all of the cost of enlarging the seat area for bigger valve seats for the bigger valves.  He already has an N47 also.

 

Plus the realignment of the cam towers, hoping that they work, moving the valve train over, etc.  I don't see why anyone would use an E31 on an L28 unless they had to.  Just not making sense.  How much does that bump in CR buy you, and is it usable on pump gas?

 

He's  "not building a high performance engine, just close to stock and reliable."  Post #3.  Your advice might be good, but it's off-target.  He's not building a race engine.

Edited April 2, 2015 by NewZed

[1 tuff z]

I have 2 heads.  E31 [just dropped off to get pressure tested & checked for 'straighness'] and the N47 from the 78 280z [which I was told had a bad head gasket, Z was parked and I purchased as a parts car].

 

This evening I'll check the 280 cylinders [as Pete suggested] for a ridge as well as cross-hatching.  I also have to bring the N47 cam home so it can be sent to ISKY for regrind.

 

I stripped the N47 head about a month ago and have all the parts & pieces from it.

 

Pete, you're correct on the square port header.  I have one, it's in good condition and I see no reason to purchase another header unless the E31 head is bad and I have to go with the N47.

[Tony D]

Well...there is a fresh new head you might be able to use, I'm sure it would fit the bill for a basically hot street car:

 

http://forums.hybridz.org/topic/119641-twin-cam-head-for-the-l6-from-derek-at-datsunworks/