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Expectation From New Engine Build?


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Hey guys, I have a 1978 Datsun 280z, Currently running an N42 Block with a rebuilt E88 head from a 260z (least desirable from what I hear but was all I could find at the time), I have triple weber dcoe 40s and headers from topendperformance. I also have an MSD ignition 6AL and 280zx Dizzy and a rebuilt 5 speed with the longer gear rations I am also running a felpro 1.2mm head gasket which has 89mm bores (My L28 bores are 86mm). Also have a lightweight flywheel to add to all this. I have had this setup for almost 2 years now and never touched the block in the 5 years I have owned the car. The car also weighs a surprising 2460lbs As of right now my compression is pretty low in the cylinders. The compression measured ~100-120psi in the cylinders. My car burns about a qt of oil every ~1500-2000 miles which all leaves me to believe the rings are toast. My car is also losing coolant in the overflow tank and have to fill it up constantly after every couple hundred miles, I only see a very minimal amount of white smoke on cold startup, not really sure what's causing this loss.

 

I plan on tearing apart the engine and rebuilding the block in 2-3 months and wanted to get some info on what is worth it and what isn't. Any input would be great!

-With the N42 Block I planned on having the machine shop just honing the block/clean the passages and reusing the original dished pistons with new oem rings and new bearings (According to OZDAT my static compression is 8.280), however I wanted to know if it's worth it to instead bore out the walls to 87mm and run 87mm ross forged flat top pistons from MSA (static compression would be 9.980). Would the power gains be worth it? We only have 91 octane so not sure if Id run into issues with ping or maybe valve clearance? (This is all assuming I get the same 1.2mm felpro headgasket too).

-Even though my E88 head was rebuilt (Not sure where or what they did exactly) I plan on changing all the valve seals anyways, however I was looking at maybe potentially getting a Schneider Performance Camshaft kit from MSA, either Stage 2 or Stage 3. I do drive the car mostly on the street with occasional spirited driving in the Canyons and race track about once or twice a year. I have Triple weber DCOE 40s too and not sure if the 40s are too small for either of these cams. Which camshaft kit would be the best suited for what I have and how much power gains could be expected or should I just stick with the stock cam?

Any other things I should take into consideration or that I am missing would be greatly appreciated. My friend who is a master tech and works on a ton of engines and cars in general is going to be tearing the engine apart at his house as he is also going to install an aftermarket AC for me and restore the dash while the engine is out.

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@Diseazd

I would think upping the compression and a better cam would really help. Diseazed would probably endorse the stage 3 cam. The bigger cam with more overlap will help with dynamic compression. I am basing this on the assumption that you don't have to do emissions testing as I have no idea where Canyon country is...

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1 hour ago, Patcon said:

@Diseazd

I would think upping the compression and a better cam would really help. Diseazed would probably endorse the stage 3 cam. The bigger cam with more overlap will help with dynamic compression. I am basing this on the assumption that you don't have to do emissions testing as I have no idea where Canyon country is...

Would 91 octane be enough? My biggest concern is also would I have to worry about the flat top pistons and valves potentially hitting with the bigger cam? And smog isn't an issue for me

1 hour ago, SteveJ said:

Emissions testing would be real there.

image.png

Smog isn't an issue for me

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1 hour ago, Reptoid Overlords said:

I think with carbs and a big cam high compression pre ignition isn't all that much of an issue.

Thanks for your input, hopefully this is the case

 

9 minutes ago, Patcon said:

Many flat top pistons have valve reliefs for this reason. I dont know that forged pistons are really neccessary.

Not entirely sure if the Ross Forged Pistons have valve reliefs. And I agree forged pistons seem overkill but the options in terms of pistons are pretty limited right now for Z cars.

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Posted (edited)

You have a lot of good, but mostly bad. Get rid of the boat anchor E88. Get an N47, N42 or shave a P79 (the best, but a number of steps to follow). Don’t go forged, but do go flat tops……040 over is good. Dump the dished pistons. Get Isky to grind a stock cam to stage III…..no the valves won’t hit the pistons. Patcon is right…..the higher duration, higher lift cam allows you to run on 91. Put all that together and you should have a motor that is a lot more fun to drive all IMO. All of these changes will require questions on this site as you proceed. We all stand ready to help. “Enjoy the Ride”.

Edited by Diseazd
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21 minutes ago, Diseazd said:

You have a lot of good, but mostly bad. Get rid of the boat anchor E88. Get an N47, N42 or shave a P79 (the best, but a number of steps to follow). Don’t go forged, but do go flat tops……040 over is good. Dump the dished pistons. Get Isky to grind a stock cam to stage III…..no the valves won’t hit the pistons. Patcon is right…..the higher duration, higher lift cam allows you to run on 91. Put all that together and you should have a motor that is a lot more fun to drive all IMO. All of these changes will require questions on this site as you proceed. We all stand ready to help. “Enjoy the Ride”.

Thank you for the help! I know my head is pretty bad but it's what I will have to stick with for now until I can find a better deal for something in my area when I can dish out some more money. The E88 I have is already rebuilt, ported, polished etc. Any recommendations for non forged pistons? I can't find anything with an 86 or 87mm bore for less than $1000. With a stage 3 would anything need to be done to the rocker arms or springs or will stock components work fine?

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If you go with the Stage III .490 lift can, you would need a set of Isky Springs and some .160 to .180 lash pads to geometry the cam…..your engine buider should be able to handle that.

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On 4/28/2022 at 7:51 AM, siteunseen said:

Lots of good info on here. That P79 head mod Diseazd mentions is on there too. Click on the drop down MENU.

https://datsunzgarage.us/

Thank you, went ahead and did some reading.

On 4/28/2022 at 2:33 PM, Diseazd said:

If you go with the Stage III .490 lift can, you would need a set of Isky Springs and some .160 to .180 lash pads to geometry the cam…..your engine buider should be able to handle that.

Thank you, me and my friend are the ones who is building the engine, he does not have experience with these engines but he has rebuilt many engines, I am mostly there to help as I am still learning. Most shops want too much money nowadays just to tear a motor apart. Decided I will be going with 87mm flat top pistons and bore (forged pistons since I can't find any new cast pistons), Stage 3 cam, higher compression but I will be sticking with the E88 head for now to save on money since it's already a rebuilt head and does not need any work done at a machine shop. Hoping to gain at least another 50hp (that's on top of the fact my cylinder compression is low and probably drying me of power), and hoping to have a reliable motor for the years to come. that can be driven more often.

One last question, would it be wise to get the engine balanced too? I wouldn't mind being able to rev the engine beyond 6k (which is the most my motor currently goes). But I heard it's not necessary to for these engines. Some feedback on that would be great!

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8 hours ago, Ownallday said:

 

One last question, would it be wise to get the engine balanced too? I wouldn't mind being able to rev the engine beyond 6k (which is the most my motor currently goes). But I heard it's not necessary to for these engines. Some feedback on that would be great!

No need to balance an engine for 7000 rpm. One more thing. If you install a Stage III cam, you’ll need to geometry the cam with .160 to .180 lash pads (center the wipe pattern on the rockers) but in the E88 head, you’ll also need the shorter valve seals to prevent the valve retainers from contacting the seals with the higher lift. If you guys are doing this build, you’ll need to seek advice as you progress from those on this site that have done this before.

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Posted (edited)

I've gotten lazy over the years after building my 2.4. I did balance the rods and piston cups out of boredom, they were very close from the factory but older 240 aren't as close as the 280s from all I've read. Anyhow the darn thing runs so good and fun to drive-iness I attribute to the 10Lb aluminum flywheel I put in. It's fast enough for my weekend drives around here. One day I'll put the e-31 and cam kit together but no rush. Anyway...

Diseazd is talking about this I believe. He gets his from Eiji at Datsun Spirit I think but I bought felpros for a Ford after reading a whole helluva a lot about all this.

https://forums.hybridz.org/topic/25807-improved-l6-valve-stem-seals/

My still in the bag, on the shelf with the rest of the goodies waiting for life to get back to boring. LOL

20220503_202349.jpg

Edited by siteunseen
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14 hours ago, Diseazd said:

No need to balance an engine for 7000 rpm. One more thing. If you install a Stage III cam, you’ll need to geometry the cam with .160 to .180 lash pads (center the wipe pattern on the rockers) but in the E88 head, you’ll also need the shorter valve seals to prevent the valve retainers from contacting the seals with the higher lift. If you guys are doing this build, you’ll need to seek advice as you progress from those on this site that have done this before.

Sweet, 7k is what I wanted to shoot for! Having the car die off before even hitting redline is dissatisfying. And sounds good. I have a set saved already. What valve seals do you recommend, is it the Fel-Pro #SS72686 or something else? And 100%. I will have to revive this forum and make a new one once the progress starts. Any other things that I should have done to the block that have not already been mentioned? Thanks for the info again!

 

15 hours ago, siteunseen said:

I've gotten lazy over the years after building my 2.4. I did balance the rods and piston cups out of boredom, they were very close from the factory but older 240 aren't as close as the 280s from all I've read. Anyhow the darn thing runs so good and fun to drive-iness I attribute to the 10Lb aluminum flywheel I put in. It's fast enough for my weekend drives around here. One day I'll put the e-31 and cam kit together but no rush. Anyway...

Diseazd is talking about this I believe. He gets his from Eiji at Datsun Spirit I think but I bought felpros for a Ford after reading a whole helluva a lot about all this.

https://forums.hybridz.org/topic/25807-improved-l6-valve-stem-seals/

My still in the bag, on the shelf with the rest of the goodies waiting for life to get back to boring. LOL

20220503_202349.jpg

Okay so no balance necessary. Thats what my goal is to have a fun car that can be daily driven if needed but not get beaten by everything on the road haha. I do already have a 10lb flywheel also. The car revs nicely as is. Is it the same felpros mentioned in the forum or will anything else work nicely? I believe I saw Fel-Pro #SS72686 for the part number. Thanks for the info!

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Mine are fel pros I'm 99.9% sure. They were easily available at the time from local chain auto parts store. 

I have some more info from my build thread I can post too, also on my laptop unfortunately. I can get that for you this weekend when I'm off work. Hopefully you're in the planning stage and not in a hurry...

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19 hours ago, siteunseen said:

Mine are fel pros I'm 99.9% sure. They were easily available at the time from local chain auto parts store. 

I have some more info from my build thread I can post too, also on my laptop unfortunately. I can get that for you this weekend when I'm off work. Hopefully you're in the planning stage and not in a hurry...

I just saw on the forum I actually have the right part. Thank you. They are indeed felpros for a ford. I am far from doing the build, right now I am just gathering the parts needed for the build. Don't plan on pulling the motor till July when my friends schedule frees up so no rush.

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On 5/4/2022 at 1:57 PM, siteunseen said:

Mine are fel pros I'm 99.9% sure. They were easily available at the time from local chain auto parts store. 

I have some more info from my build thread I can post too, also on my laptop unfortunately. I can get that for you this weekend when I'm off work. Hopefully you're in the planning stage and not in a hurry...

I found this after a quick look a my thread. Me and @madkaw had figured out a repeatable depth procedure as they will bulge if yo put them on too far/deep. Hope it helps. Ask again and I'll try harder but I remember using feeler gauges stacked together to get the same depth/height, whichever way you're looking at it. I used the distance from the head up to the bottom of the seal's bottom side of the metal band. 

https://www.classiczcars.com/forums/topic/50909-72-240z-rebuild/?do=findComment&comment=475701&_rid=23570

 

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Posted (edited)
On 4/27/2022 at 7:25 AM, Ownallday said:

compression measured ~100-120psi in the cylinders

 

On 4/27/2022 at 7:25 AM, Ownallday said:

According to OZDAT my static compression is 8.280

 

On 4/27/2022 at 7:25 AM, Ownallday said:

E88 head was rebuilt (Not sure where or what they did exactly)

 

On 4/28/2022 at 6:23 AM, Ownallday said:

E88 I have is already rebuilt, ported, polished etc

 

On 5/4/2022 at 9:30 AM, Ownallday said:

7k is what I wanted to shoot for!

I haven't built any engines but a few things popped out at me when I read through the thread.  Did you use an adapter when you measured cylinder pressure, and did you open the throttle bores and get a good cranking speed?  Your pressure numbers are way low, they look like adapter numbers.  The adapter makes the combustion chamber seem bigger.  With 8.3 CR you should have higher pressures.  Like 150 - 185. I got 185's on a stock 1978 L28.  No adapter, small gauge volume.

What, exactly, is in the head will be important.  The main advantage of the other heads is the bigger valves and ports.  You need that if you want to hit 7000 RPM.  The E88's have a smaller intake valve, I think, than the L28 engines.  I have read about two forms of E88 head also.  I think the difference is in the size of the combustion chamber.

You probably won't be able to make a good decision until you get the head off and see what's in it and has been done to it.  The people that do engines say the power is in the head.  Or, conversely, the head is what's holding the engine back.  The heads just don't flow well in stock form.

Just regurgitating...

p.s. you can look up some of jmortensen's old posts and he says that all of the "Stage" cams are pretty low on the "radical" scale.  He tried all of them I think and didn't really have any problems.  He always recommends going bigger, the 1 and the 2 are barely changed from stock.  He was unimpressed with them. 

 

 

Edited by Zed Head
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On 5/7/2022 at 4:21 PM, Zed Head said:

 

 

 

 

I haven't built any engines but a few things popped out at me when I read through the thread.  Did you use an adapter when you measured cylinder pressure, and did you open the throttle bores and get a good cranking speed?  Your pressure numbers are way low, they look like adapter numbers.  The adapter makes the combustion chamber seem bigger.  With 8.3 CR you should have higher pressures.  Like 150 - 185. I got 185's on a stock 1978 L28.  No adapter, small gauge volume.

What, exactly, is in the head will be important.  The main advantage of the other heads is the bigger valves and ports.  You need that if you want to hit 7000 RPM.  The E88's have a smaller intake valve, I think, than the L28 engines.  I have read about two forms of E88 head also.  I think the difference is in the size of the combustion chamber.

You probably won't be able to make a good decision until you get the head off and see what's in it and has been done to it.  The people that do engines say the power is in the head.  Or, conversely, the head is what's holding the engine back.  The heads just don't flow well in stock form.

Just regurgitating...

p.s. you can look up some of jmortensen's old posts and he says that all of the "Stage" cams are pretty low on the "radical" scale.  He tried all of them I think and didn't really have any problems.  He always recommends going bigger, the 1 and the 2 are barely changed from stock.  He was unimpressed with them. 

 

 

No additional adapter was used, And I used my friends Snapon Gauge so it's not some cheapo one. I had the engine at operating temp, throttles open when cranking, and battery was on a tender while testing too. Not sure if I mentioned this but I am losing about a QT of oil every 1k miles. Exactly what I thought as I saw most people are getting in the 200s with a good motor.

So I can confirm the head was port and polished as when I got the head that was the only thing the guy told me he knew was done to it and it was obvious as you can see the ports were nice and polished. I thought the 260z E88 had bigger valves but just had worse flow compared to say the N42? I also think the guy had the current cam just cleaned up and new valve seals.

I have been told this too. The main reason I want to stick to the E88 is because it's what I have already and works as I don't want to spend so much money buying another head and having to get a machine shop to work on it.

Interesting, I will keep that in mind but most likely will end up going with Stage 3 since that what was recommended and even my friend helping me build the engine said Stage 3.

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I wonder if there was some combustion chamber valve unshrouding done.  Those pressures just seem really low like the combustion chamber is enlarged.  You could use one of those calculators, like OZDat, and back track to combustion chamber volume.  Then recalculate to what CR would be with flat-tops.  You might find that you'll still have low CR.

Or maybe you just have really bad rings.  Seems like if you had bad rings you'd have some variation across the six.  One or two cylinders much worse than others.  Good luck.

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