Expectation From New Engine Build?

[Ownallday]

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.

[Patcon]

@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...

[SteveJ]

Emissions testing would be real there.

[Ownallday]

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.

Smog isn't an issue for me

[Reptoid Overlords]

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

[Patcon]

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

[Ownallday]

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.

[Diseazd]

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 April 28, 2022 by Diseazd

[Ownallday]

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?

[siteunseen]

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/

Edited April 28, 2022 by siteunseen

[Diseazd]

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.

[Ownallday]

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!