Jump to content
HybridZ
1973_240z_

How much power would my motor make???

Recommended Posts

Ok, my dad and I are about to put together my motor for my 73 240z and we have no clue how much power this motor will make. The head is rebuilt to stock its a 1973 E88 head. We have the Z Car Source master rebuild kit with .040 over flat top pistons, the pistons dont work with the head so we are having valve reliefs cut...we found this issue once we had the pistons and most internal in, check the clearance with #1 at TDC and the valves are coming in contact with the piston. Mods are; over bore(.040), header and AZC 4 barrel manifold/Holley 390. Any guess on horsepower at the crank would be greatly apreciated, I am geussing around 175hp at the crank.

Thanks for any help.post-43928-0-11552600-1407784876_thumb.jpgpost-43928-0-77878700-1407784910_thumb.jpgpost-43928-0-31801300-1407784925_thumb.jpg

Share this post


Link to post
Share on other sites

Why would the pistons from a "master rebuild kit" not work with the head and cam?  Something is weird and probably wrong.  You need to list part numbers or links.  Master rebuild kit is too general.

 

If it is just a stock rebuild but with 0.040" pistons, and you get it put together right, I don't think that you've listed anything that will add power over the stock engine.  From what I understand, the stock manifolds flow pretty well, so the headers won't add anything, and flow to and from the cylinders is restricted by the head, so no gains with the manifold and carb.  These engines aren't like old small bccok chevys with small carburetors and restrictive exhaust manifolds.

 

It actually sounds like you're about to put together an engine that won't run on pump gas with timing optimized for power.  It will probably be down on power when you get it running, because of retarded timing.  Better do some more research, take some measurements, and re-calculate.

Share this post


Link to post
Share on other sites

Thats what I was afraid of. I would've liked to stick with doing head work and going to triples or rebuilding the factory carbs. My dad decided (like many muscle car guys) that there is no replacement for displacement when the engine needed to be rebuilt (sat for 18 years) and also that the "side draft carbs are junk"-My dad. He made the decision to just do a factory rebuild of the head, which I knew was the wrong decision for more power. Any suggestions for mods to make down the road. I am 14 so I have time to get stuff for the car.

http://www.zcarsource.com/engine-kit-master-240z-260z-70-74-new_8_55783_65878.html

Link to rebuild kit^

Share this post


Link to post
Share on other sites

It doesn't make sense that the pistons won;t work or you need to cut reliefs on a stock rebuild. I would say that the cam is not timed properly and making you think there is an issue-when there's not. Recheck your valve timing. 

Share this post


Link to post
Share on other sites

If you want to make power you will need head work, carbs and intake to match the head work, a header to match the head work and an exhaust sized to match the head work. If it is all done right you can get 100 hp per liter and still be streetable. All it takes is $. But since you have time you can learn to modify the head yourself. With lots of reading and searching and patients you can do it yourself. The pros like Rebello get the 100hp/litre but you can get up way past stock yourself. The factory motor had about 125-135 at the crank. I don't think you'll get 175 from what you are doing, maybe closer to the factory claimed 150.

Share this post


Link to post
Share on other sites

It doesn't make sense that the pistons won;t work or you need to cut reliefs on a stock rebuild. I would say that the cam is not timed properly and making you think there is an issue-when there's not. Recheck your valve timing.

 

^^^^^^Agree! Check that cam timing, stock engines unless lash is adjusted incorrectly or cam timing is wrong should not require cuts.

 

What you did was "follow the bolt-on-list" which universally has poor results compared to well tuned stock.

 

The power in the L-Series is, was, and always will be in the head. The stock SU's are eminently capable to 175-180 to the wheels if the head flows and and the gasses can get out.

 

Slapping parts on an otherwise stock bottom end generally just results in starting at ground zero in terms of making the parts work together properly...behind where you were with the old stock components you just replaced! Sorry for that bad news... You have some tuning to optimise what you now have. Step-by-Step, One-by-One!

Share this post


Link to post
Share on other sites

Just thought I should point out that your post is more coherent then those of many members several times your age. Happy wrenching!

That is so true and funny!!

 

 

To the OP- might want to tell dad that the tune is more important then the displacement.

Share this post


Link to post
Share on other sites

I have the how to rebuild your Datsun OHC motor.  I will probably be ordering the other 2 books/manuals (how to modify and how to restore). Thanks for all of the help and tips I will definetly be coming back for more answers, as I am sure I will have more questions being a newbie haha I have a lot to learn.

-Josh

Share this post


Link to post
Share on other sites

Ok, my dad and I are about to put together my motor for my 73 240z and we have no clue how much power this motor will make. The head is rebuilt to stock its a 1973 E88 head. We have the Z Car Source master rebuild kit with .040 over flat top pistons, the pistons dont work with the head so we are having valve reliefs cut...we found this issue once we had the pistons and most internal in, check the clearance with #1 at TDC and the valves are coming in contact with the piston. Mods are; over bore(.040), header and AZC 4 barrel manifold/Holley 390. Any guess on horsepower at the crank would be greatly apreciated, I am geussing around 175hp at the crank.

Thanks for any help.attachicon.gif20140530_160025.jpgattachicon.gif20140617_130048.jpgattachicon.gifIMG_20140807_142127.jpg

With that head laying down like that and a camshaft installed, I wouold check to make sure no valves got bent. It is possible avalve is sitting proud of the head.

Share this post


Link to post
Share on other sites

After tuning is done with a relatively small amount of aftermarket bolt on stuff unfortunately won't see a lot of extra ponies. Might notice a little change but mostly it will be in throttle response and in some cases members have seen a little bit better mpg. Still kind of a win and in the end after a while those extra bucks will help get better stuff like better flowing heads and other stuff that will really get you more power. Do your research and you'd be surprised what all info you will find here!

Share this post


Link to post
Share on other sites

I doubt the 4 barrel on a stock engine will have better throttle response or get better economy.  You're dad is right though, the triples are junk, that is why they are on 90% of the seriously impressive n/a L series'.  Good thing you grabbed that extra 3 cubic inches while you were in there.

Share this post


Link to post
Share on other sites

with just the over bore,not much gain will be seen...Now if you up the Compretion Ratio to around 10.0:1 and add a mild to hot cam, (im running 560 lift but you need stiffer springs to run this) and a 2.5in exhaust (free flowing) it will pull pretty nice.Also,since it is a 240z,a great upgrade for wicked Light to Light power is the 82-83 5 speed with the 3.90 Diff or even the 4.11 Diff from the 240sx (85-86).if you really want some L6 power in your 240z,either get a junked L28et or just the l28 and go stroker with it.the turbo stuff is way cool though and much cheeper for your HP in the end.cheers

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...