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sweatybetty

sweatys rebuild

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 I agree, if the bearings and crank look good go with it. It was a good day if you made that kind of progress without any broken bolts or studs.

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Those pistons indicate that somebody had plans for lots of valve lift and duration.  The head and cam might be interesting.  

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20 hours ago, Mark Maras said:

 I agree, if the bearings and crank look good go with it. It was a good day if you made that kind of progress without any broken bolts or studs.

that is one of the things i was dreading, but not 1 broken bolt or stud :D i am going to replace them all though

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12 hours ago, Captain Obvious said:

That's an externally oiled cam, right? Your spray bar in good shape?

the 2 short end pieces are a little loose in their sockets, but i think i can braze them. other than that, it looks like new

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turned out to be another good, productive day. the whole bottom end is new. all the rod and main bearings are new, but still standard size. i miked all of them, and used some plastic gauge, everything checks out within tolerances. im debating a new set of bearings since its all apart, but they look fine.

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pistons right out of the block before cleaning

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block washed inside and out and ready for paint

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even water jackets are clean.

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primed and painted

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100_1974.JPG

 

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20 hours ago, Zed Head said:

Those pistons indicate that somebody had plans for lots of valve lift and duration.  The head and cam might be interesting.  

did stock pistons have a valve relief? i measured the lift at the valve and came up with .433 which is what my haynes manual says is factory lift. id like to jump up closer to .500 but am worried about valve-piston interference. do you think these would work with a higher lift cam? 

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None of the four stock motors I've taken apart had any piston wedges or eyebrows cut into them.  Two 2.4s, flat tops.  One 2.8 with dished pistons the other a ZX with flat tops.  None had any unless the dished ones would be considered because they are deeper?

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39 minutes ago, sweatybetty said:

did stock pistons have a valve relief? i measured the lift at the valve and came up with .433 which is what my haynes manual says is factory lift. id like to jump up closer to .500 but am worried about valve-piston interference. do you think these would work with a higher lift cam? 

Yes.....the 1973 low compression 240Z's came with fly cut Pistons......and yes you can go up to .500 lift (Isky Stage III is .490 lift) as long as the L24 block is over bored .030 inches or more.

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More importantly I would measure deck height of Pistons . Unless they are waaayyyy out of the top of the block I would go with what ever cam you want. I'd say with reliefs you could go 550+


Sent from my iPhone using Classic Zcar Club

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thank you guys. from what i can measure, the bore is .7mm over and the pistons were even at the top of the block. am i right in thinking the over-bore is to keep the valves from hitting the cylinder wall? ive read that can be fixed with a little grinding.

im still thinking that  bigger valves and a little head work might help get a few more horsepower out this block, even if it is only a 24. i have the webers and a header, so if i can get it to breathe................

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If you have the low compression E88 head, I'd dump it for an early E88 or E31 head. The 73 heads are low performance. If your car is a 72 with the original motor, you should be running an early (good) E88 head. Get steel seats (L28) installed and L28 valves and a higher lift cam and you'll get a nice boost in performance:rolleyes:

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i have an E31 head. i dont think that this is the original block, though. my car is an early 72 and i have a E31 block.

Edited by sweatybetty
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Awesome....steel (L28) seats, valves and a nice Stage III cam and you'll be all set! BTW, when you install a higher lift cam in the L24 head, you'll need to install low profile valve seals to keep the bottom of the valve spring retainers from beating against a stock (taller) valve seal. Your block has already been over bored .75 mm (.030 inches), so you should be all set there.

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3 hours ago, Diseazd said:

Yes.....the 1973 low compression 240Z's came with fly cut Pistons.....

I did not know that.  More learning.

sb did say L28 block but it's all looking like low CR L24.  Reading back looks like he meant that he took the L24 head off to use onthe L28 but changed his mind about the L28 since the L24 was in good shape.  Diseazd seems to know what's going on.  Collecting the facts, it looks like a rebuilt, ovebored low CR, 1973 L24 with an E31 head.  Maybe it could have just been left together and run?  Surprise.

 

 

Not L28.PNG

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Here's mine from an automatic '73. It has the bigger cap bolts but no reliefs?  It was an early version I guess, it had the good E88, it's on my car now until I get my E31 put together. 

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Stroker rods!!!



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37 minutes ago, madkaw said:

How early Cliff was the 73?
Bo's car is a late 72, so maybe he still has small chamber head!


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Steve, I'm sorry but I have no idea.  I bought just the motor for the 3 screws SUs someone had put on there and luckily it had that head and the big rods with flat pistons. 

I've always read the perfect stamped E88 is the good one.  This would be the later version with more quench, miss matched letter sizes, from what I've read.

Image result for E88 240z head identifying

I think this is the early version, same size letters.  I'm not positive about this, just what I've read.   Both of my '72s have the same size lettering like this.

Image result for E88 240z head identifying

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Does anyone else think that those hone cuts look awfully big? I think if it were me, I'd have another machine shop do another hone cut.....wouldn't cost much....good insurance. BTW, I think you can still get Nissan 73 Pistons at your local dealer. The flat top without reliefs are NLA........and I also believe if I remember correctly, ITM pistons come fly cut for the L24 motors. SB.....can you look and see if the Pistons that came out are ITM or Nissan? And Siteunseen....can you take a pic of the chambers in that E88? Just curious. Love your dog....looks as crazy as my pooch;)

image.jpeg

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17 minutes ago, Diseazd said:

Does anyone else think that those hone cuts look awfully big? I think if it were me, I'd have another machine shop do another hone cut.....wouldn't cost much....good insurance. BTW, I think you can still get Nissan 73 Pistons at your local dealer. The flat top without reliefs are NLA........and I also believe if I remember correctly, ITM pistons come fly cut for the L24 motors. SB.....can you look and see if the Pistons that came out are ITM or Nissan?

Guy's got some eyes!  Here's what mine looked like when I got it back from the machinist.

DSC01067.JPG

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On 9/5/2016 at 9:24 AM, madkaw said:

I thought this was the L28 block. I took a 73 block apart and the Pistons had reliefs like this.
How big are the rod bolts- 8 or 9 mm?

ok guys, it sounds like there is a little confusion. i have an e31 head and an e31 l24 block that came in the car when i bought it. my original plan was to buy a l28 block and put the e31 head with bigger valves on it. bit, since tearing into the l24 block and finding that it has been newly re-built, i am going to stick with the l24 and e31 head. i think with bigger valves, webers, a header and a little porting work, it should breathe well enough.

madkaw, they are 8mm rod bolts.

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i decided that since i have everything torn apart, i might as well replace the main and rod bearings. they should be in my hands monday. so in the meantime, im getting everything else ready to put back together.

here are a few parts that got powder-coated.

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a little trick i learned is to put aluminum foil under the parts. the over-spray powder sticks to the foil, and then you can scoop it up and use it again. there is quite a bit just from the distributor

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oil pan all clean and painted

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got the head torn down. not 1 broken stud or bolt

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if you havent tried this stuff yet, its worth every dime. it was only $7 a can. i was sure that the heater hose fitting would snap, but it came out like a greased turd

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