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Engine & Drivetrain

Post messages here about engine mechanics, exhaust, intake, etc. Anything to do with the engine system as a whole.

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Flex Plate Drama That Didn't Happen.

March 11, 2015 by djwarner
2 replies

944 views
The 3N71A Transmission was slowly eating the low-reverse return spring to the point the car wouldn't reverse uphill when warm. I found a 3N71B out of a 280Z and set about removing the old and installing the new(er). After dropping the old transmission, I took the time to thoroughly inspect the flex plate and found some radial cracks 180 degrees apart. Fortunately, the new transmission came with the flex plate. A second surprise came when we removed the backing washer. There was a circular crack with a substantial gap just underneath the washer. There is perhaps two or three points of contact. I can't tell whether the crank had spun the portion on the backup w…
Last reply by rossiz, March 11, 2015
Valve Adjustment.

March 9, 2015 by rcb280z
2 followers

9 replies

3.1k views
Can someone explain to me why a hot valve lash adjustment is more desirable over a cold one? I have always done a cold one only. Maybe I'm missing something by not doing a hot one. It seem to me like you wouldn't get a good one "hot" anyway. It takes time and I think by the time you get to the last cylinder the engine has cooled enough to not be right. (?)
Last reply by rcb280z, March 10, 2015
Cool Exhaust/header Tools

March 8, 2015 by 240260280z
2 replies

1k views
Many other interesting items on the website too: http://www.trick-tools.com/Exhaust-Header-Design-and-Fabrication-Tools-863

Last reply by 240260280z, March 8, 2015
71 240Z. Leaking Diff.

March 4, 2015 by glassguy
5 replies

2.2k views
Last winter I pulled the entire rear suspension out to replace all off the rubber bushings with urethane. Since I had pulled the diff out, I went ahead and cracked the fill and drain plug and refilled it while it was out of the car. It never leaked before this. After everything went back together and I started driving it, it started leaking. I had overfilled it and it was blowing out the top vent. So, with the car in the air and level, I removed the fill cap and about a cup of oil drained out. But, even after that it continued to leak all summer long. Nothing terrible, maybe an occasional dime to nickle spot. So could I have damaged the axle seals by overfilling it, or is…

Last reply by Travel'n Man, March 7, 2015
Another Coolant Leak 1 2

March 3, 2015 by rcb280z
1 follower

20 replies

2.1k views
About 8 months ago my 77 280 developed a coolant leak at the head gasket between 3 and 4 cylinder. I used a good quality stop leak and it did slow it down however, while I was working on my "leaky injector" issue I found another coolant leak. This one is near the firewall below the #6 exhaust port. It's about and inch forward of the corner of the head. Here is a pic. I guess with this new coolant leak I should consider doing a head gasket soon? Attachments_201532.zip Almost forgot one important thing. It starts leaking on cold start up and stops once the engines comes to temp.
Last reply by rcb280z, March 6, 2015
Rocker Geometry Woes 1 2 3 4 13

November 24, 2014 by rossiz
1 follower

145 replies

22.1k views
been losing a lot of oil and not a drop is on the ground. we're talking a quart every 2 tanks of gas, maybe more. oddly there is no tell-tale blue smoke and it doesn't smell like it either. a good amount of oily, cruddy buildup on the plugs. i have good, pretty even compression, so i'm guessing valve stem seals. i didn't know just how much oil it was losing until i saw the oil pressure was lower than usual, and it took 2 quarts - yikes! i keep topping off, but on friday it started making a HORRIBLE squealing/screeching sound from the valve cover - in time with the engine - sounded like dry metal contact. i mean, it was really loud, scared the crap out of me. i added oil (…
Last reply by rcb280z, March 1, 2015
7/71 240Z Pedal Box Dilemma.

February 27, 2015 by glassguy
7 replies

4.4k views
I have a 71 240Z, manufacture date is 7/71. I am currently removing its original automatic transmission and putting in a 5 speed from a 78 280Z. Over the last year or so I have bought all of the bits and pieces I need to do this job. So, right now, I'm in the process of installing the pedal box I bought off of Ebay a while back. According to the seller, this pedal box was usable on a 70-78 Z. I cant remember what it came off of. Most likely a 75-78 is my guess. Anyway, my problem is that the new manual pedal box lines up with all of the "under dash" connections, but the brake booster bolts are off. Two of them. and the tear drop shaped cut out for the brake booster is of…

Last reply by glassguy, February 27, 2015
Rear Engine Plate Difference.

February 26, 2015 by glassguy
6 replies

1.6k views
I'm finally removing the automatic transmission out of my 71 240Z and installing a 5 speed thats out of a 78 280Z. After checking out as many threads on this subject, it seems that the "rear engine plate" is different for either transmission. So whats the difference between the two? Just curious.

Last reply by Patcon, February 26, 2015
Question on modified E31 HEAD 1 2

August 31, 2008 by Diseazd
17 replies

6.2k views
I just got my E31 head back from the Z Doctor. The head has an Isky Stage II cam with .480 lift. The head was not shaved other than clean up. We put 260 Z exhaust valves; 35mm vs 33mm (1.38 in. vs. 1.30 in.). Intakes are 1mm oversize (43mm vs. 42mm ; 1.69 in. vs. 1.65 in.) Is there any mods that have to be done to the block for clearance reasons, or should I be OK as is? I know eyebrowing the block will let it breathe, but is it necessary for clearance?
Last reply by Mark Maras, February 25, 2015
Water Inlet Housing Modification

February 18, 2015 by Jamaican_Z_Lover
1 follower

9 replies

1.4k views
This may seem weird to you guys or a waste of money but has anyone cut off the heater branch on the water inlet housing and welded it up. The heater has no use to me in the Caribbean and I was wondering if any of the skilled welders on here think this is worth the effort. I was just thinking of a nice clean inlet that didnt look like something is missing. Sent from my iPhone using Tapatalk

Last reply by Jamaican_Z_Lover, February 20, 2015
Grant Piston Ring Quality Control (Gap Variation)

May 31, 2011 by 240260280z
11 replies

7.3k views
Just doing rebuild for first time and learning a lot. I just came across different ring sizes in the same package and it seems unusual. Is this a quality control issue or is it normal? (GRANT P1297.000 from Black Dragon) Here is what I measured in the set of new top rings (I measured ring gap in same cylinder & same depth): 2 X 0.53mm 2 X 0.50mm 2 X 0.45mm My cylinders measured with same ring are (Top Bottom): 1 0.44 0.44 2 0.44 0.44 3 0.43 0.43 4 0.44 0.44 5 0.44 0.44 6 0.53 0.47 With this set I should be able to achieve: 1. 0.41 2. 0.41 3. 0.43 4. 0.44 5. 0.36 6. 0.45 However the spec is 0.23 to 0.38mm so all but one cylinder will fail. The bores are …
Last reply by Chickenman, February 19, 2015
Redline Diff Oil Question

February 15, 2015 by S30Driver
8 replies

1.4k views
Since the weather is great here lately, I'm getting ready to change the diff oil in my R200. Redline makes two 75w90 gear oils. One has the additional friction modifiers, and the other (75w90 NS) does not. Since this is not a LSD, I would assume the NS to be the proper choice. Redline's application guide however recommends the regular 75w90 for all the S30 cars. I am guessing overall it probably does not make much difference, but which is right. Is there some reason Redline recommends the regular gear oil?
Last reply by siteunseen, February 18, 2015