Topics

1

General Discussion / Balancing Question

« on: October 20, 2023, 01:05:03 AM »

I've recently swapped out pistons on a previously balanced rotating assembly.  The new pistons, pins, and locks are, on average 13 grams heavier than the original assembly.  The old pistons, rods, bearings, pins, locks, and rings weighed between 1457 and 1459 grams.  The new assemblies weigh between 1470 and 1472 grams.  Is that enough of a difference that I need to have the rotating assembly rebalanced.

2

General Discussion / z28 intake

« on: September 19, 2022, 10:00:02 PM »

Is there a consensus about when the first 67 z28 rolled off the assembly line? I was digging through old parts today and came across a 610 intake.  When I turned it over to look at the bottom to see if the heat shield was there, I noticed it was dated 3-14-67.  Seems to me that's awful early for a z car.  Did they use these intakes on 327 engines also in 67?

3

General Discussion / Looking for advice on short block assembly

« on: August 06, 2022, 02:56:48 PM »

I'm stumped.  In an effort to explain my problem, this will be a long winded post. The machinist I have used for years and several engines has always been spot on.  In fact, I don't even purchase bearings anymore, he has the correct bearings packed when I pick up the parts. I always check bearing clearance, early on, just with plastigage, but years ago I purchased a set of micrometers and a dial bore gauge, learned how to use them, and now rely on those measurements.

So now I'm measuring the main journals.  I take 8 readings on each crankshaft main journal at different points, average the results for each journal, and zero the bore gauge to that value for each journal.  One journal at a time, I clean everything, install the provided standard bearings and torque the caps to 70 lb-ft.  On journals 1 - 4 I get readings right at .003. Main 5 comes in around .0035 with the oil pump torqued to 50 lb-ft.

So now I'm thinking if I put a set of .001 unders in the caps, I should be right where I want to be at .0025 on mains 1 -4 and at .003 on main 5.  So I do that.  Recheck everything and according to the bore gauge I'm right where I want to be.  As one last cross check, I decide to plastigage each journal also.  I install the crank dry, torque each cap 25 -50- 70, add the oil pump at 50.  When I remove the caps the plastigage is really wide on each journal. Easily showing less than .002 clearance on each journal 1 -4 and right at .002 on number 5.  I repeat the process.  Same result.

I've never had this happen before and I don't understand why the readings are so different. The one thing I wonder about is how I install the caps. As it should be, the caps are an interference fit in the register. Right or wrong, I've always used a rubber mallet to seat the caps in the register.  Could that hit on one side of the cap be smashing the plastigage?

4

General Discussion / Why no reproduction 67 68 headrests

« on: July 04, 2022, 03:53:47 PM »

The one option I wish my 68 car had would be bucket seat headrests.  With all the reproduction parts available for 67 - 69 Camaros, I'm just astounded that no one has stepped up to re-create the early headrests.  I've been waiting years for headrests to be available.  I realize a person would likely have to buy a whole new seat to get the seatback support for the headrest but to me it would be worth it.  Am I missing something here?  Are they available but I just don't know it?  Am I the only one who thinks the standard seats look wimpy without a headrest?

5

General Discussion / Looking for advice

« on: July 01, 2022, 11:32:15 PM »

Hi. I'm a new member but an old guy. I really don't know what to do and am looking for some advice.  In the spring of 1977 I purchased a 68 Z/28 in Des Moines IA. At the time it had 72.000 miles on it.  It was smoking a bit and needed a some oil with every tank of gas as I recall.  My local mechanic told me it was tired and needed a rebuild.  He also informed me that Chevrolet was unloading their inventory of fitted 302 blocks at that time (77 or 78) and it might be a better idea to buy a new fitted block that to rebuild the original engine so that's what we did.  Soon thereafter I had a chance to buy a rebuilt M21 transmission so I bought it and stored away the original muncie along with the original engine.  Fast forward 45 years and I'm considering rebuilding the original engine.  However. in light of the fact that I'm an old man and getting older every day, I'm also considering selling the car.  Here's my question.  Would it be better to rebuild the original engine, reinstall it in the car with the original transmission and sell it that way or is it better to let some future buyer rebuild the engine and refresh the original transmission?  Thanks for you time and consideration.