Messages

1

Decoding/Numbers / Re: 186 heads - 1.94 vs. 2.02 valves

« on: October 19, 2021, 05:30:08 AM »

Thanks again Stingr69...  I really appreciate the info.

So from those pics and info it looks to be pretty clear that these are original big bowl heads then, as you can see that sharp edge; and also the cut area in the chamber (and throat) looks quite different on that example you showed of a modified 1.94.  My 186's look much more like a factory cut, for lack of a better term.

I'm going to say these are real 2.02's, unless anyone has something else to add.

2

Decoding/Numbers / Re: 186 heads - 1.94 vs. 2.02 valves

« on: October 18, 2021, 05:42:37 PM »

Yes, I suspect it should be easy to tell, but I can't tell!!  It might be easier if I had a stock 1.94 186 head to compare.

It definitely looks like there was an extra cut made to unshroud the valve, however it looks like this was done over the original unshrouding cut from the factory and removed a little more material at the top.  (Again, comparing to the stock 2.02 492 head).  You can see this cut blend with the original factory cut line towards the bottom, as the new cut is not concentric with the valve seat surface.  The throat sizes are the same as the stock 2.02 492 head, so is it possible they did that cut to blend it more to the throat with emphasis to the top? (like perhaps someone might do to fine-tune a factory 2.02 head?).

 - - What gets me is the throat size being the same with these 186's and 492's...  Were 1.94 throats the same as 2.02 throats or not?  If 186's which were 1.94's to begin with have the same throat sizes as the 2.02's, then why would they require extra machining with a bowl hog to open up the throats (as Stingr69 mentioned earlier) when modified?  As mentioned, the throat has not been opened up in this 186, so I'm still leaning towards this being an original 2.02.

Again - just looking for something definitive one way or the other whether these 186's started life as 1.94's or 2.02's...

Pls see pic below...

3

Decoding/Numbers / Re: 186 heads - 1.94 vs. 2.02 valves

« on: October 17, 2021, 09:12:26 PM »

I may have found my answer in a previous post...

http://www.camaros.org/forum/index.php?topic=18666.0

The photo below posted by jdv69z shows the face of the head is different between the 1.94 and 2.02 versions.
If this is in fact correct, then it would appear that I have a set of original 1970 2.02's.

I'd appreciate if anyone can chime in to agree or disagree with this dimension being a correct way to identify original 2.02's.

Thanks again - Len.

4

Decoding/Numbers / Re: 186 heads - 1.94 vs. 2.02 valves

« on: October 17, 2021, 05:37:54 PM »

Thanks very much for the reply Stingr.

You're right, it doesn't look like there was any machine work done at all below the shroud area.  The throats look to be original - which is where my question stems from.

My understanding is the 492 head was a direct over the counter replacement for the 186 2.02; so therefore should have the same throat size as a factory 2.02 186, correct?
 - If the 1.94 version of the 186 head had the same throat size as a 2.02, then this is a moot point.

I was lucky to have a 492 head handy that I could compare those throat sizes, and they are nearly identical - if anything the throats are a touch bigger in this 186, which makes me think these are indeed factory 2.02 186's.  The way they machined the area below the valve seats (unshrouded) gives the optical illusion in the photo that the throat is narrower below that shroud than the 492, but it isn't.

To your point that 1.94 conversions typically have the throats opened up...  if the throat is already the correct 2.02 size and I'm going for "stock"; I'm not sure I should touch them further?

To be clear, at the end of the day, I'm simply trying to determine if these 186 heads were originally 2.02's or 1.94's.  Is there any way to tell for sure?

Thanks!  Len

5

Decoding/Numbers / 186 heads - 1.94 vs. 2.02 valves

« on: October 17, 2021, 01:51:29 AM »

Hello All,

I have a question for anyone who has experience with '69/'70 186 heads... 

Are the castings and port sizes/runners identical for 1.94 vs 2.02 186 castings??  In other words, would 1.94 heads upgraded to 2.02 valves flow the same as factory 2.02's without additional port work?? 

Ultimately I want the correct casting number and spec heads on my '69 302 so that it performs exactly as new once it's rebuilt - I'm not worried about date codes.  It has a CE engine dated 1971 - warranty replacement, and has been running a set of 492's since the original heads gave it up in the 80's... 

So I located a set of 186 castings and had them completely rebuilt.  These 186 heads were supposed to have come off a '70 LT1, and are date coded for May 1970.  They did have the screw-in studs and guide plates when I got them, but of course these could have been added if they had been upgraded to 2.02 valves in the past.

However...  when I picked them up from the machine shop, they said they thought these heads had started life as 1.94's...  they were unclear on why they suspected this.  I have to decide whether to use these heads, or maybe do more work to them; so I popped an intake valve out of both the 186 head and a 492 head (2.02's) to compare the bowls and runners. 

 - I couldn't find any dimensions that were smaller in the 186's, and although the "uneven" machined shoulder below the valve seating face makes it look narrower; in fact if anything all the 186 bowl dimensions were marginally wider than the 492.  I think either these 186's actually are factory 2.02's, or there's virtually no difference between the 1.94's and 2.02's other than the larger valves.

I've posted some photos below compare the 186 and 492.  Appreciate if anyone can point out something I'm missing...
If it looks like these are legit 2.02 186's, (or nearly identical), then I'll bolt them on and be happy.

What do you guys think???

Thanks! Len 

6

Decoding/Numbers / Re: '69 Z/28 Muncie M21 Date Code - Missing digit?? "P903B"

« on: October 17, 2021, 12:27:16 AM »

Thanks guys - appreciate it.  Who knows what happened here, but it's odd that somebody would know enough to restamp a trans in the right spot, but not know enough to put the month code in.  Does anybody have any pics of another M21 "B" transmission code stamp that you could post for comparison? 

Thanks, Len

7

Decoding/Numbers / '69 Z/28 Muncie M21 Date Code - Missing digit?? "P903B"

« on: October 06, 2021, 07:52:28 PM »

Is anyone aware of any irregularities in date codes on early '69 Muncies?  Here's a pic of my (believed to be original) M21 in my '69 Z/28. 
02D build date on the car, partial serial number is correct - what you can see of it.  It looks like the month code is missing - I would expect it to be "P9A03B" perhaps; but it simply shows "P903B"??   ... Also, the "B" appears to be inverted?

I'm relatively confident this is the born-with transmission.  I bought the car from older owners (long-time friends) who have had it since 1974.  To their knowledge the transmission was never replaced (or they forgot); and if it was in the early days, did people bother to re-stamp back then?  Nobody cared about numbers when these cars were nearly new...

As the car has a CE engine (replaced under warranty in '71); it's possible the transmission was replaced under warranty as well at some point. 
Would there have been different date designations for warranty Muncies which may explain this?

Thanks in advance!