<VV> 61 Loadside update and questions

Tue Nov 25 17:32:18 EST 2008

Wow, I never thought that my questions would create so much discussion. 
First off let me thank everyone for their responses. It has given me insight 
into how I should move forward. I know already that I will be using my 110 
HP parts and early V block to build my new motor. I will give updates as I 
slowly, because of lack of time, rebuild the motor. It sounds like I should 
also clarify my thoughts on how I know the engine overheated and how much. 
We will never know for sure because the previous owner has passed on. All I 
can do is speculate using the stories I have heard and the things I observed 
as the engine was disassembled. The story I was told is he was driving from 
Marshalltown to Cedar Rapids for a car show or an ICE meeting. Probably on 
I-80 at interstate speeds, but I don't know this for sure. The engine 
started to lose power and finally smoke was observed from the rear of the 
truck and he pulled over. By this time there was a fire in the engine 
compartment and the Fire Dept. was summoned. This is the story and now my 
observations. The fire was contained to the distributor and the area 
underneath the distributor. The fire burned up the spark plug wires and what 
looked like the fan belt which I believe had come off at speed and piled up 
under the distributor. There does not seem to be much impingement into the 
lower shroud area around the filler tube as the o-ring on the tube is in 
tact and pliable. What started the fire? I don't know. Did the belt come off 
and pile up under the belt pulley and friction start it? Maybe. Or did the 
engine get so hot that some small amount of oil caught on fire. Less likely. 
As for explaining my 600 degree comment. After engine disassembly I noted 
that the cyl. bores were of a dark color indicating that they were hot 
enough that the oil was frying off of the cyl. walls. There was hardly any 
carbon build up on the piston heads or in the heads so it was easy to see 
that some of the valve heads were dark blue-black in color indicating that 
they had been at least 600 degrees in temperature. How hot was the engine 
really. I don't know but I would guess more than 600 degrees. Now as far as 
Bob and Lon's comments I think they both could be correct in some areas. 
Now, I am not an engineer or a metallurgist. I was a auto and diesel 
mechanic and a tool maker so my comments are purely opinion. First we have 
to realize our favorite engine is a relatively simple engine made up of 
multiple components. Components which are made of three different metals. 
Aluminum, Cast iron, and steel. In example: cast iron cylinders sandwiched 
between an aluminum block and aluminum heads held together with steel studs. 
All of which expand with heat at different rates. Now the tops of the cyl. 
and the top head studs sit right under the cooling fan blowing cool air on 
them constantly from start up. While the bottom of the cyls. and studs are 
receiving heated air from the top of the engine. There can be many different 
temperatures at various places on the engine at the same time creating 
various amounts of expansion.  There has to be some flexibility built in to 
the entire engine or it just would not work. Now the outside dia. of the 
early cyls. is 3.736. My .040 overbore cyl. inside dia is 3.477. that's a 
difference of .258. The gasket. sealing surface is .129 wide. Bore the cyl. 
.020 more and the sealing surface is .119. That's pretty thin but it should 
work if all the parts are to the correct tolerances. Meaning: the block deck 
surface is in a straight plane, the block bores and the head bores are all 
on the same centers, all the cyl. measure the same distance from the block 
surface to the head sealing surface, all the bores in the head are inplane 
with each other, and no nicks in either head gskt. sealing surfaces. It is 
probable that the narrow width of the sealing area might swedge the aluminum 
head through cooling and heating cycles, but I have seen this on stock late 
model heads with standard bore. GM changed the outside dia. of the cyl. from 
3.736 to 3.796. A difference of. 060 or .030 per side. This would make for a 
larger surface area to seal on but add only slightly to rigidity.  As for 
the inside mic. in the cyl. trick. I have used inside mics alot. if you set 
it just right in a cyl. bore you only have to flex that bore one tenth of a 
thousanth to get it to fall out. In conclusion I believe the cyl. flex is 
built in. It just has to be. Just my .02 worth.

Jamie
----- Original Message ----- 
From: <BobHelt at aol.com>
To: <corvairduval at cox.net>; <virtualvairs at corvair.org>
Sent: Tuesday, November 25, 2008 11:43
Subject: Re: <VV> 61 Loadside update and questions

> In a message dated 11/24/08 7:06:09 PM Pacific Standard Time,
> corvairduval at cox.net writes:
>
>> Hi Bob,
>>
>> You seem amazed that 600 degree head temp didn't instanly destroy the
>> motor.
>
> Hi Frank,
> No, not at all. Both the turbo and 140 hp engines had their overheat 
> sensors
> set at 575 degrees, so it is possible to hit this temp and not destroy the
> engine. However this temp should not be considered a normal operating
> temperature. And it should not be considered a "good" thing that it is 
> encountered.
>
> But you seem to have taken my reference to 600 deg as some kind of actual
> temp. My inclusion of it in my last post was simply a reference to Jamie's 
> use of
> 600 as an indication of significant overheat. I don't know what caused his
> engine to overheat or just how hot it got. But my approach is to be 
> consevative
> in the reuse of any parts that have been overstressed. I just hate to have 
> to
> redo any mechanical repair work because I took chances with marginal 
> parts.
> Regards,
> Bob Helt
>
>
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