<VV> Corsa update - compression and temperature

[BobHelt at aol.com]

Hi Guus,
I'll try to give you some info as I see it. Please see below.
Regards,
Bob Helt
 
In a message dated 6/24/2006 1:06:32 PM US Mountain Standard Time,  
corvair at corvair.nl writes:

Really a  story for diehard engine guys ;-))

Follow up on the compression test of  last week. After installing  
(new) points (I wanted to rule out  problems with the Ignitor) and  
cleaning the spark plugs the car ran  pretty decent again. Took it for  
a drive but it ran hot again very  soon. Even at low speeds like 40/50  
mph it runs at 400F. 
 
400F is somewhat hot but not really bad. I suggest that you check your  
gauge, or alternately verify the temp by someother means (laser gauge,  
thermocouple, etc).
 
To verify the temp, I suggest you run up the speed and time for doing so.  
The purpose is to see if the temp goes higher or it stabilizes at some temp. You 
 know of course the overheat system triggers at about 575F. Don't get that 
hot  but just see what it does at higher speeds and lengths of time.
 
Are the air damper doors fully open when hot?
 

Contrary  to a "normal"  water cooled car with  
heat problems the  temperature goes quickly down again if you just  
leave it idling. My  guess is it could idle all day and never run hot.  
It's definitely  connected to higher revs.

Just out of curiosity I also measured the  compression again with the  
engine hot. Almost burned my fingers  removing the spark plugs so hot  
it was. The whole engine compartment  gets incredibly hot. You can  
hardly touch anything in there after  the engine has run for a while.  
Even the spare tire rim was hot when  I took it out.
 
could be good or bad. It's too subjective.



The hot values are as expected lower but with almost the same  spread.  
Cylinder 1 is also lower now.
Cylinder     Cold    Hot (all psi)
1         174        133
2       138        123
3     160        152
4   145         141
5            160       152
6            145     138
 
These differences could well be showing the changes in the cylinder  
dinensions (roundness) from cold to hot. I wouldn't get too concerned tho. But  as 
Craig mentioned some do seem high for the open-chambered 180 hp heads  with 
8.25:1 CR. But even tho, that's not going to cause a heating problem. Your  
problem, if it exists, is most likely in the air flow or incorrect  gauging.



I think that the only real problem is the car running hot. If I  keep  
it low the car runs good. The shrouding is all in place, spark  plug  
boots are there and the seal is in place.

So what can  make an engine run hot on higher revs?
I think two things could be  wrong.
The more the engine works, the hotter it will get. Higher revs means more  
horsepower being generated and thus a higher engine temp. Heat developed pretty  
much corresponds directly to the engine output.
 
 



Option 1
Valve timing.
How can one check if the hydraulic  lifters have collapsed? If I had  
adjusted them like that this woud  result in solid lifter wouldn't it?  
Can valves that are adjusted to  tight make a car run hot? (I mean  
really hot!)
 
No connection. A collapsed lifter would be caused in either of two  ways. 
Either the lifter failed and then it would be really noisey. Or someone  
overtightened the valve adjustment.  But that would screw up the  compression and the 
cyl would read low. Neither of these is your problem.
 



Option 2
Distributor trouble
Like I mentioned before the  distributor is the only (main) part  
that's not rebuild. I've timed  it at 20-24 degrees at 850 rpm like  
the manual suggested. How can I  check if the centrifugal and pressure  
retard are working correct? I  looked at the manual and at 2000 rpm  
the pressure retard should  retard the time. If it doesn't and the  
timing stays at 20-24 degrees  would that make an engine run hot?
 
Unlikely. Check the centrifugal adv by connecting your timing light and  
watch the mark on the harmonic damper while revving the engine up to 4000 rpm in  
neutral gear. Be sure parking brake is set. You should see the timing mark 
stay  stable until 4000 rpm and then see the advance move it at around 4000. you 
can  estimate the adv by seeing how much the mark moves. There is no boost 
then so no  press retard will occur. I doubt you have any problems with that unit 
anyway. Th  get boost you have to load the engine at moderate-to-high rpm. 
You are not doing  that.



There's only one big BUT concerning this retard thing. There's  an  
Safeguard retard unit on this car. This unit can  electronically  
retard the timing if detonation (pining) occurs. The  display however  
shows very little action of the unit. At least it  doesn't act in the  
range the car is already running hot. Only when I  really boost it the  
Safeguard takes over every now and then. Nice  unit btw.

The Air/Fuel ratio indicator on the Safeguard also give an  almost  
perfect ratio (13-14) while driving. Only running a little  lean on  
acceleration but quickly becoming normal again. That's why I  rule out  
fuel problems.
 
 
I see no problems here.



First I could adjust the valves again. But then I would like to  know  
how I can detect one or more collapsed lifters. With the  distributor  
probably the best option would be to ship it to Dale Mgt  for a  
rebuild but I would like to be sure if that's really necessary  and if  
it's really the reason the engine runs hot.
 
Forget valve adjustments.



What else could cause it? Opinions welcomed.
 
Probably your gauge is off. I'd verify actual temps first.
 
If your temps are real, then check for possible cooling air restrictions.  
Check for restricted head air passages. Check for proper air damper door  
operation.
 
How does the car run at all speeds and conditions? I'd see how it performs  
first, then evaluate temps.
 
I hope that this helps.
Bob Helt




Sorry for the long post. The good news is that tonight I took it  for  
a nice drive through the woods nearby. As long as you keep the  revs  
down you would never know it has a problem  ;-)

Regards,

Guus de Haan
The Netherlands
'65 Corsa  Turbo-Charged Cvt