<VV> Cylinder assemblies vs Pistons/rings + rebore

Fri Feb 11 22:24:29 EST 2011

  HI  Mark, 

           Boat  Racing  is  very  similar  to  the  airplane  stress  you  describe.  The  engine  is  direct  drive . Sealing  the  cylinder  is  everything.  WE  never  get  a  chance  to  check  cylinder  wear, coz  when  the  leak-down  gets  near  90%  the  motor  comes  apart ,...... OR , ...  You  get  a  blast  of  water  from  your  competition ,  and  the  sudden  change  in  cylinder  temp  kills  your  valve  job.  WE  do  make  sure  the  cylinder  is "TRUE"  and  round  [they  don't  always  stay  that  way  in  an  air-cooled  engine] 

           The  Corvair  drove  us  crazy , because  it  would  go  like  hell  the  1st  heat  [6800], then  gradually  lose  RPM  until  it  got  down  to  the  basic  torque  curve  of  5600rpm.  The  culprite  ended  up  being  our "TRICK"  exhaust.  The  motor  would  "SING"  on  the  dyno.  Then  we  ran  it [the  1st  heat] , either  won , or  ran  a  close  second  to  the  National  Champion [Record  Holder].  When  the  boat  returned  to  the  pit  the  driver  killed  the  ignition  and  the  hot  pipes  settled  into  the  water. This  made  steam  which  rose  into  the  exhaust  port  and  warped  the  exhaust  valves [MAN!,...  it  took  us  forever  to  figure  that  out]. 

  Bob 
----- Original Message ----- 
From: "Mark Durham" <62vair at gmail.com> 
To: moonpie8n at comcast.net 
Cc: virtualvairs at corvair.org, cityhawk at pobox.com 
Sent: Friday, February 11, 2011 9:22:31 PM 
Subject: Re: <VV> Cylinder assemblies vs Pistons/rings + rebore 

Bob, I might have a different opinion if I was in the racing game 
where better materials really shine, but for every day use where I am 
going to put maybe 3000 miles a year on the car, the Grants will do 
just fine. Just like the cast rings I used in my original Corvair back 
in the 60's and 70's easily went 90-100K miles and I didn't baby the 
car, either, I was a teen and college student that started the car at 
-20F and drove away, and drove in the high temps in the summer too, 
yet your severe service really eats them up. 

The reason I brought up the Aircraft part is that those engines run at 
full power on takeoff, and then run at 75% to 80% power while flying, 
far more stress than what a automobile engine ever is put through, 
accept for your racing engines. How do the cylinder bores hold up? 
With the rings going bye bye so fast? 

Regards Mark Durham 

On Fri, Feb 11, 2011 at 8:19 AM,  <moonpie8n at comcast.net> wrote: 
>   WELL,  Mark.......... 
> 
> 
> 
>                 I  guess  that's  why  they  make  Chocolate , and  Vanilla 
> ice  cream ............. 
> 
>        Bob 
> 
> Moonpie  Racing 
> 
> ----- Original Message ----- 
> From: "Mark Durham" <62vair at gmail.com> 
> To: cityhawk at pobox.com 
> Cc: virtualvairs at corvair.org 
> Sent: Friday, February 11, 2011 10:48:18 AM 
> Subject: Re: <VV> Cylinder assemblies vs Pistons/rings + rebore 
> 
> Karl, the cost to have a set of cylinders bored oversize is about the 
> same as the cost to get them already bored exchange from Clarks or 
> larry's shop. Since you are on the east coast, the cost to ship from 
> Larry's shop in CA would outbalance the cost to bore, or get a set 
> exchange from Clarks. 
> 
> I doubt that Grant Rings are junk. Check out their web site. They are 
> in many (1000's) OEM applications and they make a set of chrome rings 
> for the Corvair. I just installed a set in the engine I am prepping to 
> go back into the car in a week or so. I've overhauled engines since 
> 1967 and the Grant rings look the same quality as Hastings, total 
> Seal, or any other brand, in fact, they looked identical. I've also 
> overhauled many air cooled aircraft engines and the rings used in 
> those high temp engines also looked the same as Grants. 
> 
> I did a lot of comparison shopping between Clarks and Larry's shop. 
> Larry's shop was cheaper for the same products, like Clevite bearings, 
> total seal lifters, Isky 270 Cam, and since I am on the west coast, I 
> decided to use Larry's shop for most everything because of shipping. 
> But, you are in the same state as Clarks. If I was in Boston, I would 
> use Clarks. 
> 
> If you want to save a few pennies, Clarks also has some $ saver cyls, 
> ones they have shaved .010 off the top to clean up the gasket surface, 
> also available in kits. The shave off will slightly increase 
> compression which will also slightly increase HP and gas mileage. 
> 
> If you have any further questions, drop me a note. Mark Durham 
> 
> 
> 
> On Thu, Feb 10, 2011 at 11:58 AM, Karl Haakonsen <cityhawk at pobox.com> wrote: 
>> Perhaps this question is premature, since I haven't yet had the chance 
>> to take my engine apart (I need to use my limited Corvair time to repair 
>> my snowblower since we're having a ridiculous amount of snow in Boston 
>> this winter).... but does anyone on the list have insight as to the 
>> wisdom of buying new piston/cylinder assemblies from Clark's vs just 
>> getting oversized pistons/rings and having my existing cylinders 
>> rebored? It seems as though the difference in price for the parts is a 
>> few hundred dollars, but how much does reboring cost? 
>> 
>> Also, what of the "full fin" cylinders available from Clark's? Any 
>> thoughts? 
>> 
>> Thanks! 
>> Karl in buried Boston 
>> www.chezhawk.com/VairBlog 
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