Corvair Forum

Hello folks. What is the largest size cylinder bore that a Corvair case will accept? I ask because I've been doing research on engine modifications and discovered that the Big Bore configurations use VW jugs. I know you can purchase VW jugs as large as 105mm these days, so that started the gray matter (mostly hardened like cement) churning.

As far as I know 94mm is the largest cylinder that will fit.

Beyond that you could use a stroker crank for even more displacement.

I've been toying with the idea of a stroked big bore for about 3.6 liters.

Thank you for responding UNSAFE. Today, I began my journey into the corvair world with the purchase of a running 1964 110hp motor. My plan is to take it apart, take some of measurements and most likely convert it to big bore. I'm no expert, but I got into this hobby for the fun and learning experience, besides I'm a self proclaimed DIYer and like to understand how things work. I know a lot of this has probably been done, but finding the information I need has proven to be a challenge. I've found a good bit, but would like to find more. Oh well, the search continues.

If you want true big bore power, contact LN Engineering: http://www.lnengineering.com/type1.html

If you give them enough money, I'm sure they can make you a set of billet aluminum cylinders at 104mm or so. There are very good reasons for having aluminum cylinders, main one being that beyond a certain size the iron ones just don't cool well enough. I put a set of 103mm jugs in my Type 4 Porsche engine, but that's as big as I dare go for the sake of reliability. The cylinders touch each other at just about every point, and there's next to no meat left in the case.

If you give them enough money, I'm sure they can make you a set of billet aluminum cylinders at 104mm or so

Having enough money usually gets in my way. I imagine if you spent enough cash you could do anything tho !

I think that one problem with going over 94mm is that you'd have to relocate the head studs . This likely could be done but the cost would be huge. This would mean that the rocker arms would be relocated also .

I'm also not sure about the piston skirts clearing the crankshaft ?

Seems like beyond a 94mm bore -- stroking would be the way to go .

bigbredaalmighty wrote:.....I know a lot of this has probably been done, but finding the information I need has proven to be a challenge. I've found a good bit, but would like to find more. Oh well, the search continues.

Welcome to the forum - have you seen this article about building a big bore engine?

http://corvairkid.com/mm01.htm

Marty Scarr

Here's a couple of pics to illustrate why it would become a major job to go bigger than 94mm.

You can see how close the cylinders are to the head studs as it is with the 94mm. The studs are already touching the cylinders. The base of the cylinder where it fits into the case is already paper thin . About 1/16th"

You would have to weld up the stud holes in the case and add material and then locate and tap new holes.

This would mean drilling new holes in the heads and modifying the pushrod guide plates . This would also change the pushrod angle.

And if you did all of that there still might not be room inside the crankcase for the pistons to clear the crank etc.

Thank you all for replying. I was away for the weekend with limited access to internet (can't believe that's possible in the US in this day and age), so I had to suffer through it. On a positive note "The PATRIOTS are going to the big dance" I have a few jugs laying around that I'll play around with

It's always fun to play with the "jugs"!!

If you want true big bore power, contact LN Engineering

WOW -- 3 grand for pistons and jugs and that's just for a set of 4

UNSAFE. Do you do your own machine work? I'm searching for someone to do some work on my 110hp heads after I disassemble the engine. I plan to shave the intake plenum and run individual runners. I also want to use larger cylinders.

UNSAFE wrote:WOW -- 3 grand for pistons and jugs and that's just for a set of 4

You pay for what you get, those parts will allow you to do things you just plain can't do with the iron stuff. Heat dissipation is a lot better, in the VW realm they get used to build camper engines that get lugged a lot. It's not uncommon for those to see more than 150,000 miles before a rebuild, so I hear. A guy called Wally has a 2.2L in his Bug with those, he runs 20+ PSI boost relaibly- in his daily driver. Try that with iron.


http://shoptalkforums.com/viewtopic.php?f=3&t=131253

How much does your 3.1 make?
Check the cheatin' 2.2L 4-banger out!




Don't really like the whale tail, but I guess the intercooler has to go somewhere.

UNSAFE. Do you do your own machine work? I'm searching for someone to do some work on my 110hp heads after I disassemble the engine. I plan to shave the intake plenum and run individual runners. I also want to use larger cylinders

No , I have my machine work done.

I highly recommend Michael LeVeque at Levair Performance & restoration. He can do anything you want done to your heads . He does good work in a timely manner at a fair price . He's also a forum sponsor .

Nick - I don't doubt that the cylinders are superior to iron but Ouch !!!!!!!!!

Except for the kerosene incident in 2008 I haven't had any trouble with my cylinders ------

Of course I'm not "Cheatin"

I remember that thread miniman82. Lots of good information on the type4rum. I still visit there for my other projects. I guess that's where my ideas are coming from. I even remember you miniman82 loved reading your input, project

UNSAFE wrote:Nick - I don't doubt that the cylinders are superior to iron but Ouch!

They are very expensive, but you have to stop and think about what you're getting. It's a custom, made in the USA, billet aluminum cylinder with nikasil plating. Chnaces are none fo us will ever make enough power to need them, but it's nice to know the option is there.

miniman82 wrote: They are very expensive, but you have to stop and think about what you're getting. It's a custom, made in the USA, billet aluminum cylinder with nikasil plating.

they arent a billet - they are a extrusion. at least they arent cast. gg

-Scott V.