TheSamba.com :: View topic

Fri Jul 18, 2008 8:33 am

Can anyone tell me what the stock valve sizes are for a '65 40HP engine?

Thanks,

Scott

Fri Jul 18, 2008 9:19 am

For the 40HP 1200 engine:
31.5mm intake
30 mm exhuast

Fri Jul 18, 2008 2:46 pm

I'm going to rebuild my '65 40hp engine and I'm probably going to use a set of 83mm "Big Bore" jugs and pistons when I do it. I'm not looking for a lot of performance, I just want a good driving engine that looks stock on the outside. I'd like to put in a set of stainless steel intake and exhaust valves and seats. I don't think you can find these for 40hp engines (or at least I haven't been able to find them). I think the 1300cc engines used 32mm valves. Could I cut the head for the larger seats and use these valves. The extra cylinder volume could probably benefit from larger valves. I've got the later model heads that have the larger square bosses. If anyone has any opinions feel free to share them.

Fri Jul 18, 2008 2:56 pm

1300 is 33mm intake, same exhaust. I'm sure you could find a machine shop somewhere that would install those seats - those were the ones that 1975-79 EFI 1600s used. But even if you did, the intake ports on top of the head are still the small 40HP size.

You could always go with some 1300 heads - but you'd have deal with the intake manifold being different.

Fri Jul 18, 2008 5:14 pm

If you don't end up going beyond the 83mm P&Cs, know that you will probably be satisfied. I daily drive a 1385 and feel quite good about its performance, and I'm sure others here (glutamodo, for one) would tell you the same thing.

So by all means, try fiddling with valves, but if it doesn't happen, you'll still end up with a nice little engine.

Fri Jul 18, 2008 5:24 pm

So where are the good 83mm p&c's coming from now? Are they all still requiring the skirts to be modified like Mahle? What is the correct pin size, I think there are multiple versions of 83mm pistons, but different wrist pin sizes, correct?

Fri Jul 18, 2008 6:07 pm

Thanks for the info guys.

I got these 83mm P&Cs from CIP several years ago. They are Mahle. I had heard about having to modify the skirts on the pistons and to be honest I don't know if the set I have will require that. What are the details of that situation?

Thanks,

Fri Jul 18, 2008 6:43 pm

I've got a couple of new or near new old stock sets so I'm set, but I did buy a new Mahle set "just to have". To know if you have the ones that need modified, all you have to do is look at the pistons, the ones with the really wide skirts are the ones that give problems.

Fri Jul 18, 2008 7:23 pm

Thanks for the info. So, is the problem that the skirt interferes with the con rod? Is the fix to machine away part of the skirt?

Fri Jul 18, 2008 7:34 pm

Oh, I thought you knew - the rods are fine. It's the engine block that is a problem, those wide skirts can hit the case, as shown here:

Sorry, thought you had heard the whole story.

Actually, if you have the block apart you can just clearance it in those locations.

Those photos were all ones I did up a long time ago for the original thread talking about this issue. That thread is this one:

http://www.thesamba.com/vw/forum/viewtopic.php?t=129792&

Fri Jul 18, 2008 8:06 pm

Thanks, I really do appreciate the information. I knew that there was an issue with the later Mahle P&Cs, I kinda just decided to worry about it when I got closer to the rebuild. With the information that you've given me I might look for an older NOS Cofap set. I kind of hate to grind on the case if I don't have to.

BTW, I've sort of assumed that stainless steel valves and seats are not available for 40hp motors. I've checked the usual suspects and no one seems to carry them. Have you ever see 31.5mm & 30mm valves and seats for sale anywhere?

Once again, I really appreciate the information,

Scott

Fri Jul 18, 2008 8:10 pm

Nope, I've never seen anything other than stock valves for sale, never even seen seats, but I 've not looked for them either. I'm thinking though that maybe the 1200 Industrial Mexican-built heads I have on the shelf for future use might have the harder valve seats in them.

The '65 heads I have in my 62, they've held their adjustment much better than any of the of the older heads I've used in the past. I've seen valve seats slowly erode away to nothing in the past, but with the engine I'm running now, it's been surprisingly nice.

Andy

Fri Jul 18, 2008 10:52 pm

Just looked at my Mahle 83mm P&C set and it is indeed like what you show in your picture. Is Mahle the only vendor left making 83mm Big Bore pistons and cylinders? What about Cofap? Are they still in the market for these P&Cs?

Fri Jul 18, 2008 11:08 pm

As far as I know, those Mahles are the only ones you can get new now. When they came out, I remember hearing it was a limited, one-time-only run to satisfy current demand, so get'em while you still can. (and I did!) But considering the shape of those pistons, I wonder if Mahle sort of hedged on the deal, using a similar but not quite-right piston from some other car's application and adapting it to make it work with the 40HP specs. But neglecting to check for that case clearance issue. I'd not be too surprised if that was the story behind these, as I've never seen a VW piston that was shaped like that before!

-Andy

Fri Jul 18, 2008 11:14 pm

Do you think removing material from the piston is practical? If I did go that route I'd probably want to take it to a machine shop if they could do it so that the work would be uniform from piston to piston. Don't think I could achieve that with a Dremel or die grinder. In your opinion is that something a decent machine stop could handle? Of course I'd have to weigh and match weights on them when they were done (which I would do anyway).

Fri Jul 18, 2008 11:16 pm

I removed material from one of mine, then planned on doing the rest of them at a later date..... which never happened, at least not yet. But I think if you made a template and used a sensitive scale to ensure equal weight it's do-able...!

Sat Jul 19, 2008 6:31 am

So what is the correct pin size for 65' 1220 40hp? I was a a swap which had multiple sets of 77mm p/c's, but I was told the pin size was wrong for me. If this was the case, I was wondering if the 83's have the variances in pin size as well.

Sat Jul 19, 2008 7:10 am

engineerscott wrote: Do you think removing material from the piston is practical? If I did go that route I'd probably want to take it to a machine shop if they could do it so that the work would be uniform from piston to piston. Don't think I could achieve that with a Dremel or die grinder. In your opinion is that something a decent machine stop could handle? Of course I'd have to weigh and match weights on them when they were done (which I would do anyway).

I was afraid to do it myself as well, so I took it to my local machine shop. The owner had done it before for someone else in the same position. They came out looking beautiful. I should've taken a picture.

Sat Jul 19, 2008 7:13 am

glandnut wrote: So what is the correct pin size for 65' 1220 40hp? I was a a swap which had multiple sets of 77mm p/c's, but I was told the pin size was wrong for me. If this was the case, I was wondering if the 83's have the variances in pin size as well.

Yes. That's why the 1500 83s don't work. I don't have any numbers, but they're different.

Sat Jul 19, 2008 9:40 am

engineerscott wrote: Just looked at my Mahle 83mm P&C set and it is indeed like what you show in your picture. Is Mahle the only vendor left making 83mm Big Bore pistons and cylinders? What about Cofap? Are they still in the market for these P&Cs?

Mahle owns Cofap. and Cima, and several other piston manufacturers. Most engine components you buy now days, Mahle had a hand in making them.
(I am a retired Mahle Employee.)