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Wed Mar 11, 2009 6:31 am

Ok

I have a 1950 25 hp case with a stock crank and rods

I'll fit bigger valves (33 inlet 30 exhaust I think) and do some small porting work to some 36 heads, and up the compression to about 7.5:1

Twin 28pci carbs, 383 dizzy, 6volt. unsure on cam, straight cut gears cos I love the sound

83mm barrels and pistons using 1500 remachined barrels

I don't want anything too mad, 50hp would be great, 60hp would be fantastic. Its running 1950 brakes :shock: . Something like my old stock but very well built (not by me) 1300sp would be good.

My Preferences are

Reliability
Rebuildability, if I break it I can buy it again!
Cost
Power

The 40hp big bore pistons are tempting but I can't get them in the UK. Are they abundent in the US? I know of several sources but will they all dry up in a few years?

Now back to these pistons.............

Cheers

Seb

Wed Mar 11, 2009 8:40 am

Whats the Compression height on a 36hp piston?

I'm away from home till the weekend so can't measure it.

its the centre of the wrist pin to the top of the piston if anyones got one about

Seb

Wed Mar 11, 2009 10:32 am

in my mind is 38mm

Wed Mar 11, 2009 11:23 pm

83.50 is about the safest I would go...

Thu Mar 12, 2009 7:34 am

I'd like to go bigger on the next one but I think I'll need to run a counterweight crank too.

With a stock 64mm crank, I agree 83mm is as far as I'd go, I'd like to do a 87mm with a 74 or even 76mm crank, but thats a pipe dream for a while.

Seb

Fri Mar 13, 2009 4:47 am

counterweight is not really needed except you will run over 6000 rpm.
its more important to keep the moving mass low. balanced stock 64/74mm cranks will be the best way. 87mm bore is a real dream in a 36hp head and case too ;)

Fri Mar 13, 2009 7:14 am

The engine I'm doing now needs to be reliable and nippy. The other one just wants to be nuts and quick 8) I don't even have a car lined up for it.

Anythings possable espesially with a big hammer :lol:

Seb

Fri Mar 13, 2009 9:56 am

I have been reseaching the idea of having some "H" beam connecting rods made up for the 36hp engine. As bigger pistons and longer stroke crankshaft are being used nowadays, the need for a stronger link is necessary to prevent the little beast from blowing itself up! I have taken apart engines that were built by "experts/Bozo's" and found bent conn. rods?!?! I will post more info. as progess continues....Cheers! Mr. Okrasa 8)

Fri Mar 13, 2009 2:40 pm

Mr. Okrasa wrote: I have been reseaching the idea of having some "H" beam connecting rods made up for the 36hp engine. As bigger pistons and longer stroke crankshaft are being used nowadays, the need for a stronger link is necessary to prevent the little beast from blowing itself up! I have taken apart engines that were built by "experts/Bozo's" and found bent conn. rods?!?! I will post more info. as progess continues....Cheers! Mr. Okrasa 8)

Your Not the only one :D I've been measuring up 2" chevy rods with overseized bushes for the 50mm journals of the 36hp. You could do something similar on the porsche crank

Seb

Mon Mar 23, 2009 10:42 pm

Julio Iniguez wrote: grueni wrote: changing the 36hp rods from 20mm pin bearing to 22mm work and up to 100HP I wouldn't think about problems.
but there are a1ot aftermarket pistons with 83,5mm or 83mm with 20mm pin diameter.

You are correct, that's how Mark H. found the ones for my motor. Hint, you can check out pistons for late '80's early '90's Japanese.

Julio

Give it away why don't you :wink:

henry roberts wrote: possibly nissan CA18DET ?

getting close?

Wrong Manufacture

Another HINT look for piston for stock motors.
Hastings still makes rings for these pistons.
Running with a Porsche rod is not a problem

Tue Mar 24, 2009 1:46 am

I'm still stuck

Mahle has a good search on their website but I can't find anything jap.

The Peaugot 205gti pistons are close and are the way I may go

But someone PM me the answer, please!

Seb

Tue Mar 24, 2009 10:08 pm

beetleseb wrote: I'm still stuck

Mahle has a good search on their website but I can't find anything jap.

The Peugeot 205gti pistons are close and are the way I may go

But someone PM me the answer, please!

Seb

What Cam?
You are still running 64 stroke? You say you want to run this in a 25hp case
I would not use the 25hp case because you are going to have to change the studs if you run 36 heads, and good one are not a euro a dozen The cylinder head tin for the heads have to be changed. Run what ever you want , just my suggestion.

It is not like you are doing a 1600 to a 1641 swap here. Each step is different. first you start with the 25hp non accelerator pump carb and swap that out and hone the venturi and you think you 25hp is a new car. then you swap the dist, and that car is even more alive. Then the next step what ever you do is a big step. The pistons that Julio has in his car might pop out of the top of your motor. And none of this stuff is at the corner speed shop. Actually the piston that he is using actually will not work in you car because he is using a different crank.

Here is another hint that will help you in your piston search

"TOTO, I don't think we are in Kansas any more"

Suck, Squeeze, Bang, Blow is some times the same as Intake, Compression, Power, and Exhaust , but some times it is not!

Wed Mar 25, 2009 3:10 am

I've sussed the piston, just gotta buy some now. Looks like mk1/2 Mazda MX5 1800 8valve will do the job. (Now that really does give it away) :D

My cars a 50 so making it look like a 25hp is a non brainer to me. I'd have thought you where more worried about me full flowing and boring out the cylinder holes on my 25hp aluminium case. 36hp heads can be modded to use early tin etc.

The engine I have is made from parts and swaps. I started off with a free 36hp and by some generous swaps and blags I've got several 36 heads and cases, a 25hp longblock, 383 dizzy, split bug genny and reg etc and the project so far owes me nothing. The only stock bits I need are tinware. I'd not be doing this to a mint stock 25hper. The case I'm using is okay but the cam gear had started to rot away :shock:

I'm planning on running a mr okrassa cam, I have both 36 and 25hp heads. Yes its a 64mm crank, simply becouse I can. I do have a 356 crank on its way but I'll save that for the next one.

All hints and tips welcome

Seb

Mon Sep 15, 2014 2:58 am

so what happened with this? did it get built?

Wed Feb 01, 2017 4:14 am

I am wondering if there is a difference in the VW 1500 83mm piston & cilinders and in the 1385cc 40hp 83mm big bore kit for a 1200? Are the cilinders the same? Which will fit better?

I am able to buy a 1385 big bore kit for a 40hp motor but would like to fit that to my 36hp motor, icm with a 74 DPR crank,
What machining must be done and which challenges might be faced?

Currently running a 1192cc with WW Okrasa kit, with later 1200 domed pistons and some other mild modifications (WW okrasa camshaft, lightened flighwheel, lightened & balanced rods, carbs by Joe)