21 replies to this topic

[Dusky]

You will have to measure the CC's of the combustion chamber. The 295 Is best as standard casting, bit a 202 can be made as good by a good port and polisher.

[maxmaniac]

Thanks for yout reply!

 

I'll have to take it out and do some measuring... At least just to know if the compression ratio is somewhat near acceptable values.

In any case, I'm waiting for a couple of Vizard's books to arrive, and hopefully it will shed some light on this topic!

[timmy850]

The 202 head is a good upgrade on the original 998 head (stock for stock, without any flow work). They would have come on 1098 and 997 engines originally. The inlet valve is slightly bigger.

 

Graham Russel in Aus has been doing more work recently on small bore engines, here is one of his articles about cylinder heads. He actually prefers the 998 and 202 heads, as they can be shaped to give more flow than the 295, which doesn't have much meat left in it to direct the flow...

http://russellengine...cylinder-heads/

 

And his 3 part series: 

http://russellengine...re-engine-pt-1/

http://russellengine...small-bore-pt2/

http://russellengine...small-bore-pt3/

Edited by timmy850, 03 October 2014 - 12:57 AM.

[maxmaniac]

Thanks a lot timmy850!

 

I also found the first article, but not the other three. This is gold!!

 

This head is quite interesting and its demand doesn't seem to be that high.

After a brief search on some buy/sell portuguese sites, I found one 202 selling for 95 Euros (something like $135 AUD or £74 GBP).
Perhaps this is plain ignorance, but it's not that expensive at all...

 

While I'm at this, I thought I would ask you something else: it seems to be fairly cheap to buy old HS2's here in Portugal.
For a twin setup, any pair of HS2's would do it (one left handed and one right handed) or they have to have other specifications to be matched?

I would guess the needles should be identical and the pistons must be matched with the suction chamber on both carbs, but otherwise do they really need to be 100% identical?

 

Other thing that bothers me a bit is the vacuum advance (I guess that's how it's called the tiny tube that connects the distributor to the carb).
On a twin setup, both carbs will have that vacuum connection and we just need to connect one to the distributor or one carb will have that connection and the other won't and, in this case, we use the only connection available.

[timmy850]

You can make a twin setup from two same side carbs, which is what the performance kits in Australia in the early days had. You need to have a modified throttle linkage to join them up, and most only had a single choke. They would need to be exactly the same spec to give good performance (the SU Carburettor High Performance Manual is a good resource)

 

Like these:

http://www.ebay.com....e-/111476817088

 

The Cooper S didn't have vacuum advance, only mechanical, so the proper Cooper S carbs didn't have a vacuum port on them.

 

It's cheap enough to pick up a set of HS2 carbs. The main problem is cheap carbs are worn out and will need rebuilding to get them to stay in tune. If the spindles are worn they will always be causing you issues. You also need to make sure you get the correct 30 degree fuel bowl and matching manifold (as Austin Sprite/MG Midgets had 20 degree ones).

 

Unless you are 100% decided on twin SU carbs, it's probably best to go with a single HS4 or HS6. In part 3 of that article, you'll see the HS6 was an extra ~8hp over the twin HS2 carbs!

 

Along those lines, picking up a rusty old head is cheap, what isn't cheap is cleaning it up, valve inserts, bigger valves, porting etc. 

[maxmaniac]

Oh, that's an interesting twin setup with both same side carbs

 

Well, the interesting part of purchasing cheap old parts is that I can learn a bit by dismantling them and re-assemble them afterwards.

I'm a bit of a DIY kind of guy who once built an electric guitar just because I had a couple pieces of mahogany left...

 

Actually, one of my ideas was to purchase a 998 standard head and see what I could do with it.

(having friends owning metalworking and auto mechanic shops makes it easier for me to access the right tools/help in case I need them)

 

But you are totally right regarding old parts: one never knows its true condition until it's a bit too late and the expenses can be really high.

In any case, thank you very much for your answers.
You're being trully helpful!!

[maxmaniac]

Ups...
Double Post...

Edited by maxmaniac, 03 October 2014 - 03:06 AM.