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Thoughts on this 202 combo

Started by SA EH , Oct 16 2013 11:14 PM

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#301 _Bomber Watson_

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Posted 12 June 2014 - 10:43 PM

I very carefully drilled the step out of mine with no apparent ill effects, well head gasket never let go, combustion chamber did first haha. . 

 

Cheers. 


#302 SA EH

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Posted 12 June 2014 - 10:51 PM

Got to cover all the bases this time round, otherwise I'll turn gay, buy a f@rd & paint it pink.

#303 warrenm

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Posted 13 June 2014 - 12:35 AM

To shift the head over, normally fill then relocate the dowel holes as well as moving the head bolt holes & push rod holes by the same amount.


#304 _oldjohnno_

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Posted 13 June 2014 - 07:14 AM

I'm not convinced it's worth the effort. The shrouding is mainly around the side of the valve, and flow tests I've done have shown little if any improvement from sliding the head over. I know everyone does it but that doesn't necessarily make it right. It might make a small difference if the intake valve was too big I guess.


#305 Dave6179

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Posted 13 June 2014 - 07:26 AM

If you've milled the head and decked the block, I've heard that sometimes the head original dowels effectively become too long and hold the head up.

Have you shortened the two front head bolts? Mine were too long in the blind hole, the others go into the water jacket.


#306 looznugtr

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Posted 13 June 2014 - 08:20 AM

Which way and how far do you move the head over?

#307 SA EH

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Posted 13 June 2014 - 08:27 AM

It really shouldn't be a problem Dave, only because I'm running head studs, but something else to think about I guess.
Keen on hearing from others with tips on shifting the head over...
I know moroso do offset dowells, and I've heard about offset helicoils, and warrens suggestion, any other options??
Moving the head to centre the valves more, so that's to the inlet exhaust side, I think, by 2mm.

Edited by SA EH, 13 June 2014 - 08:29 AM.

#308 looznugtr

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Posted 13 June 2014 - 08:42 AM

Is it worth all that work for what gians.
I'm busing apt or at the moment so really like to consider it.

#309 _oldjohnno_

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Posted 13 June 2014 - 10:21 AM


Moving the head to centre the valves more, so that's to the inlet exhaust side, I think, by 2mm.

 

Before you do it, stick it on a flow bench with the same size bore adaptor as your engine's bore. Measure the flow, slide it over 2mm and check it again. I think you'll be surprised at the result.


#310 warrenm

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Posted 13 June 2014 - 11:39 AM

It really shouldn't be a problem Dave, only because I'm running head studs, but something else to think about I guess.
Keen on hearing from others with tips on shifting the head over...
I know moroso do offset dowells, and I've heard about offset helicoils, and warrens suggestion, any other options??
Moving the head to centre the valves more, so that's to the inlet exhaust side, I think, by 2mm.

If you do use an offset dowel, I think you"ll still have to machine the head bolt holes accross by the same amount as the offset dowel.


#311 warrenm

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Posted 13 June 2014 - 11:57 AM

Before you do it, stick it on a flow bench with the same size bore adaptor as your engine's bore. Measure the flow, slide it over 2mm and check it again. I think you'll be surprised at the result.

I don't know for sure, but did hear that the port can be ported differently when the head is moved. If you need clearance for valves it would be easier to fly cut the block. 


#312 _oldjohnno_

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Posted 13 June 2014 - 12:28 PM

I don't know for sure, but did hear that the port can be ported differently when the head is moved. If you need clearance for valves it would be easier to fly cut the block. 

 

Even with different porting I just can't see that there would be big gains to be had. If it was practical - and it isn't with a factory casting - I'd much rather shift the intake valve towards the exhaust.


#313 greens nice

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Posted 13 June 2014 - 12:32 PM

It does work well at getting more valve lift.
Chances are if the head has been machined to the thumbprints with a 1.7 intake valve, the valve will hit the bore where the top compression ring comes to with around .560 lift with .040 clearance
Offset boring the block helps too

ARP makes head studs for sb2's that are 7/16 on the block end and then stepped to 3/8 ($300!!!) that will get the head .030 further over.

If your not looking to fit more lift in, don't bother.

#314 orangeLJ

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Posted 13 June 2014 - 01:31 PM

Would you gain more from angle milling the head rather than offsetting it?

#315 N/A-PWR

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Posted 13 June 2014 - 02:51 PM

Angle Milling


#316 SA EH

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Posted 13 June 2014 - 11:37 PM

Thanks for the responses guys.
I've had a change in direction for this engine build, and it's more trying to achieve better volumetric efficiency. It's really come about after having a chat with the great man, Ian Moodie.
The theory behind it being, if V8 supercars(for example) can make over 2hp per cubic inch, running 10:1 compression, why does a 202 need 12:1 to make good power?? Answer, it doesn't.
To put it simply, get it breathing properly, big cam, big valves & big ports. The more air into the cylinder, the more power made, while not relying on compression.
I'm not hugely keen on angle milling, but shifting the head over was said to be heading in the right direction to gain rewards.
I don't want to make this sound like I've found god or anything, but it was a moment of clarity, so I'm gonna run with it...
And OJ, you're spot on. If the inlets were a little closer to the exhausts from factory, we wouldn't be having this discussion....
Reminds me of a certain alloy 9 port I started a thread on.

#317 rodomo

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Posted 14 June 2014 - 12:06 AM

You might need 14:1 compression though?
Ask Dave?

#318 _oldjohnno_

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Posted 14 June 2014 - 08:33 AM


I've had a change in direction for this engine build, and it's more trying to achieve better volumetric efficiency

 

 

I seem to remember covering this, it's always been the primary goal of any Holden six build:

http://oldjohnno.id.au/page2x.html (Horsepower and where to find it)

http://oldjohnno.id.au/page3x.html (An Introduction to Airflow)

 

I'm still sceptical on the head shifting deal though - I don't care if God himself say it's a Good Thing, I'll take the flowbench's opinion anytime.


#319 _STRAIGHTLINEMICK_

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Posted 14 June 2014 - 10:57 AM

Yep, that's it. Hoping if I can move the head over I won't even need them. But this block is now really the "trial" block.

 

Hey Jonesey ,  you will still need the bore reliefs not to just clear valves but to assist flow from the outer edge of the chamber into the cylinder . When u move the head across you will need to bolt yr head down to your empty block and scribe the bore to the  head face and open the chamber on the inlet side to the bore diameter . You will see the issues with the inlet valve open about 1/2" . Lots of us have been down this path and it works . I have seen photos of a dissasembled Ian Tate engine and it had oval cylinder head holes proving the head is moved  and large scollops in the bores .I have done it on my engine and it and I know it works .


#320 _oldjohnno_

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Posted 14 June 2014 - 12:44 PM

The second link in my previous post was meant to point to this page: http://oldjohnno.id.au/page3x.html An Introduction To Airflow.

 

While I'm shamelessly quoting myself, this page is my favourite - http://oldjohnno.id.au/pageADD.html


#321 _STRAIGHTLINEMICK_

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Posted 14 June 2014 - 06:07 PM

Jonesey , if you were to start again a good combo might be a long rod stroker with an alloy 9 port and a cam with about 250@050 on 108 deg and 1.6 or 1.7 rockers .


#322 _2ELCS_

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Posted 14 June 2014 - 09:24 PM

Love # 17 and 20 in the addenda John


#323 SA EH

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Posted 14 June 2014 - 10:04 PM

Thanks for the read OJ, might have to canvas the whole thing over again. Not sure when you updated it last but i dont remember reading much of that a couple of years ago... Cheers  :)

 

And thanks for the info Mick, might have to PM ya to chew over a few things.


#324 _mervx_

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Posted 18 June 2014 - 03:34 PM

I wonder if this type of head would work better? Its a 9 port modded to be a 12 port and has XU1 size valves .

It has dividers fitted to the inlet ports to tidy up flow.I think it would be best suited to Webbers for individual ports.

It was on a succesfull speedway car I believe.Your thoughts Old Johnno?

 

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#325 _oldjohnno_

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Posted 18 June 2014 - 04:58 PM

I haven't done any more than some brief testing with a 9 port and some body filler. The results weren't encouraging so I abandoned the idea. Which is not to say that it can't possibly work, just that it seemed more trouble than it was worth to me at the time.


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