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Compression ratio blue head v's red head

Started by _Muzzy_ , Dec 24 2013 04:38 PM

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38 replies to this topic

#1 _Muzzy_

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Posted 24 December 2013 - 04:38 PM

Hi changing over from red to blue head
Funny thing
The manual quotes 9.4:1 on red engine and 9.0:1 on the blue head
Is this a mis print or do a need to go thru the whole cc process and deck the blue head
As its pointless lowering the compression ratio to defeats any gains
Thanks

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#2 _Bomber Watson_

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Posted 24 December 2013 - 04:49 PM

Ultimately because these heads arnt new anymore and they have likely been reco'd at some stage it always pays to CC the chambers to see where you are.

So yes, i would spend 5 minutes ccing the new head personally.

If your not happy, flick it to a machine shop to get a bit nicked off, you can work out how much roughly by figuring out what capacity chamber you need, pumping that much fluid into the chamber, then measuring down to the top of the fluid from the head face.

Cheers.

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#3 _Muzzy_

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Posted 24 December 2013 - 05:16 PM

Thanks I have a cc kit, the red head has never been off, as I knew the owner, and the blue head has been faced, so the easiest option is to do a cc jobbie
I played around when I built my RS 2000 to get static to 10.5:1
Cheers
Muz

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#4 yel327

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Posted 24 December 2013 - 05:23 PM

I can't remember exactly but I think the piston dish (dish or dome in the case of the 253) is how the various HQ-WB engines showed varying compression ratios (apart from the low comp 173 that is). As above though a cc check will give it up.

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#5 _Bomber Watson_

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Posted 24 December 2013 - 05:27 PM

Yeah TMK the piston dish is the same red-blue 202, but may be wrong.

Ultimately things like deck height come into play, if the engine has ever been reco'd the deck may have been faced a few thou which will bump it up a point or so...

Heaps of people ask "if i put this on this what will i have" but there is no way of telling besides getting out the syringe.

To long ago, to many things have been changed. Something that SHOULD be 9.5 may well end up being 10.5 due to previous work done. If an engine/head has been reco'd several times etc etc....

Cant buy something off some lad down at the pub and know its full history.

Generally they get disgruntled and upset when there not presented with an exact number, this is a nice change.

Cheers.

Edited by Bomber Watson, 24 December 2013 - 05:29 PM.

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#6 _Muzzy_

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Posted 25 December 2013 - 04:35 PM

Both heads came in at 46cc
So I have no idea why holden quote 9.0:1 and 9.4:1
Could only suggest the deck height is different in the 2 engines
It would make sense to have lower CR in the blue, as this would help reduce NOX emissions

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#7 _Bomber Watson_

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Posted 25 December 2013 - 04:59 PM

I do find this curious, i assume your playing with high comp heads.

Run of the mill 202's never got a high comp head, red/blue/black, perhaps the cr figures you have are for a 202/3.3 and the 173/2.8 were the same?

Now im tempted to find the two least bastardized looking low comp heads i can, one red one blue, and have a play....

Cheers.

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#8 _Muzzy_

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Posted 25 December 2013 - 05:49 PM

I do find this curious, i assume your playing with high comp heads.

Run of the mill 202's never got a high comp head, red/blue/black, perhaps the cr figures you have are for a 202/3.3 and the 173/2.8 were the same?

Now im tempted to find the two least bastardized looking low comp heads i can, one red one blue, and have a play....

Cheers.

My Manual quotes same CR for 202/173, I had trouble getting a small chamber blue head(2850) as most blue engines were 3.3,
I know from reading if you put a small chamber head ( 2850/173) onto a 202 it puts up to about 10.5:1
Isn't the L on the head relating to large chamber as 202 have the large chamber and 9.4:1 CR

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#9 _Bomber Watson_

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Posted 25 December 2013 - 05:57 PM

Yeah the L is low comp, so large chamber.

46cc from a low comp head? Must have had more than a "skim"

Cheers.

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#10 _Muzzy_

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Posted 25 December 2013 - 06:07 PM

Both heads are 46cc and have H stamped on them

My comment was does L stand for large chamber, as a 202 has a large chamber, so what head is fitted to a high comp 202 can't be small chamber one for a 173, perhaps there are 3 head combo

1. 202 large chamber

2. 173. Small chamber, but due to bore and stroke differences the CR is the still high

3. 173 fitted with a large chamber 202 head which would provide a low comp engine

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#11 _Bomber Watson_

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Posted 25 December 2013 - 06:13 PM

Honestly not sure there. I think the high/low comp 202's had different piston dish, but alas it was done years before i was born and i dont have enough totally stock engines to compare properly.

L imo means Low. You could say Large.

Cheers.

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#12 yel327

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Posted 25 December 2013 - 07:29 PM

L and H are for 149, 161 and 173 to give low and high.
I always thought red and blue engines used the same chambers for the same engines, just different pistons. 4.2 and 5.0L did the same to achieve differnt CR's along the way.

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#13 _Bomber Watson_

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Posted 25 December 2013 - 08:01 PM

Yeha i know i said otherwise earlyer, but the more i think about it your probably right.

If only i had a pile of totally stock ones as opposed to a pile of ones in various states of overbore to compare....

Cheers.

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#14 _Muzzy_

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Posted 26 December 2013 - 04:05 PM

Did some measurement today here are the valve sizes
Red head In 37 mm. Ex 33 mm
Blue head. In. 42 mm. Ex 37 mm

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#15 _Muzzy_

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Posted 26 December 2013 - 04:15 PM

Blue head all done cleaned all the casting dags from the ports, and removed the blank air injection casting that protrudes about 1/4 way into exhaust port

Attached Files

image.jpg 70.48K 5 downloads
image.jpg 122.67K 4 downloads

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#16 _Bomber Watson_

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Posted 26 December 2013 - 04:21 PM

Nice stuff, and your flogging me with putting info up lol.

Suppose i shoudl be saving this, checking it for my own contentness and reposting it as my own work....

Cheers.

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#17 _Muzzy_

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Posted 26 December 2013 - 05:04 PM

It just happens that I'm building a 173 and fitting a blue head, i don't care if you use the info, I have been a heavy vehicle mechanic for 35 year and teaching in TAFE for 20 plus years, so I enjoy sharing information and learning, must admit I know stuff all about holden 6 's

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#18 _Bomber Watson_

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Posted 26 December 2013 - 05:11 PM

Cool stuff mate.

Bet the kids at tafe love your projects.

Cheers.

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#19 _Muzzy_

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Posted 26 December 2013 - 05:18 PM

It's a funny thing, kids nowadays aren't interested in cam, heads and comp ratio etc, however in saying that I'm not connected to Light auto, the heavy auto kids all they want to know is how do I get into the mines.
It is handy I have 4wd dyno dynamics dyno at work, so the Torrie has had a before run ( 66RWHP), I used it quiet a bit setting up the RS 2000

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#20 _Bomber Watson_

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Posted 26 December 2013 - 05:31 PM

Thats surprising a few of the younge lads at work doing diesel are into mods, mind there mostly keen on what size turbo to fit to there GU patrol.

They always sit around the smoko table and listen to myself and a select few other lads talk about this that the other regarding cars and always throw an ear up, so im sure if those guys were in your class they would follow intently.

Cheers.

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#21 _Muzzy_

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Posted 26 December 2013 - 05:33 PM

Yer they do talk turbos.

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#22 _Bomber Watson_

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Posted 26 December 2013 - 06:02 PM

Then learn turbo's . Edumacate them upon such, then lead them to the light side.....

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#23 _Muzzy_

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Posted 26 December 2013 - 06:05 PM

I good with turbos. I will think of you next time I teach that subject
HV industry is into electronic controlled VGT 's big time

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#24 _oldjohnno_

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Posted 26 December 2013 - 06:24 PM

I have been a heavy vehicle mechanic for 35 year and teaching in TAFE for 20 plus years, so I enjoy sharing information and learning,

Good information is always welcome.

In my experience there are proportionally many more competent HV mechanics than LV mechanics. The LV mob seem to have more than their fair share of goofballs...