Javascript Disabled Detected

You currently have javascript disabled. Several functions may not work. Please re-enable javascript to access full functionality.

Compression ratio blue head v's red head

Started by _Muzzy_ , Dec 24 2013 04:38 PM

Prev

Please log in to reply

38 replies to this topic

#26 yel327

Oh My, Don't you post alot

Members
13,861 posts

Joined: 10-February 08

Posted 26 December 2013 - 07:36 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

I don't think you want a large chamber blue/black head on a 173. This is how you make a low comp 173!

Unless of course you are boring it +0.065 or +0.125" to make a 179 or 186.

Edited by yel327, 26 December 2013 - 07:37 PM.

Back to top

#27 _Muzzy_

Guests

Posted 26 December 2013 - 08:10 PM

I'm fitting a small chamber blue head onto a 173 after comparing chambers the comp ratio will be same as the red motor 9.4:1

Back to top

#28 _Bomber Watson_

Guests

Posted 26 December 2013 - 08:12 PM

Cant all be blamed on the guys doing the courses men.

A lot comes back on the instructors and the course there doing

I have met plenty of LV mechanics who are keen to learn but there course doesnt teach them what they need to know.

FFS i had to help a 4th year apprentice LV mechanic put a holden six together, he didnt know how to dial the cam in, he didnt know how to check the deck height, he didnt know how to check the bearing clearances, he didnt know how to tension the frOcking head ffs.

He was keen as to learn, but all tafe taught him was how to plug the obd2 plug in and how to read the computer. Occasionally change spark plugs.

Cheers.

Back to top

#29 _dkvmatt_

Guests

Posted 26 December 2013 - 08:22 PM

Im a LV mechanic and your right, TAFE dosent teach the basics of assembling a motor, Mainly because I think that's a more specialist job nowadays, most mechanics including myself sub out bottom end rebuilds.

Back to top

#30 _Bomber Watson_

Guests

Posted 26 December 2013 - 08:30 PM

Yep,

Picture this, yoru in a dealership.

"oh, the bottom end needs a rebuild"

Suddenly one appears in a crate.

You uncrack it, fit whatever is needed to it, and away the customer goes.

Apparently this is quicker, cheaper, and more environmentally friendly (this last one i question????) than teaching an apprentice a good old ring and bearing job.

Cant say much, but i have been querying the local Ford for 12 months now about any XR6 bottom ends tehre going to send to teh scrap...Still havnt seen shit. frOcks me what they do with them after the crate is cracked and it is replaced.

Cheers.

Edited by Bomber Watson, 26 December 2013 - 08:31 PM.

Back to top

#31 _Muzzy_

Guests

Posted 26 December 2013 - 08:36 PM

We still teach full engine overhaul in HV course, the LV industry has moved away from this.
The HV industry is still based on overhaul and repair the LV course has moved into service , this is lead by industry and while there are exceptions to this , most auto mechanics will never overhaul an engine in a std dealership it's R/R and fit replacement.
TAFE cops a lot of flak over this, however if I teach something to an apprentice like LV engine overhaul, how can the work place provide 3rd party work reports to ensure the apprentice is competent in the task.

Back to top

#32 _Bomber Watson_

Guests

Posted 26 December 2013 - 08:54 PM

Yeah na good as call..

I fully understand its due to the way the industry is moving.

FFS, im a spray painter and if it wasnt for the cars/bikes i'd sprayed in acrylic laquer pre trade i wouldnt have a frOcking clue what it was, not a mention in the entire four years. Not even mentioned how to go over it.

Still think its a bit rough you lads putting flack on the LV apprentices when its not really there fault though.

To elaborate, i would assume most lads taking up a LV course would think they would learn the full extent of light vehicle mechanics, ie building engines gearboxes diffs etc, not just how to change them out.

Atleast the ones i have known have expected that upon signing up.

Cheers.

Edited by Bomber Watson, 26 December 2013 - 08:56 PM.

Back to top

#33 _Muzzy_

Guests

Posted 26 December 2013 - 09:00 PM

I think you may misunderstand my comment
HV industry pays more and expects more, that doesn't mean LV students aren't up to speed, they can't help that spend their life servicing vehicles, I have a lot of guys who change over from LV to HV, it's a money thing

Back to top

#34 _Bomber Watson_

Guests

Posted 26 December 2013 - 09:12 PM

And i've done in the workplace about 90% of a HV mechanics work, its not hard, and its no different to what a LV mechanic SHOULD know, just the shit is bigger.

Whats the difference between a Dana 44 and a Banjo? frOck all, just the Dana 44 has heavyer parts.

Whats the difference between a 6BT cummins and a 202 short motor? frOck all, just one has heavyer shit that the other.

Never, at any point, have i intended to have a go at you or what you do, i just took this thread way off topic with a bitch about what should be against what is.

I find this mildly disgusting, IRL, as i was doing what is apparently HV work when i was 14, and competent at what is apparently LV work at the age of 6.

Cheers.

Edited by Bomber Watson, 26 December 2013 - 09:18 PM.

Back to top

#35 S pack

Scrivet Counter

Members
15,772 posts

Name:Dave
Location:Luggage Point
Car:73 LJ
Joined: 25-January 10

Posted 26 December 2013 - 09:17 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.

Yes Byron, Red low and high comp 202/3.3 engines used the same 173 low comp head. The different compression ratios were achieved by varying the piston dish. Not completely sure what they did with the blue engines though.

Interestingly, I hadn't really noticed this before (and I damn well should have), the LJ parts book lists high and low comp pistons as well as high and low comp heads for the red 173.

Edited by S pack, 26 December 2013 - 09:19 PM.

Back to top

#36 _Bomber Watson_

Guests

Posted 26 December 2013 - 09:22 PM

Da farq? ^

I see your future, it involves photocopying....

Cheers.

Back to top

#37 yel327

Oh My, Don't you post alot

Members
13,861 posts

Joined: 10-February 08

Posted 27 December 2013 - 02:11 AM

Yes Byron, Red low and high comp 202/3.3 engines used the same 173 low comp head. The different compression ratios were achieved by varying the piston dish. Not completely sure what they did with the blue engines though.

Interestingly, I hadn't really noticed this before (and I damn well should have), the LJ parts book lists high and low comp pistons as well as high and low comp heads for the red 173.

I noticed this a while back. When you think about it the compression ratio wouldn't be right on the low comp 173 with the 202 head on it if the same pistons from the 173HC were used. This works in 161 but with the extra cc in the 173 bumps the CR up slightly too much for RON 87 (standard) fuel. I think you can see it in the high comp transitions from 161 to 173 and 186 to 202 where the CR goes from 9.2 to 9.4 for RON 97 (super) fuel. Whereas the low comp 161 was 8.2 but the 173 is 8.3, it must have been too high for RON 87 fuel with the high comp piston given the cam they used.

Late addition, I just found the specs in the HX features manual. Lists the cc of the dish in the pistons tops:

173HC - 1.92cc.

173LC - 3.71cc.

202HC - 2.36cc

202LC - 19.89cc.

So it looks like the 173LC if built like the 161 using the high comp pistons and 202 head must have been slightly too high in CR for GMH (probably 8.4:1), so they had to use a special piston with an extra 1.8cc in it to get down to 8.3:1.

You also see the change in the 173HC and 202HC pistons to have the small 1.92cc and 2.36cc dishes added to keep the CR to 9.4:1, whereas the 161 and 186 had a flat top piston. So if they'd kept the flat top style piston for the 173 and 202 they probably would have ended up around 9.5-9.6:1 which must have been too high for RON 97 fuel given the cams used. Obviously it must have been cheaper to dish pistons rather than stuff with cylinder head chambers.

Edited by yel327, 27 December 2013 - 02:14 AM.

Back to top

#38 yel327

Oh My, Don't you post alot

Members
13,861 posts

Joined: 10-February 08

Posted 27 December 2013 - 02:17 AM

I'm fitting a small chamber blue head onto a 173 after comparing chambers the comp ratio will be same as the red motor 9.4:1

That is correct if it is a red 173 bottom end you are using with proper red 173 pistons. If it is a blue 173 or the engine has blue 173 pistons it'll be 9:0:1 as I think pistons had a bigger dish in the blue engine.

Back to top

#39 N/A-PWR

CABIN ENGINE CONTROLS GALORE

Members
9,654 posts

Name:Dave I
Location:Wooroloo, 65km's East of Perth
Car:'1969' LC RAT TORANA
Joined: 08-December 12

Posted 20 September 2014 - 04:21 PM

Hi Yel,

I just cleaned up a bit and measured this 208 piston, which has a dish of about 23cc:-

IMG_6016.JPG 79.01K 0 downloads

so would that be because the piston is 60 thou oversize?

Late addition, I just found the specs in the HX features manual. Lists the cc of the dish in the pistons tops:

173HC - 1.92cc.

173LC - 3.71cc.

202HC - 2.36cc

202LC - 19.89cc.

Had a short motor made new, and that piston is what they put in,

and boy the power was gone when I got the LC 'S' 2door Torana up and running,

so they had to come out. :furious: