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LC GTR 2850s camshaft

2850s CF GTR LC

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#26 sibhs

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Posted 23 February 2021 - 05:13 PM

This is why people don't like to use this forum these days. These cars are too valuable to build from peoples memories of what the cars were. If members won't share their hard copy proof / documents they have what's the point?

Hi Darryn, I don't agree with your third sentence.  I think this forum is where you come for the best info on these cars.

 

Regarding the first sentence, I think people have left the forum or not joined because of the difficulty in uploading pictures/videos compared to FaceBook and the speed at which answers are given on Facebook and those are the only two good reasons FaceBook has.

 

I love this forum and it's fantastic members including you.

 

Smiley Face Marty



#27 Ice

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Posted 23 February 2021 - 06:18 PM

Yeah Marty is correct the best info comes from here and and you know it 

I suppose you take all the info from here and plaster it on you’re Facebook page 

Thats working ok for you ? 



#28 gtr_161

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Posted 23 February 2021 - 06:42 PM

Yeah Marty is correct the best info comes from here and and you know it 
I suppose you take all the info from here and plaster it on you’re Facebook page 
Thats working ok for you ? 


The info from here isn't put on my page,
There are a few of us that have original cars that exchange info and it works well. That is why I asked my initial question.
The info that has been given in this post except for one person hasn't been from owners of original cars as I asked and only from the usual people that post here. 3 owners have messaged directly that owned original cars and have helped with correct info.

#29 claysummers

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Posted 23 February 2021 - 07:13 PM

Hell yes the forum. frOck facebook wtf that?

early Holden nut

#30 S pack

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Posted 23 February 2021 - 08:23 PM

3 owners have messaged directly that owned original cars and have helped with correct info.


So does your above statement imply the manufacturers engineering specifications are incorrect and the observations from a couple of so called 'original untouched' (use that term very loosely) 50 year old cars is more reliable?



#31 Bazza

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Posted 23 February 2021 - 09:16 PM

Hi

 

I don't have the answer to this question, but I do have a question. Wouldn't the installation of a XH camshaft in the 173 GTR (presumably with the same cam specs as the LC XU-1) require the fitment of a double diaphram booster to overcome the same vacuum issues as the XU-1?

 

Bazza



#32 Rockoz

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Posted 24 February 2021 - 07:15 AM

Are we going to end up with another situation where the poster doesnt agree with what should be considered the correct info?

Will the good info be ignored and some sort information they hope might be correct be considered as gospel?

Have seen it here before when the facts have been ignored and a belief considered to be more accurate.

Seems to happen in the little Toranas often.

Finding an unmolested engine in this day and age would be difficult I would assume.

There would have been more engines run through the likes of Gem or whoever the mob was back in the day that supplied off the shelf exchange engines than would have been reconditioned by the owner.

By the mid 80s none of the local GTRs I knew had the original engine fitted.

The blokes usually blew the engines at night, and got an exchange engine the next day to have it running by that night.

 

Cheers 

 

Rob



#33 S pack

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Posted 24 February 2021 - 07:27 AM

Hi

 

I don't have the answer to this question, but I do have a question. Wouldn't the installation of a XH camshaft in the 173 GTR (presumably with the same cam specs as the LC XU-1) require the fitment of a double diaphram booster to overcome the same vacuum issues as the XU-1?

 

Bazza

Better upgrade the compression ratio, valves and valve springs, distributor and carburetor to XU1 specs as well to get the full benefit of the XU1 camshaft.
 



#34 Bazza

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Posted 24 February 2021 - 11:45 AM

Speaking of which, the CR did go from 9.2 to 9.4 (additional 12 cid into the same chamber space). Coupled with the subject XH csmshaft improvement and the 7.5% increase in engine capacity one would expect significantly more the 5 bhp claimed in the literature.

#35 S pack

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Posted 24 February 2021 - 11:55 AM

Speaking of which, the CR did go from 9.2 to 9.4 (additional 12 cid into the same chamber space). Coupled with the subject XH csmshaft improvement and the 7.5% increase in engine capacity one would expect significantly more the 5 bhp claimed in the literature.

Unfortunately the longer duration of the valve timing the XH camshaft would have provided probably would have drained off more dynamic compression than the .2 increase the extra 12ci provided.
 



#36 yel327

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Posted 24 February 2021 - 12:28 PM

HD-HR X2, HR-HG 186S and all manual and Powerglide HT-HG 186HC/LC used the same camshaft as the 161S. For a standard road car I can’t see why a 173S would need a larger camshaft if 186S didn’t. As far as I know the defunct HQ GTS’s engine (202S) had the same cam as well. As I stated before, if it’s not an error in the later LC parts catalogue then there will be a reason for it, and other paperwork will exist.

The rated hp of the standard HT-HG 186 is only 5hp more than the HK 186. The HK has the 161 cam and the HT has the S cam. But those are all advertised hp, and they are all fluff anyway. They were always significantly inflated above GM20 SAE Gross test figures until HJ. If you compare LH engine figures against LX release figures you can see the drops for the same engines (except 5.0L).

#37 gtrfreak

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Posted 24 February 2021 - 02:21 PM

Thanks for your help Crabba,
Yel327 and S pac I guess you both have not owned or stripped down an original c.f. engine?
I'm interested in info from owners or members that have owned them. Cheers.


This is why people don't like to use this forum these days. These cars are too valuable to build from peoples memories of what the cars were. If members won't share their hard copy proof / documents they have what's the point?
My original question was directed at members that have owned these cars so I can fit the correct camshaft back into my gtr and others do the same. We have identified an early car with a 161s cam and 2 later cars with the XH so far.



Make up ya mind. So you want memories or documentation? Doubt you will ever get both to agree.

Which page is yours on Facebook?

#38 gtr_161

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Posted 24 February 2021 - 06:07 PM

There are differences in the distributor, carburetor and exhaust systems in the 2850s cars as well as compression ratio. The 3 people I have been in contact with had documented what they had found when the engines were stripped. What has been discovered so far is that the early cars had 2600s camshaft and later had XH.
These cars were not 50 years old when this was all discovered.
Believe what you like but I have the info I need now.
Cheers

#39 yel327

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Posted 24 February 2021 - 06:17 PM

Keep hunting, there will be internal paperwork for that big of a specification change if GMH fitted the cams in the engine plant.

#40 S pack

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Posted 24 February 2021 - 07:12 PM

Keep hunting, there will be internal paperwork for that big of a specification change if GMH fitted the cams in the engine plant.

Didn't happen.

 

Yes the 2850S has a different distributor to the 2600S. Thing is all 2850 engines (CD, CE & CF) use the same distributor. Just as the 2600H, 2600L and 2600S all used the exact same distributor.

 

On another note I had an interesting day. A friend in Melbourne hooked me up with Clive at Clive Cams.

Had a good chin wag with Clive, he is a really nice bloke and he certainly does know his stuff.

Asked him about GMH fitting XH Camshafts in 173S GTR engines and he said it didn't happen. If any XH camshafts have been found in 2850S engines then they were installed after they left GMH.

Clive agrees that the 2600S camshaft carried through to the 2850S engine, as the LC Engineering Technical Specifications clearly show.
 


Edited by S pack, 24 February 2021 - 07:13 PM.


#41 gtr_161

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Posted 24 February 2021 - 07:20 PM

My engine builder and I spoke to Clive late last year and he said that he had profiled and supplied the XH for the late gtr but who knows...

#42 S pack

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Posted 24 February 2021 - 07:39 PM

My engine builder and I spoke to Clive late last year and he said that he had profiled and supplied the XH for the late gtr but who knows...

Who Knows? GMH knows because they designed, engineered and manufactured them.

The specifications that GMH published are definitive and apply until further documentation with revised specifications, if any exist, are discovered.



#43 gtr_161

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Posted 24 February 2021 - 07:55 PM

Thanks to all for your input.
Cheers.

#44 Ice

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Posted 24 February 2021 - 08:27 PM

Whack a decent bump stick in there and wake that little red screamer up  :P



#45 gtrfreak

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Posted 24 February 2021 - 10:29 PM

What a waste of time this thread was.

#46 S pack

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Posted 24 February 2021 - 10:42 PM

What a waste of time this thread was.

I don't know about that.

It made me want to contact Clive at Clive Cams to find out for myself his knowledge on the subject.

 


 



#47 sibhs

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Posted 25 February 2021 - 09:22 PM

I think this thread has been worthwhile. We have all learnt a bit more.

I make my decisions on getting as much info from as many sources as possible and making my own conclusion.

I respect the knowledge and helpfulness of SPACK and yel327 who are very informed and well read on these cars and from my experience are rarely wrong. 

You must also realise mistakes were made on the production line, this doesn't mean you restore your car to how someone else's car came off the line. Build it how they were meant to be.

 

Marty






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