LM V8 advice

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aussieblackjack
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LM V8 advice

Post by aussieblackjack » Wed Aug 19, 2020 8:30 am

Hi guys
I’m looking at what model v8 would be ideal for ip and why. I had a thought of acquiring a ex commodore cup car and converting to ip with good engine and holinger etc. this seemed appealing as a vs had a light shell and decent suspension geometry.

I’m curious though why the vt-vy struggle to handle aswell based on what I’ve read? What is it about the rear end that can’t be fixed?

There seem to be decent value vt’s for sale with 6l etc already in them which would be a cheaper way to start.

Any recommendations on best models? BA-BF are obv good and VN-VS plus later model VE seem best.

If I could find a caged base like ex CC or saloon car then that would be ideal and a cheaper option than starting from scratch.

Thanks guys

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Re: LM V8 advice

Post by moylee19 » Wed Aug 19, 2020 12:44 pm

Most CC or Saloon cars have had mods to the floor which would need to be fixed for IP.

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Re: LM V8 advice

Post by aussieblackjack » Wed Aug 19, 2020 1:01 pm

yeah i heard they cut part of floor out for exhaust, but obv easy to reweld in new panel.

Im really interested in the rear suspension of the commodore and if there are mods to make it work.

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Re: LM V8 advice

Post by TwinTurbo » Wed Aug 19, 2020 1:32 pm

The 1970's trailing arm suspension was dropped from the GM European range for a reason, Holden picked up the tooling cause it was cheap. There is a vicious circle of pain around bump steer, toe change, excessive camber change and having to use way above ideal (for traction) spring and damper rates to limit those undesirables. There is no perfect solution it's just a bunch of compromises. Up to VS with an LRA is a superior solution and the VE/VF IRS is the best solution.

Keep in mind that there is a 1455 kg minimum weight limit for a VS etc with an LS.

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Re: LM V8 advice

Post by aussieblackjack » Wed Aug 19, 2020 2:02 pm

hi gary thanks for the reply. Yes thats what I thought. It will be a decent setup, the vt, but will never be as good as vn-vs or ve/f as you said.

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Re: LM V8 advice

Post by mikrace » Wed Aug 19, 2020 2:57 pm

AU with Boss Motorsport engine is the best LMv8 combo for a front running IP car built as "cheap" as possible. VN with LS possibly second most value for speed build but with possible weight needed to be added...
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Re: LM V8 advice

Post by aussieblackjack » Wed Aug 19, 2020 5:43 pm

ideally commodore would be great VS model
what is the maximum wheel size for LM? 17inch for a VS?

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Re: LM V8 advice

Post by mikrace » Wed Aug 19, 2020 6:46 pm

No limit to any LM car rim diameter... save for what sizes the tyre comes in. I believe 18 in is the largest A050 available? I think 17x9 using the 255 tyre is most common but not entirely sure being a rx7 driver :)
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Re: LM V8 advice

Post by Born Again Racer » Wed Aug 19, 2020 7:47 pm

Au, according to the experts is by far the best bet. Maybe Rick Newman from Newline homes in Vic might be interested in parting with his IP car

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Re: LM V8 advice

Post by TwinTurbo » Wed Aug 19, 2020 9:29 pm

Most LMV8’s run the 255/35/18, the 265/30/18 is a bit wide for the 9” rim.

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LM V8 advice

Post by aussieblackjack » Thu Aug 20, 2020 9:03 am

Ok thanks Gary
If a car was built in 2008 with extensive cage etc
Would that cage meet current cams regs in terms of steel thickness and tube diameter? I guess the main things are side intrusion, gussets and the diagonal bar down from main hoop to floor
Last edited by aussieblackjack on Thu Aug 20, 2020 9:03 am, edited 1 time in total.

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LM V8 advice

Post by davel » Thu Aug 20, 2020 9:07 am

aussieblackjack wrote:Ok thanks Gary
If a car was built in 2008 with extensive cage etc
Would that cage meet current cams regs in terms of steel thickness and tube diameter? I guess the main things are side intrusion, gussets and the diagonal bar down from main hoop to floor]
Was it log booked at the time of the cage being built? If so, the 2008 rules apply. If not, it probably won’t comply with today’s rules and would need modifications or replacement. Main hoop diameter rules changed if memory serves correctly since 2008. Others can verify that.
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Re: LM V8 advice

Post by TwinTurbo » Thu Aug 20, 2020 12:19 pm

aussieblackjack wrote:
Thu Aug 20, 2020 9:03 am
Ok thanks Gary
If a car was built in 2008 with extensive cage etc
Would that cage meet current cams regs in terms of steel thickness and tube diameter? I guess the main things are side intrusion, gussets and the diagonal bar down from main hoop to floor
CAMS compliance should be on the cage and/or in the log book. If not, then best to contact who made/installed the cage and ask them about compliance.

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Re: LM V8 advice

Post by aussieblackjack » Thu Aug 20, 2020 1:32 pm

many thanks for all info guys appreciate it

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Re: LM V8 advice

Post by aussieblackjack » Mon Aug 24, 2020 11:19 am

questions guys

the VS commodore model with IRS, is that the same as the IRS setup in the VT etc? Does it still have the same inherent issues as the VT?

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Re: LM V8 advice

Post by TwinTurbo » Mon Aug 24, 2020 11:38 am

aussieblackjack wrote:
Mon Aug 24, 2020 11:19 am
questions guys
the VS commodore model with IRS, is that the same as the IRS setup in the VT etc? Does it still have the same inherent issues as the VT?
Yes and yes.

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Re: LM V8 advice

Post by aussieblackjack » Mon Aug 24, 2020 11:59 am

thank you
what is your opinion on a LRA vs VE IRS?
I heard the VE has severe roll centre issues when lowering the car, therefore the rear needs to be sitting quite high in order for the car to handle. What are the limitations of LRA compared to VE IRS? Does teh 200kg lower weight of a LRA VN become more attractive than a IRS VE at 1650kg?

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Re: LM V8 advice

Post by TwinTurbo » Mon Aug 24, 2020 4:54 pm

Personally I'd be running a VF they are quite bit lighter (70 kgs apparently) than the equivalent VE. Plus aerodynamically superior, particularly for the rear wing. There are more than sufficient freedoms in the IP regs to easily optimise the roll axis.

As for weight I'd be surprised if, with a lot of effort and a little bit of money (in motorsport terms), a VF couldn't be well under 1600 kgs with driver. I spend a lot of time working to minimise weight, every square cm of the body work and every single mechanical component gets the "do I really need it" and "can I use/find/ buy/fabricate a lighter one".

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Re: LM V8 advice

Post by aussieblackjack » Mon Aug 24, 2020 6:22 pm

Ok. If building a vf wasn’t an option due to budget and time (acquiring car and doing all work from scratch is huge job) what would be another option? My thoughts were buying a car with running gear then upgrading parts like brakes and diff etc. hence why an older car was attractive

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Re: LM V8 advice

Post by TwinTurbo » Tue Aug 25, 2020 7:19 am

My view, and it’s only that, is there are 2 choices in Commodores, the VN to VS (LRA) or the VE and VF (proper IRS). An ex saloon car or Commodore Cup car is not a bad place to start in the VN/VS, but finding a “decent” one is the trick. Then reversing the “illegal” for IP mods and fixing the questionable engineering are the immediate tasks. But ultimately the only really long term useful bits are the body shell and the cage. Pretty much everything else is not IP level. There is a substantial cost in overcoming the LRA limitations, floater, camber, toe, watts link, decent shocks, LSD/locker etc. I’d suggest doing your homework on that as a good place to start.

Cheers
Gary

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