LT95 1.113:1 - Suitable for Low Comp 3.5 V8?

**I Love My Landy!** · 2nd June 2017, 10:10 PM

Good evening all,

I am putting some money into rebuilding much of my (530,000 km old) 1984 110 V8. I am rebuilding a 3.5 V8 from a Discovery 1 but keeping my carbies and using an early pre-pollution camshaft. It is a low compression motor. I have access to a LT95a gearbox with 1.113:1 transfer gearing. Can anybody advise me of how well it would suit the low comp motor? My rough calculations suggest it would rev at 2650 rpm at 100 km/h (3.54:1 diffs, 32 inch tires). This seems fine to me (my current 1.3:1 gearing is a bit low i feel). I am rebuilding the motor on a budget, but i could invest in high comp pistons if it would make a considerable difference.

Many thanks,

Edward

**justinc** · 3rd June 2017, 08:16 AM

Hi mate i would certainly entertain the high compression pistons idea more seriously. The difference between the 8.13:1 and 9.35:1 compression engines is quite large😮. The SU carbs accentuate low end torque, so an SU carb fed 9.35:1 engine feels a lot bigger than it is. I would use an EFI cam too, and EFI exhaust manifolds with a 2.5" exhaust system.
They are a great engine the 3.5 😍

Jc

**I Love My Landy!** · 3rd June 2017, 12:44 PM

Thank you JC for your advice. I would prefer a high comp motor, but i'm building the motor on a budget. It's going to cost $611 for 'original equipment' high comp piston assemblies from LRDirect.com. It actually works out to be $485 extra (considering that i need to buy pistons rings for the low comp pistons). I guess $485 isn't that much. People spend more than that on one normal car service! I’ll think about it a bit more. My Landy also runs on LPG, and I know LPG likes compression. I already have extractors and a 2.5" exhaust that you mention.

Thanks again,

Edward

**Vern** · 3rd June 2017, 12:48 PM

You will probably save that $485 in gas/fuel in the long run going for the high comp pistons 😊

**Tins** · 3rd June 2017, 12:57 PM

Originally Posted by I Love My Landy!

My Landy also runs on LPG, and I know LPG likes compression. I already have extractors and a 2.5" exhaust that you mention.

Thanks again,

Edward

I don't want to hijack this thread, but I'd love to hear more about LPG and SUs. I'd love to dump the Holley on my 3.5 LPG only car. Maybe I should start a different thread.

**djam1** · 3rd June 2017, 01:41 PM

Originally Posted by I Love My Landy!

Thank you JC for your advice. I would prefer a high comp motor, but i'm building the motor on a budget. It's going to cost $611 for 'original equipment' high comp piston assemblies from LRDirect.com. It actually works out to be $485 extra (considering that i need to buy pistons rings for the low comp pistons). I guess $485 isn't that much. People spend more than that on one normal car service! I’ll think about it a bit more. My Landy also runs on LPG, and I know LPG likes compression. I already have extractors and a 2.5" exhaust that you mention.

Thanks again,

Edward

If you can spend the extra there is nothing more useless and fuel consuming than a low compression Rover V8 particularly on gas
On the other hand a high compression 3.5 with the right cam can be a great little unit and will serve you well.

**Bearman** · 3rd June 2017, 05:24 PM

Originally Posted by djam1

If you can spend the extra there is nothing more useless and fuel consuming than a low compression Rover V8 particularly on gas
On the other hand a high compression 3.5 with the right cam can be a great little unit and will serve you well.

And you could then go 0.996:1 transfer gears.

**djam1** · 3rd June 2017, 07:04 PM

I always used 1.336:1 and a high compression engine went well

**I Love My Landy!** · 3rd June 2017, 07:08 PM

Originally Posted by Vern

You will probably save that $485 in gas/fuel in the long run going for the high comp pistons 😊

Thanks Vern. It's interesting that you say this. Back when this motor was fresher and had more compression (150 - 160 psi) my mileage on LPG would be 19 L/100 km. Now that the motor is down on compression (110 psi) the mileage is now 23 L/100 km. If my maths is correct, the high comp pistons will pay for themselves after only 17,500 km

**PLR** · 7th June 2017, 09:13 PM

Originally Posted by I Love My Landy!

Good evening all,

I am putting some money into rebuilding much of my (530,000 km old) 1984 110 V8. I am rebuilding a 3.5 V8 from a Discovery 1 but keeping my carbies and using an early pre-pollution camshaft. It is a low compression motor. I have access to a LT95a gearbox with 1.113:1 transfer gearing. Can anybody advise me of how well it would suit the low comp motor? My rough calculations suggest it would rev at 2650 rpm at 100 km/h (3.54:1 diffs, 32 inch tires). This seems fine to me (my current 1.3:1 gearing is a bit low i feel). I am rebuilding the motor on a budget, but i could invest in high comp pistons if it would make a considerable difference.

Many thanks,

Edward

G`day Edward ,

the Range Rover with the 1.113:1 used the 8.13:1 ratio .

The difference that LR give between the 2 engine ratios is 7 hp and torque is 1 difference . 132 power , 186 torque and 125 power and 185 torque

In both cases according to what LR give the lower is the 9.35:1 ratio .

The main difference in the numbers is they are achieved 1000 rpm apart the 8.13 at 5000 and the 9.35 at 4000 and reason given is mostly camshaft .

If you use composite gaskets in place of tin and don`t remove some material the ratio will be around the difference between 8.13 and 9.35 or give around 7.13 and 8.35

Our RR 84/5 twin carb dual fuel was 3.5 now 4.0 .

I have used 14 bolt heads with around 2.4 mm removed on a 9.35 stamped block and used Felpro composite 3.5 gaskets .

It ran mostly on LPG but could run on petrol but never gave it a hard time or towed with petrol .

I have also used those heads on a 8.23 stamped 4.0ltr with Elring gaskets and it also ran LPG and on Petrol it could tow a tandem with another RR on it with out problem .

That engine now has 10 bolt heads with earlier exhaust valves which are flat across the valve head unlike the original which are concave and Elring and drive ability even though the later heads breath better is not as good as it was . It averages 150 cold comp test , uses a Wade after Cam and rollmaster timing set as it still uses the original cover .

For LPG running higher compression ratio is better , you could look at the difference if you think relevant between static and dynamic and how cams affect dynamic with long and short duration etc

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