8:1 Conversion and Overdrive question

[Regan]

Considering a 8:1 conversion with hardened seat, valves, etc. for winter project (after about the 10 others before). Anyone have any idea on average cost and benefits for a '67 Series IIA, 2.25L? I am told it should give addtional needed power to this 4 cyc. engine. Also, Farley, Roverdrive, etc. - Does anyone have any suggestions on best one for lower RPM, install, service, cost? I hope to add one (new) in next 6 months.
Thanks, Regan with Possie

[thixon]

Hi Regan,

Your gonna get a wide range of opinions on the 8:1, hardened seat issue. Some will tell you won't see much of a power gain, others will say you will. Some will tell you that the hardened seats aren't worth it because it takes so long for bad things to happen that you may as well spend the money on something else. Just get ready.

In my experience, I noticed a small difference going to an 8:1, on a fresh motor. Mainly, I noticed that the truck would hold uphill speed a little longer on some local hills I drove daily. Top end wasn't effected.

As for the overdrive, I've only ever owned a fairey. I can't speak for the roverdrive, toro, or the high range box sold by our hosts. However, I can say that if you do any interstate driving at all, its not a bad investment. I've seen people post that with an overdrive, you won't increase your top end, just reduce the RPM's. In my experience, i was able to increase my top speed by 10 mph or so on flat stretches of interstate. I tested this quite a bit with a buddy in another car after installing the fairey to make sure I was'nt imagining things. Also remember, this was on a freshly rebuilt motor. My only complaint is that it was loud, and did'nt hold enough oil.

[TeriAnn]

Considering a 8:1 conversion with hardened seat, valves, etc. for winter project

A lot depends upon the condition of your engine. Tired rings, stretched timing chain, out of spec distributor and you will get a big yawn.

A 8:1 head or one milled to 9:1 would be more noticeable with a 2.5L cam & a good condition engine. A lot depends upon the condition of your engine.

An overdrive is always great for splitting gears in the hills. I loved 3 over in the hills. As to how useful 4 over is all comes down to engine HP vs vehicle weight. It is a lot more useful on a topless 88 than on a 109 stationwagon. And if you are going to get that 70 HP the factory rated the 8:1 2.25L engine at you need a healthy engine.

No one can tell you how much a fresh head would help without knowing the condition of the rest of the engine.

[LC_rover]

Regan,

I have a used Fairey OD in my garage. I don't know how much use the previous owner put on it, but it was working fine when I pulled it out. Let me know if you're interested.

[scott]

i spent about $1800 for parts and a machinist. machinist is a friend of a friend so i gotta him cheap. rmfr head 8.5:1, harden seats, oversized pistons, new rod and main bearings, 2.5 cam and i have a fairy od. my little truck screams. i'm thinking maybe some wheelie casters next

[Tim Smith]

I've got a Roverdrive in the airportable and had a Fairey in the 109. Both help but I've got to put my money on the Roverdrive. It's a better design in my opinion and certainly doesn't make as much noise. That's not to say it's quiet and if I could only get my hands on a Fairey then I wouldn't hold out.

As for the head, I'll agree with the others. It's not going to be a cure all. If everything else is in good order you'll probably notice more power but otherwise you might want to spend your time on overall maintenance before jumping into a high compression head.

It sounds like you might be new to rovers. If so then I'd highly advise spending time getting to know the truck with some personal one on one with all the maintenance tasks you can do. Timing, points, valve adjustments, carb tuning (make sure it is actually opening all the way ) all make a huge difference. Best to get familiar with all that first before jumping in on a big investment like a new head.

[Nium]

Are you sure you don't already have an 8:1 head?

I have a Fairey overdrive and haven't any complaints.

[Donnie]

I've got a Roverdrive in the airportable and had a Fairey in the 109. Both help but I've got to put my money on the Roverdrive. It's a better design in my opinion and certainly doesn't make as much noise. That's not to say it's quiet and if I could only get my hands on a Fairey then I wouldn't hold out.

As for the head, I'll agree with the others. It's not going to be a cure all. If everything else is in good order you'll probably notice more power but otherwise you might want to spend your time on overall maintenance before jumping into a high compression head.

It sounds like you might be new to rovers. If so then I'd highly advise spending time getting to know the truck with some personal one on one with all the maintenance tasks you can do. Timing, points, valve adjustments, carb tuning (make sure it is actually opening all the way ) all make a huge difference. Best to get familiar with all that first before jumping in on a big investment like a new head.

Does anyone know what gear train the Roverdrive is useing?

[Nium]

Does anyone know what gear train the Roverdrive is useing?

Roverdrive bolts to the back of the transfer case same as Fairey and other overdrives. Remove the mainshaft gear for transfer box and insert Roverdrive (basically) and bolt it up. Reduces engine RPM by 28%.

[redmondrover]

3.54 & R380

We had a Fairey. It was very loud. It had a catastrophic failure about 5 months ago. Just shipped it to George at RDS as a core.

This would be a totally different direction for you, but we are installing 3.54 diffs and an R380 5 speed in our 109. Mated to a Chevy 250 6 cylinder.

[east high]

A major difference between the Roverdrive and the Fairey is the way they hold oil. Roverdrives share oil with the transmission where as the Fairey is a separate circuit (if you can call it a circuit).

[TedW]

A major difference between the Roverdrive and the Fairey is the way they hold oil. Roverdrives share oil with the transmission where as the Fairey is a separate circuit (if you can call it a circuit).

My Fairey is always overfilled because it gets topped off by oil from the Transfer case. Not supposed to happen, but it's been that way since new in '92. I use synthetic oil, which may be a contributing factor. No negative effects detected (so far).

BTW, the oil capacity of the Fairey is relatively small, so it's considered a good idea by some to use synthetic, as it runs cooler.

I believe that TeriAnn (?) has a chart showing the relative final ratios of different overdrives and transfer case options. IIRC the Roverdrive runs just a bit higher than the Fairey - which might be a good thing if you run big 16's and/or have a tired engine.

[Eric W S]

We had a Fairey. It was very loud. It had a catastrophic failure about 5 months ago. Just shipped it to George at RDS as a core.

This would be a totally different direction for you, but we are installing 3.54 diffs and an R380 5 speed in our 109. Mated to a Chevy 250 6 cylinder.

you found the correct R380? Last I heard they were difficult to find even in the UK. Someone posted a link to a source not too long ago...

[TedW]

IIRC the Roverdrive runs just a bit higher than the Fairey - which might be a good thing if you run big 16's and/or have a tired engine.

Did I say higher? I meant to say lower.

[gudjeon]

I could be wrong, but, I read somewhere that the Roverdrive uses a planetary gearset from some commercial GM transmission in its innards.