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Old RV8 3.5 Dry Sump project


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In 2011 we got an oil light warning, which went with a stuck relief valve and finished with a warped block. This led to this disco engine;

http://s146.photobucket.com/user/teamidris/media/BeastEngine5low.jpg.html'>BeastEngine5low.jpg

This wasn't much better than the one we took out. I was begining to think the rope-seal engine would be coming back out of the shed!

I did use the old +20 pistons out of twisted engine, but it still cost a lot of money to rebuild, so I wanted to protect my investment and get a bit more engine :)

I thought it was time to match piper cam and ARP stud set with an improved lubrication circuit. The RV8 pump is icky at the best of times; the suction is too long, relief valve recirculates, gears have end float, timing cover wears (especially after eating the cam). And oil covers the plugs when nose downhill. And its just a hydraulic system when all said and done, right?

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There is suprisingly little depth of knowledge on the internet about dry sumping. Which is why I'm thinking this write up maybe handy? There are some gems of articles, if you can find them. I trawled everything I could find.

My first problem was managing the risk in my head. There are loads of machines out there with dry sump that work fine. But I was going to be one rubber belt away from disaster!

I figured a rubber belt can drive a pump to work a hydraulic winch at 30 litre/min and 3000psi. I have 10 litre/min with a 40 psi relief valve, so no torque/load at all by comparison :)

Next was the sump design. And I could only copy what was out there. Normal seemed to be as shallow as possible with a drainage channel. I folded some steel and finished up using the lip off the old sump. If I started again I would make a new lip out of thicker steel. I finished up with a sump full of stress and twists. I see why billet is popular!

http://s146.photobucket.com/user/teamidris/media/DrySumpMay2011.jpg.html'>DrySumpMay2011.jpg

After two gaskets I stuck it one with silicon only last week. To be fair the pump raft makes it all worse, as it has to be bolted up tight.

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By this stage I've decided on a 3 pump set. That's one pressure pump and two scavenge. All segments are 10litre min on mine, so one scavenge can keep the sump clear. One pick up is at the front and one right at the back. I had many thoughts on this, but really, when all said and done, the farthest points make sence. On the flat both working together just makes gurgling noises in the tank.

Then the weird stuff started; I wanted to avoid a dry scavenge pump segment at steep angles, so my supplier drilled the inside so they lube each other.

I think that was overboard? If I had made the front pump suck from the back and the back pump suck from the front, the common out let would have let oil run into the pump sucking air. You know oil, it gets everywhere. Crossing the suction lines would have been much simpler :)

http://s146.photobucket.com/user/teamidris/media/DrySumpSept2011lowjpeg.jpg.html'>DrySumpSept2011lowjpeg.jpg

Anyhoo, I didn't do that, but I still got to the point of a pinted sump!

The rear segment is the lube pump and the screw thing behind it is the relief valve. This had a very narrow window of adjustment, so I fiited a 40psi 3/8" bsp relief valve just after the remote filter on a 'T'.

I also needed a goodly cut-out bit for the axel.

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That's a big pulley - you might ask? Nothing like that on the net?

That's because it's a big old compramise :wacko:

Because the flexi drive is up the middle of the pulleys I was a bit limited. Dunsfold fixed us up with a 3 sheeve cast pulley, so I run nearly 1:1 instead of half speed. Dave Lazenby thought I would be okay as his pump is designed for fast race engines. And he has done a lot of dry sump experimentation, so trust his word.

I'm not against the extra flow created and see 18psi at tickover with the auto in cog, dragging it below 800rpm. Most of the engine work is low rev. High rev on a carbed RV8 doesn't really happen. And it's bad for the winch pump.

http://s146.photobucket.com/user/teamidris/media/PumRaftSept2011.jpg.html'>PumRaftSept2011.jpg

More guessing about strainer mesh.......

I cut the pump raft to put the belt through. (Very very carefully to avoid warping the plate)

I fit a normal V8 tensioner pulley in there on a stay. There are a lot of bepoke parts in there so I like to find OE parts where I can. It's bad enough to fix this truck as it is :i-m_so_happy:

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http://s146.photobucket.com/user/teamidris/media/DrySumpOct2011Tank.jpg.html'>DrySumpOct2011Tank.jpg

Apart from the head scratching and avoiding anything hot with the pipe work, the next bit was the tank. In 1.6mm steel, 200mm diameter and 400mm deep I chuck in about 10 litre of 20/50. 100mm up from the bottom is another screen. The scavenge line squirts against a plate that blows oil up the side. I'm kind of relying on oil depth to seperate air.

The suction pipe needs to be oversize compared to the pressure pipes and have a trumpet inlet to avoid cavitation. In an ideal world the tank would be slightly vacuumed to pull the air from the oil. Any pressure in there has the oposite effect (bad). My lid bolts on as the tank is difficult to remove from the vehicle.

I have 'T' in the bottom that does 'drain' and sight tube.

http://s146.photobucket.com/user/teamidris/media/DrySumpOct2011cab.jpg.html'>DrySumpOct2011cab.jpg

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One prediction that was spot on, was that the oil does indeed drain from the tank into the sump over a few weeks. A spare 1/2" bsp port I put in the wrong place connects to a boat sump-drain pump to re-fill the tank.

Just another job to add to the list really :)

Priming can also be done at the pump. The belt is slackened (quick job really) and a speeder bar with 10mm socket goes on the front of the pump. Turny turny = oil pressure ^_^

http://s146.photobucket.com/user/teamidris/media/EngineUnderneath20123.jpg.html'>EngineUnderneath20123.jpg

I chucked a bit of loacalised armour on to protect the rear fittings. The front gets a thin belly pan.

The sump just got stuck on with silicon only, as a third attempt to fix it. But it leaked worse after a month when the oil level was half way up the crank. So any gaps show up worse.

For an engine breather I linked the OE ones to the tank. Then the tank to the outside world. I figured it would sort itself out then.

It has a very noisy buzzer to warn of low oil pressure (just in case)

No distick, just a sight tube!

On reflection I'd say a good mod and dry sump did the job. Nose down for a while doesn't foul the plugs and oil pressure is pretty constant.

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The pump came from http://www.useful-tools.co.uk/ but no sooner than I had them from David, he'd flogged it to a mate :)

Worth tracking down the product as its different to Pace's. Normaly you have an inlet and an outlet cresent slot. But this one has two inlet cresents, one on either side of the G-rotor. So even less chance of cavitation on a cold morning.

A tough strong sump that had the pump bracket on it would be better, if only because the suction pipes can be solid all the way. It all looks nicer with a toothed belt and billet sump.

Worth noting that there are half-systems, where the old pump is kept and two scavenge pumps are used. I was pretty close to this. The little bit of plate welded into the sump is where the OE suction pipe was to exit the sump and go to the dry sump tank. But I decided to go the whole way and ditch the OE pump. The cost isn't much more (relative).

I think it starts better now after being left for a few weeks? Difficult to prove, but the RV8 does seem to start when it has oil pressure and not before?

As diesel fitters me and Terry thought the landy turbo's would be happier off road with a constant oil supply?

I'm glad the thread is a good read. Any questions please ask away. There's stuff I learnt along the way that is only going to leak out if prompted ;)

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Great write-up and tech, I'm not currently thinking about dry sumping, but still very useful info, and worth having some day I'm sure! ;)

On a side note, could you not just have used the stock pan and removed the "boxy" bit that contains most of the oil? Then warping shouldn't be that much of an issue..

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I thought about that with the spare sump or just fitting suction ports to it? (does a deep bucket matter to the dry sump). I really wanted that centre trough though. If I was fair I'd say the current sump was just far enough over the line to avoid the bin ;)

If this one doesn't work it's a 10mm water jetted ally ring, a 4mm 5083 grade tray and a miller :)

One method we considered is a thin edged sump trapped by a thick support ring. Kind of forceing the fab warping situation into something that is flat?

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  • 2 weeks later...

Took it trialing today and tried to drive up something daft, resulting in the vehicle trying to roll. And it should have rolled as it was way past the point of tip over, but didn't go all the way due to rock against the door. I reached down and put it into reverse putting it back on its wheels. As the left bank must have been lower than a flat-four I was pleased to see no smoke. And no buzzer, so I guess we kept oil pressure :)

I was also impressed that the carbs kept the power up.

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