Cam Sprocket - Nylon vs steel

[Duane]

Hi Team,

I am building an SD1 engine I acquired in bits to put in my P6b (as the newly rebuilt P6b engine (early one) has lost all oil pressure for some reason). I've had that engine apart so many times I've had a guts full, so a new version is going in. Anyone with a bright idea about sudden loss of oil pressure and oil light on I'd love to hear from you. Everything is new apart from main bearings. I checked the pressure relief valve and it was fine. top end clasttering like hell so there is no oiol getting to the heads.

Anyway, the SD1 has a steel camshaft sprocket, and the new kit from Wins is nylon. The original seems to be in really good condition, as does the chain which has much less flex than Wins replacement.

Should I use the nylon sprocket or the steel one? I've heard nylon is quieter, but is there much to that?

 

[jp928]

I doubt you will hear much from inside the car. A good roller chain and wheels should outlast you, and hold timing well. Sudden loss of pressure (have seen it myself in an MX5) is most likely from a stuck pressure relief valve, most unlikely an oil gallery plug (rear of block) coming out; possibly bearing shells spinning? Clattering will come from no oil to the hydraulic tappets.

 

[cobraboy]

Agree, you won't be able to hear the difference.
I would use the chain with the least slack in it, I take it we are talking the stock type chain here. I once bought an engine that came with a new S&S duplex roller chain set, the chain was so slack I threw the lot in the bin and on Turner engineering's recommendation fitted a new stock timing set with a steel cam gear, never had a problem with it.
If the sump has had a pounding, or an encounter with a trolley jack the base can get pushed upward, this can get so close to the oil pickup gauze that it will cut off the oil supply.

A friend bought a 289 FIA Cobra with a new near to race spec 289 engine. Prior to delivery the dealer did a service, they could not unscrew the side of block mounted oil filter, so the tech jacked up the engine using the sump so the filter would clear the chassis rail.

Couple of weeks later my friend was feeling more confident in the car and decided to give it the beans, the engine was starved of oil, at least two conrods came out of the side of the block, crank broke in two, the engine was a gonner.

When putting your new motor together do check the oil pickup to sump clearance.

 

[colnerov]

Also I think the problem could be the one item not checked/changed ie. main bearings. The pump produces flow, pressure comes from resistance to flow, The first port of call in the oil's journey is the main bearings.

 

[Duane]

Have found that all but 0.5L of oil has exited the engine somehow - hence the lack of oil pressure and clattering top end. Absolutely no visual indications of where it has come out other than a bit of wetness to halfway down the exhaust. Could 4-5L of oil be ejected from the rear main seal in 100km of driving if it was knackered. That is the only place if could have gone.

Result is I am totally over this engine so am building an SD1 up from a bare block and putting that in.

 

[harveyp6]

I had an SD1 V8 throw out 5 litres of oil in about 65 miles because the breather system was blocked solid

 

[quattro]

I had a P6 with blocked breathers, that used to blow the dipstick out, then oil all over the exhaust. That was a bit alarming.

 

[GRTV8]

My P6b chucked oil out of all sorts of orifices when the flame traps didnt get serviced. Short lesson learnt.

 

[Duane]

I had an SD1 V8 throw out 5 litres of oil in about 65 miles because the breather system was blocked solid

Jeepers. There is no oil anywhere on the engine so it must be out the old rope seal.

I must admit I have had the rocker breathers vented to air because of too low an idle when coming to a stop under braking. No it isn't a leaky brake vacuum - the carbs seemed to like having the breather vacuum ports blocked off. A guy in the local club has his the same and it works fine. There are no emission regs here. The crankcase vent is filtered back into the air filter.

Could a lack of vacuum have caused it?

 

[Stuck-in-1972]

Hi Duane, sorry to hear of your misfortune.

I would re-fill the oil and drive it for a bit to see where the oil is going.

It could be leaking...that should be simple enough to find by running the car and looking at the floor underneath it; or taking for a drive and getting under to look every now and then....one great thing about the Rover is that you can slide under the car without jacking it up, unlike most modern motors.

Or it could be burning the oil, if an oil ring has been incorrectly fitted or not yet seated; or valve stem oil seals incorrectly fitted, or crankcase scavenging is excessive. 5 litres in 100 clicks is a lot to burn, so would expect that to be visible at the tail pipe.

You'll want to understand what is wrong before building up a replacement engine.

Anyway, good luck working it out.

Happy Motoring - Munro.

 

[Duane]

I have the old engine on the floor and took the rear main bearing off to have a look. The bearing was completely stuffed - copper coloured. The rope seal was still intact but I wouldn't say it was flexible enough to be sealing much, and pretty flat to the bearing shell.

It was pretty oily inside the bellhousing so I assume that is where the oil has exited and just dripped out the bellhousing drain at a rate of knots.

 

[Stuck-in-1972]

That was quick Duane. Good find. What will you do then, refit this engine?
Tip my hat to you for rapid work. It'd take me a week of sucking my teeth and looking at my boot tips and head scratching just to start thinking about engine removal....then I'd have a cup of tea before starting.
Happy Motoring. Munro.

 

[Duane]

When I start something I like to finish it.

I have just finished building up an SD1 engine I had sitting in boxes (got it free off a guy who took it out of a Capri to upgrade to a 3.9L). 10 years newer, bigger oil pump, bigger inlet valves, and electronic ignition.

Done this one properly - new lip seals front and rear, polished the very good crank journals, new main bearings, honed the near perfect bores, new rings and big end bearings, new camshaft and lifters, new valve pushrods, new waterpump. Lifted it in at the weekend and just have some ancillaries to put back together.

I'll probably put the P6B engine in a corner and strip it back down again at some point. It is a shame as it has reconditioned heads, new rockers, new cam and tappets, new rings, new big end bearings.

In hindsight it was a mistake to do an in car rebuild, as the main bearings and rope seal have caused the problem.

 

[Duane]

Next question:

The distributor from the SD1 is a 35DM8. Electronic with a remote ignition module. I assumed the distributor cab from the P6B 35D8 would fit it but it doesn't. The SD1 cap must be taller.

Does anyone know the part number for the right cap?

 

[DaveRover3500s]

Hi Duane. I am also running an SD1 block with SD1 electronic Dizzy (but P6 timing case and P6 oil pump connection). Yes dizzy cap is different mine have always been blue in colour - ANG parts do them as do Rimmers etc. If this helps!

Dave