Austin A35 1275 engine oil

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riggaz

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Howdy all I have an Austin A35 and i'm putting a tuned (100HP) 1275 BMC A series engine in it and was wondering what oils you lads would think about using. I work at a car dealership and we use Shell oil so I can get any of their UK products on our account. The original spec was for 10w-50, 10w-40 or 20w-50 but was revised in the 70's for most A series engines to 10w-30 API SF to increase oil flow and reduce bore wear, but due to the higher valve spring rates and increase in temp the standard oil will not be up to it I suspect. I was thinking about a 10w-40 motorcycle oil.... cheers Riggaz
 
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I use Mobil-1 15w-40 in two MGBs and a Sunbeam Alpine. All seem happy with it showing good hot oil pressure, proper coolant temperature, and a willingness to rev (of course within their long stroke design limits). Sounds like your A35 will be an energetic performer.
 
You may want to look at Helix HX7 10W-40. I know a few Morris Minors with the 1098 A series BMC engines running it with no problems, cam and bore wear is not an issue with this oil.
 
Originally Posted By: MG_Guy
I use Mobil-1 15w-40 in two MGBs and a Sunbeam Alpine. All seem happy with it showing good hot oil pressure, proper coolant temperature, and a willingness to rev (of course within their long stroke design limits). Sounds like your A35 will be an energetic performer.
Yeah, she'll be rapid 660kg 100HP Rae Davis racing suspension rear wheel drive smiles all round! We don't get Mobil 1 15w-40 over here only 15w-50 or 10w-60 they do a mineral 15w-40 but it might not be able to handle reving to 6000 - 7000 rpm Riggaz
 
Originally Posted By: Trav
You may want to look at Helix HX7 10W-40. I know a few Morris Minors with the 1098 A series BMC engines running it with no problems, cam and bore wear is not an issue with this oil.
I was thinking about that as we have that in our bulk oil tank (1350 litre) but thought as this is a tuned engine it might not have the additive pack for a stressed little engine revving so hard with high valve spring compression. Having said that it is the oil recommended by Shell on their lubematch tool for Mini Cooper S which have similar compressions.
 
Originally Posted By: Trav
You may want to look at Helix HX7 10W-40. I know a few Morris Minors with the 1098 A series BMC engines running it with no problems, cam and bore wear is not an issue with this oil.
What do you think of the Shell Advance Ultra 4T 10w-40 I was thinking that the 10w-40 would be the right viscosity for high oil flow and the additive pack in the motorcycle oil should be good for the high revving flat tappet engine in the A35 as most bike engines are this design. Riggaz
 
I would suggest Rotella in 10w-30 or 15w-40, I use the latter in my 100hp Triumph Spitfire and have had no problems in 20k miles. I suggest you monitor old temps (Don't just aromatically fit a big oil cooler!) I would think your most likely problem wound be NOT Bore wear, but Cam and Tappet wear. What are your cam specs? Is it a reputable brand? What Lube do the manufacturers want for Break-in? I don't know much about Bike oil, but I know most Bike oil is designed to work with Wet Clutches (not your problem) There are many Hot 1275cc and 1380cc Mini's out there, What do they use?
 
Quote:
flat tappet engine in the A35 as most bike engines are this design.
Yes and no. Most high revving bike engines are OHC with lobe over bucket directly over the valve, this design has very light lobe loads. Take an engine with excessive cam lobe load like a OHC with each lobe actuating 2 valves by way of a single non roller slipper, essentially more than doubling the lobe load depending on the ratio. The HX7 performs well in this high stress situation. Even in older push rod bike engines it holds up well.
 
Originally Posted By: expat
I would suggest Rotella in 10w-30 or 15w-40, I use the latter in my 100hp Triumph Spitfire and have had no problems in 20k miles. I suggest you monitor old temps (Don't just aromatically fit a big oil cooler!) I would think your most likely problem wound be NOT Bore wear, but Cam and Tappet wear. What are your cam specs? Is it a reputable brand? What Lube do the manufacturers want for Break-in? I don't know much about Bike oil, but I know most Bike oil is designed to work with Wet Clutches (not your problem) There are many Hot 1275cc and 1380cc Mini's out there, What do they use?
It varies from one engine builder to the next most say 20w-50 but they are the ones that would put 20w-50 in all classic engines assuming that it will be the correct grade. The oil pressure relief valve opens at 60lbs so anything after that and you are getting no extra oil flow, it's just returning back to the sump. I figure that if BMC changed the oil recommendations to 10w-30 from 20w-50 they must have done it for a reason, maybe 20w-50 is too viscous. I've heard one race engine builder recommend Silkolene Comp 4 10w-40 motorbike oil which is why i was thinking of it. I can't get Rotella despite hearing such good things about it I think maybe here it's called Rimula here? cheers Riggaz
 
Originally Posted By: Trav
Quote:
flat tappet engine in the A35 as most bike engines are this design.
Yes and no. Most high revving bike engines are OHC with lobe over bucket directly over the valve, this design has very light lobe loads. Take an engine with excessive cam lobe load like a OHC with each lobe actuating 2 valves by way of a single non roller slipper, essentially more than doubling the lobe load depending on the ratio. The HX7 performs well in this high stress situation. Even in older push rod bike engines it holds up well.
Cool, nice to know I was thinking the bike oil, despite being relatively lightly loaded on the cam would still have the additive pack to protect the gears in the gearbox which are operating at high pressures, thus protecting my cam too. Riggaz
 
Hi, Riggaz - In NZ these engines used Castrol's XL (30-40) or Castrolite (20W-30) when new - it was standard fare! Both Austin, Morris and BMC were bred on these Castrol products. XXL was used for the oil burners!! Of course once the Mini was released in 1959 it only got the 20W-50 that Duckhams formulated especially for it (followed by Castrol) and this viscosity gradually fed into all the "A" (and "B") engines at Dealership level for "standardisation" reasons Because of the oil pump and other engine design features etc the lighter oils are best for all "A" engines except the Mini of course. Your suggestion of a 10w-40 is a good one - and this viscosity is very popular in Europe too I would avoid the SAE60 lubricants unless racing for extended periods (fuel dilution) or in very high ambient temps - 40C etc
 
Originally Posted By: riggaz
[quote=expat] The oil pressure relief valve opens at 60lbs so anything after that and you are getting no extra oil flow, it's just returning back to the sump. I figure that if BMC changed the oil recommendations to 10w-30 from 20w-50 they must have done it for a reason, maybe 20w-50 is too viscous. I've heard one race engine builder recommend Silkolene Comp 4 10w-40 motorbike oil which is why i was thinking of it. Riggaz
I think the bike oil is a good idea or the HDEO 10W-40 you mentioned. What you want is a high phosphorus content of at least 1,100 ppm . Obviously you don't want to run an oil that is so thick that you can't use maximum rev's once up to temperature without the oil pump going into by-pass mode. You could even consider a 5W-30 bike oil for the maximum flow as long as you're getting 50 psi of OP at maximum rev'.
 
Quote: I can't get Rotella despite hearing such good things about it I think maybe here it's called Rimula here? Funny, Rotella was 'the' Shell Heavy Duty Engine oil when I worked in the UK in the 70's, I guess they call it Rimula now. It used to be common practice to 'shim' the by-pass valve spring on 'A' series engines to increase oil pressure a little. By the way, Have you read/You Tubed David Vissard, He literally 'wrote the book' on Tuning the 'A' series engine. I'm sure he has opinions, But possibly based around Who his current sponsors happen to be.
 
Motorcycle oil should be a good choice. The are all higher in ZDDP than most car oils (no cat to worry about). Mobil 1 list the ZDDP levels on their web site, you should find a suitable offering there.
 
Originally Posted By: mechtech2
Oh.... the engine and gearbox share the sump like an old Mini? A 20-50 may be a good idea, then.
Engine and gearbox are separate on the A35, it's like an Austin Healey Sprite underneath (they used A35 chassis and drivetrain in the Sprite and MG Midget) so i don't have to worry about it having to protect/getting sheared by the gearbox. Riggaz
 
Originally Posted By: Doug Hillary
Hi, Riggaz - In NZ these engines used Castrol's XL (30-40) or Castrolite (20W-30) when new - it was standard fare! Both Austin, Morris and BMC were bred on these Castrol products. XXL was used for the oil burners!! Of course once the Mini was released in 1959 it only got the 20W-50 that Duckhams formulated especially for it (followed by Castrol) and this viscosity gradually fed into all the "A" (and "B") engines at Dealership level for "standardisation" reasons Because of the oil pump and other engine design features etc the lighter oils are best for all "A" engines except the Mini of course. Your suggestion of a 10w-40 is a good one - and this viscosity is very popular in Europe too I would avoid the SAE60 lubricants unless racing for extended periods (fuel dilution) or in very high ambient temps - 40C etc
Cheers Doug have a pint on me! Riggaz
 
Originally Posted By: CATERHAM
Originally Posted By: riggaz
[quote=expat] The oil pressure relief valve opens at 60lbs so anything after that and you are getting no extra oil flow, it's just returning back to the sump. I figure that if BMC changed the oil recommendations to 10w-30 from 20w-50 they must have done it for a reason, maybe 20w-50 is too viscous. I've heard one race engine builder recommend Silkolene Comp 4 10w-40 motorbike oil which is why i was thinking of it. Riggaz
I think the bike oil is a good idea or the HDEO 10W-40 you mentioned. What you want is a high phosphorus content of at least 1,100 ppm . Obviously you don't want to run an oil that is so thick that you can't use maximum rev's once up to temperature without the oil pump going into by-pass mode. You could even consider a 5W-30 bike oil for the maximum flow as long as you're getting 50 psi of OP at maximum rev'.
I didn't think the 5w-30 would have the film strength to protect a high lift cam In the standard 948cc (34hp) engine that's in the car at the moment I'm using Shell Harvella T 10w-30 universal tractor oil which is perfect for it, i'm doubting it would stand up to the tuned engine though. Riggaz
 
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