Head swap

So I have a rover 3.5l v8 it's the 10.5.1cr motor I have read about people swapping the heads to sd1 heads so they can use unled fuel is this the same if I was to put rover 4.6 heads on? And will I need the 4.6 rockers or can I use my 3.5 rocker Assembly and push rods? I'm guessIng I will have to change to the compost head gaskets too? (Will I need the composite inlet gasket too? Or I keep it steel?) Then shim the cam And I just don't use the 8 extra cylinder head bolt holes?
Thanks for any information you can give me
 
All cars with alloy heads have hardened valve seats so can use unleaded fuel safely. If you go to later heads with smaller combustion chambers (28cc vs 36cc I think) you will need to go to composite(thicker) gaskets for the heads, not sure about the valley gasket. If you have any decent miles on the 3.5 I would bet the rockers and shafts are done for and the engine would benefit from new assemblies. Below is one of the shafts from my car showing 14k kms - probably 214k. It was a bit rattly up top, now much better. The early engines need regular, frequent oil changes , or even better an uprated oil pump, as in an SD1 timing cover.
jk6Rkdd.jpg
 
All cars with alloy heads have hardened valve seats so can use unleaded fuel safely. If you go to later heads with smaller combustion chambers (28cc vs 36cc I think) you will need to go to composite(thicker) gaskets for the heads, not sure about the valley gasket. If you have any decent miles on the 3.5 I would bet the rockers and shafts are done for and the engine would benefit from new assemblies. Below is one of the shafts from my car showing 14k kms - probably 214k. It was a bit rattly up top, now much better. The early engines need regular, frequent oil changes , or even better an uprated oil pump, as in an SD1 timing cover.
jk6Rkdd.jpg
Thankyou for that info I'm really new to all this stuff and kinda winging it I got the engine to run but was running rough could be a bunch of different things as I have found out but one thing I read seems to suggest that changeing the heads to newer was good for the engine to have lower octane fuel (I was running 95 but was told it has to be 98 or it is going to grumble)
So I thought if I changed the heads that I can use 91 or 95 maybe I have my information wrong? I saw a cheap set of rover 4.6 heads but they don't have the rocker assembly I actually didn't check the rockers on the 3.5 I have...so I'm guessing they will be similar to yours as it's on something like 250000ks if it's the original engine but now I have started reading about people switching to a 4.6 engine for better mileage and power they then have to change the diff and driveshaft and I wasn't prepared to do that though someome else said about a 3.9 being as high as you can go without needing to change gearboxes and diffs and such and that should give me better milage too? So I'm thinking do I just get a whole new 3.9 engine or adapt what I have since I beleave I need to do the rockers and cam shaft and tappets

anyone who's running a 3.9 or 4.6 from the standard 3.5 in a p6 have some pros and cons for me?


Also that oil pump do I just need the sd1 cover? Or do I need the cover and the high flow parts I have seen for sale? Or could I just use the high flow oil pump parts directly to the 3.5? Thanks
 
You should tell us your year and gearbox please. There are people here who have a 4.6 with an auto box, no big issues. A 3.9 should not over stress things. You can get a bigger oil pump kit for the P6B timing cover to make it same size as an SD1 pump. An SD1 cover will also give you a better front oil seal, less likely to leak. These engines do NOT Need a higher oil pressure, just more volume flow. With the 10.5:1 CR you have you should run the highest fuel octane you can or retard the timing to TDC. IMHO the best CR is the 9.25:1 - more tolerant of lower octane but still revs, better low end torque. Composite gaskets with your current heads would lower the CR. CR in these is mostly controlled by the shape of the piston crown - expensive, lots of work to change. A 1mm thick head gasket would bring the CR down to ~9.4 with your current heads.
 
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You should tell us your year and gearbox please. There are people here who have a 4.6 with an auto box, no big issues. A 3.9 should not over stress things. You can get a bigger oil pump kit for the P6B timing cover to make it same size as an SD1 pump. An SD1 cover will also give you a better front oil seal, less likely to leak. These engines do NOT Need a higher oil pressure, just more volume flow. With the 10.5:1 CR you have you should run the highest fuel octane you can or retard the timing to TDC. IMHO the best CR is the 9.25:1 - more tolerant of lower octane but still revs, better low end torque. Composite gaskets with your current heads would lower the CR. CR in these is mostly controlled by the shape of the piston crown - expensive, lots of work to change. A 1mm thick head gasket would bring the CR down to ~9.4 with your current heads.

It's a 1972 p6b with automatic transmission I'm pretty sure it's a bw35 when the dipstick is on the driver's side? I was mostly hopeing I could get better milage and so looking for what I should be changeing I suppose I should look for a 9.25.1 engine? I currently have the original 3.5 heads with a metal gasket should I be switching out for the 4.6 or the sd1 heads for better preformance? Or I should just stick to everything as standard Im guessing I'm going to have to pull it apart again and new camshaft and tappets and rocker assembly timing gear and now the sd1 oil pump but I was thinking if I'm going to do all that then maybe I find a 9.35.1 engine I'm guessing since the 3.9 engines are latter they should all be 9.35.1? So I could either go a latter 3.5 or 3.9 and rebuild that one well I use the current 3.5 with high octane till the other is ready to drop in

I was also going to look around for the parts to convert to a 5 speed manual I have seen a full conversion kit for about $5000nzd but was hoping to slowly accumulate what I need

Am I going to notice much preformance increase with the 3.9? I know I'll eventually have to switch to a webber carb to get better milage too
 
Guess you are in NZ? A 3.9 with injection would give best economy, but that will involve some work on your fuel system for injection. If you can find a 3.9 there, check its CR - here in Oz almost all are low compression (8.13:1) - good low end, but dont rev freely IMHO. I would find out why its running poorly first, and that may indicate which way to go. Weber carbs and manifolds and tuning will cost you $$$$. LT77 5 speed boxes are getting rare now , start searching. Mine cost me A$1300 complete with bellhousing and gearchange. Your current prop shaft will fit the LT77.
 
Guess you are in NZ? A 3.9 with injection would give best economy, but that will involve some work on your fuel system for injection. If you can find a 3.9 there, check its CR - here in Oz almost all are low compression (8.13:1) - good low end, but dont rev freely IMHO. I would find out why its running poorly first, and that may indicate which way to go. Weber carbs and manifolds and tuning will cost you $$$$. LT77 5 speed boxes are getting rare now , start searching. Mine cost me A$1300 complete with bellhousing and gearchange. Your current prop shaft will fit the LT77.

Yes I'm in NZ
Only going to a 3.9 would mean I don't need to update the dif and everything like I would with a 4.6? The LT77 are rather expensive here when they do turn up but I'll keep looking are the other options like supra and r154 more trouble to use?

If the 3.9 is low compression there then it probably will be here in that case should I stick to looking for a 9.35.1CR 3.5?

Thankyou for all your replies and help
 
As I said above there are others who have 4.6 std engines on std drive line (auto) without problems. Adapting a Supra box can be done, but the bellhousing is A$800 from Dellow in Sydney. Or even an MX5 box can be done - check out Dellow.
I am on my second 3.5 with 9.25:1 CR and I find them very nice to drive (manual box). Check out the cost of a rebuild of yours with the correct pistons.
 
As I said above there are others who have 4.6 std engines on std drive line (auto) without problems. Adapting a Supra box can be done, but the bellhousing is A$800 from Dellow in Sydney. Or even an MX5 box can be done - check out Dellow.
I am on my second 3.5 with 9.25:1 CR and I find them very nice to drive (manual box). Check out the cost of a rebuild of yours with the correct pistons.
Oh so with an auto I'm not likely to rip everything to bits? Maybe ill still look for that 4.6 then and just upgrade the auto transmission at some point but I'm still going to need the rover sd1 timeing cover? Have you done the sd1 timeing cover swap? Do I just need the cover and then the rover p6 high flow kit? Or just keep it standard unless the gears are stuffed?

Thanks for the info on that dellow place it never came up on any google searches for me the rebuild with the difrent pistons is to change the compression ratio is that right? (Still new to all this sorry)

Just looked and found the mx5 gearbox is cheap and alot of them here so maybe that's a good option thanks for the info on that

I looked it up here and that mx5 seems to be for a 4 cylinder engine not the v8? Or I'm looking up the wrong one? Thanks
 
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A low CR engine would do well with an auto box - lots of low end torque with a 3.9 or 4.6 engine. I would just fit the SD1 timing cover - maybe check the pump gears and replace if worn. I havent done this myself - not yet anyway. The 5 speed MX5 engine will carry the power fine - I have one with a turbo and 215RWHP - they have been used with a Lexus 4.3L v8. You can get 9.25:1 CR pistons for the 3.5 engine.
2vQfNqF.jpg
 
A low CR engine would do well with an auto box - lots of low end torque with a 3.9 or 4.6 engine. I would just fit the SD1 timing cover - maybe check the pump gears and replace if worn. I havent done this myself - not yet anyway. The 5 speed MX5 engine will carry the power fine - I have one with a turbo and 215RWHP - they have been used with a Lexus 4.3L v8. You can get 9.25:1 CR pistons for the 3.5 engine.
2vQfNqF.jpg
Well now I need to decide if I stick with the 3.5 and use the mx5 gearbox or if I go for the 4.6 and use an auto

There are full rebuild kits from rimmer bros if I buy the 9.35.1 rebuild kit this will change my 10.5.1 engine into a 9.35.1? Or I'm way off track? Rover V8 Full Engine Rebuild Kits | Rimmer Bros

They even have 3.9 conversions Rover V8 3.5 to 3.9 Conversion Rebuild Kits | Rimmer Bros
But I'm almost positive that's just more issues than it's worth?

With the timeing cover is one of these two at the top from rimmer bros the cover I'm looking for? Or I need the sd1 cover
Rover V8 Timing Cover and Fittings | Rimmer Bros

I like that vehicle honestly no idea what type it is but very flashy did you build it?
 
Converting a 3.5 to a 3.9 will involve boring out your block for bigger liners - $$$$$. Look at Rimmer prices on the front covers - surely you can find a used SD1 cover there, or even from Oz? The Clubbie above is built from a kit from Almac in Wellington - Clubsprint.
Almac Cars NZ
I suggest you make contact with a local Rover club in NZ and talk directly to somebody who knows the P6 v8 - general advice, and the best places to get work done on your car, and where to buy parts from. First thing is decide on a budget.
 
Converting a 3.5 to a 3.9 will involve boring out your block for bigger liners - $$$$$. Look at Rimmer prices on the front covers - surely you can find a used SD1 cover there, or even from Oz? The Clubbie above is built from a kit from Almac in Wellington - Clubsprint.
Almac Cars NZ
I suggest you make contact with a local Rover club in NZ and talk directly to somebody who knows the P6 v8 - general advice, and the best places to get work done on your car, and where to buy parts from. First thing is decide on a budget.

I have followed your advice and messaged the rover club here about parts and to see if they have any information
I do feel it's a really long road ahead since every time I fix something another part is broken so I'll slowly just keep sinking money into the pit but I wanted to make sure I was happy with the motor before I went too far really but found there is so much to figure out with just the engine types and such I thought the timeing covers on rimmers where sd1 clones or something but I'll try find a second hand original thanks

I can always rebuild the 3.5 to have the lower compression it was half the price to get to the 9.25.1 compression anyway

Thankyou for everything you helped me with
 
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