The V8 Owners Forum -

hey all i have a rover p6 with a 10.5 engine everything is all standard and i have been told i have more performace and better to the gallon with the sd1 heads is this true as i would like a bit more power out of it also i got the standard su's on it HS6 carbs with a set of k&Ns dont want to change nothing bit as i have just put in all new big ends and stuff i also got the sd1 front cover with the oil pump is there any 1 can tell me the best way to go

Hello Gareth,

The SD1 heads will breath and flow with more efficiency compared to the P6B heads, but any difference in performance and fuel economy will be marginal.

If you have the K & N filters fitted directly onto the carburettor adapters, then this arrangement will cost you both power and torque compared to running the filters on the end of the cast elbows.

The factory set up with the elbows and the large circular airbox actually helps to improve engine torque.

Does your engine ping under hard acceleration Gareth?

Ron.

hi ron here what my set up is like at the bottom yea its only just starting to pink when i had it out last going up a hill the other problem i had is when i put this engine in i think the timing pointer got knocked so i think that might be out a bit so i dont know if that the course as well i have been told to get the timing to TDC because its the 10.5 engine so are these filters in the right black or no or have they got to be on the elbos so it means it goes nearer the the heater box

thanks gareth

Hello Gareth,

That is the major problem with the 10.5 : 1 CR is that in order to minimise pinging the timing has to be retarded, so running the initial timing at TDC is the normal thing to do. Every 10.5 : 1 Rover that I have driven would ping, some worse than others.

Modern engines can run similar compression ratios without noticable drama as the engine management system will retard the timing the moment the knock sensors detect the onset of pinging.

Unfortunately you don't have the same degree of luxury with a distributor. Having said that you can have the distributor regraphed. Doing so should largely eliminate the onset of pinging under most conditions.

Did you change the needles when you fitted the K & N filters? If you didn't the mixture will certainly be too lean so this will contribute to pinging.

That is true, running the filters on the ends of the elbows will bring them much closer to the heater box. I dare say that the filters that you currently have fitted won't fit over the elbows anyway, so you would need to purchase another pair featuring a larger diameter inlet.

In any case while ever the engine pings, changes that you make to the air filter arrangement will be largely of no consequence.

Ron.

so do you think its worth me changin over to the sd1 heads as i said bout that timing pointer i dont know is thats in the right place how can i tell as for some reason somthing is saying its not the problem i got its pulls well but not as much as i though it would do

Without using a piston stop or a dial gauge to locate TDC with the heads off, you can run a series of road tests to set the timing by sound and feel.

Loosen the distributor retention bolt so that you can just move it by hand and then road test. If the engine pings...retard the timing slightly and test again. Keep testing until you are satisfied with the results. Does the engine then idle smoothly? Increase the engine idle speed to 650rpm or so if required, or advance the timing slightly if you are unhappy with the result.

In either case, the 10.5 : 1 engine in standard trim will never pull as well as a lower compression engine which can run all of its timing.

I suspect changing to SD1 heads will make little difference as far as the pinging is concerned.

Does your engine run tin head gaskets? If you fit the SD1 heads with composite gaskets, the CR will drop to approx 9.9 : 1 which in essence is still too high to eliminate pinging in all conditions.

What temperature thermostat are you running?

Ron.

yea my engine is running the tin gaskets i thought u 10.5 engine would be the best as it got more bhp then the later engines the reason i am thinking of changine the heads to sd1 as loads of people say the p6 heads are not good compared to the sd1 and they say they run better so if i change them i could turn the engine over to number 1 pistion is level and have a look with the timming pointer will be as fare as i know the temperature thermostat is a standard 1

The 10.5 : 1 engines produced more power when fuel was 100 octane or more. These engines were designed to run best on this fuel. Why do you think all subsequent Rovers run lower compression ratios? Even the Rover Vitesse ran a maximum of 9.75 : 1 from memory.

Like I said, the SD1 heads are more efficient, but that does not translate to lower compression ratio...unless of course you fit composite gaskets. By all means change the heads and fit composite gaskets, and you can check TDC while you are there.

I fitted composite gaskets to my 10.5 : 1 engine during the mid 1990s. It still pinged.. A friend of mine owns a P6B with the 9.25 : 1 engine. That engine has never pinged.

Ron.

The difference between the P6 heads and early SD1 heads is not as great as people seem to think - The improvement in heads came with the SD1 Vitesse heads which subsequently became the norm in the 3.9's and even then the improvement is not exactly significant.

Big improvements are only made with opening up the ports area about an inch behind the valve.

I ran a 10.5 with no issues with pinking at all no matter how hard it was driven - modern unleaded is pretty quick burning though and its usually timing rather than compression ratio's - most modern engines are 10+ and bikes are 12+ on regular unleaded.

I suspect and pre-ig issues are down to incorrect timing/vac advance/worn dizzy.

Andrew

Hi
I think you will be much better off with the original set up, the set up you have now will be getting hot air from above the exhaust manifolds, also the cast bits the filters are bolted onto are really bad for flow especially without the elbows. An aftermarket trumpet would be much better inside the filter if you do want to get rid of the old setup, but you still really want to get cold air in there and keep the heat from the exhaust away from the inlet side.
Best regards
Mike

so do you all think its better to get rid of the k&ns and go back to the old airbox i thought with the k&n filters it would be better 2 suck up more cold air