p6 v8 engine mods

SydneyRoverP6B

Well-Known Member
Staff member
#21
quattro wrote,...
I changed the heads for some SD1 ones as they were, IIRC, 12% more efficient than the P6 ones (Stage 1 P6 ones were 9%),

replaced the old worm out cam and followers with a standard set up (the 3.9 is better but they didn't have them in those days)

Fitted 4:2:1 tubular manifolds (the only expensive bit)

Had the flywheel lightened by 30%

Fitted an SD1 electronic dizzy

Had is set up on a s rolling road with AAA needles and K8N filters
Hi Richard,

The needles, don't you mean BAA as AAA are 0.90" needles?

Ron.
 
#22
LeeEFi said:
IMOHO I think we all want a happy medium. A nice sound with a fair bit of effortless grunt. I think that screaming around at high revs is fun, but the novelty wears off quite quckly. I think it's most impressive when you get to that happy medium and have an RV8 engine that performs all the time instead of just at 6500rpm 8)
I thought RV8's were only safe to rev up to 5200RPM?
 

SydneyRoverP6B

Well-Known Member
Staff member
#23
darth sidious wrote,...
I thought RV8's were only safe to rev up to 5200RPM?
The P6B engine has that imposed, with later engines it typically ranges up to 5800rpm. The hydraulic lifters won't work as they are designed to do once engine rpm exceeds 5800rpm or so, hence they effectively work as rev limiters. The rocker assemblies are also fragile when revs exceed 5800rpm so it is best to not exceed this limit on later engines.

Ron.
 

quattro

Well-Known Member
#24
SydneyRoverP6B said:
quattro wrote,...
I changed the heads for some SD1 ones as they were, IIRC, 12% more efficient than the P6 ones (Stage 1 P6 ones were 9%),

replaced the old worm out cam and followers with a standard set up (the 3.9 is better but they didn't have them in those days)

Fitted 4:2:1 tubular manifolds (the only expensive bit)

Had the flywheel lightened by 30%

Fitted an SD1 electronic dizzy

Had is set up on a s rolling road with AAA needles and K8N filters
Hi Richard,

The needles, don't you mean BAA as AAA are 0.90" needles?

Ron.
Hi Ron

I was recommended the AAAs for the state of tune (as a starting point) but also advised to go to a rolling road. When on the rolling road, the fuelling was just about spot on, and according to the rolling road peeps, it wouldn't be any better changing the needles, so I am certain they were AAAs.

Richard
 

SydneyRoverP6B

Well-Known Member
Staff member
#25
quattro wrote,...
Hi Ron

I was recommended the AAAs for the state of tune (as a starting point) but also advised to go to a rolling road. When on the rolling road, the fuelling was just about spot on, and according to the rolling road peeps, it wouldn't be any better changing the needles, so I am certain they were AAAs.

Richard
Hi Richard,

The reason I suggested BAA as opposed to AAA is that the former are 0.100" needles and run with 0.100" jets as fitted into all HS6 and HIF6 carbs, but the AAA is a 0.90" needle and runs in a smaller 0.90" jet. The needles match the jets in terms of starting diameter, so a 0.90" needle would never be used in a 0.100" jet.

Did you fit smaller jets?

Ron.
 

quattro

Well-Known Member
#26
SydneyRoverP6B said:
quattro wrote,...
Hi Ron

I was recommended the AAAs for the state of tune (as a starting point) but also advised to go to a rolling road. When on the rolling road, the fuelling was just about spot on, and according to the rolling road peeps, it wouldn't be any better changing the needles, so I am certain they were AAAs.

Richard
Hi Richard,

The reason I suggested BAA as opposed to AAA is that the former are 0.100" needles and run with 0.100" jets as fitted into all HS6 and HIF6 carbs, but the AAA is a 0.90" needle and runs in a smaller 0.90" jet. The needles match the jets in terms of starting diameter, so a 0.90" needle would never be used in a 0.100" jet.

Did you fit smaller jets?

Ron.
Hi Ron

It was 25-30 years ago, what can I tell you :shock:

Richard
 
#28
SydneyRoverP6B said:
The P6B engine has that imposed, with later engines it typically ranges up to 5800rpm. The hydraulic lifters won't work as they are designed to do once engine rpm exceeds 5800rpm or so, hence they effectively work as rev limiters. The rocker assemblies are also fragile when revs exceed 5800rpm so it is best to not exceed this limit on later engines.
Hi Ron,
I know the road testers at the time of the SD1's introduction said that the engine would rev to the red-line(6000rpm), but it was pointless in doing so, as the car would actually take longer to accelerate in testing. I think I might have got close to 6000rpm on my SD1 by being a bit keen with the kickdown :shock: Obviously the P6 spec V8 is limited by it's valve and lifter set-up. The 6500rpm I mentioned was the maximum revs for a standard production Rover V8, albeit assisted by uprated cam' and lifters.
 

SydneyRoverP6B

Well-Known Member
Staff member
#29
Hi Lee,

The rpm at which maximum power is delivered has dropped since the RV8 no longer found a home within a Rover car. With the introduction of the 3.9 and subsequent engines, maximum power would come in at around 4750rpm. After that the power quickly drops away although the engine will continue to rev quite happily up to 5800rpm or so. Using a 3.9 camshaft in a 3.5 litre engine will see the same result, maximum power coming in at lower revs. The duration of the P6B camshaft was from memory 285 degrees, but the 3.9 (not sure about the 4.2 camshaft) 4.0 and 4.6 camshafts all run at about 265 degrees or even less, so the engines run out of puff earlier on. The profiles however for all factory Rover camshafts were quite distinct from each other.

Ron.
 
#30
That makes a lot of sense, Ron. A pity really, as for the sort of driving I do, that rather puts me off the 3.9 cam! I'm afraid I have been known to use quite high road speeds now and then and the 3.9 cam sounds like it would take the edge off that capability. Perhaps the answer is to fit that ZF box lurking at the back of my garage to raise the final drive ratio a tad, then use that gain to allow a lower rpm max power. Oh dear, too many compromises, makes my head hurt trying to weigh them all up! :cry:

Chris
 

rockdemon

Administrator
Staff member
#33
I'm more of an effortless torque fan myself. Chris still has p6 heads i believe - are they better at high revving with their twin springs?

Rich.
 
#34
Very unlikely! As said earlier, the limiting factor on revs with a standard engine is the valve lifters "pumping up". The difference between twin and single valve springs is much more likely to be due to improving spring steels over the years.

I heard recently that when Rover were developing the V8 they ran it on test to see at what speed things would let go. The answer was 14,000 rpm :shock: And it wasn't the bottom end that couldn't take the strain, but the flywheel!

I've no wish to drive a rev monster, but I would like the engine to carry on gently running up at high speed. An RP4 or similar cam with a suitably free breathing head is probably the answer.

Chris
 
#36
chrisyork said:
Perhaps the answer is to fit that ZF box lurking at the back of my garage to raise the final drive ratio a tad, then use that gain to allow a lower rpm max power.
That sounds like the answer Chris :idea: With high torque and high gearing I think that would be very effortless P6 8) Umm...ZF autobox conversions for Rover's. A cottage industry perhaps :idea:

I've tried the 4HP22 in a Range Rover, and I was very impressed...smooth changes, good kickdown response, high gearing, and a lock-up in top gear which didn't lock until about 52mph, perfect. But, I wasn't too keen on the first gear inhibit when cold idea, or the occasional tendancy to stay in first gear when cold. But I suppose this was down to the 130k on the clock :?:
 
Top