The V8 Owners Forum -

Finishing off a top end rebuild on a '73 3.5 P6B. P6 heads replaced with 3.9EFI (thanks Rossco!), new standard lift 3.9EFI cam. Intention is to replace the stock airbox with a pair of K&N RC-2600's.

I'm keeping the HIF6 SU's and was just wondering which needles to start with? (I think the) current needles are BBG, or possibly BBV.

I'd got in mind BAK for starters?...or richer?

Stan

Hello Stan,

I am pretty sure that with the modifications that you are making the BAK needles will prove to be too lean.

I would be more inclined to start with BAF and work from there.

When overhauling the carburettors, a very good idea is to remove the standard poppet valve equipped butterflies, and replace with a pair of solid ones. This will allow for a much smoother air flow into the carburettors. Along with all new seals and floats set to 40 thou for the 3.5 plus a new pair of 8oz yellow graded springs.

Will you be retaining the cast elbows and fitting the K & N airfilters onto each end or will the filters be fitted directly onto the SU adapters?

Ron.

RoverP6B wrote:Hello Stan,
When overhauling the carburettors, a very good idea is to remove the standard poppet valve equipped butterflies, and replace with a pair of solid ones. This will allow for a much smoother air flow into the carburettors.

Completely agree, I had butterfly's with worn poppet valves which was causing revs to hold slightly when coming off the throttle. I replaced with Genuine SU butterflys from berling fuel systems for around £16 delivered. This comes with the screws and all gaskets I needed, and some I didn't. I would recommend them

RoverP6B wrote:When overhauling the carburettors, a very good idea is to remove the standard poppet valve equipped butterflies, and replace with a pair of solid ones. Ron.

P6B's were never fitted with poppet valves, they arrived with the introduction of the SD1.

For a 3.9 with k&n type filters, start with BAC needles. I use them in 3.9's all the time, a perfect match for k&n's and a viper hurricane cam.

badger wrote:For a 3.9 with k&n type filters, start with BAC needles. I use them in 3.9's all the time, a perfect match for k&n's and a viper hurricane cam.

Thanks mate,

BAC certainly shoots up richer beyond the 7th point, compared to what's in at the mo, and BAK.

The 3.9 valves and the K&N's should flow a lot more than the P6 setup, but it's a 3.5 with a standard 3.9 cam..bit less lift than the hurricane probably? Would you still go for BAC?

Stan

Harvey wrote.....P6Bs were never fitted with poppet valves, they arrived with the introduction of the SD1.

Sorry Harvey, this blanket statement is incorrect. P6Bs sold in Australia all had poppet valves fitted as standard.

Ron.

Stan,

With an OEM 3.9 cam, the BAC needles will prove to be far too rich, even with K&N filters.

Ron.

Hi Vaultsman, I'm following your top end rebuild on the p6roc forum with interest at the moment. My '73 P6 3500 auto has a balanced 10.25:1 SD1 bottom end from 'Rovercraft'/Progress Engineering with their version of a Kent 214 cam, K&N cone filters straight on the SUs without elbows, through a BW35 slushbox, has BAK that have been further polished incrementally whilst on their rolling road. Sweet as the proverbial nut! Should soon be recomissioned into my bare base unit rebuild... Good luck with the preload malarky! My current project engine isn't that far, heads aren't back on yet but the bottom end seems to be binding...

Many thanks Ron, badger & al,

I've been doing a bit of digging and phoning around...going for BBW as a starting point - somewhere between BAF & BAK.

Sure most people will know this site, but mintylamb gives see-at-a-glance comparisons.

Cheers,

Stan

P.S. al (mrtask I presume!), thanks! - I've been following your restoration on the P6 forum too - looks great!)

Sorry, I misread the original post. As I said, for a 3.9, BAC. For your 3.5, start with BBW as you've now discovered. Sorry for creating confusion, best I go find some reading glasses......

RoverP6B wrote:Harvey wrote.....P6Bs were never fitted with poppet valves, they arrived with the introduction of the SD1.

Sorry Harvey, this blanket statement is incorrect. P6Bs sold in Australia all had poppet valves fitted as standard.

Ron.

I don't count the ones that went to Australia!

Wherever they first appeared, they were a waste of time, I must have soldered up hundreds of the things.