standard cam vs piper cam on v8
Paul Everett
Hello,
It's about time to decide what cam to fit to my 9.35:1 3.5V8 that's
going into the 110. I have a choice. Either a standard 3.9 cam
(supposedly +8-10bhp) or a Piper 270/110 (supposedly +18bhp). The kits
from RPi are 175+vat and 255+vat respectively. I mainly use the motor on
the road, but I also trial, so low end torque shouldn't be lost. Both
those cams supposedly keep the bottom end torque at least as good as the
standard 3.5 cam, so that's not an issue. The question is will the Piper
give me enough more economy and top end to justify the extra 80+vat?
This is something I would like to get right, as I'm keen to avoid
swapping the cam again...
Anyone any experience of the piper cam? I know the 3.9 one works pretty
well in the 3.5 as I've been in motors with it, but I don't know anyone
with a Piper. RPi really rate them, but that's hardly surprising as they
sell them...
TIA,
Paul
--
Paul Everett
repton at repton dot org
http://www.repton.org/
PDannyD
news:3DBFF759...@spam.repton.org...
>
> Hello,
>
> It's about time to decide what cam to fit to my 9.35:1 3.5V8 that's
> going into the 110. I have a choice. Either a standard 3.9 cam
> (supposedly +8-10bhp) or a Piper 270/110 (supposedly +18bhp).
Going off a conversation a few months ago I'd say go for the Piper cam. I
think you'd need a mild road cam if you want to do some off-roading as well
but I could be wrong.
Paul Everett
> Going off a conversation a few months ago I'd say go for the Piper cam. I
> think you'd need a mild road cam if you want to do some off-roading as well
> but I could be wrong.
The 270/110 piper is supposed to be a very mild cam. I'm certainly not
considering anything wild as I need to keep the bottom end as strong as
possible.
Ta,
vince
Nothing wrong with Piper cams - been used by race and rally boys for years.
See if you can have a look at the torque curves - offroad you need peak
torque as low as possible unless you intend high speed offroad work such as
rallying!
To get 18bhp more I suspect the torque curve will be quite different from
standard models - you may well have more torque as well - but at a different
place.
Still the V8 has so much torque a few ft lbs less here or there shouldn't
make too much difference.
NigelFur
Apart from RPI I know V8 Developments have been doing some cam work and
testing. The Piper RP4 cam has had one or two good mentions.
--
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Badger
believing all the hype from RPI!!!! First, let's start by saying that this
cam DEFINITELY boosted the lower mid-range torque on my engine. It also,
however, ran out of steam at 4500rpm and if you went over that rpm it
rattled. The rattle turned out to be the valve spring retainers contacting
the top of the guides. I would advise anyone contemplating this cam to ease
the guides by 0.1" minimum to prevent this contact, even though the seller
will tell you it's a straight fit. Fuel economy was relatively unaffected,
surprisingly enough. Rpi reckoned that it'd be more economical due to
running at lower rpm's for longer in a higher gear, but then they'd say
anything to get a sale, in my opinion. I reckoned that if you're modifying
the power and torque curves you'd more than likely end up using more fuel.
Now for the negatives!
1. You need to alter the fuelling, easy with SU carbs, fit cone filters and
BAC needles. No suitable needle profiles available for Stromberg's though,
so it'll run very lean and possibly do damage.
2. This cam will not work with an autobox, the engine will stall when
selecting reverse or drive due to the cam having less torque at idle than
the std one.
3. Applies to all cams. Get a vernier timing gear, not necessarily a cloyes
duplex set-up, and time the cam in properly. I've found new cams with a 4
degree error!!! The quality varies, regardless of who is selling it, as does
the accuracy of the original rover crank and lower sprocket.
That's my tuppenceworth, for what it's worth, and I've built more rover V8's
than I care to mention.
Happy cam swopping, Badger.
Phil Gardiner
Badger <bad...@badger-co.freeserve.co.uk> spouted forth:
You say, fit BAC needles. Exactly what air filters, exhaust system
(including manifolds), compression ratio, distributor advance curve and
static ignition timing were you running?
I'm stating this because after spending what could be a considerable amount
of money in modifying the engine it seems ridiculous to me that people don't
take their pride and joy to a rolling road who specialises in (at the very
least) the type of carburettors fitted to the engine. The factors stated
above and probably some I've forgotten about all influence the fuelling and
ignition advance curve required.
I have learnt this from experience having built 5 modified engines. They
all seemed very good once run in. After a rolling road session where the
cam-timing, distributor advance curve and carburettor needles (or jets) were
optimised, they were unbelievably good. The best case I had was when I
modified a 998cc Mini. After running in it was quicker than most 998cc
Minis in the area. After getting a decent rolling road session it would
whip the a*se off a standard 1275cc Cooper S. I could also return at least
40mpg and on some occasions in excess of 50mpg, when with a standard engine
(in good tune) I would return from 35 to 40 mpg. [ I drive my vehicles
damned hard before anyone comments on the apparent poor fuel consumption ]
Phil
Paul Everett
> 2. This cam will not work with an autobox, the engine will stall when
> selecting reverse or drive due to the cam having less torque at idle than
> the std one.
This one point alone has made my mind up. OEM 3.9 cam it is. I'm on a
manual atm, but seriously considering converting it to auto, so I would
be daft to fit anything that doesn't work with one.
Thanks,
Nick C
> You say, fit BAC needles. Exactly what air filters, exhaust system
> (including manifolds), compression ratio, distributor advance curve and
> static ignition timing were you running?
>
> I'm stating this because after spending what could be a considerable amount
> of money in modifying the engine it seems ridiculous to me that people don't
> take their pride and joy to a rolling road who specialises in (at the very
> least) the type of carburettors fitted to the engine. The factors stated
> above and probably some I've forgotten about all influence the fuelling and
> ignition advance curve required.
>
> I have learnt this from experience having built 5 modified engines. They
> all seemed very good once run in. After a rolling road session where the
> cam-timing, distributor advance curve and carburettor needles (or jets) were
> optimised, they were unbelievably good. The best case I had was when I
> modified a 998cc Mini. After running in it was quicker than most 998cc
> Minis in the area. After getting a decent rolling road session it would
> whip the a*se off a standard 1275cc Cooper S. I could also return at least
> 40mpg and on some occasions in excess of 50mpg, when with a standard engine
> (in good tune) I would return from 35 to 40 mpg. [ I drive my vehicles
> damned hard before anyone comments on the apparent poor fuel consumption ]
>
> Phil
i totally agree with this post!
you may think your V8 is good at the moment in standard spec - but
give it all new plugs - leads etc and take it to a rolling road and
you may recover the same 10-20bhp you`ll get from this different cam
by just having the original engine setup correctly.
bung a new cam and cone filters and a nice SS exhaust and get the
rolling road people to make you new needles for your SU (yes, some
garages will do this for you out of blank needles) and you`ll be
amazed.
I too had a mini - clubman with a bored out 1340cc, stage 3 head and
twin 1.5 inch SU`s.
It was fast - then i took it for a proper session at a rolling road in
stockport who made two new needles for the carbs to suit the
application perfectly and i went from 85bhp when it went in to 95bhp
when he gave me it back. The difference was awesome in throttle
responce and driveability,
plus it could murder a golf gti from the lights!
torque steer was a nightmare though with the lsd i fitted.
nick c
series 2a `67
wakefield uk
Badger
was about 5 years ago!)
3.5 ltr stiff block with studded mains, 9.75:1cr, piper 270/110 cam and
vernier timing gear, mildly gas flowed heads, inlet manifold matched to
ports, combustion volumes matched, pistons and rods all weight matched
individually, su carbs (obviously), pipercross air filters - cone type, std
110V8 manifolds and big bore system, later replaced with 3.9efi manifolds
and std stainless system. The ignition system was heavily modified, the
static advance being 12 degrees with the max advance stop welded up to limit
the total advance to the same as original, with centrifugal advance starting
just above idle (about 900rpm) and being fully advanced by max torque rpm
(around 2400).
Needle profile was arrived at by very tedious means indeed, set up idle
mixture then carry out plug chops as you would with a 2-stroke at differing
points and loads, eventually building up a picture of where on the needle it
was rich or lean and then referring to the su needle charts to find what I
felt was needed. No rolling roads capable of 4wd in my neck of the woods
(Northern Scotland) and I wasn't putting it on a 2wd road with a prop off
and the diff lock engaged - I'm sure that can't do the transfer box any
good. I eventually found that I was getting very close so ended up modifying
a pair of needles (small lathe, the finest possible emery - micromesh - and
a micrometer) until I was happy then went back to the charts and found that
BAC was as close as was going to make no real odds. Vehicle was weighed at
2550kg (msa licenced rally recovery vehicle), it did 0-60 in roughly13
seconds and at a steady 65 gave 19mpg. It now has an LPG powered 3.9, giving
approx. 210bhp, with only slightly better acceleration figures which is
probably down to the engine's torque curve as opposed to pure bhp, so I
don't think the tuned 3.5 was far off 200ish brake. Badger