CAMSHAFT TIMING

[Patrick M]

Hi Blokes,
I am currently doing a top end rebuild on the old 3.5 V8 I, rebuilt heads, rocker gear, camshaft, cam followers, timing chain and gears to both crankshaft and cam.
I have in the past on other V8,s used camshafts with a slightly different grind and dialed them in with a two degree advance this made a very noticeable (in a positive way) difference to the performance of the engine.
With this engine though, I am replacing the camshaft with a standard grind unit but was wondering whether I should put a two degree advance or retard on it when setting it up and is it worthwhile with a standard camshaft grind?
If anyone has done this can you please give me the benefit of your experience?

Regadrs:-
Patrick M

[justinc]

If using a std cam profile, then leave at std marks. However it wouldn't hurt to check actual lift with a degree wheel, and may be advantageous to adjust if the specs are out due to mass production tolerances. My previous experience has always been successful leaving standard cam timing alone.

[Patrick M]

If using a std cam profile, then leave at std marks. However it wouldn't hurt to check actual lift with a degree wheel, and may be advantageous to adjust if the specs are out due to mass production tolerances. My previous experience has always been successful leaving standard cam timing alone.

Hi Justin,
Thanks for your reply, you are spot on with your comment on mass production and specs becoming distorted during the manufacturing process and yes I intended dialing the new camshaft in just in case.
I have dialed in camshafts on a number of occasions but it has been a few years since doing so, I still know the procedure and steps to go through but are not to sure of the amount of lift that the standard camshaft has to be set at on TDC.
I was wondering if you have the specs handy and if you do would you mind sharing them with me?

Regards:-
Patrick M

[justinc]

Hi Justin,
Thanks for your reply, you are spot on with your comment on mass production and specs becoming distorted during the manufacturing process and yes I intended dialing the new camshaft in just in case.
I have dialed in camshafts on a number of occasions but it has been a few years since doing so, I still know the procedure and steps to go through but are not to sure of the amount of lift that the standard camshaft has to be set at on TDC.
I was wondering if you have the specs handy and if you do would you mind sharing them with me?

Regards:-
Patrick M

Hi, I'm sorry no I haven't, it has been many years since I've fitted a cam to these, too!. The EFI cam is the best profile for allround use, maybe Google 1986 on 3.5 EFI cam specs?

[rick130]

And a FWIW, retarding the cam timing moves the power and torque up the rev range, advancing it moves it down.

[rover-56]

Well, Rick's experience doesn't match mine.
I have often advanced the camshaft 2-3 deg on various engines to move the torque peak up a bit.
Most recently when I rebuilt the S3 2.6 I advanced the camshaft 3 deg. (took a whole day of fiddling) and the difference is very noticeable, you can hear and feel it. The std timing puts the torque peak at 1500rpm (where Rover says it is)
Advancing 3 deg. puts it at2200, and you can feel and hear it in the exhaust note on hills.
Also advancing gives you a bit of insurance for when the chain and sprockets wear a bit, the timing comes back closer to std.
Terry

[Blknight.aus]

Well, Rick's experience doesn't match mine.
I have often advanced the camshaft 2-3 deg on various engines to move the torque peak up a bit.
Most recently when I rebuilt the S3 2.6 I advanced the camshaft 3 deg. (took a whole day of fiddling) and the difference is very noticeable, you can hear and feel it. The std timing puts the torque peak at 1500rpm (where Rover says it is)
Advancing 3 deg. puts it at2200, and you can feel and hear it in the exhaust note on hills.
Also advancing gives you a bit of insurance for when the chain and sprockets wear a bit, the timing comes back closer to std.
Terry

this^^^

mr used to have a couple of nice cams for the 3,5/9. might be worth a ring.

[Patrick M]

Well, Rick's experience doesn't match mine.
I have often advanced the camshaft 2-3 deg on various engines to move the torque peak up a bit.
Most recently when I rebuilt the S3 2.6 I advanced the camshaft 3 deg. (took a whole day of fiddling) and the difference is very noticeable, you can hear and feel it. The std timing puts the torque peak at 1500rpm (where Rover says it is)
Advancing 3 deg. puts it at2200, and you can feel and hear it in the exhaust note on hills.
Also advancing gives you a bit of insurance for when the chain and sprockets wear a bit, the timing comes back closer to std.
Terry

Yep I have found the same thing with the cams that I have dialed in and advanced them.

[Patrick M]

Hi Blokes,
Has anyone out there got the specs for dialing in a standard 3.5 EFI cam, I have done the Google thing and come up with nothing.
Regards:-
Patrick M.

[rick130]

Well, Rick's experience doesn't match mine.
I have often advanced the camshaft 2-3 deg on various engines to move the torque peak up a bit.
Most recently when I rebuilt the S3 2.6 I advanced the camshaft 3 deg. (took a whole day of fiddling) and the difference is very noticeable, you can hear and feel it. The std timing puts the torque peak at 1500rpm (where Rover says it is)
Advancing 3 deg. puts it at2200, and you can feel and hear it in the exhaust note on hills.
Also advancing gives you a bit of insurance for when the chain and sprockets wear a bit, the timing comes back closer to std.
Terry
this^^^

mr used to have a couple of nice cams for the 3,5/9. might be worth a ring.Funny, every race engine we built (Ford 1600) where the stock cam was forced on us by regs (Ford GT cam) we'd retard the cam timing, the more retarded, the more it moved the torque peak up the rev range.
Might depend on lobe centres


Road engines I've always run at stock timing.

[rover-56]

The Rover 2.6 is a bit unusual compared with more modern engines with the peak at low rpm.
With the 3.5 the peak is around 2500 already so you might not want to take it much higher.
Lowering the torque peak speed on an engine like the 3.5 could give an apparent increase in torque at lower rpm?
I fitted a "towing" cam to an '82 RR I once had which lowered the peak and worked well for towing a heavy trailer but there was not much torque available over 3000. It was a bit disappointing for normal road driving.
I guess it depends what you want to do with it, the std cam timing is a reasonable compromise for a RR.
Terry

[Patrick M]

Hi Blokes,
Oooops, and Doh,
I was wrong, I checked up on what the scribes say about Advance and Retarding the cam timing and they say that Advancing the timing shifts the power torque curve down the rev range and the other way obviously when retarding it, so apologies to all who may have been a bit confused about my comment when agreeing with Rover-56.
Anyway I still have not got those specs that I need.
Regards:-
Patrick M.

[PhilipA]

OK , tuning Rover V8 engins gives camshaft as

30/75/68/37

But no lift figures.
This is given as used in P6B,SD1 ,TR8,and Rover Vitesse so is probably for non emission RR.

OK how to power tune Rover V8s gives lift as0.39in/9.9MM in all cases

Regards PhilipA
BTW my understanding is that 3.9 injection cam is a 3.5 injection cam with 5degrees advance.
You may find that a non emission cam performs as well as all 3.5 injection and 3.9 cams were `emission cams.

[Blknight.aus]

Well, Rick's experience doesn't match mine.
I have often advanced the camshaft 2-3 deg on various engines to move the torque peak up a bit.
Most recently when I rebuilt the S3 2.6 I advanced the camshaft 3 deg. (took a whole day of fiddling) and the difference is very noticeable, you can hear and feel it. The std timing puts the torque peak at 1500rpm (where Rover says it is)
Advancing 3 deg. puts it at2200, and you can feel and hear it in the exhaust note on hills.
Also advancing gives you a bit of insurance for when the chain and sprockets wear a bit, the timing comes back closer to std.
Terry


Funny, every race engine we built (Ford 1600) where the stock cam was forced on us by regs (Ford GT cam) we'd retard the cam timing, the more retarded, the more it moved the torque peak up the rev range.
Might depend on lobe centres


Road engines I've always run at stock timing.

not surprising,

what needs to be watched is the initial cam profiling, theres a range of degrees a certain amount of overlap and lift can be tweaked around in to good effect, depending on a few other engine factors what effect shifting the cam timing on stock lobes has will vary, Rover engines have all followed a more or less "British" style build of being setup to run at lower speeds so the cams and runners are set up to provide the torque down low, Advancing the cam timing gets things happening earlier on and so restricts engine performance at the low end but at the higher end when fluid velocity becomes more effective you gain it back at the overlap. the downside of this is fuel consumption goes up, not quite the British ethos in automotive design called for at the time.

the americans on the other hand tend to go about it the otherway happy to have faster revving engines with bigger fuel consumptions. so unsurprisingly with their cams optimised for this with different overlap timings and lifts they react differently to the British standard form.

[Patrick M]

Hi Blokes,
WOW, thanks heaps, I am really happy with your responses and it is comforting to know everyone has contributed with something positive.
Regards:-
Patrick M.