Rover V8 cam timing, retard by 2°, any difference?

ratwing · Post by **ratwing** » Mon Oct 05, 2015 1:16 pm

The engine is a 4.6 with a 3.9 camshaft, Peter Burgess Econotune heads with 41.4mm inlet/35.5mm exhaust valves, 1¾" SU carbs and a cam chain set with a choice of 3 positions, 2° retarded, 0° and 2° advanced.
I don't know the compression ratio but it'll be higher because the block and heads have been skimmed.
Its a light vehicle, I'm guessing probably under ½ ton, and I was wondering if its worth retarding the cam 2°?
Is this likely to make a noticeable difference to the driveability?

stevieturbo · Post by **stevieturbo** » Tue Oct 06, 2015 11:57 am

I really doubt you'd feel a difference either way, and likely over time the chain would stretch by a couple of degrees or so anyway.

kiwicar · Post by **kiwicar** » Tue Oct 06, 2015 8:32 pm

Hi
As Stevie says you probably would not notice any changes, on an engine in a higher state of tune retarding the cam a little would bring it into the power band a little sooner but flattening the power peak and advancing you would probably get a couple more BHP, especially if the engine was short on timing. However on a rover you won't get enough difference to notice, especially it the cam chain had more than 10K miles on it.
best regards
Mike

mgbv8 · Post by **mgbv8** » Tue Oct 06, 2015 8:37 pm

I've tried both on my enghines with the cam gear and the difference on the dyno was not really noticeable to be honest. The three dyno runs were on different days with different atmospheric conditons and the cam on all 3 settings seemed to have a variance of a few hp at most. Not much noticeable on the rpm vs power and torque either?

And on the Drag strip it ran the same numbers on any setting ?

Maybe its a fuel economy thing??

My engines are a bit de tuned to run nitrous. And the cam setting made no difference to me

SimpleSimon · Post by **SimpleSimon** » Tue Oct 06, 2015 8:38 pm

kiwicar wrote:Hi
As Stevie says you probably would not notice any changes, on an engine in a higher state of tune retarding the cam a little would bring it into the power band a little sooner but flattening the power peak and advancing you would probably get a couple more BHP, especially if the engine was short on timing. However on a rover you won't get enough difference to notice, especially it the cam chain had more than 10K miles on it.
best regards
Mike

You have that back to front but we knew what you meant

and agree with a stock cam you wont notice

ratwing · Post by **ratwing** » Wed Oct 07, 2015 4:48 am

Cheers for the replies guys, I mainly went for a roller chain because they're supposed to last longer before wearing/stretching but I might as well go for the middle position if its not really going to make any difference then.

DEVONMAN · Post by **DEVONMAN** » Wed Oct 07, 2015 9:10 am

ratwing wrote:Cheers for the replies guys, I mainly went for a roller chain because they're supposed to last longer before wearing/stretching but I might as well go for the middle position if its not really going to make any difference then.

Given manufacturing tolerances of both the chain set and the cam, you may well find that the timing is in any case 1 degree out either way.

Denis

DaveEFI · Post by **DaveEFI** » Wed Oct 07, 2015 12:30 pm

DEVONMAN wrote:
ratwing wrote:Cheers for the replies guys, I mainly went for a roller chain because they're supposed to last longer before wearing/stretching but I might as well go for the middle position if its not really going to make any difference then.
Given manufacturing tolerances of both the chain set and the cam, you may well find that the timing is in any case 1 degree out either way.

Denis

Makes you wonder just how accurately the cam is made if they can't get simple things like the keyway(s) in the correct position?

Different timing on each valve and cylinder?

Surely if you can grind 16 lobes - all different - on a cam accurately, the rest would be trivial? At least until things wear. But then so do the cam lobes.

kiwicar · Post by **kiwicar** » Wed Oct 07, 2015 1:58 pm

SimpleSimon wrote:
kiwicar wrote:Hi
As Stevie says you probably would not notice any changes, on an engine in a higher state of tune retarding the cam a little would bring it into the power band a little sooner but flattening the power peak and advancing you would probably get a couple more BHP, especially if the engine was short on timing. However on a rover you won't get enough difference to notice, especially it the cam chain had more than 10K miles on it.
best regards
Mike
You have that back to front but we knew what you meant and agree with a stock cam you wont notice

If you say so.

Mike