The V8 Owners Forum -

Hi guys, newbie here. I usually frequent PH but answers to this question are somewhat limited.

I have a 4.6 in a TVR with various mods and have recentely rebuilt it with a solid cam, lifters and adjustable pushrods.

I have bored out the guide holes for the rods in the head and all seems as it should be.

I have set the clearances to 6-7 thou on the heal of the cam by using this method suggested.

http://www.centuryperformance.com/adjus ... g-149.html

When starting cold, the tappet noise is acceptable but when warm isn't, imho.

How noisey/quiet should this setup be?

Hi
in referance to your link.
That reads like someone is trying to make a simple job complicated. I've been adjusting tappets since I was about 10 and never found a problem with it, it is a simple job and does not really have that much effect provided you are carefull and stay in a sensible range of clearances.

However a couple of comments, 6-7 thou cold is too tight, 20 to 25 is the normal range (read cam spec sheet to check) I would treat 15 thou as an absolute minimum, use the adjustment order in the sticky on here, and put the feeler gauge between the rocker and the valve top (not quite sure where you are measuring).
I presume you are using a mechanical flet tappet cam here ? ?
I think you may be hearing blow past a slightly open valve, not tappet noise because when warm the valves are partially open.
Personally I would get rockers with adjusters for a set up using a mechanical cam, adjustable push rods are not really stable enough to adjust acuratly, you need too many pairs of hands to do it accuratly with them.
Best regards
Mike

Hello Peter

Right, I admit it!

I stripped off the rocker boxes last night after running the engine for 2-3 minutes and not being happy with the sound.

I had set the clearences at 6-7 thou and when warm, they had increased to approx 9-10 thou just as a few people had said.

Anyhoo, the more important thing is, one was loose, (keep it to yourself, I couldn't stand the embarresment on PH!).

Now all checked and reset it is queter but not like a hydraulic!

I suppose running solid, you just have to accept that.

You mention adjustable rockers for the Rover V8, any recommendations?

Chilliman wrote:Hello Peter

Hi Richard .

The rocker to valve clearance got bigger when warm!

How does that work....

Shouldnt it get smaller as things heat up and expand?

mgbv8 wrote:The rocker to valve clearance got bigger when warm!

How does that work....

Shouldnt it get smaller as things heat up and expand?

The block grows in height and with it being ali it grows more than than the steel pushrod and valve stems.

sidecar wrote:

mgbv8 wrote:The rocker to valve clearance got bigger when warm!

How does that work....

Shouldnt it get smaller as things heat up and expand?

The block grows in height and with it being ali it grows more than than the steel pushrod and valve stems.

Exactly, so why not set them at 0 or thereabouts?

They aren't quiet at 6-7 thou as I have just had my head under the bonnet this last hour looking for a possible air leak as it idles at 1600 rpm!

Any suggestions?

Hi Peter, because if you set them to 0 you would have no buffer whatsoever for higher differing/expansion rates the end result burnt valves you would also have a lack of lubrication between tappet & camlobe + your running outside of the cam designers profile glad you found your major source of noise

sidecar wrote:

mgbv8 wrote:The rocker to valve clearance got bigger when warm!

How does that work....

Shouldnt it get smaller as things heat up and expand?

The block grows in height and with it being ali it grows more than than the steel pushrod and valve stems.

However the valve train components are operating at a higher temperature than the block . . . as a result the valve clearances do close up when the engine gets warm.
Still doesn't get around the fact that 6-7 thou is far too tight!
Best regrads
Mike

kiwicar wrote:

sidecar wrote:

mgbv8 wrote:The rocker to valve clearance got bigger when warm!

How does that work....

Shouldnt it get smaller as things heat up and expand?

The block grows in height and with it being ali it grows more than than the steel pushrod and valve stems.

However the valve train components are operating at a higher temperature than the block . . . as a result the valve clearances do close up when the engine gets warm.
Still doesn't get around the fact that 6-7 thou is far too tight!
Best regrads
Mike

Fair enough but I would have thought that only the valve would get hotter than the block, the pushrod must be around the same temperature give or take 10 degrees. (unless the oil is absolutely boiling!)

Remember the rockers reverse the direction of the applied force to the opposite of the block expansion. So although the pushrod may expand roughly the same as the block, the valve expansion will tend to close up any clearance.

Comparing the difference between cold and warm is going to confuse the thinking about which parts are expanding relative to each others.
The recommended settings are determined by the cam/engine designers, keeping in mind the highest valve temperature when the engine is running full pelt. Checking the clearances when the engine has stopped and the valves have dissipated their heat to the seats will not give a true reading of the minimum gaps likely to occur when running.

Theoretically, the inlets will run cooler and usually have smaller gaps.

Never run tighter than the makers recommendation has always been my rule.

The Rover has hydraulics as standard to satisfy the market's need for a quiet engine and once you deviate from this with a solid cam , you have got to expect and put up with some cam noise.

Cheers Denis

I have been using Real Steels M238 cam for about 4 years now (on my second one) and have experimented with clearances. The cam sheet says 0.022 measured hot.
This is very noisy indeed. I have ended up using cold clearances of 0.010 for the inlet and 0.012 for the exhaust. The car is driven absoluteley flat out on track and doesnt show any signs of valves not closing fully. Its still quite noisy when warm but I think that is to be expected. I check them regularly and they dont seem to change much.

Mark

Good to know that they don't change much.

I set mine at 7 thou cold on the heal of the cam as reccomended by Rob of V8 Developments who build a lot of RV8 engines.

Still a bit tappetty but to be expected.

Haven't really given it the beans since set up to see if it all settles down as I have been solving other minor issues and it keeps hissing down!