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DECIM8

By DECIM8,
in Engines & Forced Induction

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R338OY Veteran

R338OY

Posted
Posted
Good man! You end up using that redline I gave yoU?

Not yet, i'm not sure if there's enough (i think the diff takes 1.7L???) so i was going to get more and do the box and diff together :(

Too bad it won't make me as fast as your new setup :D

Swiper the Fox Grand Master

Swiper the Fox

Posted
Posted (edited)
Hey Gary, we are installing the cams into my car in 2 weeks time, could you quickly describe what "shimming the standard springs" is and does? I've never heard of this and was wondering wether we should be doing this with my standard springs.

Thanks man.

the lifter bucket has a shim inserted in it to set the lifter to cam base circle clearance.

the shim sits between the top of the valve stem and lifter bucket and unless a spring has failed to the point it cannot properly close the valve shut, it (the spring) has zero determination on what shims are selected.

not sure what Gary/Sydneykid is on about

Edited by DiRTgarage
PM-R33 Grand Master

PM-R33

Posted
Posted
the lifter bucket has a shim inserted in it to set the lifter to cam base circle clearance.

the shim sits between the top of the valve stem and lifter bucket and unless a spring has failed to the point it cannot properly close the valve shut, it (the spring) has zero determination on what shims are selected.

not sure what Gary/Sydneykid is on about

Oh ok, thanks for the reply man. Ill see if Gary replies and explains what he ment, hoping these cams go in nice and simple :P

700HP-GTR33 Mentor

700HP-GTR33

Posted
Posted
$400 to install, fair enough.. Wont be grinding as they are direct drop in tomei items.

Nothing is a direct drop in.....

More than likely you will need to spend more

Your springs could need replacing....

http://www.nengun.com/tomei/valve-springs

Your shims may be out after measuring...each of these cost $30+..I know I needed 21

Luckily some where close and we only changed 17

And if your doing it right....you will also need these...

http://www.nengun.com/tomei/cam-bearing-cap-studs

Good luck

Swiper the Fox Grand Master

Swiper the Fox

Posted
Posted
Oh ok, thanks for the reply man. Ill see if Gary replies and explains what he ment, hoping these cams go in nice and simple :P

worn valve seats and/or valves may cause you to run a thinner shim than standard...but always check the clearance when changing camshafts even with the same base circle. Remember the intake will be different to the exhaust when using STD valves.

Adriano Grand Master

Adriano

Posted
Posted

By shimming the spring, you fit a shim/washer at the bottom of the valve spring between it and the head. It increases seat pressure to reduce valve float/bounce, whilst maintaining the same cam/valve tip clearance. You just need to be careful to ensure that you dont go to thick which causes spring bind/fatigue.

It is used very commonly in the cylinder head repair industry, just need to be careful with the measurements.

PM-R33 Grand Master

PM-R33

Posted
Posted
By shimming the spring, you fit a shim/washer at the bottom of the valve spring between it and the head. It increases seat pressure to reduce valve float/bounce, whilst maintaining the same cam/valve tip clearance. You just need to be careful to ensure that you dont go to thick which causes spring bind/fatigue.

It is used very commonly in the cylinder head repair industry, just need to be careful with the measurements.

You reckon any of this is needed if your not going over 9mm lift?

Swiper the Fox Grand Master

Swiper the Fox

Posted
Posted
By shimming the spring, you fit a shim/washer at the bottom of the valve spring between it and the head. It increases seat pressure to reduce valve float/bounce, whilst maintaining the same cam/valve tip clearance. You just need to be careful to ensure that you dont go to thick which causes spring bind/fatigue.

It is used very commonly in the cylinder head repair industry, just need to be careful with the measurements.

on low reving V8 dinosaur engines yes...but given the relatively cheap price of aftermarket springs and the high reving multi valve application this is a process id strongly advise against.

but everyone is entitled to their own ideas. :)

stock springs will be fine to use with 8.5mm lift if they pass a free length, pressure load and squareness test

700HP-GTR33 Mentor

700HP-GTR33

Posted
Posted
cams dont sound fun any more :laugh: would there be a relation to age and replacing these parts? I dont think the stud bearing is needed as its only 8.15 lift from memory correct me if im wrong i forget

You will only know when you open it up...that's the only dis-advantage to after market cams.

As far as what they do when installed....that is quite obvious....you will be very happy when they are dialed in with a tune.

Sydneykid Grand Master

Sydneykid

Posted
Posted
on low reving V8 dinosaur engines yes...but given the relatively cheap price of aftermarket springs and the high reving multi valve application this is a process id strongly advise against.

but everyone is entitled to their own ideas. :laugh:

stock springs will be fine to use with 8.5mm lift if they pass a free length, pressure load and squareness test

My experience with building RB race engines (9 years and over 60 of them) is that all valve springs need shimming. Regardless what brand name is on them, they have minor differences in seat pressure, every head is different. Then you add in the differences in valve seat height accross individual heads and the variations in seating become more obvious. No spring manufacturer could possibly make a spring that is going to have the same seat pressure on every valve in every engine, so to do the job properly you need to shim their bases. We're not talking about thick shims here, less than 1 mm is common, occasionally 2 mm. Sometimes the reverse is required and we machine the spring bases in the head to decrease the seat pressure.

Obviously we aim for a higher level of precision on a race engine, but that doesn't mean the same process isn't followed for a road engine.

Cheers

Gary

DCIEVE Mentor

DCIEVE

Posted
Posted (edited)

Definately recommend tomei studs (per 700hpgtrs post) even for the straight fit cams, makes the install much easier with no risk of stripping the thread in the head when trying to pull the cam down. If the install is being done by a shop with plenty of experience I expect you can do without (but it is cheap insurance).

Edited by DCIEVE
Swiper the Fox Grand Master

Swiper the Fox

Posted
Posted (edited)
My experience with building RB race engines (9 years and over 60 of them) is that all valve springs need shimming. Regardless what brand name is on them, they have minor differences in seat pressure, every head is different. Then you add in the differences in valve seat height accross individual heads and the variations in seating become more obvious. No spring manufacturer could possibly make a spring that is going to have the same seat pressure on every valve in every engine, so to do the job properly you need to shim their bases. We're not talking about thick shims here, less than 1 mm is common, occasionally 2 mm. Sometimes the reverse is required and we machine the spring bases in the head to decrease the seat pressure.

Obviously we aim for a higher level of precision on a race engine, but that doesn't mean the same process isn't followed for a road engine.

Cheers

Gary

as i said...everyone has their own ideas...all the big revving RB race engines built in this country that ive been around and/or involved with (and ive been around a few) have never had this sort of modification...Yes Jap springs that are used in all these engines have always been spot on JUN Tomei etc....

and im talking about 1000hp+ engines revving over 10 000rpm...if they don't require it im bloody sure a street engine wont.

Does that 60 engines include the ones Harris' have built for you or the ones that never *********** and people demanded their ***** back on?

Edited by DiRTgarage
PM-R33 Grand Master

PM-R33

Posted
Posted
as i said...everyone has their own ideas...all the big revving RB race engines built in this country that ive been around and/or involved with (and ive been around a few) have never had this sort of modification...Yes Jap springs that are used in all these engines have always been spot on JUN Tomei etc....

Ok thats good to hear, aslong as the springs are fine (which im hoping they will be) ill drop my cams in and hopefully not have to worry about the shims. Suddenly went from an easy job to a nightmare when uz started talking about $30 shims lol.

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