Head Work

[Barney]

Well :)
I decided to replace my valve springs and camshaft.
After talking to performance valve spring manufactures and performance workshops, they all said the engine wont rev or perform well at high RPM because of valve float. This means, as the engine revs and the cam turns the rockers are surposed to run on the cam, but. if you are running high boost at high RPM the rockers start to loose contact with the cam, causing the engine to loose timing and hence the power drops off and the engine feels like it wont rev.

so after removing the valve gear and cam, i notice the are score marks on the cam and head. so the head has to come off :(

Now it gets good 8)
I work for a oil company, who sponsor a Drag car in WA. It just so happens the the owner of the drag car (Aaron Deery), also owns a engine recon Workshop :) and has a keen interest in mitsubishi's, he has a scorpion 2.6 Peter Wherret turbo system with methanol injection.

Aaron recomends that i drop the off the head, intake manifold, exhaust manifold and throttle body, so he can rebuild the head port match the manifolds and port and polish the head on there flow bench, FREE :D
The only thing i have to pay for is the parts

I will be replacing the Cam with a crow cam (as they are crow agents) and also heavier valve springs.

The reason i post this in the technical forum is because,
What have people experienced after having the head ported and polished?And what head gasket is best to use?

ASHLY

[pcuser51]

:) ASHLY do you think this valve float is the reason we are all (well neally
all)droping power and revs between 4500 to 5000. if this is the case all
we nead is double valve springs or stronger springs,this will be intersting
keep posted after you get back togeather

[Cookiemonster]

Nxtime is running double valve springs but still hits a wall at 4500rpm.

[NXTIME]

And I don't have a problem with the engine revving out. It rev;s easily to 6,700. The problem that Darryl and I are having is the power stopping at about 4,500 rpm and holding til 5,300 then dropping off until redline. It is more than likely the cam. Darryl is in the process of fitting a new cam now so we shall see what the effect of this will be.

[Barney]

from what i am being told, you must use heavier valve springs if you are after more power. other wise you will have valve float.

I will let you guys know how i go

What about the head gasket? are there any performance ones? mine was on its way out

ASHLY

[Alspos]

I bought one of these. Shiny carbon based one. Better than regular gasket. No problems so far. Oh yeah, it was a valve regrind kit, has the gaskets and rubber bits etc as well as valve stem seals.

Durapro Gaskets
GS-DH061T*D
Valve Regrind Set
Mitsubishi 4

Got it from www.vpw.com.au for about the same price that retail would sell me a normal one.

[Starion VR4]

Having worked at Camshaft engineering for 11 Yrs, and helped John Whittiker from Brisbane Turbo and Tuning with the cams for his race starion, let me part with a little information.
1: The STD springs will run with the STD cam easely to 5500RPM, by putting heaver valve springs on a few bad things happen, the contact point is increased, by how much you say, if you increase the fully open pressure by 30lbs, the point contact increases by 40-70% resulting in more load to turn everything and increaseing wear!
2: if you want more power up top YOU WILL LOOSE POWER/TORQUE DOWN LOW! if it was that easy, then Mitsubishi would have done it in the first place, every manafacture want there engine to have the most power for fuel used, they spend millions to designe the cam in the first place.
3: The only reason you may need different valve springs, is if you have increased the lift of the cam lobe, and the springs Coil Bind( spring compresses to solid mass) or you want more RPM.
if you get valve float it sounds very mechanical trashing and engine may back fire, but in reality you will of run out of useable power before this point. In short the best comp. is to open the lobe centres, use the same profile. 8)

[davidbek95]

Hi dude,John Whittiker,he the man for starion,as 90% of my mod are his ideas on work done at his shop.
regards david :beer

[Barney]

Hi David

I have spoken to you B4 about the cam. But mine is stuffed as its heavly scored, the head and valve gear are also scored. :(

The workshop is cutting up an old head to see where improvments can be made. then the original head will be flowed and match ported to the manifolds. looks like they are also fitting Magna valves, which are 3 - 4 larger than the starion ones.

the valve springs were very week. i could push the valve in easily with my hands.

Crow cams have come back to us with a recomendation, i will get the details next week. i do know that the opening duration is 10deg more.

i did stress that i didn't want to loose low down torque. i was then advised that torque will be higher than B4 also lower in the revs :?

another thing is that the new intercooler will be fitted by then, so i will see what happens.

I will view the dyno readout once tuned

ASHLY