Oem Valve Tolerance

[dwdsm]

So I was considering to squeak a little more power out of the 6bolt. I was interested in taking the redline somewhere between 8-8,500k. I have the old comp 101200 cam with an all stock head. Turbo is a pte 3051 so it should like the extra 1,000 rpm to boost. My question is do the stock valves take the added pressure on the stem? Anyone have the oem valves pull apart? I'm worried about the added 75lbs of pressure on the tips.

Oem specs.
Closed position
pressure & Length (intalled specs)
[email protected] Valve closed

Open position
Pressure & length Valve Open
[email protected]

BC valve spring specs.
Spring Pressure: BC1100 Seat: 1.550" @ 84 lbs
Open: 1.000" @ 235 lbs
Coil Bind: 0.935"

 

[BogusSVO]

Valve float is what snaps a valve, it is an uncontrolled slam on the valve seat that will pop the head of the valve off.

I have installed BC1100 springs on stock valves with out issue.

http://www.dsmtuners.com/forums/newbie-forum/341209-4g63t-valve-spring-info.html

 

[dwdsm]

Valve float is what snaps a valve, it is an uncontrolled slam on the valve seat that will pop the head of the valve off.

I have installed BC1100 springs on stock valves with out issue.

http://www.dsmtuners.com/forums/newbie-forum/341209-4g63t-valve-spring-info.html

Thanks for the quick reply. So float even if there is no contact with the piston can cause the oem valves to seperate? I should be safe with the BC singles since my cams are not aggressive and I keep the boost reasonable.
Thanks,
Dave

 

[dwdsm]

So I am getting ready to install these springs and retainers soon and I start to read all these stories of people not recomending the bc springs and retainers. What is the deal? I have a comp "272" cam and was hoping to go to 8500 on this setup (if the airflow allows me to). Is the combo appropriate for one another? Is there a write up somewhere on how to properly install, measure, and shim this spring combo. I have a few hundred dollar credit with cornwell tools so I'll buy what ever I need to properly measure. Bogussvo if you will help me I will do a write up with photos and give you credit!

 

[BogusSVO]

Most of the BC failures I have read have been guys running a cam(Kelfords) too big for the BC1100 spring.

I know I have not done a write up on measuring and installing of valve springs.

As far as what tool to get, the common spring installed height gauge will not work/fit on a 4g head.

I had to make the set up that I use for this.

 

[daonlyillwiz]

the comp 272 cams are trash and their powerband stops around 7400-7500 so ive been told by comp them selves. I WAS running them up until today in my head my setup was:

Manley springs + Ti retainers, stock valves, stock lifters and rockers.

Im on a sc6152 turbo @30psi and im experiencing no valve float what so ever however like i said their power band does not go too far because they arent as aggressive as other cams out there. Currently the ones to have are the GSC S2 cams which are what i upgraded to along with GSC beehives. I would say not to look into it too much and just put it on, the turbo you have is smaller than mine i dont see a problem.

 

[dwdsm]

Well I'll check out my oem book and look at the procedure in there. I would like to see a write up from an experienced vet however think that I can find enough information to do it. One of my good friends has a few nice micrometers for his work so I'll check with him. I agree that the comp cams are not aggressive but overall I am happy with the car and just wanted to fine tune a few things. If the power drops off then I guess I won't be taking the redline up to the planned 8k but the extra guard against float will be worth it.

 

[dwdsm]

Starting the head today and will be installing springs and checking their installed height to see where I'm at with them. If they need shimmed I'll have to order those and finish them at a later date. To check the coil bind I simply place a feeler gauge 360 degrees arond the spring at full lift correct? This obviously will be after the spring is shimmed if that is needed. Also any tricks to get a proper valve spring height reading? Measuring from head surface to retainer and then subtracting out the thickness of the shims and retainer sound like it would be accurate enough?

 

[BogusSVO]

Measure from the the top of the factory spring seat to the bottom of the retainer. This will be your installed height.

Take the full lift of the cam plus .060

so if full lift is .410

.410 + .060 = .470

Intalled height is 1.550

1.550 - .470 =1.080

The spring should compress this much and not be in spring bind.

Spring bind is where all the coils just touch.

 

[dwdsm]

Bogussvo what do you use to shim your springs? Do you buy the tomei shims or do you just get some appropriate sized washers?

 

[BogusSVO]

I use VSI (Valve spring Inserts) they come in 3 thicknesses, .060, .030, .015

 

[dwdsm]

Is there anywhere I could order those online?

 

[dwdsm]

Everything is installed.
They range from 1.58 to 1.55
So I should shim anything above 1.55?
I think of how little .03 is and it's crazy that it could cause valve float