[TVR383]

Hi,

I have used brodix 8 aluminium heads(1987 model)for my 383. I had the heads redone and checked at the time of the engine rebuilt. I do have an oil consuming problem and can't find the problem...recently two persons I have shown pictures of the heads without the covers asked me about the large sized springs...So i have just checked lunati web site to see what size/type of springs they recommend to use with the cam I have wich is a 1004 hydraulic flat tappet . I have on hands a spec sheet as checked by the builder and it goes as follows: (springs )Iskenderian model 235 D heights installed: 1.750=126 pounds and 1.250 =280 pounds,coil bend:1.100. They are double springs.This is what's on the motor actually.


When I refer to the lunati web site here is their recommended springs for my cam: Single spring,installed height is same for both intake exhaust:1.750 pressure are:110 and 345 at 1.230 and their coil bind is:1.160.This is what should the heads have as far springs are concerned.

So the springs I am using are different from their recommendations in terms of pressure,double compare to singles,and installation height it seems I have two different one for exhaust one for intake while they want one only and am having a slightly different coil bind:1.10 compared to 1.160.

Could this explain my oil burning??
If not what other consequences could it have??

thanks, Ronald.

[Rick WI]

The spring won't cause an oil burning issue but the spring you have does not have nearly the pressure recommended by the cam manufacturer. The result would be valve float, unless that cam lifts out higher than .590. Then you'd have a heck of a coilbind issue which would show up right away as major carnage.

[Steve karch]

To the best of my recollection, valve springs wont cause oil consumption but if they are weak will cause performance issues, ie valve float. Side loading of the valve through incorrect rocker geometery or using stock rockers on a high lift cam can cause valve guide wear which can contribute to oil consumption. Have you tried running the engine without a pcv, just 2 breather and compare consumption.

[TVR383]

Originally Posted by Rick WI

The spring won't cause an oil burning issue but the spring you have does not have nearly the pressure recommended by the cam manufacturer. The result would be valve float, unless that cam lifts out higher than .590. Then you'd have a heck of a coilbind issue which would show up right away as major carnage.

The cam lift is around .480 with 1.5 rockers.

Could you be more specific about the valve floating issue? Would this affect the performance at only really high revs. like over 5,000 rpms or so or could I indeed have really lousy performance all the way through the RPMs right of the line?
thanks,Ronald.

[BOBCRMAN@aol.com]

Insufficient spring pressure will only rear it's ugly head at high rpm. But, the springs you are using should be ok for that cam. Your seat pressure is at max for a hydraulic cam and that cam lift is easy on springs.

I would look at an improper intake gasket seal. Sucking oil up on the underside of the manifold. I've seen it happen many times with aftermkt aluminum heads.. Or possibly a bad valve seal install.

[TVR383]

Originally Posted by Steve karch

To the best of my recollection, valve springs wont cause oil consumption but if they are weak will cause performance issues, ie valve float. Side loading of the valve through incorrect rocker geometery or using stock rockers on a high lift cam can cause valve guide wear which can contribute to oil consumption. Have you tried running the engine without a pcv, just 2 breather and compare consumption.

Steve,

Yes I have tried the breathers only without the PCV and after only 30 miles oil was getting out the covers through or around the breathers grommets..so I came back to the PCV...I have a leak down tester and just can't wait to check those cylinders.
Ronald.

[Rick WI]

Bob covered the spring quetion. You do seem on the right track though with the leakdown test. It' going to run like crap with an oil and gas mixture in the combustion chamber.

Not a lot of places it can be caused by, intake gasket, rings, guides. With the breather issue I'd have to guess rings/ blowby issue.