Broken Valve Spring in new 4.6 L V8

Gram · Post by **Gram** » Mon Jun 21, 2010 2:39 pm

Hallo..everyone

I wanted to hear if anyone can help me with my questions.

I have an 4.6 L V8 (short engine from John Eales) with Peter Burgess Heads with standard valve, guides and spirngs. The Camshaft also from John Eales.

I did not build the engine, but bought the car car recently with the new engine in it.

Yesterday a spring broke in 2 places and dropped a valve...

The whole engine is no more than 1500 miles old..

My question is if it is a common problem for 4.6 L? maybee because of to high revs..or if I was just unluckly..?

Regards Troels

kokkolanpoika · Post by **kokkolanpoika** » Mon Jun 21, 2010 6:08 pm

http://www.v8forum.co.uk/forum/viewtopic.php?t=7461

I have got same proplem, but i have got realsteel "performance" spring..

CastleMGBV8 · Post by **CastleMGBV8** » Sat Jun 26, 2010 5:24 pm

Troels,

What camshaft is fitted? if the lift exceeds the available compressed height of the standard springs then this could have caused the problem.

Also with a higher lift cam you normall have to machine 100thou. off the top of the valve guides otherwise the spring retainer can hit the top of the guide.

Inspect everthing carefully including the cam.

Kevin.

Post by **katanaman** » Mon Jun 28, 2010 5:40 pm

need more info like the spec of the cam. As others have said if the springs and guides dont match the lift of the cam your in trouble.

mgbv8 · Post by **mgbv8** » Mon Jun 28, 2010 8:50 pm

If you have already done 1500 miles I dont think it will be excess lift. Excess lift will normally clip the oil seals and bend a pushrod in instantly. Or at least once the whole lot has warmed up and expanded in a couple of minutes.

Maybe you have the correct guide height but the springs are just binding by a few thou. I can see this causing spring trouble. But I would still say that the effect of this would cause a rod to bend first.

If the lift is high and the springs are ok but the valve top hits the guide, the result again should be a bent rod??

Strange??

CastleMGBV8 · Post by **CastleMGBV8** » Wed Jun 30, 2010 11:12 am

Without full information it's just guesswork but performance cam? and standard springs and high RPM? would point to the valve spring being stressed beyond their normal limit with resultant failure, but as I said I'm just guessing.

Kevin.