454 Mag Valve Springs?
 

I'm looking at new heads for my Mark IV 454s. Thinking about Dart p/n DRT-15100112. My engines are stock, no mods. Original cam, flat tappets.

I'm concerned the spring rate may be too high on these new Dart heads. Does anyone know what the stock spring pressure is on Mark IV 454 heads?

Re: 454 Mag Valve Springs?
 

ThirdBird,
What is the year and rating on the original engine?
Bob

Re: 454 Mag Valve Springs?
 

rm,
1989 454/365 horse.

Re: 454 Mag Valve Springs?
 

My book says, and this is without the damper, single spring 24-75584, closed at 1.88"=74-86lbs. open at 1.38"=288-312lbs. Installed at 1.875.

Re: 454 Mag Valve Springs?
 

My heads have dual springs.

Re: 454 Mag Valve Springs?
 

ThirdBird,
That spring is GM part # 3970627
1.487"
105 # seat force @ 1.880"
350 # nose
Stack @ 1.280"
450 #/in rate
Carries a 3964264 retainer
Bob

Re: 454 Mag Valve Springs?
 

Thanks for clarifying that Bob, Ive found that quite a bit of the info in this Merc manual is bogus. Their cam specs for one, Im not surprised the spring info is wrong too. That didnt seem right.

Re: 454 Mag Valve Springs?
 

Formula31,
You are correct, there is a great deal of incorrect information in the Merc manuals including camshaft spec on certain engines. It's my understanding that Merc sometimes issues service bulletins with corrections, but that material goes to dealers.
Bob

Re: 454 Mag Valve Springs?
 

If you're doin new heads, you should just do a new cam at the same time also. Its only a couple hundred $$$ more and a couple hours more work.

Re: 454 Mag Valve Springs?
 

Thanks rm. :cool: