Scott's dart
Well-Known Member
Why on earth do they recomend a valve spring that can't possibly fit on a stock head!? I realize maybe I should have done some measuring but I didn't think I could go wrong with the manufacturers recommendations!
Lunatic valve springs frustration!
- Thread starter Scott's dart
- Start date
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Can a double spring fit a stock head w/o machining?
Nope. Heads have to be cut for double springs.
These aren’t OE parts, if you want a performance cam you need performance springs, and that means doing the machining necessary to make it work. It’s not Lunati, any bigger cam needs higher spring pressures. Just how that works.
pishta
I know I'm right....
What is interference, ID over valve seal?
Usually no. There are some cases though.
running into same problem.. have a comp xe274 that requires double springs. im trying to find a single spring that will work so i dont have to machine nothing
PRH
Well-Known Member
I’m guessing someone didn’t read the footnotes.
For a BB Mopar, all the listings I see for dual springs have footnote 1.
For a BB Mopar, all the listings I see for dual springs have footnote 1.
Demonic
Well-Known Member
Post 4. Answer right there. You're going with a dual spring with a damper. When they engineered the spring seats back in 67, that is not what they were thinking of, nor over .500 lift.
80fbody
Well-Known Member
There's a big single that should work. Possibly minor machining. Can't remember the number. It'll work for a street car to about .500" and keeping the rpm down around 6k. Otherwise just pop the heads, have them freshened for $3-$400 and cut the pockets and guides for dual springs. Be done with it. Common mod. Can even do it yourself if you think your heads are good and have a drill press and some skill. They sell the cutters that locate off the guide.
Don’t do it. Just machine the heads and use the right springs. The guy that did the porting on the heads for my 340 told me I would be fine running single springs with my Lunati cam, I believed him because I didn’t want to spend more money machining the heads and installing the required positive seals. And he was a long time machinist and Mopar guy so I believed him.
Guess what? I destroyed a set of rockers, because that guy didn’t know crap about my cam or what it needed (despite the fact that I told him exactly what I was using). The singles he said would work didn’t have all the same spring pressure specs, and I destroyed a set of rockers before I figured it out.
You already have the right springs and hardware, just have the heads done to use the right stuff.
Scott's dart
Well-Known Member
Thanks for setting me straight, you guys are right, I should've looked into it further, I'll just have to get the work done!
Oh I should have looked for that! I ordered off of summit racing and didn't see anything there about machine work being necessary! Thanks though!
PRH
Well-Known Member
Unfortunately, even when you read everything...... you can still end up with the wrong stuff.
The cam companies should put a disclaimer in the catalogs stating that the “recommended components” are listed for the popular versions of the factory heads only.
(And usually...... the most generic version of a particular head.
Not a somewhat oddball version....... like.......a 318/360 SBM truck engine that uses exhaust rotators and very short springs on the exhaust.)
Many times aftermarket heads can have installed heights that are different enough from the factory heads that the recommended parts list ends up being completely wrong, along with the fact that they often use valves with different stem diameters than OE.
Case in point....... I have some SB Ford heads here.
Lunati roller cam was bought along with the matching component kit.
Motor was put together and had made passes at the track....... with the results being less than expected.
Heads show up here, I don’t know how or why the heads have the springs they have on them....... but I pull one off, measure the installed height, test spring...... it’s about 132lbs on the seat.
For a .640 SRC. Not good.
They are aftermarket heads.
The installed height is .130 taller than what the spring is designed for.
The spring is designed for the stock heads.
It’s the wrong spring for the new heads.
Sometimes....... you need to assess what you have before ordering the parts.
Like, the SM SBM heads.
They have at least .100” more installed height than a stock SBM head with a stock valve/retainer/locks.
So, when you look in the Comp/Lunati/Howard’s catalog for the recommended springs to go along with the cam you’re going to buy....... just know that the recommended components are based on you having stock heads........not aftermarket heads that have a taller installed height.
Anytime you replace something on the heads(or the heads themselves) that isn’t an exact duplicate of the piece you’re replacing....... just assume it will have an impact on other components...... until/unless you verify it’s doesn’t.
That means springs, retainers, locks, valves.......and even the castings themselves.
As Jim said....... it helps if you’re smarter than your heads.
The cam companies should put a disclaimer in the catalogs stating that the “recommended components” are listed for the popular versions of the factory heads only.
(And usually...... the most generic version of a particular head.
Not a somewhat oddball version....... like.......a 318/360 SBM truck engine that uses exhaust rotators and very short springs on the exhaust.)
Many times aftermarket heads can have installed heights that are different enough from the factory heads that the recommended parts list ends up being completely wrong, along with the fact that they often use valves with different stem diameters than OE.
Case in point....... I have some SB Ford heads here.
Lunati roller cam was bought along with the matching component kit.
Motor was put together and had made passes at the track....... with the results being less than expected.
Heads show up here, I don’t know how or why the heads have the springs they have on them....... but I pull one off, measure the installed height, test spring...... it’s about 132lbs on the seat.
For a .640 SRC. Not good.
They are aftermarket heads.
The installed height is .130 taller than what the spring is designed for.
The spring is designed for the stock heads.
It’s the wrong spring for the new heads.
Sometimes....... you need to assess what you have before ordering the parts.
Like, the SM SBM heads.
They have at least .100” more installed height than a stock SBM head with a stock valve/retainer/locks.
So, when you look in the Comp/Lunati/Howard’s catalog for the recommended springs to go along with the cam you’re going to buy....... just know that the recommended components are based on you having stock heads........not aftermarket heads that have a taller installed height.
Anytime you replace something on the heads(or the heads themselves) that isn’t an exact duplicate of the piece you’re replacing....... just assume it will have an impact on other components...... until/unless you verify it’s doesn’t.
That means springs, retainers, locks, valves.......and even the castings themselves.
As Jim said....... it helps if you’re smarter than your heads.
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Purchase a cutter and install it in your hand drill.
Also purchase a valve spring mic. Now you can check your valve spring height.
I made a wooden plate, two plywood rectangles out together with the bottom cut out for room for the nuts to attach to the bolts that run through the head to attach the head and hold it there.
I C clamped it to my bench. Ran the cutter in the drill gun until I cleared the obstruction and lightly shaved the outer spring seat.
I realize iron is way harder than aluminum. It’ll take time to do each one. But you can do it.
Also purchase a valve spring mic. Now you can check your valve spring height.
I made a wooden plate, two plywood rectangles out together with the bottom cut out for room for the nuts to attach to the bolts that run through the head to attach the head and hold it there.
I C clamped it to my bench. Ran the cutter in the drill gun until I cleared the obstruction and lightly shaved the outer spring seat.
I realize iron is way harder than aluminum. It’ll take time to do each one. But you can do it.
Scott's dart
Well-Known Member
Thanks for all the responses! I'll take a look at machining costs and those cutters and valve spring mic and see what the better option is! Any advice on what positive valve stem seal to buy and any other things to do to the heads before putting them back on? I didn't want to spend a lot of money into them because I planned on buying some trick flows when I the exchange rate gets better or I become rich! Lol
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