I stumbled across this info last night. (May not be a surprise to some, but it was news to me.)
It appears that the Allante and the 4.9 "export" engine use a taller valve spring, in addition to the steel rocker supports.

According to Rockauto...
The taller (Allante) spring is a Sealed Power VS1551 @ 2.193" free height.

Max Outside Diameter - 1.317
Wire Diameter - 0.181
Coils - 6.9
Closed Height - 1.732
Closed Press - 89.8
Open Height - 1.264
Open Press - 218.5
Type - S

The shorter (Deville) spring is a Sealed Power VS1552 @ 1.949" free height.

Max Outside Diameter - 1.348
Wire Diameter - 0.199
Coils - 6.5
Closed Height - 1.732
Closed Press - 68.9
Open Height - 1.346
Open Press - 211.9
Type - S

It would appear that the Allante spring is spec'd for a higher lift, and has slightly higher open and closed pressures.
Since Rockauto lists the same cam (CS1540) for both engines, I wonder if that implies that the rocker arms are a different ratio, or just that the Allante spring can accommodate a higher lift.

Edit - Rockauto also lists the same rocker arm for both engines, so a different ratio is out.

Regardless, it seems that the Allante springs would be a desirable swap into a 4.9, along with the steel rocker supports. This is assuming you don't need or want to go aftermarket.

Thoughts?

------------------
Raydar
88 Formula IMSA Fastback. 4.9, NVG T550

Praise the Lowered!

[This message has been edited by Raydar (edited 08-31-2011).]

Cool!

That would make them the only stronger drop in replacement springs that I know of. I wish I could pick up a set to try them out.

I wonder if the pressure would be enough for the E303 cam profile that fieroaddiction used? He machined his heads for the SBC springs IIRC.

[This message has been edited by Fieroseverywhere (edited 08-31-2011).]

And one bump.

[This message has been edited by Raydar (edited 09-02-2011).]

Where can these springs be purchaced?

I guess I know what my next mod will be.

quote Originally posted by MaxCubes: ....p.s. ...now if only if I could find the steel rocker supports

Contact Dick@allantesource.com. They have everything when it comes to the Allante.

quote Originally posted by Fieroseverywhere: Contact Dick@allantesource.com. They have everything when it comes to the Allante.

Except that he was going to send me a memory module to read the Allanta bin out of.
When it didn't show up after several weeks, I called him. He said that he had gotten busy and that it would go out the next day.
That was over a year ago. Still haven't gotten it. Fortunately, I found the bin elsewhere.

Admittedly, he wasn't going to charge me, even though I offered. Still...

CRAP !

..... I just attempted to purchase those valve springs (vs1551) and it says that they are NO LONGER AVAILABLE

.....

Sorry about that.

I'm guessing that there is something similar (or better) available, though.
It's not like these are for a super high performance application, or anything.

I was told by Bud aldeman that the valvetrain on my '91 allante motor is 1 of like 250 limited edition allante valvetrains made.. it sits in the garage, waiting to be used one day. Obvious differences: thicker pushrods, different rocker arms, individual rocker supports instead of the "bridged" rocker supports normally seen on each set of rockers, and possible spring upgrade, but i havent disturbed the valvetrain to take a spring measurement:

[This message has been edited by stickpony (edited 10-18-2011).]

THAT is way interesting. Is that a 4.5? What year?
I wonder what the specs are on the cam. (Rockauto lists the same cam for the Allante and the 4.9.)

quote Originally posted by stickpony: I was told by Bud aldeman that the valvetrain on my '91 allante motor is 1 of like 250 limited edition allante valvetrains made.. it sits in the garage, waiting to be used one day. Obvious differences: thicker pushrods, different rocker arms, individual rocker supports instead of the "bridged" rocker supports normally seen on each set of rockers, and possible spring upgrade, but i havent disturbed the valvetrain to take a spring measurement:

You know. You really should "disturb" that valve train. Check everything out and get the specs (or part numbers if possible). Another motor like that may never be found. I would be nice to have it documented.

Did Bud mention what he thought the redline would be?

[This message has been edited by Fieroseverywhere (edited 10-18-2011).]

There is an amazing number of valve spring types avaliable the GM engines, just mix and match with the proper tyep of seats to get what you need. I used the pink stripe ls6 type for a 3.1 build with a top hat type seal and seat. You can find most any seat and open pressure you want if you just look through the types. Larry


12589774 Valve Springs
• Beehive style springs
• Standard L76/L92 springs
• 1.800" installed height @ 90# pressure
• 1.300" @ 264# pressure
• Max lift .530"

12586484 Valve Springs • Beehive style springs
• Standard LS6/LS3 springs
• 1.800" installed height @ 90# pressure
• 1.250" @ 295# pressure
• Max lift .570"