[tjlowery]

I have #48 heads and I am not sure which rockers and valves and springs to use.
In particular I am looking for which length of Valves, 1.52 or 1.65 rocker arms, and which valve springs??

This is my first rebuild on heads -- so needless to say i am not all that familiar with which parts to use

I also have a set of 4X heads -- would they be better? Can I use the valves from those? If so what length would they be -- theyy are stock

Thanks

[tjlowery]

I have #48 heads and I am not sure which rockers and valves and springs to use.
In particular I am looking for which length of Valves, 1.52 or 1.65 rocker arms, and which valve springs??

This is my first rebuild on heads -- so needless to say i am not all that familiar with which parts to use

I also have a set of 4X heads -- would they be better? Can I use the valves from those? If so what length would they be -- theyy are stock

Thanks

[67cruiser]

always buy cam with springs to match,its the only way to go!! Any mods to the motor?? just stay with 1.5,s looking for some h.p. then go 1.65 on the exhaust only or all of em.

[tjlowery]

I got the motor with the cam already installed -- as far as mods go -- its been bored .30, and has a xe186 ibelieve for the cam (Crane Cams)

[Will]

How you build the heads depends on what you are trying to accomplish performance-wise.

Which heads you use, either #48 or 4X depends on the size of the engine, how much compression you can live with, and which 4X heads you have. There are several varieties of 4X heads, some of which are useless for anything but a low compression 455 application. Find the secondary stamping on them and we can tell you what they are. Here's a pic that shows the location of the secondary stamping:



What 67cruiser said about cam determining which valvesprings to use is true. You need to make sure the springs are right for the cam in terms of seat and open pressures and that they have enough travel before coilbind to handle the lift the cam produces. Therefore, you need to figure out for sure which cam you have, and it sounds like you might be a bit confused there. 'XE' series cams are generally made by Comp Cams. I don't know of any cams designated 'XE' made by crane. Nor do I know of a cam by either manufacturer with '186' in it's designation.

There are several ways to figure out what cam you have, but the most straightforward would be to pull it out of the engine and look for identifying numbers stamped into the ends of the cam blank. Once you know for sure what cam you have, and that it's the right cam for what you want to do with your engine, then you can make choices about which heads, valves, springs, rockers, etc. to use.

As far as swapping valves between those heads, the 4X valves will be shorter, and possibly smaller diameter than the #48 valves. Therefore, you can't use the 4X valves in the #48 heads. However, you could use thhe #48 valves in the 4X heads if you wanted to achieve more installed height for a taller spring. And, if the 4X heads are small valve, having the seats cut for the larger valves should be easy enough for the shop doing the work and produces a fresh, brand-new seat which is something you don't often get in older heads.


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'72 Formula 400 Lucerne Blue, Blue Deluxe interior - My first car!
'73 Firebird 400/4-speed Black on Black, mix & match.

[tjlowery]

thanks for the help -- I'll double check the cam -- like i said i am going off of what i was told.

If i were to go with the 1.65 roller rockers what length of valves should I use?

Also what is the difference between the 48's and the 4X's. I've heard that the 48's are better is that true?

[Will]

Whether the 48 is "better" than the 4X comes down to which 4X variety you have and what you're trying to accomplish.

All 2.11" intake valve Pontiac heads flow pretty much the same in stock form. If you're not having them ported then which one is "best" becomes a question of which one offers the right chamber size for your application. And, when it comes to 4X heads, you also need to figure out what valve sizes they have and whether they are pressed or screw-in studs. 4X heads were available in several different configurations, as I mentioned, so we need to get the secondary stamp code to know what they are.

I can't answer your 1.65 rocker question. It depends on what cam you use and how much lift you'll end up with. Stock length valves might be just fine, Crower makes a spring that works with stock installed heights and is good up to at least .530" lift. This is why it's important to know which cam you have, as you need to know how much lift you'll end up with or you'll break things in the valvetrain.


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'72 Formula 400 Lucerne Blue, Blue Deluxe interior - My first car!
'73 Firebird 400/4-speed Black on Black, mix & match.

[tjlowery]

Thanks I'll get that info!!!

Things are starting to make more sense now!

[tjlowery]

The 4x heads are 4x-4h, I'll get the cam number this weekend.

What are the spec on the 4x-4h heads?? are they beter than the #48's?

[mgonzo44]

The specs are: 1.96 intake and 1.66 exaust. The chambers are 98cc's. They are used on 350 and 400's, probably pressed studs.

Mike