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Old 05-25-2004, 05:48 PM
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Question on Aftermarket valves & machining heads

Hey everyone,

I feel like I have a thousand things going with this project all at once.

Next week I'm going to NY and I'm going to take my BBC heads to my old shop teacher and he's going to open them up for bigger valves. I've got some good castings to do this. (#353049)
2.06 intake/1.72 exhaust.

going to open them up to 2.19 intake/1.88 exhaust...from what I read this is the hot ticket for using stock heads...and for the time being I think I can get away cheaper than buying new castings.

Anyways, here's the questions.

#1-If I buy some Manley valves to fit the bigger size, will I need new retainers or will the stock ones fit?

#2-Won't I need the valves before the heads leave the shop so I can have them lapped (and possibly ground) to seat right?
(pretty sure I do...but just checking)

I might end up needing new seats all the way around because I'm told that some of the seats don't cut very well...so if that's the case would I still need to get the valves ground?

thanks

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Old 05-25-2004, 06:47 PM
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unstable,

Lets see if i can answer all the questions without going back to see what they were.

Yes the shop teacher will need to have the valves so he can grind the seats so the mating angles meet near the center of the valve.

I did this same stuff to a set of 340 heads to put on a 383 and yes you will need all new seats. I used stelite so the car could run on unleaded without any worries.

I am thinking you will want the new retainers and new springs too. These valves are heavier so will need the extra help to get them closed.

As for "lapping" the valves I think this is sort of old school. I do not teach my guys to do this since hard seats in heads came out. Now for lawn mower engines we lap them so we get good compression right from the first pull of the rope.

(I had to look)

And lastly, yes have the new valves ground. Just in case they were bent or scratched from the parts house.

Have Fun
Scholman
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Old 05-25-2004, 07:23 PM
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You will only need seats on the ex. side for the unleaded gas .You will be removing so much materail from the int. side that you should have no problem getting a seat on the head.



mike
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Old 05-25-2004, 07:41 PM
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NARBI

I,am a cylinder head rebuilder and most of your info is wrong.

1) On the older heads when you cut for a ex. seat weather it is for a bigger valve or not the cast iron usely will still sink on a every day driver.

2)we don,t install seats just because they cut easier. I try if at all possible not to put seats in.

3)there is no proven fact that the factory seats will flow better in fact most big block chevy heads the seats are to big for the valve.

4)why would you want to increase the bowl area on a Big block chevy head when they are to big from the factory allready. The bowl to seat ratio is way off on the factory heads in most cases the need to be down sized.



mike

Last edited by Rogers Performance; 05-25-2004 at 08:05 PM.
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Old 05-25-2004, 08:01 PM
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I have to agree with Roger, even though he IS a year younger than me.



As far as hard exhaust seat are concerned, I recommend them highly. I just have seen too many ex. seats sunk deeply too quickly to advise otherwise. If a customer wants otherwise, I make sure that he knows the possible consequences and signs the work order with a statement to that effect.

After opening the seats on BBC heads to the larger valves, a simple blending with a die grinder is all that is needed, keeping the short side radius generous.
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Old 05-25-2004, 08:04 PM
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Ohhhhhhhh Boy,,,,,,Here we go! LOL
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Old 05-25-2004, 10:13 PM
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I stick with what i said and i,am not going to get draged into a pissing match.




mike
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Old 05-26-2004, 06:41 AM
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lol. thanks guys. I figured I would need the valves on hand. The heads are already good for unleaded, so I shouldn't need new seats UNLESS there's no room to cut them.

this guy knows what he's doing so I wouldn't worry about him installing seats when he doesn't need to. That's the only reason I'm taking these heads 500 miles back to him...because I trust that he won't screw me over and have me do needless crap. He teaches shop but he also runs a machine shop in his off hours. He's been in the business for years and years...real cool guy. Definitely one of the teachers you remember from High School.

Anyhow, someone mentioned the valves being heavier. I wonder, although I figure it's neglible---do I need new springs as well? lol. Watch, after I finish with this, I could have purchased some Brodix heads.
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Old 05-26-2004, 06:57 AM
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heads

The one thing i would add is( if i am not mistaken) the 049 big block heads have the hardened exhaust seats...

I will guarantee that mike know 100 percent what he is talking about when it comes to heads.......So listen to him!!!! No wizzing match required.. L.O.l.

Keith
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Old 05-26-2004, 08:50 AM
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hardened means it runs unleaded right? But does that add an additional level of PAIN when it comes to cutting?
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