Quesion about big block heads?
Thread Starter
Racer
Joined: Jun 2001
Posts: 289
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From: Duluth GA
Quesion about big block heads?
Currently in process of rebuilding my matching numbers 427 L36 and the machine shop said that my heads are the small chamber oval port.
The number on the heads is 3931063. I have already had them enlarge
the intakes to 2.19 and exhaust to 1.88. Should any additional work be
done to these heads to maximixe performance? :confused:
The number on the heads is 3931063. I have already had them enlarge
the intakes to 2.19 and exhaust to 1.88. Should any additional work be
done to these heads to maximixe performance? :confused:
Racer
Joined: Apr 2001
Posts: 446
Likes: 62
From: Sugar Land Texas
Re: Quesion about big block heads? (Pat 69BigBlock)
Have you changed specs on the cam or pistions? (higher performance) If so, you might look at the chambers and exhaust ports for better combustion and flow. You really should contact, if you haven't already, some head people, to see how far you should go with them, considering your new set up.
If you stayed with the stock cam and piston specs, you might see some performance gain with what you have already done and a fresh motor rebuild. I can say from experience, that too big heads are just as bad as too small heads.
If you stayed with the stock cam and piston specs, you might see some performance gain with what you have already done and a fresh motor rebuild. I can say from experience, that too big heads are just as bad as too small heads.
Racer
Joined: Oct 2000
Posts: 329
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From: Ft Walton Bch FL
Re: Quesion about big block heads? (Pat 69BigBlock)
You didn't mention whether they put in hardened exhaust seats or not; definitely a should-do. Also, some mild valve pocket clean-up and port matching would gain a little hp too. Those are some good heads. I had a set on my 468 in my dually, and it would boil the tires.
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Re: Quesion about big block heads? (Pat 69BigBlock)
I don't know what process they used, but you might want to look at how close the valve is to the chamber wall. Many times flow actually decreases with large valves because they become shrouded too much.
The Serdi machines do a good job of taking care of this when the seats are cut. You might want to really check how well the new area under the valve in the bowl is blended into the port. Make sure you clean it all up or you won't get any benefit, maybe even lose some flow.
I doubt you're using a monster cam, and I don't know what pistons you are using, but you really need to check the "radial" clearance in the valve pocket. The lo-HP pistons get pretty tight in the valve pocket with 2.19's and with a healthy cam can barely touch the edge of the valve eventually causing it to fail.
Otherwise sounds like you're on track!
Jim
The Serdi machines do a good job of taking care of this when the seats are cut. You might want to really check how well the new area under the valve in the bowl is blended into the port. Make sure you clean it all up or you won't get any benefit, maybe even lose some flow.
I doubt you're using a monster cam, and I don't know what pistons you are using, but you really need to check the "radial" clearance in the valve pocket. The lo-HP pistons get pretty tight in the valve pocket with 2.19's and with a healthy cam can barely touch the edge of the valve eventually causing it to fail.
Otherwise sounds like you're on track!
Jim
