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049 oval port on 396

General engine tech -- Drag Racing to Circle Track

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cpmotors
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Re: 049 oval port on 396

Post by cpmotors » Mon Sep 30, 2019 5:00 pm

tenxal wrote:
Mon Sep 30, 2019 7:40 am
gmrocket wrote:
Sun Sep 29, 2019 4:21 pm
Dont worry about the valve shrouding on the cyl wall...very little flow goes that away,,its majority biased to the center of the cyl along the common wall of the port. You do not need a bigger exh valve than you have..its big enough.
Agree 100%.
X3
The 2.19 is worth power, the 1.72 can handle more than most people give it credit for ( assuming you are doing the proper sizing and shaping of the SSR and throat area for both valves)
Pete Graves
CPMotorworks,Inc.
Custom Engine Machining
Cylinder Head Fixture for Vertical / Surfacing Mills

F-BIRD'88
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Re: 049 oval port on 396

Post by F-BIRD'88 » Mon Sep 30, 2019 5:26 pm

But both the new 2.14" in and the 1.84" ex then allows the porting meat to create the valve job and bowl throat contour you want.. 396 friendly.

tenxal
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Re: 049 oval port on 396

Post by tenxal » Mon Sep 30, 2019 5:45 pm

A little back side work on the 2.07's and you'll be in good shape. The 1.72's will be fine as is. Take a look at what the rules restricted engines that have to use stock valve sizes and no porting make for power (think NHRA Stock Eliminator).

And the whole bore notching thing is more urban legend than anything. :wink:

TLK396
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Re: 049 oval port on 396

Post by TLK396 » Tue Oct 01, 2019 6:06 pm

Thanks for all the input. I think I will stick with the small valves for the 396. If I build a larger street motor later I will definitely up the valve size. It would be interesting to flow these heads with a small bore fixture on the flow bench, say 4.125 and compare numbers with a larger bore fixture 4.350, with both the small and large valves. Thanks again to everyone's input.

F-BIRD'88
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Re: 049 oval port on 396

Post by F-BIRD'88 » Tue Oct 01, 2019 7:45 pm

You're on the right track.. The best thing to do for serious power on a 396 is upgrade to a bigger 454-468-496 based engine.

1980RS
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Re: 049 oval port on 396

Post by 1980RS » Tue Oct 01, 2019 10:05 pm

TLK396 wrote:
Tue Oct 01, 2019 6:06 pm
Thanks for all the input. I think I will stick with the small valves for the 396. If I build a larger street motor later I will definitely up the valve size. It would be interesting to flow these heads with a small bore fixture on the flow bench, say 4.125 and compare numbers with a larger bore fixture 4.350, with both the small and large valves. Thanks again to everyone's input.
You are going to like the way the 049 heads work on the 396. I did it back in the late 80's and the car was a lot quicker and faster with the change just make sure you do the best valve job you can afford.

levisnteeshirt
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Re: 049 oval port on 396

Post by levisnteeshirt » Wed Oct 02, 2019 12:22 am

What piston gave you 10.5-1 with that huge chamber

TLK396
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Re: 049 oval port on 396

Post by TLK396 » Wed Oct 02, 2019 2:41 pm

I have a 396/375 style piston with a 39cc dome, at .008 in the hole with a .018 compressed steel shim head gasket. Should be in the ballpark +/-.

tenxal
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Re: 049 oval port on 396

Post by tenxal » Wed Oct 02, 2019 6:15 pm

TLK396 wrote:
Wed Oct 02, 2019 2:41 pm
I have a 396/375 style piston with a 39cc dome, at .008 in the hole with a .018 compressed steel shim head gasket.
Pretty tight on the total deck.....

TLK396
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Re: 049 oval port on 396

Post by TLK396 » Thu Oct 03, 2019 11:43 am

Yes, probably should go with a composite head gasket and sacrifice a little compression in this case.

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