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Old 08-24-2008, 04:13 PM
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Mismatched heads

A couple weeks ago I picked up a single dart head on ebay super cheap since it was a single head.

Last week I went to go pickup a balancer at a guys shop and he had a whole set but one was just blown to #### (scrap metal). Gave me the good one for free. Now, they are similar heads the only difference being one has has some minor chamber work done and had the valve guides cut significantly smaller for more flow. I havnt CC'ed them but I figure the chambers are about 2cc bigger and the intake ports about 10cc bigger.

Will I run into any problems running these on my sbc400? I can rework the chambers on one set but I have to get this engine together and running perfect in 6 days so I dont wanna spend hours on the ports. Thanks.

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Old 08-24-2008, 04:56 PM
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If you were class racing it would need to be mathced on a street strip car you will never notice it.
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Old 08-24-2008, 05:58 PM
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If the one bank of cylinders was pullin' harder than the other, it might go around corners better. Could be the ultimate oval track speed secret.
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Old 08-24-2008, 06:45 PM
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Quote:
Originally Posted by F-BIRD'88
If the one bank of cylinders was pullin' harder than the other, it might go around corners better. Could be the ultimate oval track speed secret.
Haha. Thanks I'll bolt em on. They are replacing my "diy ported 305 heads on a 400"
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Old 08-24-2008, 06:54 PM
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Quote:
Originally Posted by Nsomnia
Haha. Thanks I'll bolt em on. They are replacing my "diy ported 305 heads on a 400"
I have a good bit of experience with DIY modified 305 heads and a good bit of 400 SBC experience. What is the problems you're seeing with the 305 heads on your 400? (Not to say you won;t like the Dart heads.)
Maybe I can help.
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Old 08-24-2008, 10:26 PM
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I already had a post and we discussed the possabilities.

I cut down the valve guides, tried to put bias towards the spark plug and really unshrouded the valves since im working with a 4.125 bore as well as smoothing the short side radius and such. Also got 1.94's and 1.6's But dont think they will be worth it.
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Old 08-24-2008, 10:31 PM
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Can you post a pic of the ports/bowls?
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Old 08-24-2008, 11:28 PM
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It is always best to match your ports on a high horsepower engine.
That being said, a DUAL PLANE intake is such that it incorporates both short runners (horspower) & long runners (torque)
If I were you & running a true dual plane intake I'd put the stock unported head on the long runner side & the modified head on the HP short runner side.

Also if I were you & building a Horsepower engine that will do better all things being equal (open plenium intake) I'd not rush a job that isn't complete.
I've "slapped together" many an engine for whatever reason & was always unsatisfied for having done so later on when it was in use.

I guess it wouldn't hurt to try it. There's lots of good running engines out there that have LARGE cc Variances from cylinder to cylinder due to carbon buildup, valve recession, 1 cylinder leaking more than another, and so on and so forth.

It wont run "perfectly" but it wont run like trash either.
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Old 08-24-2008, 11:44 PM
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Quote:
Originally Posted by jbvcw71
If I were you & running a true dual plane intake I'd put the stock unported head on the long runner side & the modified head on the HP short runner side.
Now thats great advice, never thought about that.

Dont have pics of the finished work. Only one picture after a few hours.
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