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Motor box after rebuild

Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=50557
Printed Date: July-04-2024 at 2:02pm


Topic: Motor box after rebuild
Posted By: beebe
Subject: Motor box after rebuild
Date Posted: April-12-2022 at 11:10pm
My motor box won't fully close after having the engine rebuilt. Any ideas? Video explanation here:

https://www.youtube.com/watch?v=Rz1AshaURnU


Replies:
Posted By: KENO
Date Posted: April-13-2022 at 7:19am
If you go to page 10 of the link below you'll find PCM's measurements of about everything you can think of on a 351w with the exhaust manifolds installed.

For example 27.5 inches wide at the top of the manifolds outside edge to outside edge.

Then if you have a different width, you can measure manifolds, risers to see if it's due to them or the  aluminum heads.

http://www.correctcraftfan.com/downloads/PCM_Owners_Manual_Ford_and_Chevy.pdf" rel="nofollow - link

Posted By: beebe
Date Posted: April-13-2022 at 1:39pm
Nice resource. Thanks! It turns out my manifolds and risers are an inch further apart than they should be. But as far as I can tell the new manifolds are the same size and shape as the old ones. So I think it must be that the heads are a different size/shape.

I guess I need to find an alternative aluminum trim for the bottom of the motor box that is slightly taller.

Thanks!

Posted By: GottaSki
Date Posted: April-14-2022 at 12:44pm
A machine shop could resurface the manifolds,  and cant them inward 2 degrees or so, 
that would get you a half inch each


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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."

River Rat to Mole

Posted By: JoeinNY
Date Posted: April-14-2022 at 1:41pm
Edit - watched the video and the risers are not different- More information on the heads and other changes would be helpful, there are aftermarket designs with raised exhaust port locations for better exhaust flow. Agree that a good machine shop putting on an angle would be a solid option if they are stock valve covers you would likely have enough clearance to tilt in. I would put on of the old manifolds back on and confirm it also hits the box and maybe have it cut at an angle to test before adjusting the new ones

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http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001
1967 Mustang 302 "Decoy"
http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video

Posted By: KENO
Date Posted: April-15-2022 at 7:27pm
I measured across a pair of PCM manifolds on a 351w today and got closer to 28 inches than 27 1/2 like the manual says, just so you have an idea. It was about 27 7/8

I not sure I'd machine an angle into the mating face of the flanges because then the 8 bolts holding the manifold to the head won't sit flat on the backside of the flange and would kinda affect their holding power unless the backside of the flange got machined to the same angle and that isn't an easy area to reach

Posted By: MourningWood
Date Posted: April-15-2022 at 9:58pm
I experienced this when I installed some aftermarket manifolds on some Edelbrock heads. Not sure which was the culprit, but the motor box wouldn't 'settle' on the floor. Out came my grinder. I 'shaved' a bit off each side of the motor box. Boom. Done. Much cheaper, and the motor box is quite 'thick' in that area. 

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1994 Ski Nautique "Riot"
1964 Dunphy X-55 "One 'N Dun"

'I measured twice, cut three times, and it's still too short!"


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