port and polish
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Senior User
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From: e-burg
port and polish
i have a 351m and was going to do a basic port and polish job on it but i got to looking at the intake gaskets next to the head and there really isnt a hole lot of material that can be taken out plus i dont feal alot of imperfections so is it really worth all the hassel to do it. plus if i do a port and polish will i have to do a total rebuild on the heads or just replace anything that needs to be replaced. well thanx for the help
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Joined: Aug 2004
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From: Huntsville, AL
i think a port and polish is always worth the money. you would only need to get the worn out parts replaced. i would have the springs, valves, and guides checked out. locks and retainers are pretty cheap if they are worn.
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From: Eastern Pa
On the intake side you just want to get out any flash or lines from casting marks and cleand it up. You don't want to polish the intake side and the head should remain slightly larger than the intake runners. On the exhaust side you want to get rid of the thermactor bump. open the bowls a little and polish it to a mirror like finish. Also polish the chamber. http://www.sa-motorsports.com/diyport.shtm Try this link for some pointers.
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From: e-burg
yeah ive been there and read that artical. i was also wondering if i could rid the heads of the exhaust recirculation that goes back into the intake. i know that helps cold starts but by how much and would i pick up any power by getting rid of this. and what do u mean by the head needing to stay bigger than the intake runners i thought that u where suposed to gasket match both the head and the intake
Last edited by good 'ol ford; Nov 1, 2004 at 05:51 PM.
Posting Legend
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Please read some of the old posts on gasket matching. DO NOT gasket match. I would love to catch the numskull that started that idea. He must have been some dumb Cheby guy that had no idea about what he was doing... LOL!!! Unfortunately the idea has been perpetuated in magazines by writers that have no idea either. I guess I will be able to catch him right after I catch the guy that invented the alarm clock. I hear that was some Monk in Europe tho... 
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From: e-burg
does anyone know about the exhaust recirculation or is it a good thing to keep or what. i know that hot air makes for less preformace so i want to get rid of it if i can but i dont know how much it helps me in the colder months
any info u guys have would be great. and any info on how to get rid of it would also help
thanx
any info u guys have would be great. and any info on how to get rid of it would also help
thanx
Posting Legend
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There are a bunch of posts here on larger air filter boxes and heated or cold air intakes. I block off the exhaust passage and run a heated air intake.
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From: PacNW
EGR is an emissions issue and the 351M/400 engines came calibrated from the factory to run with it so if you eliminate it entirely you run the risk of more pinging unless you adjust the fuel mixture at the carb accordingly.
The other "connection" between the exhaust and the intake is the A.I.R. recirculation passages in the exhaust ports which lead up to the large port on the top front of the intake. In this case fresh air is pumped into the exhaust ports (2 per head) to aid the catalytic convertor combustion process.
The other "connection" between the exhaust and the intake is the A.I.R. recirculation passages in the exhaust ports which lead up to the large port on the top front of the intake. In this case fresh air is pumped into the exhaust ports (2 per head) to aid the catalytic convertor combustion process.
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If you want to block off the exhaust passage in the intake and keep the EGR, since the EGR does not hurt the engine performance. Use the parts from a 351W engine. You would need to do a few modifications but the general parts will work.
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From: e-burg
hey was looking around at old port and polish posts and i still dont quite gett what im suposed to do if i understand every thing right i should not touch the manifold and i want the head slightly larger than the manifold and the gasket slightly larger than that is this right or do i have everything messed up
thanx for the help
thanx for the help
Posting Legend
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It looks like you have it right.
Always go from a smaller opening to a bigger one. You never want a protruding shelf or a gasket protruding into the opening. Parts never bolt up the same twice, and gasket hole sizes and locations vary from lot to lot and even from gasket to gasket, never mind from one manufacturer to another. This variance is only one reason not to gasket match. Some manifolds and the Edelbrock and Weiand in particular are optimized for a flow path so you do not want to alter them. Altering the manifolds will void their warranty and also usually makes them perform worse than out of box condition.
Always go from a smaller opening to a bigger one. You never want a protruding shelf or a gasket protruding into the opening. Parts never bolt up the same twice, and gasket hole sizes and locations vary from lot to lot and even from gasket to gasket, never mind from one manufacturer to another. This variance is only one reason not to gasket match. Some manifolds and the Edelbrock and Weiand in particular are optimized for a flow path so you do not want to alter them. Altering the manifolds will void their warranty and also usually makes them perform worse than out of box condition.