porting and polishing
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From: e-burg
porting and polishing
hey guys was looking for some advice and tips from the more experianced. im going to port and polish the heads of my 351m and was wondering if jb weld would be good enough to block the thermactor holes. ive herd its really good stuff but i dont know if it will hold up to the heat 
. i was also thinking of putting it on the manifold side of the passage b/c it might be more likely to stay maybe not. also any tips or tricks for doing the port and polish job in general would be great. thanx in advance
. i was also thinking of putting it on the manifold side of the passage b/c it might be more likely to stay maybe not. also any tips or tricks for doing the port and polish job in general would be great. thanx in advance
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From: in a house
JB weld is good to 600* F but I wouldn't trust using it. especially on the intake side where it could break free and do some damage. you shouldn't need it anyway.
do a search for "no more thermactor holes" from the past couple of weeks and you will see my post explained how I plugged them up using set screws.
do a search for "no more thermactor holes" from the past couple of weeks and you will see my post explained how I plugged them up using set screws.
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From: Eastern Pa
A good primer for porting can be found here, http://www.sa-motorsports.com/diyport.shtm. I followed alot of the methods there and seemed to work real well.
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From: e-burg
yeah ive looked that over several times and it the jb weld really couldnt do any damage b/c all the port does is circulate exhaust through the intake manifold to help with warm up. but if its only good to 600* ill have to look for somthing else
thanx
thanx
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From: Stanton,Ne
One thing I've always heard and read about the 355 series motors is that when you port and polish is remember that these engines flow on the topside of the runners. You want to leave the bottoms alone to get your air fuel swirl. Also exhaust is more crucial than intake for power.
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From: e-burg
could u explain that a little more i really dont know what u mean buy flow on the top side more. and yeah i knew the exhaust side was more important but thanx for the info
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From: Stanton,Ne
What I mean is that as the air fuel mix goes into the cylinders it rides on the top inside part of the intake runner. Just like a fast running river going around a bend has a stronger current on the outside of the bend and a slower current on the inside. When you polish the top of the intake runner it smooths out the flo, but you need to leave a certain amount of roughness on the bottom to help swirl the mix to get a good burn. I hope this helps
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The exhaust actually flows backward back into the chamber at high lifts and flow. When I had my bench I could usually find a vacuum at the top of the hump and flow would suck air backward up the big slope, over the hill and down into the cylinder. I think that's why port plates are so effective, especially on the 4bbl heads.
If you really need to plug the thermactor ports, find an early set of 351C heads that aren't drilled. The exhaust ports are much more open around the guide and supposedly flow quite a bit more.
If you really need to plug the thermactor ports, find an early set of 351C heads that aren't drilled. The exhaust ports are much more open around the guide and supposedly flow quite a bit more.
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From: e-burg
ok just some info so i dont and u guys dont get confused. i have 2bbl heads. i plan to grind the the thermactor humps down to flat. and i might just use a pre 72 valley pan that doesnt have the openings for the ex. crossover. and what are port plates ive never heard of these. thanx again ive learned soooooo much