porting c9oe 351w heads exhaust bump

[Rindelmach1 14]

I got some time on my hands and a 69 mach 1 with original 351w 4brrl engine.  I do not want to change the original c9oe heads but would like the satisfaction of using my own elbow grease to find some hidden horsepower.  Has anyone grinded away the exhaust hump (aka thermactor hump, egr hump) on these heads and can let me know if they noticed a performance gain?  

[lanky 44]

While I haven't done this, everything I've read says there is power to get from thermactor removal. Mostly ppl think it's not worth it because it takes a lot of time. Imo I bet it would be worth 20 crank HP, potentially more depending on how far you go. 

People say not to touch the CC's, remove the humps, and port match for good results. 

[Ridge Runner 1,112]

I have done several ,be careful not to go through the roof when removing ,a good port match ,exhaust and intake  and bump removal will increase power ,so will larger valves ,polish the exhaust ports but do not polish the intake port ,just blend it 

[1969_Mach1 333]

I did my 1969 C9OE 351W heads like Ridge Runner mentioned.  It took a couple of weeks for a couple hours a day after work.  On the exhaust I removed the thermactor hump on the roof of the ports, port matched them to my header gaskets, smoothed and polished the ports as best I could.  On the intake I merely port matched them to the intake gaskets I am using, Fel Pro 1250S-3. That took very little effort because the intake ports on the C9OE heads are fairly large to begin with.  The machine shop then installed 1.94"  intake, 1.60" exhaust valves, and screw in rocker arm studs.  I'm happy with them.  Motor seems to run good. 

[hotrod69boss 3]

Damn Ridge is there anything you cannot do. I do believe you would tackle any project. Most of us are just jealous and wish we had  a set  of brass ones like yours. I think I can hear yours clanging together all the way out here in Texas

[Ridge Runner 1,112]

I was lucky enough to be able to hang our with some of the old time drag racers ,the area i live in was into racing big time ,went to work for a couple of off road race teams from 83 - 97 ,you pick up a few things ,cage building has to be the most fun .

You need a good burr ,a cheap one just wont cut it ,it will wear out fast . They are not cheap ,but you will have a good one for a long time ,i have ported many 289 302 351 and some 390 428s and mine is still good ,a paper roll and dowel is also needed ,good paper rolls are not cheap either . Wear a dust mask ,gloves and safety glasses ,metal shavings go every where 

[barnett468 418]

13 hours ago, Rindelmach1 said:

I got some time on my hands and a 69 mach 1 with original 351w 4brrl engine.  I do not want to change the original c9oe heads but would like the satisfaction of using my own elbow grease to find some hidden horsepower.  Has anyone grinded away the exhaust hump (aka thermactor hump, egr hump) on these heads and can let me know if they noticed a performance gain?  

removing the bump alone will do very little if you have stock exhaust manifolds, and won't do a whole lot more if you have headers, but i prefer to remove it on mild performance engines.

since you have the heads off, i would determine the compression and increase it some if it is warranted for your particular app. i would also check the deck height of the pistons and possibly use a thin head gasket from cometic to improve the quench/squish clearance to reduce the potential for detonation.

 

 

 

[1969_Mach1 333]

That is a good point about the stock exhaust manifolds.  Aside from merely fitting, they are terrible.  I use JBA headers on my 351W.

[Vicfreg 771]

These are good heads, I have used them on the past on a 289, they were modified by an old drag racer who chain smoked and spent about a week at night grinding on them.    Here is an old Ford Muscle article with a decent comparison on a couple options with the '69 heads.    1969 mach 1 had the right idea with the larger valves, makes a difference....

https://www.fordmuscle.com/archives/2000/05/heads/index1.php

On my '68 302, I used a set of cast Iron GT-40 heads from a Ford Lightning.   Cheap and great performance.  Has O-ring head and gaskets to accommodate future supercharger......

[barnett468 418]

by the time you spend the money to have them fully ported and large valves installed, you could have spent a little bit more and just bought aluminum heads, which are not only a on lighter, and will flow better and give you more hp, you can also run a little more compression with them.

[Rindelmach1 14]

Hoping to squeeze out some pony's using my original heads

my engine
351w-4v wtih eddlebrcok 600cfm
mild crane cam
weiand intake maniforld
hooker long tube headers with 2 1/4 exhaust pipes

[barnett468 418]

6 hours ago, Rindelmach1 said:

Hoping to squeeze out some pony's using my original heads

my engine
351w-4v wtih eddlebrcok 600cfm
mild crane cam
weiand intake maniforld
hooker long tube headers with 2 1/4 exhaust pipes

ok removing the exhaust bump alone is nearly pointless in your case because you need bigger valves and some professional porting done to get significant gains. you can in no way simply just start grinding on the holes to make them bigger in hopes that you will gain more hp, and in fact, you can loose hp by grinding on them incorrectly. they need to be properly modified for the bigger valves, and typically, modifying the short turn radius's properly with stock or larger valves will increase hp.

porting is a science and an art, and is therefore best left to these types of people.

 

[Rindelmach1 14]

ok thanks for the advise and most likely not do it

[barnett468 418]

5 hours ago, Rindelmach1 said:

ok thanks for the advise and most likely not do it

Removing the bumps is ok and will help a little but my point is that if you want big performance gains that you will easily notice, you need to do the other things in addition to removing the bumps.

[Rsanter 152]

I do a mild port on everything including a stock build.

why should you not squeeze a little more out of the thing.

smoothing the port and removing the bumps will help.

will you see big gains? Perhaps not.

will you see a gain, yes you will.

i have also ported and smoothed the stock manifolds (mostly the hipo ones) for some gains there as well.

 

if you have them off you Might as well do some work to them

[GypsyR 32]

Good street performance is most often satisfactorily found with a planned combination of many small things, rather than making one or two changes and expecting a fire breathing monster.

People have been porting these heads for many many years. Even after the aluminum heads became common they were still performance go-to heads in certain types of racing where choices were restricted to stock parts. Probably not really worth doing if you have to pay somebody full retail. If you want to do it yourself or can get a buddy deal on the labor, then do it. The recipes are out there to follow. Last I paid attention we weren't taking the "hump" all the way out. The guys with flow benches are saying to just reduce its height and give it a teardrop shape these days. If you plan to DIY you'd want to look all that up so as to have a good plan of attack. If you grind too much out of the wrong area you can literally turn  a good head into unfixable scrap.

Though a Dremel and it's 1/8" tooling is great to have, it's really only good for the final polishing and detailing.  You really need a high speed 1/4" grinder for porting cast iron. Seriously, that power drill you have WON'T do it. Carbide bits don't work well at all unless they are spinning a lot faster than a drill can go. So porting some heads requires investing in a bit of equipment along with the time.