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What to do to 351c 4v heads?
#1
When I go to the machine shop what all do I want them to do to my heads if I go this route instead of running aluminum's?  List please. Big Grin

What porting should I do before taking the heads to the machine shop?  gasket match intake and exhaust ports?  Smooth out exhaust ports?  Any polishing for the intake ports?

Thanks!
Wade
1972 Mach 1 351 cj 4speed
"We confide in our strength, without boasting of it; we respect that of others, without fearing it."--Thomas Jefferson

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#2
4V heads need very little work, and literally none for a street car.

https://pantera.infopop.cc/topic/sticky-...nce-tuning

[Image: 351-CHEADPORTING.jpg]


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#3
Thanks! I am still trying to decide if I want to go aluminum or keep the iron heads. Im guessing it will be about a $500 difference if I go edelbrocks or stick with machining the iron heads. Any thoughts, advice??

Thanks!
Wade
1972 Mach 1 351 cj 4speed
"We confide in our strength, without boasting of it; we respect that of others, without fearing it."--Thomas Jefferson

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#4
Minor port cleanup, do not polish the intake ports, 3-angle valve seats. Minor roughness creates turbulence which helps to mix, and keep mixed, the fuel and air particles.

Have the heads machined for adjustable rocker arms, have the valve guides checked for wear and proper clearances and replaced if needed. Knurling the guides is OK for minor wear. Have the valve guides machined for positive valve seals.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#5
I would say if you want to modify the performance, go with the Aluminum heads. 

 I really agree with the posted article above, in spite of claims of professionalism, the 4V head is kinda misunderstood.  Look at it this way, the Boss 351 engine is known for being a high performance Cleveland engine.  I don't believe there is any difference in the ports on the quench chamber 4V vs the Boss Heads.  The performance comes from the camshaft, the carb, the pistons, and the rear gear ratio.   So why go custom on such a well engineered head?  I have actually heard that the obvious"hump" on the exhaust side that all hot rodders want to grind away is actually a benefit to exhaust gas flow by creating a converging-diverging nozzle effect.

kcmash
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#6
If your not staying with cast iron I would not spend my money on edelbrock heads, they are just entry level heads much better choices out there.
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#7
(10-31-2018, 08:19 AM)scgamecock Wrote: Thanks!  I am still trying to decide if I want to go aluminum or keep the iron heads.  Im guessing it will be about a $500 difference if I go edelbrocks or stick with machining the iron heads.  Any thoughts, advice??

Exactly what is your goal?

Do you want more bottom end?

Do you want less bottom end but more rpm on top?


I wouldn't touch the ports unless you are an experienced head porter.

You will get the most overall power from chi heads. If you want big time power, you should buy chi heads.
[+] 1 user Likes barnett468's post
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#8
I went through this dilemma with my CC 4Vs. After reading and researching a lot i decided to keep the casting stock except for the valve angle job and machined for rocker screw in studs. I also cleaned and smoothed the chambers a little.

Sent from my SAMSUNG-SM-G930A using Tapatalk

        [Image: 20160929_171923_edit2_small.jpg]

1971 M-Code Mach 1 w/Ram Air, 408 stroker, 285/291 0.558" roller cam, Blue Thunder intake, TKO600, Hooker headers with electric cut-offs, FiTech EFI w/ RobBMC PowerSurge pump
4-wheel disc brakes
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#9
+1 on chi's they're what I'm running, although mine are 2v. If you wanna see them you're close enough that it wouldn't be a big deal.
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#10
If you want to make the low end a bit better, go for some Aussi 2V CC heads.  They have the best of both US 2V and 4V heads.
The only real difference between the 2v heads you have and the Aussie heads is the combustion chamber. To take advantage of the Aussie closed chamber you will need pistons that create a quench area, doing this and keeping the same compression you currently have may allow you to decrease your octane requirements. A good quench area has the ability to make the motor more resistant to knock.


Then theres also these.... if you really want something killer.....

http://www.chiheads.com.au/product-categ...-heads/3v/
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