Grinding the oval ports on a 400 tripower ???

[jims427400]

I posted a short time ago about putting a 435 hp "square port" intake on my 400 hp heads. I've been told I can use them but they'd have a sharp edge all the way around ( JohnZ )
Several decades ago I remember helping a friend grind out his heads..

What I'd do is lay the square port intake gasket over the oval ports, scribe the outline and grind away to contour the ports together.

Ant thoughts ??

I've looked on ebay, and if I find one, they're going for around $1400.00 min.

Jim

 

[67HEAVEN]

My only concern would be in how much meat you could safely remove. I did this with my old 435 rectangular-port intake, scribing the gaskets and opening the ports to the maximum, but I'm unfamiliar with how much you can open the oval-port heads.

Someone here will know.

Good luck.

 

[jims427400]

67,
I agree w/ your concern, I havent taken the intake off yet to check.
Hope someone else has some experience w/ this topic.

 

[midyear]

I have done this on several street motors years ago (budget motors with mismatched parts), I made a template of the intake, placed it on the head and went to grinding. I went in less then an inch into the head, and tried to remove the minimum amout of material, mainly just working the corners. Funny thing is that I could never tell the difference in how the car ran before and after. The port mismatch never seamed to affect the way the cars ran.

 

[ET-VIPER]

ITS NOT WORTH IT TO GRIND THE HEADS.ALL YOU WILL DO IS MESS UP A SET OF FACTORY HEADS.JUST MAKE SURE YOU USE THE SQUARE PORT GASKETS.BEEN DOING THIS FOR YEARS WITH NO PROBLEMS.
I THINK THE ONLY TIME YOU CAN TELL ANYTHING WOULD BE AT HIGH RPMS.

STEVE

 

[JoelF]

It is not my car or my decision, but if it were I would do things in this order:

Sell or trade the square port manifold for an oval port. These are being reproduced now so there is no reason you can't find one. A square port manifold has value and there is no reason you can't do this for little or no money out of pocket

Or

Remove the '391 oval port heads and replace them with a set of '840 square port heads. The '840s are relatively cheap so if you shop around you can get a set for less than 1k.

Grinding the oval ports could mess up your flow numbers and actually hurt performance.

 

[BADBIRDCAGE]

ITS NOT WORTH IT TO GRIND THE HEADS.ALL YOU WILL DO IS MESS UP A SET OF FACTORY HEADS.JUST MAKE SURE YOU USE THE SQUARE PORT GASKETS.BEEN DOING THIS FOR YEARS WITH NO PROBLEMS.
I THINK THE ONLY TIME YOU CAN TELL ANYTHING WOULD BE AT HIGH RPMS.

STEVE

I'm with Steve. Why fubar a set of perfectly good heads when you will never notice the difference on a street drive with the square port manifold on the oval port heads. I did this with a 396 in a 66 Impala. COOL FACTOR was 100 %. Performance factor on street dirve was not noticable. How many times are you really gonna take this motor up into the stratosphere of rpm?

Rich

 

[firstgear]

I posted a short time ago about putting a 435 hp "square port" intake on my 400 hp heads. I've been told I can use them but they'd have a sharp edge all the way around ( JohnZ )
Several decades ago I remember helping a friend grind out his heads..

What I'd do is lay the square port intake gasket over the oval ports, scribe the outline and grind away to contour the ports together.

Ant thoughts ??

I've looked on ebay, and if I find one, they're going for around $1400.00 min.

Jim

If you want to get hot heads, for the $1400 or so, can't you get a set of Darts or some other HP aftermarket head? I wouldn't mess with the stock stuff, why wipe out some of the value?

 

[jims427400]

I agry w/ not grinding. Not going to be racing this car "much" so just going to bolt her up w/ the square ports and square port gasket.
Great advice from all..again..