1.7L exhaust cutaway pics; I'm shocked!!

aircooledtechguy · Post by **aircooledtechguy** » Mon May 24, 2004 7:49 am

O.K. folks. So yesterday, I'm pokin' around the garage, and I'm bored, so I decided to cut one of my 1.7L heads (p/n - 021.101.371Q) in half so I could view just HOW RESTRICTIVE the exhaust ports really are on a round port head. Like most of us, I knew they were restrictive in stock form, but until viewed from the side, I was totally SHOCKED as to just how restrictive they really are!!

Note that this was a bad head whose life had long since expired due to a split exhaust guide boss and pulled header stud. Absolutely no usable parts were sacrificed for this science project.

With this view, I could now see why HAM inc and others tell you to leave the inside of the corner alone and work on the outside of the bend exclusively. There's almost no materiel to work withunder the bottom of the valve seat there and TONS on the outside of the corner.

My concern now is this: How much of the exhaust guide boss is O.K. to remove on a daily driven car in order to get better flow?? The guide boss not only gets in the way, but it acts as a heat sink for the guide to help draw away heat from the valve. I'm afraid that if I was to blend it completely away, I would have a lot of guide hanging out there unprotected from all that heat and could in time doom a set of heads/engine. . .

I hope these photos are as much as an eye opener to others as they were to me. . .

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Mon May 24, 2004 7:56 am

I have several heads opened this way that we use for displays at shows and etc..

Now you see the HP limiter on these engines and why I use so much exhaust duration and added lift!! You gotta trick that head into flowing more..

Most recently HAM and I have been doing less and less intake port work, and the power keeps growing and growing!

tuna · Post by **tuna** » Mon May 24, 2004 8:43 am

Nate,

That definitely makes the point clear. Seeing how any radical porting can destroy the engine shows us that we need a cylinder head with better designed exhaust ports.

Thanks for the images,
Tuna

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Mon May 24, 2004 8:59 am

Closer than ever before...

BUT, not gonna be as cheap as we thought..

jkeyzer · Post by **jkeyzer** » Mon May 24, 2004 10:38 am

What does the intake side look like for comparison?

Ephry73 · Post by **Ephry73** » Mon May 24, 2004 12:55 pm

Intake is a straight shot. That is a EGR head, right?

Man that's good to see from that angle. Isn't that why the later 356 heads have the exhaust valves moved away to get a better angle?

Jake, are those heads going to have a similar angle toe the Super 90 356 heads?

E

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Mon May 24, 2004 1:05 pm

Nope, just like a TI. TI exhaust will bolt right up.

Ephry73 · Post by **Ephry73** » Mon May 24, 2004 2:09 pm

That would be the most logical thing to do, since most of the Type 1 exhaust systems are pretty decent and very inexpensive.

That should also make up the difference for the extra price of the head, which I'm sure won't be too much. Type 1 Valves or type 4 Jake?

E

aircooledtechguy · Post by **aircooledtechguy** » Mon May 24, 2004 5:30 pm

jkeyzer wrote:What does the intake side look like for comparison?

Here's another head I cut a couple years ago for my CIS Injection system. So disregard the pushrod sitting there

Pretty much a straight shot. Hmmm, wonder how the inventers of Super flow heads thought up that intake port. . .

Class 11 streeter · Post by **Class 11 streeter** » Mon May 24, 2004 10:33 pm

Nate, thanks for sharing those pics.

Post by **Piledriver** » Wed May 26, 2004 5:31 pm

Anyone section a squareport yet for comparison?

The ovals almost look like they need material ADDED.

aircooledtechguy · Post by **aircooledtechguy** » Wed May 26, 2004 8:09 pm

Piledriver wrote:Anyone section a squareport yet for comparison?

The ovals almost look like they need material ADDED.

Funny you should ask. . . I just finished cutting a square port head and re-cutting the oval port head on a HUGE horizontal band saw (I decided to save my arms this time

). I'll have to get home and snap some shots of these side by side. This band saw ROCKs. I was actually able to cut the exhaust manifold studs in half on the square port head!! I'll have the intakes and exhaust ports. Pics on the way shortly. . .

Post by **Piledriver** » Wed May 26, 2004 11:59 pm

You cut the first one with a HACKSAW???

Man, you really took a bullet for us there...

Ephry73 · Post by **Ephry73** » Thu May 27, 2004 6:42 am

That's dedication Nate!

E

aircooledtechguy · Post by **aircooledtechguy** » Thu May 27, 2004 8:24 am

Here's the shots. I hope they are as informative to you all as they are to me.

2.0L on left

2.0L exhaust

1.7L exhaust

Side by side 1.7L on left

1.7L head left

2.0L intake

1.7L intake

That horizontal band saw works WAY better than the alternative. Hope you enjoy the shots.