193 Swirl Port Porting Question

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jeff swisher
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Re: 193 Swirl Port Porting Question

Post by jeff swisher »

I used a set of 193 swirl port heads on a 383 stroker with 274XE cam.
I removed that step and opened the bowls.
It would pull hard past 7000 rpm.

I would sleep better at night with removing it even in a small cube deal.
I built a few 305's and opened the bowls on those and ran 268H cams. Those would run very well.
Not swirl port though.
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Re: 193 Swirl Port Porting Question

Post by jcisworthy »

Might be money well spent to let someone with the proper cutters do a valve job for you with some blending. The attached picture is an example of what can be done with the cutters I have. I set the choke off the bowl cutter making every one equal and it sets up the direction up for porting well
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Re: 193 Swirl Port Porting Question

Post by Adger Smith »

The reason for the need for less timing is the plug location and the active chamber. The active chamber can be attributed to the way the swirl comes out of the port and into the cylinder.
Plug location is up high in the chamber and more centered. It is a flame front issue.
GM has also used better plug location in the Vortec heads.
Every Vortec headed performance engine I have had on the dyno responded to low timing tuneups.
If you have any doubts lay a 193 and vortec head beside a double hump or an 882 casting and take note of the plug location.
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Re: 193 Swirl Port Porting Question

Post by 68maliblue »

Trying not to spend much $$$ on this build so I’m trying to avoid a valve job unless I screw up and scratch a valve seat. I agree a good valve job would certainly help but the most I’ve spent so far is $80 on a used edelbrock manifold for iron center bolt heads. Everything else has been leftover parts. Its a 307 that’s been a doorstop for too long. Cam is from a 327 that got swapped for another bigger cam. Just using up sbc parts I’ve accumulated for the last 35 years to piece this together and get this old truck moving again. I’m going to put new valve seals in and get rid of the rotators on the exhaust valves. While I’ve got the heads apart I’m going to clean up the bowls given the advise I’ve gotten here, lap the valves and bolt it back together and run it. Thanks for the help.
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Re: 193 Swirl Port Porting Question

Post by Tuner »

68maliblue wrote: Fri Jun 04, 2021 4:05 pm I’m doing a low $$$ 307 Chevy build with leftover parts and I have a low mile set of 193 swirl port heads that are the best heads I can come up with without spending any $$$. Engine is going into a rat rod 46 Chevy so it’s just something to have fun with. Cam is a small solid cam 224/224 @ .050” on a 108 LSA that I used to run in a 327. Compression ratio is going to be somewhere around 9:1. Question I have is should I open the throat up to the edge of the 90 deg step or remove this 90 deg step completely and open up the to the diameter leading in to the 45 deg seat. I’m leaning toward keeping the step and clean up everything below it But I am open to suggestions on what would be best.
The nature of these heads combined with this valve timing is to require the total timing (24) to be very little more than the initial timing (18) necessary for good idle with the 224 deg. 108 LSA valve timing, so the mechanical advance curve would be short, 18 to 24 for example. In this situation you should be able to use locked mechanical advance set in the low 20s and a vacuum advance that starts near 5 or 6 in.Hg. and totals with 15-16 deg. at 14-16 in. Hg.
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Re: 193 Swirl Port Porting Question

Post by 68maliblue »

I've got an old points distributor that has the slot welded up to give 10 deg of mechanical advance that I plan on using. This cam liked about 14 deg initial timing in the 327 I had it in. with the 10 deg mech advance that should give about 24 deg all in with a 14 degree initial setting. Going to start there and see where it goes.
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Re: 193 Swirl Port Porting Question

Post by hysteric »

Adger Smith wrote: Sun Jun 06, 2021 3:32 pm The reason for the need for less timing is the plug location and the active chamber. The active chamber can be attributed to the way the swirl comes out of the port and into the cylinder.
Plug location is up high in the chamber and more centered. It is a flame front issue.
GM has also used better plug location in the Vortec heads.
Every Vortec headed performance engine I have had on the dyno responded to low timing tuneups.
If you have any doubts lay a 193 and vortec head beside a double hump or an 882 casting and take note of the plug location.
Better tell the Chrysler guys that as any mention of swirl and they begin to froth at the mouth and want to linch you. And if it doesn't make peak power at 36 total timing you built it wrong :lol:
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Re: 193 Swirl Port Porting Question

Post by hysteric »

Tuner wrote: Sat Jun 05, 2021 5:57 pm The most important thing when using these heads is use no more than 25 degrees total spark advance.

This is a post from one of the threads about these heads in the "similar topics" links at the bottom of the page.
Plaintoast wrote: Wed Jan 28, 2015 10:12 am I did a real low buck build with a set of these, left the ramp in place, pushed the pushrod pinch jump thing smooth. Using an old single plane (not the best choice) a small hydro cam, 87 octane pee water, it was making 360 ft lbs as low as we could pull the dyno down. HP was 263@ 4500, and fell off like a cliff after that. My notes also say it only wanted 22 degrees total, I think we were around 8:1. Its currently still in a magazine car with 40,000+ miles and gets 22 mpg cruising. They have a place, high rpms isn't it, but they certainly make a decent torque/low rpm head.
Hey Tuner ill have to ask you a Dorothy Dixer: Why would such a chamber/port only require so little timing to make peak power?
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Re: 193 Swirl Port Porting Question

Post by Tuner »

You tell Dot Adger answered her query.
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Re: 193 Swirl Port Porting Question

Post by hysteric »

Tuner wrote: Sun Jun 06, 2021 8:59 pm You tell Dot Adger answered her query.
:lol:
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