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Author Topic: GT40P Porting Help!  (Read 4672 times)
MustangN8S
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« on: April 17, 2013, 05:05:46 PM »

Alright fellas help a brotha out..lol

I'm pretty handy as some of you know, but i've never touched a grinder to a set of heads in my life. I like racing more than working on junk...lol
Sooo I have this set of P heads laying around that I want to install on my Ranger 302 project.

I figure before taking them to the machine shop for a surface and VJ. I can clean up any obvious, and simple area's ahead of time.
Questions:

What are some area's that normally show the most improvement that I can tackle without worrying about destroying them (I.E. getting into water etc)
Air Grinder work Ok? or will a cheap electric grinder do with a dimmer switch or something?
Best Stones/ bits for Iron heads?...where to get them? Local would be nice.

I'm definately not looking to enter the engine masters with this or spend a ton of time. I just want to clean up the ports a touch and blend what needs belnded then slap them on a budget 306 with a TFS1 or a stock cam

Thanks for any advice
Russ
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coulterracn
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« Reply #1 on: April 17, 2013, 05:58:56 PM »

if you have an air compressor an air grinder from Harbor Freight would be a good investment. I borrowed a friends electric Dremel once to do a pair of heads.
I like to use mounted stones on cast iron heads (I don't know if you have cast iron or aluminum). It's very dusty work and you'll need a filtered mask plus eye protection. 

An electrical grinder and carbide burrs are faster but more dangerous for the first time user. 40grit cartridge rolls or strips of utility cloth work good for finish.

The best advice I can give you is be careful around the valve seats until you get use to grinding. You'll probably hit the seat a couple times with the collet of the grinder.

The best gains are bowl blending and unshrouding the valves in the combustion chambers.

Ray

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347HO
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« Reply #2 on: April 17, 2013, 09:11:29 PM »

Push and pull the bit with very little pressure will probably net the best results.

I like my Foredom, foot variac, grinder because it's very quiet and I can hear what my carbide bit is doing on steel heads.

I agree to work the bowls transition to the seat and I really like working the sides leading into the bowl and very little on the short turn since this is your first attempt.
Follow up with 60 grit sand roll to remove all cast flaws and make your work smooth.
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LisaB
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« Reply #3 on: April 19, 2013, 07:24:48 AM »

- Makita GD0600 or GD0601, 3.5 amp motor.  Amazon.
- used "General Radio" 5 amp variac.  Ebay.
- Option for speed control is a dimmer switch, but if it's a 15 amp version it will kill much of the grinder's torque when you dial down the speed.  Need a speed controller that is close in amperage rating to the motor it will be driving.

- 6" long carbide burrs from carbideselect.com.  Get the aluminum cut SE-5L6 (1/2" football, egg shape) and maybe an SE-3L6.  You will have to go slower at first with aluminum cut, but as your hand control improves you'll get more bang for the buck.  I bought the smaller flute cast iron burrs at first and now they just sit in the drawer because I'm able to get more work/time out of the aluminum cut.

- 3M 747D regalite sand rolls.  Last longer, better value than cheaper (ie Merit) brands.  40 or 60 grit.  1/2 and 3/8 sizes.  Amazon.

- Extended length cartridge roll mandrels.  MSCdirect.com

All the extended length stuff will keep your grinder's collet away from the head.

- Couple of used or cheap valves that are the sizes you will end up using.  Have the margins ground down real thin and then you can use them to protect the seats while working the chamber.

- Like Ray said, be careful around the seats.  Any big divot taken off the 45* angle means sinking the valve job a bunch.
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Silverhatch
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« Reply #4 on: April 19, 2013, 08:10:32 AM »

Russ, look at this website link and maybe you can use some of the information. If I remember right, be careful on the exhaust side. There is a water passage that can ground into. Good luck.
  http://www.diyporting.com/gt40p_home_porting.htm
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LisaB
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« Reply #5 on: April 19, 2013, 11:54:02 AM »

Biggest thing about porting is it's all really about area relationships to each other and how much airspeed each of those areas can handle.

3 main areas in any port.
    a) pushrod pinch area
    b) area over the short turn
    c) throat area (minus the area taken up by the valve stem)

Decent rules of thumb.
    a) For 45* valve job, valve size minus 0.200" is a good throat diameter.
    b) Pushrod pinch area should be about 80-90% of throat area.
    c) Short turn area should be about 125-133% of of pushrod pinch area.
    d) Exhaust likes to expand, so try to get the opening to be 133% of the throat area (minus valve stem area).
    e) Air likes wider vs taller to help turn, but can't make side to side width diverge or open too fast because then air won't be able to stick to walls.  If you can get 90-95% of the intake valve diameter in width over the short turn that's good, get the rest in height.

Where someone can get into trouble is if they make one area (ie throat) bigger and flow a bunch more but don't make the area over the turn bigger.

Now the air is being pulled harder (faster) over the turn and can't stay attached.  Turbulence, noisy and you see the flow go backwards or manometers bounce around as the air struggles to stay attached.
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MustangN8S
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« Reply #6 on: April 28, 2013, 01:57:31 PM »

Thanks a bunch for the advice.
Any area's on the P heads I should be careful about water jackets? it would be nice if I had a sonic tester..lol
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Silverhatch
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« Reply #7 on: April 28, 2013, 05:25:04 PM »

Russ, this link might also help you. It has a few pictures. I can't remember where the water jacket problem was. I just remember reading it somewhere.  Getting old. Good luck.  http://sbftech.com/index.php?topic=33345.0
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LisaB
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« Reply #8 on: April 28, 2013, 06:49:48 PM »

on the P head, the exhaust port has a tilted roof where one side is lower than the other.

You can't raise the lower side to match the higher side or it will break through to water.  I saw a head that had this done.

I think in the intake you can't lay it back as far as the GT40 because it'll hit water.
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LisaB
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« Reply #9 on: April 28, 2013, 06:59:35 PM »

http://www.diyporting.com/index.html

http://www.diyporting.com/gtpex.html

This guy did a bunch of work on the E7 and GTP heads.  What he says about the water jacket in the exhaust port is what I saw on one that was expirmented by one of the shop here (before it closed up).
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