2TG head porting! Need a quick answer to save the Chop!

[MorGo]

That was a some sort of design/cost cutting mistake to use same shims in every G-head but then again;the shims are rarely broken so it is justified compromise.Not a good one but get's the job done.

Just to repeat;get the valves checked/ground/having the 30º backcut AND proper seats cut!

(I build my first 2T-G back in -86 and the turbo 18R-G in -88 so I have some experience with these dinosaurian but oh so great engines..)
Just having flowbench and porting heads since 2001 for living give some insight..be it a 502 Chevy or 250 cc 5 valve Yamaha.Air do strange things..

[BrianGT]

That was a some sort of design/cost cutting mistake to use same shims in every G-head but then again;the shims are rarely broken so it is justified compromise.Not a good one but get's the job done.

Just to repeat;get the valves checked/ground/having the 30º backcut AND proper seats cut!

(I build my first 2T-G back in -86 and the turbo 18R-G in -88 so I have some experience with these dinosaurian but oh so great engines..)
Just having flowbench and porting heads since 2001 for living give some insight..be it a 502 Chevy or 250 cc 5 valve Yamaha.Air do strange things..

Thanks Morgo I am taking note! Thanks for your help.

Thanks to everyone else who replied quickly.....it has helped me to keep going with the head work.

[71TA22]

Brian,

Do you mean the spring seat or retainer - which are both different for single or twin spring set ups.

shims are the same.

Here is a twin spring set up in pieces with the spring seat and retainer on the right.



And a single spring set up.

[BrianGT]

Thanks Mike!!
Those pics are great and show that I obviously have the single spring set up on my head. It's an 88222 and came with double valve springs but when I took it apart I didn't like the way the inner spring sat on my seat shim. Hence my question which you have answered so well!

I know my head originally would have had single springs and I just assumed it had been converted.

I will go back to single outer spring to suit my seat shim and retainer......I don't ever rev the car above 7k as it pulls like a train so valve bounce will never come in to it in my case.
Thanks.

[oldeskewltoy]

I have little experience working Toyota dual valve heads, but there really isn't much different between dual valve head porting and quad valve head porting...

The port roof will get the most air flow, try to make the ports shape smooth (shape not texture, texture below) as it transitions from horizontal to the valves head. Don't forget the short radius (floor of the port as it approaches the valves head) you want this to also have a smooth progression.


As far as texture, AFTER the port shape is established - intake - use 80 grit rotary tool drum @ about 3,000 - 5,000 rpm(slow) not applying too much pressure - enough to add texture, not so much as to change the ports shape. Exhaust - once again after the proper port shape is established - make the exhaust port smooth... polished if you can***

*** - there is some thought that in a race engine you might want a CAREFULLY texture exhaust port, but in a street ride texture surface attracts carbon build-up, where a smooth finish tends to allow less build up

[BrianGT]

I have little experience working Toyota dual valve heads, but there really isn't much different between dual valve head porting and quad valve head porting...

The port roof will get the most air flow, try to make the ports shape smooth (shape not texture, texture below) as it transitions from horizontal to the valves head. Don't forget the short radius (floor of the port as it approaches the valves head) you want this to also have a smooth progression.


As far as texture, AFTER the port shape is established - intake - use 80 grit rotary tool drum @ about 3,000 - 5,000 rpm(slow) not applying too much pressure - enough to add texture, not so much as to change the ports shape. Exhaust - once again after the proper port shape is established - make the exhaust port smooth... polished if you can***

*** - there is some thought that in a race engine you might want a CAREFULLY texture exhaust port, but in a street ride texture surface attracts carbon build-up, where a smooth finish tends to allow less build up

Thanks Oldskewl......that's good info.

I was wondering how coarse to go on the inlet finishing and now I have a much better idea. I had left them at 220 grit so I will rough them up a little.
I had planned on polishing the exhausts the best I can as I know that carbon will use any dimple or ledge to cling on to and make build up easier.

I have smoothed out the port roof the best I can but I have been wary about the short radius as I wasn't sure if it needed to be rounder than it is or left like a "cliff edge" so that air dropped off fit so to speak!

This thread has taught me a lot and made me careful about what I'm doing.

Thanks to all it's appreciated. I love my damn car!