18rg head cross sections pics.

[jeffro ra28]

Hey all,

Just thought id post these pictures up of an 88270 18rg head that i recently disected.
Should be helpfull for anyone wanting to do some serious porting work to their 88270 heads.
I have heard that there are different amounts of material in the ports on the various 18rg head castings, so it may only be accuarate to assume this will only apply to 88270.

You may have seen these posted up around the place but hopefully this makes it a bit easier to find.

More pictures and measurements can be provided on request.





I will soon hopefully be flow testing all my standard 18rg heads, 88210, 88250 and an 88270. I will post up flow figures for everyones information.

[Mr DOHC]

what did u use to cut it with

why is there the odd cutting patternt {gouge} in the first pic

can u measure the valve guide depth, that is, the valve guide hole {the alloy bit}, does that make sense

[Jonny Rochester]

This is a great pic for those that say the valves are at 45 degrees. What is the actual measurement?

It would also be good to get a pic with the valves sitting in there, partialy open. How close do the valves get to touching each other? They would get very close when using big cams and overlap.

[takai]

Ow, that big hump on the exhaust port makes me want to cry. The 18RG can certainly do with some shaping of the ports, and smoothing of lamina flow layers.

[jeffro ra28]

It was cut with a drop saw with a cement disc in it. It would have rooted the bansaw blade because the cast alu is very dry. It took a while but with constant lubing etc it went ok.

Phil, is this wat u want?

Measurements of the valve guide bores.

Johny your right, the valves would come very close when using big cams.

[Mr DOHC]

thats exacly what i want, nice toes, mmmm, foot fetish


Jonny:
thay hit with stock cams, that is, if a cam stops moving with the valve open fully

[Jonny Rochester]

I have a 2T-G but its almost the same. And yes I do have big cams. And yes I know even the stock cams/valves hit if something goes wrong. I have done it before.

It would be good to have a more complete motor cut like this, or maybe even a mathematical way, to work out just how big a cam and overlap you can run before the valves hit.

Last week I was running 305 duration cams, both timed at about 97 degrees (I had limited adjustment, aiming for 100). Anyway the motor ran, and I don't 'think' anythine was wrong, but there was a knocking noise, I think I was just running lean. It would be good to know.

[SeptemberSquall]

Jonny:
thay hit with stock cams, that is, if a cam stops moving with the valve open fully

Yes, the valves are interference with pistons in stock form. But what he's saying is that with long overlap and high lift, the valves may foul each other (not the piston) on overlap.

[Mr DOHC]

apparently 310/310 can be run without interference

[jeffro ra28]

just for interests sake, i am modelling an 18rg out on EAP, so far iv modelled this engine with 298 deg cams at 156hp at 6600rpm wth open headers. Allthough i have only provided rough single flow coeficient figures for head CFM flow and an estimate for intake manifold.
If anyone has any Flow figures or CFM ratings for their ported 18rg's or intake manifolds could you please share them so i can model out a more accurate engine.

Also i can easily model it out with a turbo on it, so if anyone wants me to i can

[Mr DOHC]

my 88270 head flowed 230hp at 500" lift

[jeffro ra28]

have u got a CFM rating, or do i have to do my calcs to find that out?

[SeptemberSquall]

apparently 310/310 can be run without interference

Yes, but that's duration, we're talking lift.

[jeffro ra28]

I dont suppose anyone has these specs for the 18rg

Total intake valve angle?
total exhaust valve angle?

intake/exhaust valve

intake and exhaust primary angle?
int/exh canted angle?
int/exh valve-deck clearance?

If anyone has CFM flow ratings for them please post or PM them!

[tricky]

Sorry about the serious digging, but I don't suppose you have a picture looking down the intake port toward the valve with associated diameter measurement? Just comparing this to earlier heads. Cheers.