6X head combustion chamber mods??
 

In Jim's book he states to remove the ridge to help flow around the valves.
Should this be done to both intake and exhaust.
Anyone have any pics of there work??
Thanks.
http://coolcars.smugmug.com/photos/116216910-M.jpg

funny you asked...I just did mine yesturday, I left the shape I just took the sharp edges off and blended it all in.

http://img.photobucket.com/albums/v2...ic206jpg-5.jpg

You should take the ridge down but also take out the curve on the top and bottom of the intake side.

I was goign to go more, but looking-feeling into the coolant passage, it looks kinda thin behind that area.

Times have changed with wet flow results. ;)

I would leave the intake side sharp to reduce vortexes and blend the exhaust ridges.

Ken, are you saying the "eyebrows" on the intake side should be left alone and to do the exhaust sharp edges instead ? This is opposite to what Jim Hand recommends so if you could elaborate a bit that would be great.

I assume the overhang/shrouding beside the intake valve should still get whacked down ?

I think PDude is refering to some of the newest theories coming from those that are using "wet flow" flow bench testing ... refer to this thread, & the link provided... interesting reading.

http://forums.maxperformanceinc.com/...d.php?t=501871

Thanks RJ :)

Has anybody had better results from leaving the intake side sharp and blending the exhaust ridges rather then the ways stated in Jim Hand's book, which I'm assuming in the normal and common method of doing Pontiac heads?

The wet flow bench is very interesting, I'd like to see some results of Pontiac heads tested and worked accordingly to show best results on a wet bench.

Dry flow is nice, but you engine doesn't run on air alone.

Mondello and Reher/Morrison are pioneers in this area.

Great article in my shop suppliment on a hemi that flowed great numbers but wouldn't run, then the wet flowed and flow vortexes in the chambercreating wet spots around the plug. Did some wet flow porting and didn't pick up any more flow but the engine came alive.

You need the sharp edge in the chamber near the plug to break up the mixture and enhance flow. Exhaust side is already burn and ya just need to get it out without turburlance. How much or long of the sharp edge and steep an angle can only be found with a camera, dye and wet flow testing.

Not that I know what I'm talking about, but the best 87 cc E-heads I ran on my car never had any chamber work and ported to only 305/310 on a dry flow bench. But big ports for Nitrous, if that mattered.

Is it possible that Pontiac engineers actually knew what they were doing with the combustion chamber shape........?

It would be nice if a retired Pontiac engineer that was involved in the designing of the D port head was a PY member to clear some of this up.

The RAIVs, SD and HOs had a much different more open chamber but still some ridge. RAVs had NO ridges. So which engineer knew the best as these were the factory premium performance heads?

It would be interesting to have one on a wet flow bench. Wonder what the going rate for that kind of work is?

Am I the only one that thinks modifying the chamber on a 250-cfm (or less) 6X head is akin to pissing up a rope?

Pontiac engineers put that ridge there for a reason. Any flow gained from radiusing it back will be negligable, especially considering most ported d-port heads flow less then 260-cfm.

'Dude has some sound advice.

here is a picture of the 87cc E heads chamber ,big eyebrows

quote:Not that I know what I'm talking about, but the best 87 cc E-heads I ran on my car never had any chamber work and ported to only 305/310 on a dry flow bench. But big ports for Nitrous, if that mattered.;
So P-Dude no mods to these eyebrows?I under stand the turbulance ,makes sense to me swirl is better then straight flow ,but these chambers look so unfinished, the machine just went in real fast and cut then went on . Rob

Like I stated. Nobody really knows. Nobody is WET FLOWING Pontiac heads and obseving the patterns inside the chamber. I'm Just absorbing what I read and talking to other head porters and their conclusions.

Untill someone spends the BIG BUCKS. I guess we can only apply what seems to be working in other head designs similiar to the Pontiac port and chamber?

Good dry flow numbers don't necessaryly make power is the current trend in flow technology. But not a bad thing and will work for 90% of the racers and hobbyists out there.

Here's one for ya.

Maybe some of the detonation thinking with pistons slightly down in the hole and smooth chambers is the possibility running near the max compression on pump gas. Things that make ya go hummmmmmmmm.

YESH U A right, the intake ridge may keep the plug clean per "wet flow" reports because the ridge keeps a vorticy away fro the plug. Such a vorticy allows fulee to wet the plug.

I done removed the ridges, and stuckwith the results. Just MAYBE I did enough ramdom-luck changes (wedge-pocket slugs) to be Vorticy-Free.

got a can of white spray paint and a shopvac/house vac hose?....

""""""It would be nice if a retired Pontiac engineer that was involved in the designing of the D port head was a PY member to clear some of this up.""""""

I asked the brother in-law, he said """"""Oh, so somebody thinks they found 100HP in the Pontiac head, hehehe Bwahaha bWHAHAHA BWAHAHAHA, tell them, gee those engine developers were looking for 1's of HP and couldn't find 100HP. do you believe that?"""""""

Mark, I am confused by your last comment. Could you explain what you're trying to say in dummy terms so it can soak into my thick head. :o

Thanks

This may be of some interest, from 1970 Pontiac Performance Brochure: