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:

Cool article kenth. A "slipstick" is a slide rule right ?

1970 Pontiac Performance Brochure
 

I wish I could see those little illustrations better but obviously a 6x head and most other D ports are "fully machined wedge with a large squish area".

So where does a closed chamber fit into the mix? I read in the HO Racing manual that the open chamber was a design improvement over the closed chamber but all the new head designs are more like a closed chamber. Maybe thats where the grooves help?

Nice article kenth.

Interesting that they show the RA IV head with 69 CC's and the RA III head with 66 cc's. I would have thought it would be the other way around.

Also the deck height of the 455 is interesting.

My virgin 614s were actually 69cc with flat valves,can't see the tulip adding 3cc.

The closed chamber heads are usually opened up in certain areas to be a semi-closed chamber (similar to the newer chambers maybe?).

Some pics of my closed chambers 670's, semi-closed chamber 670's compliments of Dave@SD and KRE's D-port.

Kenth, according to your article the Ram Air 4 was "spherized" to complement the higher compression to free up 8 to 10 horse. This would support Jim Hand's recommendation on laying back the eyebrow. Could we be jumping the gun on this new wet flow technology since no Pontiac head has been tested as of yet and it's still in the developmental stages. When the rubber hits the road is where it matters and Jim's Wagon runs pretty darn quick with the chamber mods stated in his book.


Strange how the factory ran double the deck height on a 400 when compared to the 455. What do you think the reason for that was ?

Pablo the RAIVs aren't like Jim's chamber at all. They keep the ridge just moved it out further. The entire chamber diameter is larger also. Since the chamber has a larger diameter than other "72cc " heads the valve seats and edges are closer to the deck/piston. So they would have a different piston to valve clearance than a 72cc D port head or 72cc Edelbrock head with the same cam. A 6X head the valves are actually over 0.200 further away from the deck surface! My RAIV motors did use alot less timing than my D port motors, usually 34 degrees was best.

Pete McCarthy's book has pictures. I might have some on mine somewhere. But RAIVs, HO,SDs all are a way different chamber. Maybe their chambers better effeciency is how they kept the same power band as other 455s with their much bigger ports?

Thanks for the response Skip. Here is some pictures of a ram air IV chamber beside a 6X so we get a side by side comparison.

I talked with Dave Bisschop about this last night. He tested this theory of cutting the ridge in the 6X. Flow increased...but performance lagged. Efficiency was lost and it took 3 degrees more timing to match the uncut chamber.

My take...leave the 6X chambers as designed. Just remove the sharp edge to eliminate potential hot spots.

I can't get enough of this post seeing I'm going to have my 6x-8 heads milled and worked first thing next year (Jan 07) and am now trying to decide what action if any to be taken with the modifying the chambers. Jim at MBJ in IL will be doing the work and I'll have to get his take on this whole thing.

A bit surprised we haven't seen any opinions from Mr. Hand on this.

That RAIV looks like it has been smoothed a little on the ridge.

That's an ugly 6X chamber, need a good clean one to compare! A better comparison might be a bigger HO/SD chamber, close to the same size and depth.

I wonder how the even different RAV chamber compares to timing needed also.

These changes as Dave Bisshop noted change performance unrelated to port size.

Here's is a great link to HPP with a real collection of chamber shots.

http://www.highperformancepontiac.co.../photo_14.html

Great link Pablo for this!! You can see what I mean with the side by sides. the RAIV,HO,SD is alot more open around the valves the way it's machined, you can also see the RAV has no ridges at all. You can see how flow coming in from the intake has alot different path in all of them. You can also see how different the plug is in relation to ridges in all three.

So which Pontiac enginer had it right since they have 3 different chambers and two different ones for their hi perf motors????

That would be a cool thing to see on a wet flow, but any porting is going to change the bias as it comes into the chamber over one ported slightly different.

WOW, glad I posted BEFORE I started cutting.lol
Thanks,
Would like Jim H to chime in too!!

that 6x looks like it has unshrouding work and touch ups on the ridges (eye brows). the RAV is definately odd compared to the rest.

"So which Pontiac enginer had it right since they have 3 different chambers and two different ones for their hi perf motors????"

Depending on the application of a certain head the engineers were all right, you don´t see 3 different chambers on the 6X or RAIV heads?

The different chamber styles were aimed at different goals/rpm-ranges/intake-runner-style/camlobe-lift and so on?

But Kenth the HOs and D port 455s had the same rpm range. The RAIII maybe a little less than the RAIV due to the cam. So for us tinkering types which is the best to copy? If the more open chamber of the RA/HO is more performance design than the D port might be better to copy it?

The port size was dramatically different also. My point in other discussions nothing is as simple as just port size when comparing different heads unless they have identical other parts including chmabers.

Skip, isn´t the 1971-2 455HO Pontiacs considered the most "undercammed" engine due to the heads potential?
I think Pontiac engineering were somewhat compromised by the 1971 emission laws?
There is a lot to consider choosing parts, but one can assume that Pontiac had more resources to find out what works than the average hobbyist, of wich i´m one?

I'll agree the HOs and even SDs have more potential with more cam. The D port crowd will boo me but even the stock 71 HOs I've flowed do better than a medium ported D port head. Pontiac figured out how to keep the rpm range and the HP with the big heads, and give the enthusiasts more potential also. Showing that port ccs is just part of the equation.

I talked with Jim a little over a week ago, on an unrelated subject. I got the impression that he needs to focus on some other things right now. I suspect he'll chime in when he gets caught up on things.

Lee

Lee, glad to hear from you! What's new??

Hey Skip! I don't want to hijack the thread, so I'll go post something quick in the lobby....


Lee

re 6x head
 

here is a 6x4 i worked. i laid the edge back on the intake side. i also opened the chamber on the pushrod side of the intake valve. it flows 270@ .700" with a warrior intake and 1050 carb attached. i had 50* seats cut for the intakes with a 2.18" tit valve and 5/16" stem. i believe the 50* seat helps the flow to .700". the exhausts are 1.70" tit valves 45*seat and 206cfm at .700". the reason i laid these edges back on the intake side was i felt the steep seat angle would enhance the flow at mid to higher lift. also just below the seat i opened the bowl to 1.88" to help the bigger 2.18" intake and the 50* seat. i do NOT recommend this for a typical port job as things are getting thin in this area. one better have a cut up head to check to see just how far into the bowl you can cut. i also did the Darin Morgan "pro stock trick" in this area. hehe...

just for kicks chambers on a sc and ra iv head also.....

the 6xs were not finished when the pic was taken. sorry for the blurry pic also.

Any experience yet with those 'Singh' grooves?

top secret "trick"
 

not yet on the singh groove, close tho.

here is the "pro stock trick", since my pic was fuzzy and some might have a itch to know. it's a secret, so don't tell anyone... Morgan says this mod pics up hp and i am sure he has tested on the wet flow bench. it won't work on a pontiac tho....hehe...

J.C.you

Have you moved the pushrod holes on that 6X head ??

Looks like and aluminium insert with epoxy and the hole relocated rather than just sleeving the existing hole and porting through ??

Can you post results and methods used, improvement over std location, amount of offest etc and what they picked up in flow (if any) and gain in x-sectional area at the pinch

Sorry, probably asking alot but were looking into trying this on a couple of test heads. You may save me the time and grief

Cheers

re mods
 

455 yes, the pushrods holes have been relocated. i used offset lifters to move the pushrods over. flow testing with clay in the port was done without the pushrod bulge, max area at the short turn, bowl cut, and the 50* seat. to remove the pushrod bulge in a typical port job would be a mistake IMO. port velocity and hp will suffer. BUT, with a highly modifed intake with carb attached, flow and acceptable velocity in the port is enhanced. i tried the 50* seat because there probably hasn't been much, if any, testing with a dport head. the flat chamber floor would not seem to work well with a steep seat angle. this is why i cut the "quarter moon" and pushrod side of the chamber back to become more of an "extention" of the seat angle.

for a practical build/port job i wouldn't recommend doing these things. you can sink alot of time/effort/$ in a set of iron castings when it is so much easier to "bolt on some aluminum hp". if your class requires a iron head, and you are looking for a max hp potential head, i would go with a ra iv casting if possible.

Almost finished with 1 head
 

Only did intake chamber area as per Jim Hands instructions.
Many hrs. involved, but worth it!

http://coolcars.smugmug.com/photos/118779358-M.jpg

Almost ready
 

http://coolcars.smugmug.com/photos/123126819-M.jpg
http://coolcars.smugmug.com/photos/123126793-M.jpg
http://coolcars.smugmug.com/photos/123126802-M.jpg