Porting 906 heads

[motorhead440]

According to the mopar engines book the templates for porting are for the stock valve sizes. My question is this, if i go to the larger valves do i still use the templates and then blend to match the larger valves?

[Christopher]

According to Chrysler,no.They say that using the templates are for the stock valve size only and will ruin the flow if use with the larger valves.Doesn't make sense to me,but that's what they say.

[PRO]

WHEN GOING TO LARGER VALVES HAVE YOUR MACHINE SHOP BLEND THE BOWLS AND BACKCUT THE VALVES. ALSO BOWL WORK IS BOWL WORK REGARDLESS OF LARGER VALVES, SO GO AHEAD AND PERFORM THE TEMPLATE WORK THEN HAVE VALVE JOB DONE WITH BACKCUT AND BLENDING.MAKE SURE YOU PORT MATCH THE INTAKE PORTS .ON LATER CASTINGS LIKE THE 452 AND 346 THIS IS WORTH QUITE A BIT, SIMPLY GOING TO LARGER VALVES W/O THIS WORK IS A WASTE OF TIME AND MONEY. THE KEY IS PATIENCE. YOU CAN P/U AROUND 40HP ON A STREET MOTOR IF YOU PERFORM THESE STEPS...PRO..

[DodgeMan]

I agree with PRO 100%. I used the templates on a set of 452 casting heads on my "71" Charger with a 440. Bofore doing the work I was running 92.8 mph in the 1/4 mile. After the port work (with stock valves) I was running 98.5 mph. I think the work was worth a good 40hp. Do the bowl work to the templates and let the machine shop blend in the valve seat. You won't be sorry. You might consider bronz guides at this time too. I've had good luck with them.

[340king]

The machinist that I use for my engines has a very talented head porter working for him. Together they have worked on most common and uncommon heads. They do not recommend going to larger valves as they cannot substantiate a noticeable gain on the flow bench with the 906 casting heads. Save your money on valves and get better hardware like springs and retainers.

BTW the engine builder is a former NHRA superstock record holder (the record stood until being removed mandatorily at re-indexing) and they currently have a set of SS heads on a Ford in the North West coast region kicking butt.

[speedy]

Mopar MUSCLE has an article going with the flow March 99 they said 30 percent on intake and 30 on exhaust .Use the templets then blend in the bowl area after you install the larger valves

[PRO]

340KING MAKES A GOOD POINT,IF YOU SPIN LESS THAN 5000 RPMs AND YOU HAVE A RELATIVELY SMALL CAM YOU WONT SEE MUCH GAIN, BUT ABOVE .500 LIFT AND ABOVE 5000 RPMs IT MAKES A DIFFERENCE, SBs ARE SIMILIAR, GOING TO A 2.02 INTAKE VALVE (VS. 1.88) WONT GAIN MUCH UNDER 5000 RPM OR WITH LESS THAN .480 LIFT....PRO..

[DartGT66]

I think the bigger valves will help at all rpm, they just flow better than the small ones even at lower lifts. If you go to bigger valves the best bang for buck will be doing a three angle valve job with a 70 degree bottom cut and blending it to the as cast port. Putting the bigger valves in to bare template ported bowls will not give you better flow compared to stock valve sizes, the 70 degree bottom cut is very important here. I suggest everyone reading the mopar muscle article, it's propably the best head porting text ever written about the factory BB heads. For those who say that better flow help only at bigger rpm; that's absolutely not true. If you get there by increasing the cross sectional area of the port, then it is, but if you can get more flow with only bigger valve, it will help at all rpm. But bigger is not always better. One thing that might be with the SB head is that the relationship between intake and exhaust port flow suffers from the bigger intake valve, and the result is not so good.

[Old hippie]

According to the articles in Mopar Muscle....you will gain substantial flow in the low lift area by taking a 30 degree back cut on the valve. These gains are below .250 valve lift. There are gains in the mid-lift area also. When going to the big valves ie 2.14I & 1.81 E there are really no substantual gains UNLESS you port the heads. When your machinist makes the throat cut have him/her plung the cut down into the bowl area as far as they are comfortable with. This takes out a lot of the material that using the porting templates takes out but you spend a lot less time with the grinder and carbide burrs doing the work. Then you basically blend this into the bowl area and you have a nicely flowing set of street heads. If you have not read the series of articles on the head porting I strongly suggest you do so. As one of the other respondents said, this is one of the most informative articles on head porting and the results of what did and did not work that I have ever read and I have had a subscrilption to Hot Rod since 1959 (I was 12).

The Old Hippie Hisself

[340king]

I just got off the phone with Monte the motor man and he confirmed what I posted previously. They work with a JKM automotive flow bench that is frequently calibrated. They used the 4.311" bore fixture and experimented with int. valves up to 2.19". The shrouding on the larger valves hurt the flow.

I didn't read the magazine article so I don't know the flow numbers achieved. These are the numbers Brett was able to achieve with the 906 castings and stock diameter valves.

intake lift flow exh lift flow
.100 81 .500 201
.200 149
.500 278
.600 290
.700 266

These flows were all corrected to std conditions and 28" water depression.

Brett claimed that he took out a Big Gulp's worth of material from each head after the throat cut. One interesting note was that the exhaust was still climbing all the way up to .800 lift. As you can see the flow balance is not real good on these heads and should be compensated for in camshaft selection and rocker ratio.

[DartGT66]

Nice figures, but don't necessarily draw any conclusions. A flow bench is just a flow bench, and the flow may vary a lot when a head is taken from one bench to another. The absolute numbers are almost worthless, unless all the numbers are achieved in the same bench. The numbers can also be manipulated to make a certain head look better than it actually is (=to make others look worse, that is). The flow bench is a good tool for modifying the heads and to see if the flow gets better or worse, but don't stare at the numbers alone, or you may get misleaded.

[Old hippie]

Dartgt66 makes a very valid point. The biggest drawback to comparing flowbench numbers is in the flow benches themselves. No two flow benches are alike because there has been no standardization in the industry applied to flow benches. Also, unless your facility is climate controlled, you can and will have vastly differant readings from day to day, morning to afternoon, and even hour to hour. The research facility used in the Mopar Muscle series was Quadrant Specific in California. The man on the bench was David Vizard, a very respected developer and r&d man in the industry. His flow bench will read well below what other benches will read. I like this fact. I would much rather use a conservitive flow number and build up to that figure than use real big numbers and have a vehicle that falls flat on its face because it is overcammed and over carburated. I'm pulling these figures from memory so don't quote me on them. The fully ported 915 heads with the big valves flowed 270 (?) CFM intake at .650 lift. Sorry, I don't recall the exhaust figure but I think it was in the 75% range of the intake. I also believe this was with a 210cc runner volumn, which will keep mixture velocity up. The late heads (346 & 452) were down about 10-15 at peak but the tradeoff was that they did not require as much work to get them there as the 915 heads did, plus they are a lot easier to find. As I said in my earlier posting, this series of articles was an eye opener. Beg, Borrow, or Buy these magazines and read and reread this series. You won't be sorry.

The Old Hippie Hisself

[motorhead440]

Well it seems that i have have stirred up some opinions on this one! I appreciate all of the input. I think that i may have those mm articles somewhere. I've had a script with mm for several years. I'm not sure what cam, rockers i'm gonna use at this point. I do know that i will be using 12:1 ross pistons, stock rods, stock crank. I'm not sure what rings to use at this point. I want to run high tens, low elevens with my duster. I'm thinking of a roller cam but i don't which one to use. I'm gonna dig out those mm issues and read up. Thanks again fellas.
motor

[ChristianCuda]

Just to mention that the porting can be done if you are going to larger valves but they say not to use them with larger valves because after the cuts are made for larger valves then the metal that would be removed for the templates is already removed due to the cuts for the larger valves if the cuts were done right with a cutter and not stones.

Christian
68 Flyin Fish

[caveman]

Do it the way Pro said.I've done heads like that before and they work real good.Do not go over the large valve sizes that mopar recomends unless you have the know how.The 2.14/1.86 valves are right,any more does hurt flow.Try nail head valves that size,and a unshrouding cut on the side of the chamber doesnt hurt either.