Not going to spend much time on this post other than to mention it. I cut the exhaust valve seat about 0.030" deeper to make the face of the exhaust valve flush with the intake valve. I also radiused the corner of the exhaust valve. I really thought there was going to be a 1-2 cfm gain because the exhaust valve was 'shrouding' the intake in a very highly active zone. Picture shows the exhaust valve sticking up into the flow zone before sinking. Pretty much nothing. Move on.
SM Head Modifications on a budget
- Thread starter Earlie A
- Start date
-
Have you tested the exhuast side to see if that radius on the valve changed exhuast flow?
Here's my last test of the day and my last test until we get more direction from PBR. I went ahead and worked the short side blend a little more as can be seen in the pictures below. This was done with a 1" diameter 60 grit roll and took 1-2 minutes. I basically removed the 70 degree purple line area and blended smoothly back to the SSR. This is still very easy work to do, requires little skill and is not getting near the valve seat itself. This increased the throat to 1.826 wide x 1.851 deep which is now 89.5%. The first two flow test papers show the incremental improvement over the previous test.
Here's an opinion on throat size. I would love to hear other people's opinions. I do not believe that this latest improvement was because the throat size increased. I believe it is because the shape of the short turn got better. The 91% throat was the result of the modifications, not the goal of the modification. It is my opinion that if we could keep this short side shape and reduce the throat size to 88% that flow would improve. The only way to do that is if there was more metal to work with on the long side. We could then extend some angles, blend in a different way and direct the high speed air on the long side in a different manner. This in effect is an offset throat, i.e. the throat is not concentric with the valve, it is shifted toward the short side.
I thought it would be good to show progress so far, so the last two papers compare the very first flow test of the stock port vs the improvements to date.
I'm done for the day. What's next PBR?
Here's an opinion on throat size. I would love to hear other people's opinions. I do not believe that this latest improvement was because the throat size increased. I believe it is because the shape of the short turn got better. The 91% throat was the result of the modifications, not the goal of the modification. It is my opinion that if we could keep this short side shape and reduce the throat size to 88% that flow would improve. The only way to do that is if there was more metal to work with on the long side. We could then extend some angles, blend in a different way and direct the high speed air on the long side in a different manner. This in effect is an offset throat, i.e. the throat is not concentric with the valve, it is shifted toward the short side.
I thought it would be good to show progress so far, so the last two papers compare the very first flow test of the stock port vs the improvements to date.
I'm done for the day. What's next PBR?
Last edited:
I have not. We'll eventually get to the exhaust side.
I'm kinda curious if the radius will improve exhuast flow. Thank you for what your doing!
I would like to know that as well. Thanks.
PRH
Well-Known Member
I understand the goal is 280+ by employing a process that minimizes any more rework of the SSR than necessary.
My thinking at this point is……..you’re going to have to uncover a fairly significant problem area that yields healthy gains………that don’t keep the port from being so dependent on a better SSR.
As I see it at this point of the development………it’s still all about the SSR.
It’s very reminiscent of my earlier exploits with 906 heads.
My thinking at this point is……..you’re going to have to uncover a fairly significant problem area that yields healthy gains………that don’t keep the port from being so dependent on a better SSR.
As I see it at this point of the development………it’s still all about the SSR.
It’s very reminiscent of my earlier exploits with 906 heads.
I don’t have time to get into that other question now but man you gotta get rid of those one inch sanding rolls. My biggest porting tool I have is 1/2 inch and that for rough in work. I rarely use a sanding roll except maybe short side finish work, exhaust, and chamber. (3/8 roll) You can get your proper shapes and tighter corners to get the area you need everywhere on these heads.
This whole exercise is to help guys out that aren’t afraid of getting dirty and don’t have enough money on hand to send them to you, Brian, myself, or any other head porters out there. I could never take the time to test these relatively simple mods and almost anyone could do at home and gain 20-50 horsepower. He’s willing to do these tests but like you said to hit the upper side of our target he’s going to have to get rid of the bolt bulge and I’m sure lower the shortside and some shaping. I too like you did this 40 plus years ago to gain what we could on J, X, 906, and any other junk head that we had to use back then.
Not too bad of a gain under the restraints of the exercise, the main meat between .300"-.600" looks to gain about a 15 cfm average. That's got to be around 25 hp at least on the right engine you would think.
I’m gonna push back on that pretty hard. I have all sizes and shapes of cartridge rolls. For a large diameter like I was working, the 1” is quite nice. Match the diameter of the tool to the shape of the workpiece. Worked great.
PRH
Well-Known Member
Perhaps after this thread has run it’s course, EA could run a series of tests on the cnc ported SM head he has……..using what’s been learned here regarding the valve & valve job situation.
I know it’s never a good idea to compare results from different benches, but the one pair of SBM CNC SM’s I had here put up numbers on my bench(ootb) that were considerably higher than what he saw.
I wonder if that’s a result of a different cnc program, different valve job, different flow bench……..or a bit of all three?
I know it’s never a good idea to compare results from different benches, but the one pair of SBM CNC SM’s I had here put up numbers on my bench(ootb) that were considerably higher than what he saw.
I wonder if that’s a result of a different cnc program, different valve job, different flow bench……..or a bit of all three?
Brian Hafliger
Well-Known Member
Where the yellow is, it would help to lay this back to the gasket line, and concave the chamber wall from the deck to the seat top. I also don't do my seat cuts that way, but making more room for the valve will help...it will also speed up the air so that will make the pinch and ST more critical. But I've seen 280 cfm from a very mildly touched ST, large pinch, 89.5% throat, 75/60/45/38 seat cut with a back cut on the valve. No guide boss slimming, very little head bolt bulge work, but good chamber work and proper blending of the valve job especially on the ST side. You have to not just eliminate the 75 cut, but work it in a way that makes it more of a radius into the 60. The rest of the circumference I leave a small partial amount of the 75 cut and underneath it needs to be smooth. If you lay back the top of the ST some and blend it you'll hit 280cfm. If you want to show people how to get good ports, you need to start with the WHY...in this case it's about unlocking the short comings of the port to make it more homogeneous top to bottom. Opening the pinch with all this other work done, will slow the air down and allow it to better navigate the ST. But it needs to be worked really well...roof, common wall, floor and pushrod side as much as possible. Even on a smaller 340 this makes really great power. Now keep in mind, the port will be too fast just on it's own on your bench...but if you put an intake manifold on it and bolt the carb on it you'll see why, at least on the sb mopar, a fast port is not always wrong. I won't say the FPS numbers I shoot for but you can make the port too fast. And almost never too slow!! Hope this helps, if you guys don't want any further input I'm OK with that and won't hurt my feelings ;-)
I kinda wish you would have left the 70 degree cut untouched and the throat at 90%. I cut my valve job in when I’m about 80% done with a head. After that I carefully remove any lips in the chamber and blend everything in the chamber to the valve job. I remove the lip left from May valve job in the bowl around the whole bowl. I Will slightly modify the 70 degree angle at the short turn only enough to lay it back into the short turn. At this point my common wall is straight, pinch is set, roof height is set, bolt bulge is long gone, floor is set at about 80% of my desired height before the valve job checking it with calipers up through the valve pocket across the floor and the deck surface. Then after the valve job I set my finished dimension of the floor so I can final shape my short turn and shape it into the direction I desire the airflow to travel. (Center cylinder and away from the cylinder wall)
on the common wall side. You can NOT do this with a one inch sanding roll. This is where thinking in 3D has its benefits and looking at everything from every angle pay off.
on the common wall side. You can NOT do this with a one inch sanding roll. This is where thinking in 3D has its benefits and looking at everything from every angle pay off.
I always appreciate input from you guys. It’s kinda hard explaining things when we automatically do it without really thinking about it. And harder yet trying to simplify your explanation. Guys buy heads like these with dreams of hitting 500 horsepower and it can easily be done but any airflow you can gain makes that chore easier. Next thing you know you may be leaning towards 550 HP. Lol
Perhaps I got the cart in front of the horse, but this was another move by Joe Average. On PBR's head this was a bad move. Was it a bad move on Joe's?
Thanks for the response. I'll need a little time to absorb some of this. Working on my daughter's house today.
Going back to look at the original objectives of this post, we have completed 4 of the 5 initial goals. PBR was hoping to unlock 15 cfm with some very simple modifications. We are quite close to that initial goal and we have not yet touched the head bolt bulge.
There have been several excellent posts and ideas shared about unlocking the true potential of this head. I am so excited to get the input and wisdom that many of you can share. PBR always stresses the importance of area over the short turn. PRH has emphasized the importance of getting the short turn right early in the process. Brian has given some insight into unlocking the potential of the chamber. I think we have just made the case for steps 6, 7 and 8, in no particular order. Before we get there, I think it's important to do a good job with steps 1-5.
As a reminder to everyone, the initial plan for the valve job and chamber work were limited to what a machine shop could do on the seat and guide machine. No hand blending by Joe. With that said, I do not think we have optimized the valve job. I'm going to continue playing with some things (mostly with clay) to try to come up with a better shape. The objective is still the same - come up with a valve job combination that does not include hand work or sinking the valves (which would alter valvetrain geometry).
When we feel like we have taken steps 1-5 as far as possible, I want to try one final bowl blending to remove a couple of ridges that remain between the 70 degree cut and the bowl. It will enlarge the throat a little more, but I believe the shape will be better. I'll wait on that one.
Now, unless PBR has another idea, on to the head bolt bulge. I'm going to try to get some sonic readings and measurements in the bulge area for initial data. All the pushrod holes and two head bolt holes in this head are already tubed, so I'm not too concerned about creating a hole at the head bolt. The tubing process is quite easy. I followed one of PBR's old posts for the supplies and process needed. I have had no problems with keeping the tubes in place on the flow bench. Maybe PBR will talk about how to keep the tubes in place in a running engine.
Brian, you have touched on several areas that peak my interest here. I have played around with undercutting the chamber wall. For my feeble attempt I did gain some low lift flow but hurt flow after about 0.350"-0.400". I love the idea of the steep top cut angles and would enjoy a conversation about how to make that work on this head with factory 15 degree top angle. I have played around with it by sinking valves. There are so many other things you have touched on that I would like to discuss. I fully understand there are limitations on time and information sharing. I'm grateful for anything you add.
I'm going to hold off on the chamber modifications until we are finished with our initial steps 1-5. We'll try some more stuff later. I also want to try one final blending of the valve job to the chamber walls, but I will also hold that until the end of steps 1-5.
One question for now. These factory Speedmaster heads have a top cut of 15 degrees. The factory Edelbrock RPM heads that I have are cut with a zero degree top cut. Without sinking the valves or welding the head, is there a way to incorporate a steep top cut angle? This is especially a problem on the chamber wall side (the area you marked in yellow). On the SM head, I had to sink the valve 0.090" to get rid of the factory 15 degree cut in this area.
Here's a couple of before pictures of the head bolt bulge. Minimum width at the bulge is 1.264". Sonic tester shows 0.145" aluminum thickness at the bottom of the bulge and 0.160" at the top of the port. Don't know if the brass tube insert messes with the sonic reading.
I kinda hope you leave the clay out of this test. Common sense says if you see a ridge near the valve job in the chamber throw a old valve in the head to protect the valve job and address it. I personally only sink the valve enough to give me room for a 15 degree top cut. Your last two moves if we go far enough will get you to our target. We know the bolt bulge has to be minimized and we know the short side had to be lowered and shaped. But every step we take we are going to lose the do it yourself crowd. Like I think it was Brian said an intake manifold is going to slow the airspeed some. When I first did the set of heads I run now back in 2008 I needed my quickly ported super Victor to calm the head down enough to hit 318 cfm with a 2.08 valve. I have since learned how to slow the airspeed down enough without using the intake as a crutch. And between being able to now set the throat dimension on my seat machine and giving the heads a better competition valve job I’ve picked up 16 more cfm on my next set of heads. Heck the ones on the car now had my old 4 angle valve job that I did with Neway cutters. And I know the throat is under 88%
Clay has nothing to do with ridges in the chamber. The 15 degree cutter that was used for deshrouding up to the gasket line is shown in the picture. It leaves a sharp inside corner and a vertical wall, both of which I believe are bad. With clay I can fill in the sharp inside corner, test on the flow bench before I go to the trouble of making a custom carbide cutter on the knife grinder.
I want to play with valve angles and top cut angles because it is fairly easy to make these custom cutters. Just a whole lot easier to start with clay.
I want to play with valve angles and top cut angles because it is fairly easy to make these custom cutters. Just a whole lot easier to start with clay.
PRH
Well-Known Member
For the next test my vote would be to reduce the bolt bulge a bit.
I figure, you’re going to do it at some point anyway, why not do the bulk of it now and see if it’s worth anything at this stage of the game?
It’s pretty straight forward and easy to access…….should be no problem for someone who’s decided to take on the porting job.
I figure, you’re going to do it at some point anyway, why not do the bulk of it now and see if it’s worth anything at this stage of the game?
It’s pretty straight forward and easy to access…….should be no problem for someone who’s decided to take on the porting job.
How should we approach the head bolt bulge? Many months ago when I was greener than I am now, I tubed the head bolt bulges and then ground a couple of them down flush with the common wall. I was looking for the brass and stopped grinding when I hit it. As a green DIY'er I did not find the head bolt bulge intimidating at all.
So my question is this. Should I approach this grind as if the head bolt bulge is already tubed? If so, I'm not as nervous. Just check for brass every now and then. Should we assume a DIY'er is going to install tubes?
-
