offset valve seat flow numbers

[wfolarry]

There was a company selling valve seats with a radius on the bottom with claims of big flow gains some years back. Some people believed it. The guys that actually ported heads knew better. If you're making changes & flow testing the changes you're on the right path. If you make changes without testing then you're missing the whole point.

There are some big name companies out there that would be better off leaving the seat as it was instead of blending it all in & killing the flow. There's a right way & a wrong way for everything. You'd be surprised how many heads I fix with nothing more than a valve job.

[1FSTRK]

There was a company selling valve seats with a radius on the bottom with claims of big flow gains some years back. Some people believed it. The guys that actually ported heads knew better. If you're making changes & flow testing the changes you're on the right path. If you make changes without testing then you're missing the whole point.

There are some big name companies out there that would be better off leaving the seat as it was instead of blending it all in & killing the flow. There's a right way & a wrong way for everything. You'd be surprised how many heads I fix with nothing more than a valve job.

Add the final step of confirming the new found flow actually makes more power in the intended rpm either with a proper dyno comparison or at a timed track and I am with you 100%.

[Timinator]

If adding a venturi in the seat ring below the seat worked, I'd be doing it. On a few heads it was a Band-Aid and did provide small gains, but not on decent heads to begin with. Anything current is better than that. In the old days, we did such things to Class racing drag cars, until the NHRA made a standardized valve job mandatory. That act stifled innovation, except in the Pro classes, at least until aftermarket heads flooded the scene.
Myself, my SF-600, and my Dyno Jet 250 work as a team, its a good team. But I try everything that I can think of and anything hinted at or suggested to effect improvements. Its an ongoing thing, sometimes its even fun, no, make that interesting.
Present thread not included, sometimes I have no idea where some of the stuff I read about comes from. I read the ads, go to the trade shows and look at stuff and I know that if the guy selling it had a brain, or a Dyno, he'd have kept his mouth shut and his advertising cash in his pocket!
As for the Pros everywhere, most of them  keep the good stuff to themselves.
David Vizard told me 30 years ago that any info in an article written by him was 3-5 years old, and anything in his books was 5-10 years old, he stays that far ahead of the pack. Engineers and companies pay him for the latest info, that, he doesn't give away. The old info is cheap, or free, because it is old info. Carry on!    TIMINATOR

[Matt C]

If adding a venturi in the seat ring below the seat worked, I'd be doing it. On a few heads it was a Band-Aid and did provide small gains, but not on decent heads to begin with. Anything current is better than that. In the old days, we did such things to Class racing drag cars, until the NHRA made a standardized valve job mandatory. That act stifled innovation, except in the Pro classes, at least until aftermarket heads flooded the scene.
Myself, my SF-600, and my Dyno Jet 250 work as a team, its a good team. But I try everything that I can think of and anything hinted at or suggested to effect improvements. Its an ongoing thing, sometimes its even fun, no, make that interesting.
Present thread not included, sometimes I have no idea where some of the stuff I read about comes from. I read the ads, go to the trade shows and look at stuff and I know that if the guy selling it had a brain, or a Dyno, he'd have kept his mouth shut and his advertising cash in his pocket!
As for the Pros everywhere, most of them  keep the good stuff to themselves.
David Vizard told me 30 years ago that any info in an article written by him was 3-5 years old, and anything in his books was 5-10 years old, he stays that far ahead of the pack. Engineers and companies pay him for the latest info, that, he doesn't give away. The old info is cheap, or free, because it is old info. Carry on!    TIMINATOR

Ha ha ha... 

Those that can do, do. (And keep secrets close to the vest). The exception to that is Darin, I went through
his program, and he showed me everything and anything I wanted to see. 

[Timinator]

Smaller diameter than normal seat, deeper too. Machine portend with a forming tool in lathe before installation. Now you could also do the venturi or offset seat planform with a single point seat cutter machine or CNC. Just do one and trace it!  I'm in Avondale,AZ. mebbie I'll stop in...  TIMINATOR

[sbcharlie]

come over i would like to meet you. sbc

[PanHeadRed]

i used a 2006 twin cam head for flow test
i offset the intake seat at the push rod side at .030
intake    stock               offset
.100     60                     62
.200     124                   130
.300     175                   178
.400     209                 215
.500    214                  230
.600    213                  234

no port work  89% throat ratio  standard oem valves

Impressive that it does not stall after .4"

[Don D]

I tested a stock head, cleaned, stock guides and OEM valve job
.100 66.7
.200 123.5      
.300 187.9      
.400 220.8      
.500 227.1      
.600 225.0

I then did a valve job 5 angles in and 3 + radius ex, protrusion set to 2.030 all, no back cuts stock re-faced valves 45° seats
.100 65.3      
.200 127.5      
.300 189.3      
.400 229.2      
.500 237.5      
.600 241.7

63°F, 1.7 x 2" Inlet velocity stack. 3.937 bore, 08 Mercury casting
Saenz 600 Bench calibrated with PTS plates

[Matt C]

Was the sparkplug in?

[1FSTRK]

I tested a stock head, cleaned, stock guides and OEM valve job
.100 66.7
.200 123.5      
.300 187.9      
.400 220.8      
.500 227.1      
.600 225.0

I then did a valve job 5 angles in and 3 + radius ex, protrusion set to 2.030 all, no back cuts stock re-faced valves 45° seats
.100 65.3      
.200 127.5      
.300 189.3      
.400 229.2      
.500 237.5      
.600 241.7

63°F, 1.7 x 2" Inlet velocity stack. 3.937 bore, 08 Mercury casting
Saenz 600 Bench calibrated with PTS plates

Did you offset any of the angle cuts?

[Don D]

Nothing more than what I stated. No cuts below a Serdi form tool valve job

[1FSTRK]

Nothing more than what I stated. No cuts below a Serdi form tool valve job

Ok, for some reason I thought you were testing the before and after offset results for yourself.
Not sure what your post has to do with this thread 

[Don D]

My own interest and to compare what influence a proper valve job has on the mix. I am sure there is a very nice valve job that is accompanied with those offset seats. I just wondered what the stock heads did with a centered seat plus or minus and I had some jobs in the shop already to test this.

[1FSTRK]

My own interest and to compare what influence a proper valve job has on the mix. I am sure there is a very nice valve job that is accompanied with those offset seats. I just wondered what the stock heads did with a centered seat plus or minus and I had some jobs in the shop already to test this.

And you post it here. Do you really feel it has any relevance ?
To compare you need to now offset the seat with your valve job and flow test on your bench with your inlet flange.

[Don D]

Ok

[kd]

i used a 2006 twin cam head for flow test
i offset the intake seat at the push rod side at .030
intake    stock               offset
.100     60                     62
.200     124                   130
.300     175                   178
.400     209                 215
.500    214                  230
.600    213                  234

no port work  89% throat ratio  standard oem valves

I tested a stock head, cleaned, stock guides and OEM valve job
.100 66.7
.200 123.5      
.300 187.9      
.400 220.8      
.500 227.1      
.600 225.0

I then did a valve job 5 angles in and 3 + radius ex, protrusion set to 2.030 all, no back cuts stock re-faced valves 45° seats
.100 65.3      
.200 127.5      
.300 189.3      
.400 229.2      
.500 237.5      
.600 241.7

63°F, 1.7 x 2" Inlet velocity stack. 3.937 bore, 08 Mercury casting
Saenz 600 Bench calibrated with PTS plates

I want to qualify my observation by stating I do not see this as a competition but use the expression "race" in my statement to make a point. 

Without knowing if the CBC head first had a "good' multi angle valve job before the offset cut and numbers were posted makes it tough to compare the value of the offset work. It appears to me at least that when you compare the steps in the flow test there is not enough difference between the two to call the "race" on. I would guess each set of similar heads getting a similar valve job would have a variance of plus or minus what we see between the CBC offset head and Don's head. Similarly the variance between the two we now have for comparison are so close that I would call a draw. Now, if the CBC head did not have the benefit of a good and similar valve job, but was given one and then after the offset treatment gained more, we may have evidence of a procedure that has something to offer. This would be contingent on repeatability on both counts.  Good stuff guys but I think we need more evidence to show real change and the ability to repeat the gains. Have at er. 

[1FSTRK]

I agree that at this point neither set of tests mean much.
I have seen that offsetting the the cuts both above and below the seat cut does make a difference on many heads but the direction you need to go and the amount of difference it makes will vary with head and port design. It can be enough that over the years many race sanctions with stock classes have added rules stating all valve seat cuts must be concentric. Moving cuts below the seat can effectively alter the short and long side radius of the port in one of the most important parts of the intake tract.

One other other thing to remember is the precision with which HD casts these heads, the ports are all over the place with core shift so that along will alter the results from head to head.
This is not a game changer on otherwise stock heads but on a proven port design if researched properly it can provide consistant gains.

[TorQuePimp]

Run a CNC program on two rear or two front heads along with the chamber that cleans up 100%
One valve job normal.....one offset
Pretty simple

[jsachs1]

Run a CNC program on two rear or two front heads along with the chamber that cleans up 100%
One valve job normal.....one offset
Pretty simple

The proper way to analyze. 
John

[Matt C]

Hot damn! Now that's the best idea I hurd so far. That wood put it to rest.

[Ohio HD]

Run a CNC program on two rear or two front heads along with the chamber that cleans up 100%
One valve job normal.....one offset
Pretty simple

Empirical data       

[1FSTRK]

CNC is definitely the way to go in todays world but back in the days I witnessed this testing it was done by porting a head and flow testing to achieve the best result then the seat was removed and a new test seat was installed and cut and flow tested. This test seat replacement was performed several times until the best offset was achieved then actual permanent seats were installed, cut, then dyno tested.

[Timinator]

Even CNC machined ports can vary, you would still have to flow test them first to make sure they are of the same flow, or the test goes out the window. Still I believe flow guides are a lousy way to test a head flow. Air can flow 360 degrees around the inlet guide, but with the T-Body and intake it must follow what is actually being used to supply the air. I believe that the port MUST BE ported differently with a manifold and T-body attached to get the best results. That's why we do it that way. I also believe there is more difference in porting with a manifold and the brand T-body actually used, than an offset seat alone can provide, you should actually do both. I also believe that the offset would be different from a guide to a manifold/ T-body. If you want to be the best, you need to do the most. Let the s**t storm continue....    JMHO  TIMINATOR

[1FSTRK]

Old news

[TorQuePimp]

Even CNC machined ports can vary, you would still have to flow test them first to make sure they are of the same flow, or the test goes out the window. Still I believe flow guides are a lousy way to test a head flow. Air can flow 360 degrees around the inlet guide, but with the T-Body and intake it must follow what is actually being used to supply the air. I believe that the port MUST BE ported differently with a manifold and T-body attached to get the best results. That's why we do it that way. I also believe there is more difference in porting with a manifold and the brand T-body actually used, than an offset seat alone can provide, you should actually do both. I also believe that the offset would be different from a guide to a manifold/ T-body. If you want to be the best, you need to do the most. Let the s**t storm continue....    JMHO  TIMINATOR

I have 2 programs that have been ran over 100 times for one and 70+ for the other that both clean up 100% and flow within 1% of another set to set every time.

Good bad indifferent they flow that close on the bench every time as the time was taken to make changes to vectoring and cutting speed,pre cutting the seat ID to make sure the tool doesnt deflect from taking too big a bite.

Not all heads or programs come out this good it takes cutting from a few to quite a few but it can be done

use the same valve for testing both heads on the flow bench would help as well

Then find a test engine or bike.....id prefer a engine only test OR someone with a climate controlled dyno cell

And see what there is to the offset seat profiles