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Tusky, probably Cathedral Heads with it having a unported FAST 92.
Carbuff, with a super efficient exhaust port there is less need for more exhaust bias in Cam design, can even move towards symmetrical cam or reverse split in some cases, NA of course. 75-80% is a good E/I ratio just hard to reach with massive Flowing intakes. 270 Exhaust/350 Intake = 77% @ Peak.
Super Efficient E/I ratios allow for multiple build possibilities with the same
Heads from NA to Nitrous, to FI.
Those numbers and explanation are what I have read also. I suppose I would extend my question to understand the tradeoff of using the cam vs. the port to achieve the required amount of flow?
The comment about being a bit more flexible on application does make sense also...
Those numbers and explanation are what I have read also. I suppose I would extend my question to understand the tradeoff of using the cam vs. the port to achieve the required amount of flow?
The comment about being a bit more flexible on application does make sense also...
My understanding is you want the most airflow possible from the smallest CSA which promotes velocity and you want the most air in/out from the shortest duration that will meet your target RPM, which traps more cylinder pressure I.E. Slug kicker....torque
Interesting data. On the 408 you referenced, I assume that's an NA setup?
Is it possible to have "too much" exhaust airflow? That seems like a silly question, but I would think if engines continued to need more and more than castings would be available that offer it. I recall from the deep crevices of my memory that 75-80% is the typical targeted number, but I don't know where that comes from... I'd appreciate more education in this area, particularly since it seems GM is now producing heads that are moving further away from that with the large intake flow numbers...
Thanx!
Yes....its an N/A engine and it had ported OEM cathedral castings....he used the same cam and the same intake (unported FAST 92) and the same restrictive 1.75 primary / 2.5" exhaust (that would hurt a 346 a little.....a 408 that much more).
This is the real punchline....he dyno'ed the original combo (with the OEM ported heads) at a different shop/location on a chassis dyno that produced numbers that might be considered more typical of what you would expect a combo like his to produce (with the previous choke points in place etc.). The latest dyno with my new MMS 235 heads was on a real heart-breaker Mustang dyno and it spit out a torque figure about 10 ft/lbs lower than his baseline numbers on the different dyno but when he sent me the data, just looking at the curve comparisons (mainly the shape of both curves), that told me he has to be making alot more power and I suggested he forget about what the dyno said and just get to the track. Before he went I asked him if the car "felt" alot faster on the street and he said it felt awesome and there was no question it was faster....a few days later the track results backed his azz dyno up and also backed my working theory that the second dyno had to be super stingy (only 427 RWTQ with a 408 CID and a manual trans.....that's LOW).
I will post a copy of both dyno's later....you guys can see what I mean visually. This is the problem inherent in comparing any type of data.....flow bench data.....dyno data.....its only relevant when the equipment used is the same. And when we discuss track conditions, besides the handful of human variables involved (especially with a manual trans car), air quality / DA plays a huge role in those results and must be also factored in.
Regarding your question about intake and exhaust percentage....in my book I try to strive for a minimum of 75% but some heads just wont get there due to the inherent design of the head. IMO, the sweet spot for a properly cammed N/A engine is probably 75-78%......the biggest difference is how you cam the 75% heads versus how you cam the 78% heads. Lets look at the standard MMS 235's.....falls right in my "sweet spot" @ 76% or so.....the MMS NFI head has a ratio of 78% and could certainly be used on an N/A application with excellent results if the customer cammed the engine properly and had the extra coin to step up to the NFI head which is $250 more mainly due to the additional costs of the aftermarket custom exhaust valves and some additional costs associated with the CNC porting of that head. When the smoke clears, I don't envision big power gains with an NA application comparing the standard MMS 235 against the NFI piece (Im guessing 5 HP or so).....but add boost or nitrous to the mix and the heavy demand that places on the exhaust port and you could easily triple that.....more on a big power adder build (lots of boost or lots of nitrous).
Feel like this post rambled a bit, but alot of good info here on various fronts that is all really good information to store in the back of your brain.....LOL
OK....here are the dyno comparisons of what I discussed in my previous post above.
Again....two different dyno's skewing the numbers and the comparison a bit but I'm confident the new combo would roll 20-30 more RWTQ and 30 more RWHP on pretty much any other dyno that read remotely in the middle of the pack (not stingy.....not overly optimistic)
The cam btw, which will likely be everyone's next question, is the same one that was in the engine with the original OEM ported head baseline....its fairly stout in a 408 and the specs are 247/254 on a 113 LSA with 4 degrees of advance (109 ICL).
Here is the baseline curve....kinda typical for a heads/cam car with a sizable stick in it....4700 ish TQ peak...flattening out around 65-6700 HP peak
And here is the same combo with the addition of my MMS 235 heads, a set of Johnson lifters, and the custom Manton pushrods I also helped him with. The shape of both curves are so vastly different you would immediately think a much larger cam was installed. This is one of the best carrying cathedral curves I have seen (in spite of the unported 92 FAST and marginal exhaust).....with a ported 102 / 102 and a 1.875 header and 3" dual exhaust it would have been that much sexier which is almost difficult to fathom.
Obviously power is still climbing where the pull was terminated so unfortunatly we dont really see peak and past peak performance but Scott was tagging his 7200 rev limit at his first track outing which makes sense as the optimal shiftpoint in the new combo is at least 7300 (rule of thumb is you shift 500 RPM past peak but an engine that carries power well may want/like even more).
Cant wait to see the further evolution of this combo and get some numbers from a different dyno. I assume he has plans of upgrading the intake and exhaust but I have no idea when. The owner did mention rolling on a DynoJet just to see what it would do but so far hasn't found the time to make that happen. He is pretty thrilled with the way it runs and that's what counts the most!
Cheers,
Tony
PS....He has discussed installing a well needed shift light next and heading to a private track rental soon also.....that should be interesting. At some point I suspect he may chime in here as well but I know he has been busy lately with other curve ***** life throws at you.
Hey Tony, what size shot would you recommend the NFI exhaust head over the standard head? Would it be worth while on a 150-200 shot?
IMO, the NFI head may be worth a few ponies even in an N/A application with a properly designed custom cam. Therefore ANY amount of additional horsepower in the form of a power adder is going to make even more sense.....the larger the number of ponies we are adding the greater the gains and the increase in value (power per dollar your paying for).
Is the rest of the valvetrain set up to carry past 7200rpms? Could this combination reach 8k safely? That's the extent of the wet sump oiling system, in my opinion. Anything past 8k is dry sump and solid roller territory.
Is the rest of the valvetrain set up to carry past 7200rpms? Could this combination reach 8k safely? That's the extent of the wet sump oiling system, in my opinion. Anything past 8k is dry sump and solid roller territory.
It would be out of breath by 7500 RPM in any application with a long runner FAST intake. My guess is the engine makes peaks power 67-6800 and 7300 would be an optimal shiftpoint for this combo.....impressive considering its not a small engine and it takes really good breathing to have a larger engine hang on as well.
It has the really good short travel Johnson's I sell with the axle oiling feature and beefy 11/32 Mantons and good valve spring on the heads so she would rev more with perfect valve control but this was never designed to be an 8K type of piece. A large well ported single plane would have been a better choice for that kind of RPM.....just a completely different application
Thank you for the explanation. And, if you don't mind me asking, how does designing the cam change between a 75% head and a 78% head?
I would imagine that the higher ratio heads would require much less exhaust bias built in to the cam. Maybe even a single pattern cam with a hint more lift on the exhaust lobe. Probably an aggressive ramp rate intake lobe, and a mild rate exhaust lobe. And with any sort of decent scavenging exhaust system, you could probably make better use of a smaller amount of overlap. Or at least that's my guess.
At what point does the "over scavenging" you mentioned on page one start to occur? Because it seems you could just close the intake valve sooner, or open the exhaust valve later (wide lobe separation angle?). Tune the injectors to spray after the exhaust valve closes. Or any combination of these.
And, do you think that you will make an NFI version of the MMS205, when you are done with them(the 205's, that is)?
Last edited by DavidBoren; 09-29-2015 at 09:26 AM.
Thank you for the explanation. And, if you don't mind me asking, how does designing the cam change between a 75% head and a 78% head?
I would imagine that the higher ratio heads would require much less exhaust bias built in to the cam. Maybe even a single pattern cam with a hint more lift on the exhaust lobe. Probably an aggressive ramp rate intake lobe, and a mild rate exhaust lobe. And with any sort of decent scavenging exhaust system, you could probably make better use of a smaller amount of overlap. Or at least that's my guess.
At what point does the "over scavenging" you mentioned on page one start to occur? Because it seems you could just close the intake valve sooner, or open the exhaust valve later (wide lobe separation angle?). Tune the injectors to spray after the exhaust valve closes. Or any combination of these.
And, do you think that you will make an NFI version of the MMS205, when you are done with them(the 205's, that is)?
Better exhaust port requires less cam timing....or leave the same cam timing to produce better power numbers at higher RPM (it will carry better) but it may cost you a few down low.....also allows you to bump the intake a touch also because you have the ability to exhale a greater charge without camming it up more on the exhaust. Lots of ways to play it.....really depends on the combination and the end goals of that combo.
The MMS 205's are reeeaally strong on the exhaust.....no need for an NFI version....LOL
How about 82% or so the way they sit today (close to 300 CFM intake and 246 CFM exhaust!). Those heads could benefit from a single pattern cam or a very small forward split if you want the engine to carry better. In a true truck application with the goal to boost lower end performance, you would want to go single pattern or dare I say a small reverse pattern (never been a fan)....BUT....if there was ever a head I designed that might benefit from a reverse pattern grind, this head falls into that category. It will help build more bottom end while the phenomenal E to I ratio still allows the engine to clear the spent gases at higher RPM and still make respectable power.
I have one last trick up my sleeve regarding the optimization of that new 205 program.....should have results from that soon and will share the final numbers with everyone shortly. I did decide to keep the intake and exhaust valve a 1.970 and 1.570 respectively which really pays a dividend on the true small bore applications (4.8 and 5.3 liter) I targeted with this design.
Sort of missed it the first time, 'cause of the FI posts, but those dyno comparisons aren't too bad. The first one looks a lot like a dynojet plot, and the second one says it's a mustang dyno, so, it's apples and snow cones.
The torque curve on the old heads peaks right at 4500-48--, then immediately starts to fall off. On the new one, it is almost perfectly flat from 4700-6000. So, even if the torque numbers were truly identical, the second one would be more fun the drive.
Also, check out the scaling on the graphs. The first one, the axis crosses at zero, and the second one, the axis crosses at 200. Also, the second graph is taller. If the data from the second graph was scaled to match the first graph for an overlay, it would look almost perfectly flat from 4200 to 6600!!!
And then, the horsepower is still climbing at 6600. Hasn't hit peak yet. So, if the bottom end was built for it, it might could carry power out to 8,000. I bet even though the dyno numbers "match", the new motor would trap higher based on the way it carries at the top end.
I would guess that the fast92 intake is somewhat holding it back, but I have a hard time thinking of a 515 horsepower engine as being held back.
Once again, thank you for the informative response, Tony. You are doing God's work with these heads. 82% exhaust to intake ratio is incredible. I must have it.
Hey guys, the dyno sheets above are from my car. I apologize for not commenting sooner. The car obviously runs great and picked up tons of fun over the old PRC 5.3 heads (as it should). I didnt use the lifters with the axle oiling, just the regular short travel Johnsons, Tony's 235's, the pro 10mm stud YT's and the Manton PR's. I was hoping to get the car on the same dyno that the first sheet was from but its just not going to happen soon. On the most recent dyno runs we DID spin it up to 7200. It quit making power well before 7200. I just called the shop and they are emailing me the 7200 pull so you guys can stop speculating of "what might be". LOL. I'm not planning on upgrading the exhaust or intake. If anything this set-up will get a standalone and 150-200 shot. My main goal was met. I wanted a 10 sec slip and I got it. Could I have gotten a 10 sec slip cheaper? Sure. Am I happy with my set up? Yep. Do I care what you guys think? Nope. Oh yea...one more thing. I put this new 408 shortblock in last fall. Maybe had 2000 miles on it when I swapped the heads to Tony's 235's. When I pulled the 5.3 heads off I found scoring in the cylinder walls. I contacted ATK and sent them the pics. They said it was normal and not to sweat it. I did sweat it. All the way up until it was on the dyno singing at 7200 rpm with NO SMOKE AND NO BLOWBYE. A day of flogging at the track after the dyno pulls and it hasn't so much as puffed even the smallest amount of smoke. I'm not telling anyone what is acceptable for their build. Just sharing my experience. Scoring pics attached.
Those can be eliminated or reduced by "softening" the outside corners of the rings with a file when file fitting before assembly. When a ring is file fit it leaves a sharp corner that few engine assemblers address.
What do you mean? Deburring file fit rings isn't standard practice? Who would take the time to file fit the ring and not take the time to deburr it? That's just lazy.
Hey guys, the dyno sheets above are from my car. I apologize for not commenting sooner. The car obviously runs great and picked up tons of fun over the old PRC 5.3 heads (as it should). I didnt use the lifters with the axle oiling, just the regular short travel Johnsons, Tony's 235's, the pro 10mm stud YT's and the Manton PR's. I was hoping to get the car on the same dyno that the first sheet was from but its just not going to happen soon. On the most recent dyno runs we DID spin it up to 7200. It quit making power well before 7200. I just called the shop and they are emailing me the 7200 pull so you guys can stop speculating of "what might be". LOL. I'm not planning on upgrading the exhaust or intake. If anything this set-up will get a standalone and 150-200 shot. My main goal was met. I wanted a 10 sec slip and I got it. Could I have gotten a 10 sec slip cheaper? Sure. Am I happy with my set up? Yep. Do I care what you guys think? Nope. Oh yea...one more thing. I put this new 408 shortblock in last fall. Maybe had 2000 miles on it when I swapped the heads to Tony's 235's. When I pulled the 5.3 heads off I found scoring in the cylinder walls. I contacted ATK and sent them the pics. They said it was normal and not to sweat it. I did sweat it. All the way up until it was on the dyno singing at 7200 rpm with NO SMOKE AND NO BLOWBYE. A day of flogging at the track after the dyno pulls and it hasn't so much as puffed even the smallest amount of smoke. I'm not telling anyone what is acceptable for their build. Just sharing my experience. Scoring pics attached.
HA! Best regards!
All and Scott,
We have no control of the assembly procedures or environment after it leaves ATK, any mark at all shows up on a fresh hone. The ring end gaps are all de-burred and we (ATK) have a very clean assembly area as any engine builder should, but we also get audited for cleanliness, safety and hazardous materials frequently.
This was bought as a short block and finished by the customer. Depending on how hard this engine was run for 2000 miles and this pic the worst hole out of 8 this doesn’t surprise me and there's nothing wrong with it other than cosmetics.
Agreed Dr. W.....foul attitude.
We're all here to gather new information and Mamo is like E.F. Hutton when he speaks, we all listen. I'm hoping what he said came out wrong and misunderstood....if not; agreed, it sux!
Tony....don't ever feel like your posts ramble (they do a little bit BUT.....) we all acknowledge your artistic craft and love nothing more than a chance to get into your thoughts. While many people self proclaim themselves as "the best" porters, no one backs them up on paper as consistently as you. I have yet to see, meet or read ANYONE worthy enough to hold your dremmel!!
09-28-2015, 02:21 PM
Oh yea...one more thing. I put this new 408 shortblock in last fall. Maybe had 2000 miles on it when I swapped the heads to Tony's 235's. When I pulled the 5.3 heads off I found scoring in the cylinder walls. I contacted ATK and sent them the pics. They said it was normal and not to sweat it. I did sweat it. All the way up until it was on the dyno singing at 7200 rpm with NO SMOKE AND NO BLOWBYE. A day of flogging at the track after the dyno pulls and it hasn't so much as puffed even the smallest amount of smoke. I'm not telling anyone what is acceptable for their build. Just sharing my experience. Scoring pics attached.
