Biggest limiting factor is the bore size keeps valve sizes pretty small.

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Official Cookie and Mater Tormentor.

Way back in the day Smokey Yunick who was one of the most straight forward realistic engine men who ever lived and who could make HP from almost anything said in his book that a good rule of thumb for cylinder head flow that he uses is the cubic inches of one cylinder multpied by 5 will give you the CFM he would want at 8000 RPM.

He said this is a rule of thumb but he had found it to work well.
So if that is reasonable and even though I know it isn't the be all-end all, I think it is at least a good starting point, then a 225 /6 =37.5. 37.5 X5=187 cfm.
Since we know the 225 will not live at 8000 and will even have a severely shortened life at 7000 without some very exotic parts and since we know that 220 intake cfm has been achived in a slant 6 head on more than one occasion, then the head is probably not the big problem.
And since we know that in most engines, we can expect around 2 HP per CFM (some will say 2.2 HP per intake CFM) then in theory, these little motors should be able to do that.
When flowing cylinder heads there is a point at which flow stalls... sometimes it even goes backwards above a certain point.
I often used my flow ench to establish that point when doing my SB Mopar and BB Mopar engines and then had a cam ground to suit.

I sold all my shop equipment a few years ago so I no longer have access to a flow bench. I am sure someone has published the flow figures of a well modified /6 head so when I find that info, the max lift point I want will be easily found.

All engines do not like the same cam timing. Most cam design for Hperf work is done on a 350 chev and then afterwards just transferred to other brands of cam cores. It often works better than nothing but one must realize that it will always work better in a 350 chev than anything else because that is where it was designed and tested.
Our engines are a bit different. We have a LONG stroke, 4.12" to be exact. That is longer than 80% of all engines built. We also have a small bore. It is not convienient or the "best" for valve sizing but it's not the end of the world. Jag sixes also had a small bore, as do many 4 cylinders.

So using a cam grind from a 3.48 stroke 4 inch bore engine may not be the best way to get power at 4.12 X3.4 to 3.5 bore. The longer the stroke the faster you can open the intake valve as the piston is moving away from the head at a faster rate.
Let me explain. In BB mopars. You can run a much larger cam in a 440 engine with a 3.75 stroke than in a 383/400 engine with a 3.38 stroke. With the short stroke engine you have to back off on cam or the valve will hit the piston on the way down . You can cut vlave reliefs to a point but there is still a limitation. With the 440 engine you can hammer the intake open faster since the piston moves away from TDC and the opening valve at more "s per degree.
At 4.12 stroke, our piston is moving away even faster per degree of rotation than a 440. Did the cam grinder take this in acount? Not likely since he designed the grind in all likelyhood on a 350 Chev. Why is that important? Because we want the valve as far open as possible when the piston is moving the fastest down the bore. Then we can take advantage of a greater average airflow through the port because our valve can be at a higher average lift throughout and fully open sooner. This is just the tip of the iceberg but I always check cam specs .
If their Mopar cam has exactly the same specs as the Chevy cam by the same manufacturer I KNOW that it is a Chevy grind and not specific to Mopar or my particular engine. A chevy race cam can never be the same as a Mopar one since the Mopar has the 904 lifter and therefore can be opened at a faster rate than the tiny liftered Chev.
Back in the day there used to be a real good explanation of Lifter Diameter vs rate of lift and the formula in the Erson cam book. I dont know if it is still in their tech pages or not.
Don

BTW to put this in perspective a 350 chev would have around a 4.8 stroke and a 4 inch bore to dupicate our slant six bore to stroke ratio. It is obvious that an engine such as this would have very different characteristics than the current 350 does and so does our slant six motor for the same reason.
It is not reasonable to expect a cam designed for and on a 350 to work well in our /6s.

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Don

Are you aware of the slant-6-specific cam development work that's been going on lately…much of it discussed right here on this very board?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Dolmetsch is thinking about the Slant in a scientific way, which is great. Much of this ground has been discussed on this board. From my research of the "heavies", we seem to know that 104-106 LSA is best and ~100 LCA for our cams, as well as more INT than EXH duration. 4-10 deg more INT duration seems to be the range, but this has also not been fully explored.

The consensus also seems to be that actually long duration and lower lift work best. Tilley ran some high rate, high lift cams on his dyno and said they were nowhere near as good as his lower rate 0.530" cams. This is certainly not understood, but has some basis in testing. Mike seems to like higher lifts, but not 0.600"+ AFAIK.

Head CFM could be better, but if you compare to good aftermarket heads for smallblock V8s, we are right there with them on a CFM/cu in basis with a 200 CFM intake Slant head. Most people on this site are not even approaching engine powers that are using that much CFM propoerly.

Lou

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Home of Slant6-powered fun machines since 1988

"Don't believe everything you think. Test your theories."

Just for the record, I do.

Interesting stuff. BTW
Don

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Don

I did some searching and it appears .550 is about max lift for a /6 head . That does not surprise me seeing that a well modified BB 452 or 906 head is all done at .540 (Dan Dvorak said he would even say .530")
You can port them different so they will go to .600" lift but the flow will be no more and sometimes less than you would get at .540" in a well done head. So all one would gain from going to 6 hundred is a big bill for valve springs. Apparently the /6 is similar according to that.

That's what I could find out searching.
Someone implied that they had more info but would not share it. That's nice! I have never held anything back from my fellow Mopar racers once I was sure it was valid. In my book Old Reliable I laid out exactly what and what not to do, knowing full well that someone better then me might take that info and blow my doors off with it. As long as he was also blowing off Camaro doors, I was happy.
Same goes here. If you have some info that would help I would appreciate seeing it. I know I am not really "one of the boys" (and may never be) and my square head makes me a bit abrasive at times but we are all in this Mopar thing together. If you have or know of a flow bench chart for a /6 I would like to see it. Otherwise I will have to build another flow bench. (And then I will have the secrets)
Don

Also someone implied there had been a serous cam discussion here. Could someone link me to it. I dont seem to be able to find it on my own and I would like to read through it all. .

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Don

That's it, right there for me anyway.
You have repeatedly belittled anyone who thinks any direction except the one you think is right. To an unwitting outsider it appears that you think none of the Slant racers have ever done any research or testing on their own, and that since you wrote a book you know everything.
Well, one thing I do know is that many of the teams that were involved in the race for the 10's and then 9's with Slant cars worked harder and tried more things than you will ever know. Mike Jeffrey and Blaine Mueller tried dozens of parts trying to get the Buzzin' car into the 11's on motor so they could race Super Pro at Kearney. They spent more time and money to find out what didn't work than most people even have in their cars to start with. Same for the Cox Brothers, Team Green, Cameron Tilley, Seymour Pederson, Charles Meyer, the Drakes, the Bruners, and Doug Dutra, who you just gave a tongue lashing to for trying lightweight parts, and way too many other racers to list. Sane people would have gone V-8 racing years ago instead of flogging on Slants, but we keep at it.

Sooooo, yes, you will find getting help around here may be a tough row to hoe. I would not tell you what Mike found because you seemed to believe that no one had ever tried a cam with more than .500" lift or a non-Chevy profile. Hell, Lou and I have run street cars with .530"+ lift. Trust me, there have been flat tappet cams with .600"+, and rollers tried with upwards of .700" lift. Profiles? Too many to list.

If you want to discuss theory, calculations, formulas, or just plain race cars try Dart 270. Here's a link to his job from Google.

http://www.mii.vt.edu/MACR/faculty/madsen.html

Right now the turbo guys are really putting it down. You never know, I may even go to the dark side someday. But for now I am content with a bottle and hose.

That being said, most of us Slanters are more than willing to learn, but not from someone who thinks we're a bunch of dumb hilljacks. If you learn to play nice. we may even learn something from you, or teach you something.

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Official Cookie and Mater Tormentor.

Luke, I am you father!

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11.02 @ 120.56
http://www.youtube.com/watch?v=EAxRmoDgsdY
Chassis dyno
http://www.youtube.com/watch?v=wd6hFGzLJMc

Great! Now there's Gatorade all over my monitor.

CJ

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Part of Tyrde-Browne Racing

There's been a fair amount of cam discussion, and the Erson custom-grind deal has spurred a good deal of experimentation with nonstandard, unconventional, and experimental grinds. Do some searching on the board; the discussion isn't consolidated.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

That makes two of us....

I hope we can learn some things together here.

I certainly do not want to wave any degrees around that are mostly irrelevant to racing experience. Sometimes my work comes in handy, but the real world can be far removed from basic theories.

I have been collecting data on some fast Slant buildups for several years now, and do have some things to say there about general patterns and knowledge gained. We are all into testing and re-testing and making these things faster!

Lou

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Home of Slant6-powered fun machines since 1988

It has been a decade long journey on this forum and others for me to produce a warm street slant( mebbe 175 hp. I havn t even tried a 4 barrel yet.

I spent hours on calculators and have talked for years with people who have made serious power in fast cars. I learned their methods and found ways to mimic them within my meagre budget.

Ive heard the hemi S/S guys go "what the hell was that?" when the Buzzin car laid down a 136 mph pass on half the inches they displace.

Every few months somebody walks in here with all the answers or some dream silver bullet that will bring us all to the point of stomping BBCs and LS7 Vettes. Billet heads, roller cams, 1.88 intake v/vs.....in a decade we have seen them all.

My observations have been that it has been the little things that bring our sport along. The best product I ever bought for a slant was an oil pump from Doug. The best power I made was from the Dynamic Compression Ratio theories/calculators applied to cam/compression choices. The best advice I got was an accumulation of hours of discussion with Dennis and Lou.......checked with my own math and real world use......backed up by hearing from guys like Rob (DI) trying the same things.

If Smokey hisself walked in here and said "try this" I would be skeptical.....just because it aint that simple to apply theory to a slant.

Ive run my fingers through enough of Mikes chambers to know slants have some unique traits. Ive blown up enough slants to know they have some unique traits. Ive met enough slant dudes who go stunningly fast to know it takes a unique approach to do this. Dont be thinking these guys running 9s and 10s with little inch motors dont know how to make power and keep them alive. Dont think they all run an off the shelf Comp cam or a Clifford head.

Dolmetsch: If you are here to learn how to make big power start searching and reading. If you are here to convince me I need a roller cam, .700 lift , billet head or 1.88 intake valves or over 190 cfm ports keep right on talking. ......Ill keep on getting my fingers in every Jefferies head I can access and asking questions from every fast slant guy I can meet.

So whats the DCR on your dragster motor?

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Ok I get the hint.
I was asking for info by the way. You fellows were and are refusing to share it. I am not also by the way on my first slant six build. I probably was building them for racing before some of you were born. I was even tuboing them then (1970s)but since you have made your point I get it. Whatever I do discover rest assured it wont be shared here. You wouldnt believe it anyway. As for info on my dragster , pound salt.
Don

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Don

First this:
Then this:
Y'know, Dolmetsch, we have some very strong personalities on this board, many of whom are participating in this present thread. Most of the time, we manage to get along and respect one another even when we disagree. Sometimes we get frustrated with one another and have to take some time away or go off and curse a blue streak about another forum member, but by and by, by and large, we get along.

From what I see in this thread as well as many of the others you've posted to, it's not what you're saying, it's how you're saying it. It's your approach, your tone, your attitude. It's obvious you have a great deal of good, valid experience and a great deal of skill, but your accusations of conspiracy to withhold information, repeated but baseless assertions about all slant-6 cams being Chevrolet grinds, and belligerent hystrionics make it challenging to include you in the ongoing information exchange here that has pushed the bar higher and higher for slant-6 performance results and will continue to do so in the future.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.