They made 320 out of this engine in Mopar Magazine artical. But it did have high CR of 13:1 I believe.

http://www.moparmusclemagazine.com/tech ... index.html


With that block that you have, it is possible to really make some big power. The short stroke, big bore combo's have proven to make more power than any other setup. Just look at Pro Stck 500cid engines, if I am not mistaking they only run a 3.380 stroke on a 500 inch motor.


This type of setup will allow the head to outflow any other slant six setup there is, the flow incresses on the same port as the bore size goes up. You will not have any trouble with ports being to big on that head with the setup you are going to run.

Alot has been learned on head porting in the last 10 years. The port size could be wrong for the size valve that is in the head and that will hurt torque of the engine & cause turbulance at high lift flow. But it can be corrected if that is so. Take a measurment of the smallest part of the port, and measure the throat size also. And I can tell you what RPM it will produce its power levels at for your size engine. And if making changes to the port or valve size will help.


I sure would like to get a hold of one of those 906 engine blocks, I believe with the right setup that 400hp should be possible on race gas, and 350hp on pump gas. Maybe even more. The engine in that Magazine artical reached 320hp, and I feel sure they missed some HP on that build and may have been able to reach 350hp if they had bored it bigger, ran a differnt cam, and biult a custom intake manifold.


Your build sounds very interesting. I wander if the casting cores are still around for that 906 block? That is exactly what the /6 needs, is more bore, less stroke. Then with RPM it can make more HP out of the limited head that it has, with the right porting work.


Jess

interesting articles...

Just for the record, I'd leave the 225 forged steel crank, not use the 170's. So stroke would still be 4.120, but with bore being ~93mm the motor would be close to square. Since I'll be using custom pistons, and custom rods, I would tune up the combination in order to get the longer con rod I can have, moving up the pin and consequently the rings pack as close as the crown as I can get. That's the reason why I asked doc about the max safe distance for top land to crown. Plus, since I'll be doing the ultrasonic wall thickness testing anyway, I would not hold back any safe cushion for the block to be overbored later. That means, if I can gt out a 94 mm bore, I'll go for it, and if things goes wrong, well, I'll wet sleeve. There's a set of toyota sleeves that has some sort of "t" profile on top, you need to machine the top deck for fitting them, that'd be an option if something goes wrong with the machine shop. That'd imply nearly a 1000 dollars more on jsut the sleeves, so I'll leave that as the last option.

since my steel forged crank is in 000 I would keep the con rods journals the same size as stock, that has to add for strenght there. Educated opinions here seems to indicate that girdle support would be a waste. I'd follow, there's a lot of experienced guys here, and I've learned a lot since I first begun posting and asking and sharing back and forth experiences.

on august 23 I'll be heading to mar del plata, a small town where I grew up and where I have that head, I'll measure the ports and throats.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

This is a interesting build you're doing argentina-slantsixer. I did some calculations just for the fun of it.
If you bore it to 92mm, that comes out to 255 cu.in. with a 4.125 stroke.
93mm would be 260 cu.in.
94mm= 266 cu.in.
If you used Bren's 4.25 stroke crank with 94mm bore=274 cu.in.
If you used Doc's 4.5 stroke crank with 94mm bore= 290 cu.in.

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Franklin
'61 Valiant

I see some drawbakcs in stroking the /6... ie

I keep on wandering away from square... (I want the motor to be as square a big cubes slant can be)
I'd have to let go the chance of greatly improving the con rod's ratio. If I use say 7.3" I'd have a 1.77:1 rod/stroke ratio...
I'd have to notch something down thre in the crankcase, wouldn't I? (well maybe I have to notch anyways for the custom con rods...)
I would have to reduce my redline from desired 7k rpm to 5k rpm. that's too much power to give away. I don't know if I'm going to spin it 6800 rpm, but I do want to have a motor that would pull strong well entered into the 6k mark.
I don't feel confident about welding and regrinding and I don't feel confident in reducing the journals to SBC or other smaller sizes...
greater sweep volume would render the hearth shaped chambers useless and I would need dished pistons and larger chambers...

plus not to mention that a custom crank like bren's for only adding 8cc and loosing the almost 1.8 rod/stroke ratio for the amount of money that a custom crank would imply... well, let's say that's not my cup of tea. Now doc's 4.5 crank on a 94 mm bore would be MORE than interesting... almost 300 cubes... but then again... just thinking of getting the crank reground down here is giving me the headaches. You gotta know your folks, and these guys can overbore, notch, move the coolant passages out of the block for increasing cooling capacity, etc... but I don't trust them to weld and regrind a crank. They just don't let you explain, if you take a crank and tell them to destroke it they'll do that in a hearthbeat. Opposite ways would result in akward faces and long chatter time with the machinist trying to convince him that you're not (completely) crazy and that you actually want to stroke the crankshaft a little more.

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Juan Ignacio Caino

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Dont give away any RPM. Your right thats power thrown away. As far as a girdle, I dessagree, a girdle will strenthen things a lot. It will also hold down vibration and allow the engine to rev smoother. The Jeep 4.0 went to a girdle from the factroy & you wouldnt believe how much it helped.

It could be a simple girdle that just tied all the mains together, but one that went to the oil pan rail would help even more, but would be harder to fabricate. Look at the factory 4.0 Jeep girdle, it would be easy to dulicate for the slant.

Also, its a funny think that the /6 has the same main jurnals & caps as a big block 440 Mopar. You might even be able to add some ductile iron main caps from a Big Block. People think of these kinda things as overkill or only for durability, but the truth is, it helps make more HP.

Crank stroke, I am not sure I wouldnt use the 198 crank. The head does not flow enough to feed a engine of this size. This will make it peak low in the RPM's on HP no matter what cam you run. That is why I think the 198 crank would work better. The engine will rev better, and it will not be so big that it out flows the head. If you run 250 plus CID, it will peak at around 4800 or lower depending on how big the engine is. And like I said, it will not matter how much cam you put in it, its just not going to make power above 4800rpm, it cant , it cant breath enough. Now with a 198 crank, it could peak at 6400 rpm and be shifted at 7000rpm.

WHY, Simply because of the Head. With the big bore, the head will flow more, but not enough to feed big CID displacment. Long strokes Do Not Make engines peak at low RPM, its all in the Head Flow & Camshaft. On the Big Block engines we run 4.250 & 4.500 stroke cranks & still peak on HP above 7000RPM's. But these engines have the head to flow what is needed. If we take one of these 500 plus engine's and run a factory iron head on it (limited on flow) they peak real low in the RPM's also.


Run a shorter stroke (does not have to be a 170, 198 would do it), as big a bore as you can, and turn the most RPM you can. You will make more Horse Power than anyone else has with a N/A /6 engine at compairable Compression.

With a 93mm bore, and the 4.125 crank(225 crank) you have around 260 CID. That is to much for the /6 head flow. And it will peak at 5000rpm or below. With the 198 crank & the 93mm bore, you get around 229cid. The head will flow enough to let that engine turn 7000RPM or more.


Its something to think about. This is all with around a 210cfm flow on the intake port in the /6 ( and thats more than most heads flow with oversize valve & full port/polish)
You would need 240cfm (minimum) for the 260 CID engine to turn 6500rpm.


Jess

If those have thicker walls, then 0.120" over should be no worries. Several people have gone 0.100-0.180" on stock blocks, and 0.140" is fairly commonly OK.

Seems like 300HP should be no problem if you get all those ducks in a row. You could use a bigger cam maybe??

Lou

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Home of Slant6-powered fun machines since 1988

I think so too... I even think that going thru the trouble of machining new main caps that crossbolts thru the blocks would be worth the shot.
That's why I don't like the idea of stroking the crank and fiddling with the main and rods journals. Slant six is the engine that has the biggest con rod journal and biggest main journals. That's why other makers had to use 7 mains and threw con rods like popcorn.
do these come in forged steel? Also we never had 198's so I'd have to import one crankshaft from up there (Expensive! A while back while I was depressed and just wanted out of finishing my car, I looked into how much shipping would be so I could send the 906 to doug, and it was a lot of dough.)
Mmmhh... I really need to measure that head and pass the measures up so educated folks can do the math. I remember this little rascals turning 10k (with 11k valve float) on a 93mm bore 170 stock stroke. And that was with carburetion and other class limitations. Bowls are HUGE, so are ports. I think I can stick 2 of my big fingers down the in port, wich I can't do on a stocker.
I was jumpin' to say that slant six heads are only outflowed by hemi heads, but then I recalled that this statement is true on stocker heads on 170 CID and you're talking about aftermarket hi tech heads...
I'm not really shooting for a "big cubes" motor, but a combination between something around 4 litres and a good useful range of rpm. If you peak around 5k but you continue to pull strong up to 7k I'm fine. I'd use the largest cam I can match to this combo. Lumpy idle? who's idling? One thing that I like about slant six is although they peak lower than your average built V8, the power and torque curves flatten out more gradually after peaking. Your typical SB or even BB would peak and then die (as in hearth attack die) your slant would peak and then continue pulling less and less (as in "wounded" during the peak and passing out quietly at home later) (pardon my dark comparissions!)

I want "maximum area below the curves" since this would be street'd. I can live with high gears, with a little bit bitter lower end, with lumpy, "nervous" idle, but I don't want this to be a circle track tuned engine.

so maybe I can settle around 250 cid and still have plenty of live left on the heavy wall casting block with a bulletproof bottom end just in case some of the gearheads that are secretly developing the long longed aluminium head can come up with a better head with raised ports and all.

IIRC mike had created even better breathing heads? (better than 210)?

All of this considerations is what has been holding me back thru the years, I really appreciate all your input here.
biggest cam that would make useable power on this combination.

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Juan Ignacio Caino

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225+CFM and 350+HP with about 245 cubes has been done with a factory head and 12:1 - in your hemisphere (of the Earth).

Lou

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Home of Slant6-powered fun machines since 1988

What kinda fuel was you going to run, pump gas, race fuel, E85?


The 198 crank is just like the 225 crank (except for stroke) forged, beefy & a good piece. Same size jurnals.


If you can get a head to flow more than the 210cfm then things change pretty quick. But 220, is not much differance ( but it helps alot also ). I dont know what Mikes had the heads flowing, but if you could break 230cfm then I wouldnt worry with the 225 stroke. I would just run it.

I am afraid I tend to try to get the max out of engine builds threw the combonation. I am kinda real bad for that. I hate leaving free horse power on the table.

Turning 5000rpm but still pulling to 7000rpm without falling off real bad would be pretty good. But if you do get more CID than the head can flow, it will drop off hard & just quit pulling.

I think I would base my stroke choices on what the Head did Truely flow on a good bench. Once you get those numbers (flow numbers) the calculations can be made to see how many CID can be feed @ what RPM. If the port volosity, cross sections of the port, Port lenth, CFM and all this kinda info can be had, then you can come very close Predicting the exact power & torque curve the engine will have with a given bore/stroke combo. More CID will always make more HP, if it can be feed the right amount of air & fuel. If not, a CID that matchs the amount of air & fuel you will have can make more power. And the bigger bores at a given CID will always make more power.

Its all something to think about. Becuase you have a better engine block than most anybody, and I think it will pay off in the end if you spend the time to match the whole combo together as a package. The Hp levels could just be something unheard of if you get it just right (for a N/A engine). I think you will make a lot of HP no matter what, but you might as well make all you can with that good of a setup to work with. Like I said, I think I would focus on the head, and then work from there. It will pay off with a much better power curve.


Jess

that would be cameron, right? I really look up to him.


I plan to run 98+ octane pump gas.

That's what I'd be aiming for, not leaving any power on the table. I already built a strong slant and I didn't get much more than 200 horses because I got kinda cold feet in the head porting (It was my first porting job) and got my pants on fire for finishing it and I didn't wait to get better components. Just threw it all together and beat the hell out of it.


so basically I would have to put together the head (with valves, springs and such) and and have it pro flowed on a good bench. and then move on to the bottom end.
yes, this is why I started with all the estimation thing, I need time and advice to slowly and solidly think about this and build a good strong motor. I already have a strong slant, I'd like to have a beast but no hurries. Hurrying up will just end up in screwing up this short block project. Basically I think of this as a bulletproof bottom end and fine tuning all the rest (head flow numbers, cam for the rpm range that the head could feed, etc)

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Juan Ignacio Caino

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Cameron, yes. Runs on race gasoline. His best intake port flows above 230 now. He has probably made 360-370HP before (chassis dyno), but not engine dynoed. 354 is documented. Wicked broad HP peak too. Just an overbored 225 with well done combo and essentially 1960s tech. Still runs points ignition...

Lou

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Home of Slant6-powered fun machines since 1988

I'm confused about race gas, pump gas and octane ratings (our standards for octane ratings is the same as your old standards so rpobably my 98 octane gas is like 92~93 of your modern octane gas)

354 RW HP?

the best I've heard of down here was 320 with tripple webbers DCOE 48/48. a 200 CI slant. Well, 200? 93mm bore x stock 170 stroke.

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Juan Ignacio Caino

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354 crank HP, 309 RWHP with slightly diff engine setup. About 104 octane race gas. Probably like 100 octane using the US pump rating system. Don't know exactly.

Lou

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Home of Slant6-powered fun machines since 1988

OK pictures of the head (Man! I stored away in the attic, when I had 160+ lbs more than now... I had kind of a hard time getting that head down!)

























and here's a quick draft of measurements. All in milimeters.



whada'ya think?

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Juan Ignacio Caino

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Interesting.

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