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Posted 17 August 2012 - 10:23 PM
That intake flow would help me ,Did you widen the port much?
Edited by greens nice, 17 August 2012 - 10:23 PM.
_Bomber Watson_
Posted 17 August 2012 - 10:23 PM
Forum Fixture
Posted 17 August 2012 - 10:29 PM
Kev, have you read oldjohnno's thoughts on testing at a low pressure drop with holden heads?
Cheers.
_STRAIGHTLINEMICK_
Posted 17 August 2012 - 11:04 PM
Thanks mate that would be a big help,my intake port is taller but not wider also,the dfference must be elsewhere .There are some good thinkers bouncing ideas around on this forum, I like the enthusiasm.not wider at the gasket face, was taller though, he has the book with all the measurements in it i can try and get them off him when i see him next.
_STRAIGHTLINEMICK_
Posted 17 August 2012 - 11:16 PM
Youre dead right Kevin.i have yes, but i was stretched for time and the bench wouldn't test past 10 inches, dont know why.
run's the numbers on the track though, that's what matter's right? we dont race flow bench's.
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Posted 18 August 2012 - 08:13 AM
_oldjohnno_
Posted 18 August 2012 - 08:44 AM
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Posted 18 August 2012 - 11:03 AM
Reliability is the problem......but an offset ground crank isn't as much a problem as a fully stroked motor.As a sidenote regarding strokers, no one going fast and winning races is using one.
_STRAIGHTLINEMICK_
Posted 18 August 2012 - 11:06 AM
Yep i agree , a good flowing 12 port with a small chamber would be best.I still prefer the small combustion chamber over the large, it gives a better "quench" area.
There's some interesting reading here, keep going.
_STRAIGHTLINEMICK_
Posted 18 August 2012 - 11:10 AM
Honda or BMW rods I think.
Reliability is the problem......but an offset ground crank isn't as much a problem as a fully stroked motor.
If you can still find a Kit Cullen crank, they are built for the 202 mains. I had him turn mine down for the 186.
I had 3.7L with Toyota pistons and stock rods..........machinist stuffed up and put Fraud piston clearance in and killed it.
With a GOOD main girdle, a properly ground head and block, and all the clearancing, there is no reason you can't make good regular torque if you don't aim for 7000+ rpm every time you go out. Really, if I had the money to do it again, I'd girdle OVER the head, to keep it torqued down. It was 25mm out of true at the end of it........
Grant..
_STRAIGHTLINEMICK_
Posted 18 August 2012 - 11:13 AM
_STRAIGHTLINEMICK_
Posted 18 August 2012 - 11:30 AM
G'day Johnno, yep it would be good to have a flowbench, by steeper seat angles did you mean 30deg?,I tried backcut on the intake valve and got good results but the next head we tested without back cut outflowed it.Suppose having to go to someone elses flow bench limits the amount of testing that can be done.Most of us come up with similar figures and its only after someone finds the limiting factor with these intake ports that we can move foreward .Agreed. But then we don't race micrometers, or dynos or timing lights either, and they're all extremely useful tools, just like a flowbench. One of the things I really like about them is not only do they indicate what you can realistically expect from a head but they teach you more about airflow in 20 hours than you'd otherwise learn in 200 years without one.
One thing I found when trying to get good flow from a factory 12 port is that the shape of the back of the valve becomes stupidly, ridiculously touchy. Changes almost too small to see have a big effect on high-lift flow. Steeper valve and seat angles also make a big improvement at the expense of some losses under .150".
I suspect that there is a relationship beween the rpm range and squish area, and that as the rpms rise it's actually beneficial to reduce the area.
Back to flow benches, I think these things http://www.centralva...n/121131-00.pdf are bloody brilliant. You get a useful capacity with a single motor and the variable speed lets you quickly set the pressure drop for each test with a twist of a knob.
_oldjohnno_
Posted 18 August 2012 - 11:59 AM
there is no reason you can't make good regular torque if you don't aim for 7000+ rpm every time you go out.
Grant..
G'day Johnno, yep it would be good to have a flowbench, by steeper seat angles did you mean 30deg?,
Edited by oldjohnno, 18 August 2012 - 12:00 PM.
Green Eggs and Spam
Posted 18 August 2012 - 12:03 PM
_STRAIGHTLINEMICK_
Posted 18 August 2012 - 12:20 PM
I agree,but lack of free time and other commitments slow the whole process down,sometimes you can try too many new things and go backwards,but you do'nt realise what you have learnt untill long after you have thrown the project under the bench in disgust.After the dust settled we went back to basics and got 296hp airflow @.500"from a customers yt alloy head with only valve ,bowl and chamber and short turn mods.Fair enough, but there's limits to the BMEP you can achieve with any NA engine, so being restricted to only 7000rpm will also restrict the hp. Lifting the max rpms to say 8500 would potentially enable a 12% power increase.
55deg seat angles made a big difference at mid to high lifts. Obviously no good for a streeter but fine for the strip. I found a small backcut helped a little bit but it didn't seem to like it made too wide. Flows of well over 180cfm can and have been had from 12 port heads (factory or otherwise), it's just that no-one seems to have made a serious effort to fully develop them. At present it seems that the old 9 port still has the advantage but I'd be surprised if the 12 port couldn't at least match it with a little more port and (especially) manifold development.
_STRAIGHTLINEMICK_
Posted 18 August 2012 - 04:50 PM
Far enough,the peak hp is about the same torque is much better with a long rod stroker, the 1/4 mile times will be about the same ,the big diference is with drivability , you can drive mine around smoothly all day in traffic wheras a similar std stroke/rod engine will be much crankier for the same performance level,you will see the difference after you get to try both .I have nothing against people building strokers,its just that similar results can be had without stroking so it just seems like a bit of a WOFTAM.
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Posted 19 August 2012 - 07:15 AM
Admin Wrangler
Posted 19 August 2012 - 09:44 AM
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Posted 19 August 2012 - 10:51 AM
Admin Wrangler
Posted 19 August 2012 - 08:23 PM
_STRAIGHTLINEMICK_
Posted 19 August 2012 - 10:44 PM
I'm using the powerbond race balancerMick, What balancer do you use on the stroker engines?
.
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Posted 19 August 2012 - 10:58 PM
Obviously the bigger the stroke, the more you're trying to push the piston through the side of the cylinder! Hahaha
The torsional forces increase massively as you increase stroke and then rpm
_STRAIGHTLINEMICK_
Posted 19 August 2012 - 11:12 PM
G'day Grant ,I 'll try to answer your concerns ,The torsional forces against the cylinder walls actually change with the rod to stroke ratio.(std 202 rod/stroke ratio is 1.61) If you build the old falcon crank 234 stroker with short holden rods the (rod/stroke ratio 1.45) greater rod angles place much more force on the cyl walls and the resulting quick piston acceleration from tdc does not work well with the restricted breathing.Obviously the bigger the stroke, the more you're trying to push the piston through the side of the cylinder! Hahaha
The torsional forces increase massively as you increase stroke and then rpm........the main problem is twisting the block.......I would bet that most failures traced to spun bearings are due to the caps "opening up" under this stress.
You see a much higher percentage of failures in strokers, but this is probably most due to not operating them for the reason they are built.....torque.......
The thin walls in the Holden six block also don't lend themselves to this type of stress......and the walking of the cylinders as the moulds were changed is a drama too.....you need to find a block with centred cylinders and ensure your bores are centred and true. I even sleeved the HP block to ensure the integrity of the cylinder walls.......the block is still 100% if someone wants it for another stroker.
The thing that would help them no end is not only rigidity, but breathing.........the cross flow heads would be good, and a Hemi-converted cross flow would be better. When you've got so much more force in the stroke, excess back pressure bends rods.......
If its a drag engine, not street, and you are grouting the block, this obviously lessens these issues somewhat, but you can't drive a grouted block on the street which is what most people want to do with their strokers.
You've done a lot more work on this than me Mick, and if I was still in Campbelltown I'd be running over your place quicksmart.
Dangerous (Dave) here on the forums has built many many strokers and turbo'd some, so he may be the person to talk to.
Grant..
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Posted 20 August 2012 - 05:35 AM
See above.the opposite , the longer the rod means less angle of the rod inturn less sidewall pressure
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