How would you modify this head?

[olNick]

Greeting to all from a new member,

I’ve come across this site while googling for tech info from Larry Widmer and David Vizard, and have wound up here with a wealth of additional info.

I’m planning on rebuilding my bike motor in the fall, and looking for info on performance.

Suzuki Intruder
1400 cc 45* v-twin
45* crank
chain driven 3 valve OHC
9.3:1 CR
94x98 bore x stroke
33mm intake, 40 exhaust
0.31 lift intake, 0.35 exhaust
272/276 duration intake/exhaust
71 hp (52 kW)/ 4.800 rpm, 112 Nm/ 3.200 rpm.

While the engine pulls like a tank, I feel these hp/torque figures a very low for an engine of ~700 cc/cylinder. I would like to do something about that. From what I’m seeing claimed, many 88 inch Harleys are approaching the 100 hp zone. I’m jealous!!

While the bike is fairly conventional, I think maybe the hemi style head could use some improvement. Below are pics of this head, first one from the manual which shows it’s bowl clearly, and the second an actual head

1400_head.GIF

valves111sf.jpg


Notice there is no particular squish band in this head, so I would think it’s only depending on swirl from the intakes for charge mixing. IIRC, at the time of introduction, Suzuki was touting its TSCC, Twin Swirl Combustion Chamber although I thought that all well designed dual inlets should promote good swirl.

On this next pic, I’ve outlined a bit where I’m considering welding up the chamber to add add a primary squish at 3:00 o’clock and a secondary one at 8:00 o’clock, resulting (hopefully) resulting in

Copy of valves111sf.jpg

Raise CR w/o milling or dome pistons
Improve combustion due to enhanced swirl
Drop timing requirements due to shorter flame front travel
Lower heat loss due to smaller cc surface area

I know I need to look up and understand squish band percentage, and squish velocity, but comments are welcome wrt to these issues.

If we believe in progress, the below pic is from the 1500 Intuder that came out 10 years later, with a more traditional pent roof and added squish. Albeit with dished pistons to drop CR to 8.5:1

1500_head11.jpg

Can you guys give some input. Do you see any pitfalls by going this way…
I will clean up and try to flow the heads after building the flowbench on this site.

Anyway, great site, and am looking forward,

Regards,

nick

[FlowSpecialist]

I wouldn't bother welding anything up. Too much aggro IMO. Squish is nice if you have it but it's no big deal if you don't. I find it makes a few percent difference to how an engine goes but nothing like as much as flow, cam and CR can affect things.

Stick some bigger inlet valves in there. Looks like you have room for 35mm. Port the head, cut some nice valve seats, get the CR up to 10.5 and stick a bit more cam in. 100 bhp should be easy enough to reach without losing much tractability.

Dave

[olNick]

Thanx for the response Dave,

Well, would adding squish hurt at all?
I'm a memmebr of an Intruder forum, and some members there did what you recommended above and were quite disappointed with the results, e.g 74 rear wheel hp. They expected more.....

WRT bigger intakes, possibly +0.5 mm is max,
The way I see it is this motor is app. 1/4 of a SBC size wise, but nowhere near 1/4 of a current, mild SBC's output, or 1/2 a modern 3 liter import

later,

nick

[FlowSpecialist]

Originally Posted by olNick

Thanx for the response Dave,

Well, would adding squish hurt at all?

It shouldn't hurt, as long as it doesn't lose flow

I'm a memmebr of an Intruder forum, and some members there did what you recommended above and were quite disappointed with the results, e.g 74 rear wheel hp. They expected more.....

Then they didn't get much more airflow so they need to spend some serious time on the flowbench. Obviously I can't see what potential the ports have from your pics though.

WRT bigger intakes, possibly +0.5 mm is max,

Doesn't look like that from the photo. I can see the inlets buried slightly inside a topcut and I see no reason why the valves shouldn't be nearly as big as the topcut is with bigger inserts fitted. Measuring on screen I make that 35mm.

That's 12% more valve area and properly ported you should see maybe 10% extra power from it plus what you gain from porting the standard sized valves anyway which ought to be at least another 10%. That should take you to about 85 bhp on its own and you still have cams, CR and perhaps induction or exhaust mods to come.

Dave

[Cammer]

Nick,

Find a head specialist to modify your heads. You need to do this before buying any parts.

Working with an expert will help you avoid a poor running engine.

Best of luck!

[olNick]

Originally Posted by Cammer

Nick,

Find a head specialist to modify your heads. You need to do this before buying any parts.

Working with an expert will help you avoid a poor running engine.

Best of luck!

Thanx Cammer,

If you think you are "in the woods" as per your profile, I guess I'm on an island, literally ;-)

Seriously, there's no-one around my area that does this, and the ones that do (8 hrs away) I wouldn't let them touch my moped never mind these heads...
The reason I was able to buy 2 of these bikes real cheap is cause no-one within 200 km here could start them. Now they're all over me as if I did some magic or something...

I've the parts to build the flow bench in the tech articles (thanx GFN) so this is how I will proceed, and keep out'a the pub for that matter...

regards,

nick

[Brian P]

Valve lift is rather low (lift is a bit less than 25% of valve diameter), and I'll just about guarantee that the duration given is seat-to-seat, not at 1mm lift. Very very mild camshaft in there. For a point of comparison, my Yamaha FZR400 (100cc per cylinder, 56.0 x 40.5 bore and stroke, 4 valve head with much smaller valves and designed for way higher revs) has comparable valve lift. Peak power at only 4800 rpm is another tip-off. You don't say what the redline is, but at 4800 rpm, the piston speed is around 15.7 metres per second. Production engines are usually around 20 m/s at redline - in your engine, that would be around 6000 rpm. Peak power at 80% of redline rpm is not unusual for a mild street-oriented engine (as this was intended to be). That is a long stroke engine, good for making lots of low end torque, not good for making big power.

The torque is on the low side given the size of the engine.

I think the biggest trouble isn't the combustion chamber (I agree it's not great, but in the absence of knowing what the top of the piston looks like, it's not horrible, and at least the spark plug is close to the center) but rather that the engine can't breathe and can't rev.

From those photos, there's no indication of how good or bad the intake ports are, nor of whether the length and diameter of the induction runners are appropriately tuned for the engine, nor of whether the airbox is big enough (an engine that size will want a huge airbox!) or has appropriate and low-restriction inlet into it, nor of how appropriate the diameter and length of the exhaust headers are.

Basically, you are dealing with a powertrain that simply wasn't designed with performance in mind. The H-D crowd has that situation too, and the aftermarket responds by changing *every*thing.

[olNick]

Originally Posted by FlowSpecialist

It shouldn't hurt, as long as it doesn't lose flow

I would build up the squish pads with clay or wax first and keep checking flow...I think, but am not sure this is how a pro would proceed

Originally Posted by FlowSpecialist

Then they didn't get much more airflow so they need to spend some serious time on the flowbench. Obviously I can't see what potential the ports have from your pics though.

I asked them for before/after flow numbers but haven't got a reply (yet)

Regarding the ports, I will try and make a casting next time the head is off the bike and report back. It's primo riding weather now, so it'll be a while

Originally Posted by FlowSpecialist

Doesn't look like that from the photo. I can see the inlets buried slightly inside a topcut and I see no reason why the valves shouldn't be nearly as big as the topcut is with bigger inserts fitted. Measuring on screen I make that 35mm.

O.K, I'll ask one of the machine shops here. Dave, is the primary concern not to "break-out" when boring the larger seat area?

thanx,

nick

[Brian P]

Can you get different camshafts for that engine?

[olNick]

Hi all,

WRT to before/after flow data, none were asked for, and none were supplied :-(

Originally Posted by Brian P

Can you get different camshafts for that engine?

Thanx for your insight... Brian
Below are 3 (re)grinds that one can get from Web camshafts...

The first set is 272 dur. / .350 lift and 276 dur / .386 lift.
The second is 285 dur / .400 and 284 dur / .397 lift.
The third is 268 dur / .435 lift and 282 dur / .420 lift.

I would tend to think that duration here would be at 0.050" and not seat duration as I would think most responsible companies do it this way... I asked one of the members for a camcard to verify. If I get a camcard I'll also check LSA on these.

Originally Posted by Brian P

Valve lift is rather low (lift is a bit less than 25% of valve diameter), and I'll just about guarantee that the duration given is seat-to-seat, not at 1mm lift. Very very mild camshaft in there.

The second and third cams above are closer to 0.25-0.35 of valve diameter, and would be better suited if the intake/head can flow it.

Originally Posted by Brian P

Production engines are usually around 20 m/s at redline - in your engine, that would be around 6000 rpm. Peak power at 80% of redline rpm is not unusual for a mild street-oriented engine (as this was intended to be). That is a long stroke engine, good for making lots of low end torque, not good for making big power.

The torque is on the low side given the size of the engine.

The rev limiter kicks in at 6500 rpm. I think the added lift lift would raise the tq output.

Originally Posted by Brian P

From those photos, there's no indication of how good or bad the intake ports are, nor of whether the length and diameter of the induction runners are appropriately tuned for the engine, nor of whether the airbox is big enough (an engine that size will want a huge airbox!) or has appropriate and low-restriction inlet into it, nor of how appropriate the diameter and length of the exhaust headers are.

The first thing everyone does with these things. myself included is rip out the airbox, add pods and aftermarket pipes and re-jet the carbs, for a big "seat dynamometer" increase and 5-6 horse on a real dyno.

The original piston is a flat top. Below is a pic of the piston that gets used to bump the CR to 10.5 when using a hotter cam. It looks domed and possibly might create burn problems

piston_domesmall.jpg

I working on getting a scrap head to check runner length, volume and such.

Originally Posted by Brian P

Basically, you are dealing with a powertrain that simply wasn't designed
with performance in mind. The H-D crowd has that situation too, and the
aftermarket responds by changing *every*thing.

I really like what this guy is doing in the HD circles, and is my motivation for doing some of this to the Suzuki...

About the Harley - Davidson High Performance & Reliability Specialists - cylinder head design - peak horsepower - high est torque - Johnson Engine Technology

some pretty heady duty power claims...

regards,

nick