Head porting? Is it worth it?

[pase]

Well is porting the heads a good idea. I'm going all out on the motor. Making a Wantind a drag type set up.
And are the specials any different in the motor compartment than a standard? and will a head from an 78 or 79 work better than the 80 head I got.

[pase]

Where can I find different size gear got the trans.

[natemoen]

A home port job would be worthless and probably do more harm than good. A pro port job on a flow bench may help.

Special and standard engines are the same. Later heads have bigger valves. Early heads have hotter cams.

Tranny gears would have to be custom made.

[TADracer]

As far as porting the heads goes I generally agree with natemoen but alittle bit of smoothing and opening of the of the exhaust port and roughing of the intake runners willnot hurt. All in all these heads are fairly free flowing from the factory.

If you want to do something that will give you more flow without grinding on the runners, give a 30 degree back cut on your stock valves a try. Pull your valves and take them to a grinder and ask him to do a back cut. Many shops might charge only a couple of bucks a valve and it has a greater effect on the intake valve than on the exhaust.

Easy to do and works. Here is a before and after (after is onthe left)

[Incubus]

As nate stated, later heads had bigger valves and earlier heads had hotter cams. If you are building just a drag bike the combination may work well for you. If you are building a street bike, and you like the bike to idle at times, forget it.

I made that match on Succubus, my initial XS11. I will admit, under power that bike is scary fast. It is practically a different class than Incubus, my stock xs11 (both are 79 Standards). But I spent two years trying to make that bike fire correctly on all four cylinders at idle. Sometimes it happened. I never figured out why. I just do not think the timing works with the early cams and later valves.

But if you just want incredible high end torque that will leave you streaming from the handlebars like a banner on a windy day, try it.

Patrick

[skipper]

TAD, I port heads for a living, and yes, I have a flow bench ( likely one of the most frustrating tools you'll ever use). DO NOT try a "home port job" on an eleven head!!! They are quite good from the factory. Remember one thing "size is not important, shape is". If you cut in the port in the wrong place, even if you increase the port size, you'll absolutely kill the air flow! If you can find someone with a good flow bench, and that actually knows how to use it, the ports can be improved, a little (maybe 10%,,, maybe). Back cutting the valves is a fairly good suggestion. A "PROPER" race valve job will be an improvement also. However, such a race valve grind will reduce overall valve life, sometimes by as much as 2/3.

[crazy steve]

Skipper is giving excellent advice....

[pase]

Thanks men,
I found a guy on eBay that swears by his port job it's $500 + $s is it worth that much $? What would you all say the power gain to expect out of them? I'm also going to do the 1196 big bore pistons. Will a 78 head fit an 80 porter an the big valves cut back 30 degrees? Will I see gains with that head combo

[pase]

And how may horses should I expect I have a 4 to 1 header stage 3 jet combo and did away with air box and have k&n air pods

[natemoen]

The stage 3 is most likely too much even with the 1196. Is the port worth 500+? Doubt it, you may get a horse or two but probably not much.

Find Dan Hodges in the member list and read through his posts. He spent a lot of time and money trying to get 100hp (i think that was his goal) out of these engines.

[Incubus]

The pistons are different on the later motors and the compression was lowered because of some EPA BS. I think the combination of the earlier head and the later pistons will give your the worst of both worlds....

Patrick

[crazy steve]

Pase, go find and read Dan Hodges posts from a few years ago (search that name); he's already plowed this ground and it may save you some heartburn/money.

The short story is he spent multiple thousand dollars dyno-testing/buying ported heads, custom-ground cams, big bore, etc, etc and when it was all said and done, all he gained was about 20 hp, with the last 10 costing the big bucks. He estimated to get more than that, you'd either have to go to a custom billet head (BIG $$$), or accept a motor that was a 'race-only' piece, with really poor low-end drivability.

His conclusions on the best-bang-for-the-buck? A big-bore, use the '80-81 head with it's larger valves, the hotter '78-79 cams, and the '78 centrifugal advance unit. He did a simple light 'port match' on the intakes, that's all. With proper tuning (and we're not talking about colortuners and plug-chops here; this is dyno-tuning with EGT sensing, etc at $50+ per run), you can probably see 100 RWHP, about a 15 HP gain over a really good stocker. After that, each additional HP costs about $100 for the first 5, then goes up from there...

Cheap power? Look at a nitrous kit.... just don't go overboard and drive over the crank...

[skipper]

Pase, as far as how much power you can gain, it depends on the PACKAGE you put together. A ported head can only increase power IF the ports are the restriction! If the intake or exhaust (or both) won't flow as much as the stock ports, you'll see no gain from a port job (maybe even a drop in power). A 10% gain in port flow will produce about 9.5 HP, IF there are no other restrictions. Beware of those that say they gain large flow increases. 2 cardinal rules to porting, 1; Never sacrifice flow VOLUME for more compression. 2; Never sacrifice flow VELOCITY for more volume! If you're really serious about power, have your head tech flow all the plumbing at the time he does the ports.
$500 for a good port job is about right. I'd need more for the first one. Lot of "bench" adapters have to be built just to start. If you choose to do this, be sure to have your tech use a bench adapter (under the head) that matches your final cyl. bore size, it matters a bunch!!!!

[CaptonZap]

Here is the problem with flow benches, as I see it.
In the first place, any change made to the port is non reversible, so when you get the most flow, you have gone past it with the next modification, noticed the drop in flow, and now you can't go back. Unless you have another head to replicate the best flow shape.
Second, the flow bench is a steady flow system, and the flow in a running engine is a pulsating flow, which gives a different result in overall induction. So the results in an operating engine might not live up to the gains shown on a flow bench.
Does the guy give a "money and stock head back" guarantee? If not, you are gambling with money and heads.
CZ

[pase]

Thanks a lot guys I'll have to look into all that y'all have said. I'm building this motorcycle for a friend that was killed in the line of duty. He loved xs1100 as much as any one I know and also loved drag bikes so I plan on build a over to top bike that is both. Any help is very appreciated.