Question for the engine builders

[HWB]

As some of you may know from my earlier post im in the process of building an engine for my N 1127, i am sourcing all the parts and i just acquired a 1127 90 head to replace my shim style head, my plan is to port the head myself since i live in a 3rd world country with no oil cooled specialised porter nor did i ever hear about any porter for that matter that works on cars or anything, i did my homework on porting these heads but you can never have enough info from people who actually did it i will of course not go overboard i olan on just cleaning the ports and matching the boots to the intake, smoothen the short radius and clean the bowl, your usual basic porting. I do have a couple of questions tho, this head will have 370 lift cams from ape, 30-26 valves titanium valve retainers and race springs all from ape, i want to know how much and where should i remove material to deshroud the valves and does fittin 30-26 valves require new bigger valve seats ? Plus should i bullet the valve guide or cut it flat with the port floor ? Im also going with 1216 wiseco pistons 12.0:1 compression since i did not find that comp with JE, they offet 11.0:1 and 13.0:1  either too low or too high.. cheers  

[Gixer1460]

Unless you have facilities to skim the head, I wouldn't touch the chambers as you will lose CR by doing so. Also if you are using 12:1 pistons the chamber volumes need to be accurately matched - easy to remove metal - tricky to add it back! If you are a 3rd world country what is the quality of your fuel like - not sure 12:1 CR will work too well with piss poor fuel? 30 / 26mm valves can use std. seats. What will the engine be used for as this will affect recommendations as regards porting / guides / valve seats / reliability / longevity / maintenance?

[HWB]

38 minutes ago, Gixer1460 said:

Unless you have facilities to skim the head, I wouldn't touch the chambers as you will lose CR by doing so. Also if you are using 12:1 pistons the chamber volumes need to be accurately matched - easy to remove metal - tricky to add it back! If you are a 3rd world country what is the quality of your fuel like - not sure 12:1 CR will work too well with piss poor fuel? 30 / 26mm valves can use std. seats. What will the engine be used for as this will affect recommendations as regards porting / guides / valve seats / reliability / longevity / maintenance?

Thanks for your input mate ,pump gas here is 95 octane and 98 octane pick your chose at the station, so the fuel is pretty good actually for high comp, regarding the bowls i was thinking of just round off the sharp edges thats all, does that affect compression alot ? I guess deshrouding valves is out of the question ? Wont i be within .5 cc in each chamber ? I have access to a shop that can skim the head no problems

Edited April 13, 2020 by HWB

[Gixer1460]

You have to bear in mind that you don't know what spec the 'engine' was when the piston manufacturer calculated the CR the piston will / should give! I think a std 1127 engine has a chamber vol. of 26cc? so a half or a whole cc can make a difference especially if the eventual build gives a CR closer to 12.5 or 13:1? A dry build to fully cc the chambers and calculate the ACTUAL CR is well recommended. I built a 1186 kit years ago with 12.5 wiseco pistons and run with std chambers / un-decked head and 98 octane 4* leaded fuel that used to pink like a bastard during summer use - so beware. anything is possible.

[HWB]

So it actually makes more sense to polish the chambers a bit no to reduce a bit of compression ?  And what about squish when cc'ing the chambers ? What do you reccommend doing ? I thought that well reputed companies like JE and Wiseco had it spot on when buying from them a kit that says 12:0.1 for 1127 motors ?

[HWB]

What are the steps an engine builder like yourself would take to build this engine ?

[Gixer1460]

I'm no 'engine builder' ! That's not to say I haven't built engines - the two aren't the same! Only you can answer the how's and where the engine is to be used, what you are prepared to accept and how long you want it to last with how much maintenance - all these things affect how the engine is or should be built! The piston manufacturer doesn't know if the chamber is std or worked on, stock height or decked - I'm guessing they may work backward from using a stock engine figures and change bore size and chamber volume - who knows, as they don't publish that info!

As to the squish question - 1.0mm is regarded as a safe minimum for a road bike / light race bike which (if you want to risk it) can be tightened to 0.75 - 0.6mm but carries no guarantees especially if you buzz it!

[HWB]

What do you think about cutting the valve guide flat with the port floor or bulleting it ? To max flow ? I know it reduces the life of the valves but is it by a big margin ? Im gonna be using the bike on weekends for road racing and i expect a long life out of it to be honest.

[Gixer1460]

Hmmm! IMO Class is out on valve guides. Personally i've never done it (cut them down) or felt the need to do it but I do like turbo's where valve support / heat transfer is more important. I wouldn't cut exhaust guides down whatever but bullets maybe ok (i've used tapered bronze guides)? No empirical evidence for increased wear with flattened guides but common sense says it can't be better than long guides!

[dupersunc]

If I were building the motor, I would un shroud the valves and clean up the combustion chambers. careful taking all the sharp edges in the combustion chamber, you want a crisp edge on the squish area. Once youve done this get the valve seats cut for the big  valves then measure the chambers and calculate your cr and how much you need to skim. then check valve piston clearance  and  see if you need to pocket the pistons more.

There are biggers gains here than cutting back the valve guides.

[HWB]

12 hours ago, dupersunc said:

If I were building the motor, I would un shroud the valves and clean up the combustion chambers. careful taking all the sharp edges in the combustion chamber, you want a crisp edge on the squish area. Once youve done this get the valve seats cut for the big  valves then measure the chambers and calculate your cr and how much you need to skim. then check valve piston clearance  and  see if you need to pocket the pistons more.

There are biggers gains here than cutting back the valve guides.

Seems like cutting the valve guides do more harm than good.

Do you skim from the block or the head ? 

3 angle cut would cut it ya think ?

[dupersunc]

1 hour ago, HWB said:

Seems like cutting the valve guides do more harm than good.

Do you skim from the block or the head ? 

3 angle cut would cut it ya think ?

It's all related. if you want to reduce the squish you machine the barrels, other wise you skim the head. But everything has a knock effect on something else. It's were experience is needed.

To be honest if you fit a set of known brand pistons clean up the head and combustion chambers and fit the bigger valves, it will probably work ok. But it doesn't always.

I was talking to a very experienced engine builder a few months back who's built hundreds of these engines. he had a very trick 1100m in the shop which hd all the goodies, but he'd used a slightly different combination of parts at the request of the owner. It was making 130bhp, around 30bhp short of where they thought it should be.

The builder ended up scraping the pistons and cylinder head and starting again. 

Just because it sounds simple reading it in magazine, doesn't make this stuff easy.    You can easily loose 2weeks in a well equipped workshop building a fairly basic tuned engine right, especially if it's an untried combination.

[HWB]

1 hour ago, dupersunc said:

It's all related. if you want to reduce the squish you machine the barrels, other wise you skim the head. But everything has a knock effect on something else. It's were experience is needed.

To be honest if you fit a set of known brand pistons clean up the head and combustion chambers and fit the bigger valves, it will probably work ok. But it doesn't always.

I was talking to a very experienced engine builder a few months back who's built hundreds of these engines. he had a very trick 1100m in the shop which hd all the goodies, but he'd used a slightly different combination of parts at the request of the owner. It was making 130bhp, around 30bhp short of where they thought it should be.

The builder ended up scraping the pistons and cylinder head and starting again. 

Just because it sounds simple reading it in magazine, doesn't make this stuff easy.    You can easily loose 2weeks in a well equipped workshop building a fairly basic tuned engine right, especially if it's an untried combination.

Well we all know what dreams magazines bring on all of us i am very excited actually for this build but it seems like the reality of it might make me reconsider. I AM going for a well tried combination actually (i did not come up with this setup) 1216 12.0:1 comp 30.26 valves and a slight port job plus cams, thats all. Anything to look out for with this combo ? Should i be reconsidering ? I really dont wanna be wasting money im no millionnaire lol would you reccommend against it ? 

[dupersunc]

Go for it mate, If don't try these things you'll never know, but just be aware of the pit falls, and keep asking questions .

 

[Gixer1460]

If you ain't a millionaire - who is? - then stick to bolt on goodies / easy stuff and leave the skilled stuff to people who can spend the dough! A simple port clean up with 80 / 120 grit emery through a stick as a flap wheel, take the casing marks out of the port and blend to inlet rubbers can be done at home and you could attempt the short turn radius but just blend it - leave the carbide burrs and die grinders alone. Bigger valves will require seat cutting anyway, so 3 angle cut is optimal. Wouldn't touch the chambers.

[HWB]

Thanks for the support guys really appreciate it. Ill start working on the head as soon as the stuff arrives, its just waiting from now i guess... freekn coronaaaaa

[jonny1bump]

We are using standard valve springs as head so many of the ones you mentioned break with not lot of mileage depends on your usage obviously. This then limits your lift of cam before you go coil bound. Alot of stuff to think about. 

[HWB]

2 hours ago, jonny1bump said:

We are using standard valve springs as head so many of the ones you mentioned break with not lot of mileage depends on your usage obviously. This then limits your lift of cam before you go coil bound. Alot of stuff to think about. 

You are using std springs on big valves and high com pistons ? Doesnt that increase risk of floating ? 

[jonny1bump]

Reduces the risk of breaking.

[george 1100]

You can have the best parts available but if you don't have it set it up and assembled correctly , it may disappoint or fail.  Also the cost of porting, setting up the bigger valves, replacing guides and boring cylinders can get quite expensive. I rebuilt both my engines with 81mm pistons, bigger cams, 30/26 valves, guides, porting etc and I can tell you the costs can mount. Don't just slap everything together and hope for the best, everything needs to be measured, compression ie cc combustion chambers, measure piston domes, piston deck height, head gasket and base gasket thicknesses. Measure squish, very important to get it right. Unshroud the valves, don't go crazy. As far as porting goes and if you are a first timer, just blend, cleanup and port match. Don't cut the guides. Make sure your rockers aren't worn and depending on the cam, you may need them hardfaced. Check coil bind and valve to piston clearance. Get slotted cam sprockets and dial in your cams. Get a manual tensioner. Dummy assemble everything and measure. And if you do make decent power put some money aside for a clutch

[Oilyspanner]

Read up how to dial in the cams too, you'll need to buy adjustable cam sprockets, or slot the originals - you can just use the standard markings to set the cams, but a couple of degrees on the inlet cam can alter the power curve.

As the chaps have said, know what you'll need to do, perhaps make a list of the steps. Take your time, don't remove very much material, the ports just need cleaning up and slight reshaping.

Cancel this - George 1100 has just posted a good long reply.

Take your time

When using more radical cams you have to check piston to valve clearance and they hammer the valve train more as per G1100