Slant head?
- Thread starter Fuji Moto
- Start date
i just purchased the slant head from piratecycles, its a good idea for clearance issues wwith frame,and i ve heard the slant head has had several different combustion chambers since its production. id say go with it...
The thing is I already have a regular head and I was gonna buy just a head and swap it with the one that is already there just because I heard they are higher compresssion or something, and therefore I would assume it would be better performance clearance isnt really an issue I already have room for a tall spark plug and everything just want better performance I would assume the jug and crankcase components are all the same with most of these engines,,
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Yes, it is worth it. They have a smaller combustion chamber which gives a higher compression ratio.
Note, my only experience is with the 66cc kits. If you have a 49cc, you may wish to confirm with someone who has compared heads on those models.
Check your new head for straightness, it will likely need surfacing on a piece of glass with sandpaper to make the sealing surface perfect.
Note, my only experience is with the 66cc kits. If you have a 49cc, you may wish to confirm with someone who has compared heads on those models.
Check your new head for straightness, it will likely need surfacing on a piece of glass with sandpaper to make the sealing surface perfect.
You want to use a figure 8 motion and light even pressure. Since you are asking, I will assume you don't have machinists dye laying around. Since you don't, just grab a marker. Color the raised area with the marker. This will allow you to quickly see if the surface is true. tape a sheet of 400 grit to your glass or other flat surface and make a couple passes in a figure 8 motion. Check your surface. If the marker has all been removed you are done. Your head is flat. If only parts are gone and others are still colored you have an uneven surface. The areas with no marker are high, the areas with marker remaining are low. If this is the case then take your 400 grit paper off and set it aside. Grab a piece of 180 and sand checking frequently until you have just a sliver of marker left showing. Switch back toy your 400 and sand until that last sliver disappears and the sanding scratches from the rougher paper are smoothed out.
Which means didley when the head is warped out of the box as bad as some of these are. stacking two gaskets like they do at the factory is a piss poor work around for a poorly cast piece IMHO. But, as always, you are the mechanic in charge. When you began modifying you choose your own acceptable tolerances. I prefer to start with flat sealing surfaces myself. YMMV use any and all advice at your own risk. =^)
I've had blow-by on my standard head, and at the same time decided to order a slant head. So I completely removed the ridge from my stock head, and after sealing it back up with stock gasket plus silver paint, there was no issue. Boosted performance a bit, but not as much as slant head does now. The slant head is a very good bang for your buck.
is that a dig? i'm not worried about warped slant head since we have nice new billet heads on the way from jim
Which means didley when the head is warped out of the box as bad as some of these are. stacking two gaskets like they do at the factory is a piss poor work around for a poorly cast piece IMHO. But, as always, you are the mechanic in charge. When you began modifying you choose your own acceptable tolerances. I prefer to start with flat sealing surfaces myself. YMMV use any and all advice at your own risk. =^)
i have two slant heads they are very different the 1 one from pirate has a smaller combustion chamber the othr is from bgf ther is no real difference by eye compared to straight plug head aside of the angle plug just baught one to compare parts and so on hence make sure if you want compresion make sure you get the right head !!!
There is a raised lip which is grooved on the head. It is the sealing surface. Taco is advocating not removing this surface. My position on the matter is that if the head is warped some of the surface must be machined off until the sealing surface is flat or else the clamping force will be uneven and the seal potentially compromised. Some people machine the lip off altogether like Paul to raise the compression.
Hence we come to the phrase "you are the mechanic in charge." I stole this phrase shamelessly from a man named Bob Hoover who is a talented mechanic and machinist very well known in the vw and homebuilt airplane worlds. His vw sermons are a very very good read.
His point is that when on the internet you get faced with a barrage of faceless names. It seems a natural phenom that people become instant experts after reading a few forums or building an engine for the first time. If you frequent forums you can watch the progression from asking how to change their oil to a few short months later giving a recommendation on cam shafts and engine combo's with the casual assurance of a long time pro.
They have either read enough posts to consider themselves experts, or have entered enough numbers into desktop dyno to assure themselves they are right.
So, who do you trust?
Yourself, of course. It's your motor. You are modifyiing it from it's original configuration. You are the mechanic and engineer in charge.
I personally think you should have flat sealing surfaces and verify through claying the piston or whatever your favorite method is of measuring the clearance at TDC whenever changing heads on an engine. Of course, I tend to take the time to cc and match my chambers on my vw heads and adjust them to meet my target compression ratio while maintaining a tight deck. Many do not. Their engines run well enough for them.
I outlined an issue I have found, and my solution. I have found that very few engine parts in life are truly ready to install out of the box. The time you take measuring, correcting, and improving the pieces as well as rejecting outright some of the unusable out of spec parts sold as new is what separates an engine assembler from and engine builder.
Hopefully that clears things up, and assures everyone that I was not in any way attempting to single anyone out but simply offering my experiences and opinions.
Hence we come to the phrase "you are the mechanic in charge." I stole this phrase shamelessly from a man named Bob Hoover who is a talented mechanic and machinist very well known in the vw and homebuilt airplane worlds. His vw sermons are a very very good read.
His point is that when on the internet you get faced with a barrage of faceless names. It seems a natural phenom that people become instant experts after reading a few forums or building an engine for the first time. If you frequent forums you can watch the progression from asking how to change their oil to a few short months later giving a recommendation on cam shafts and engine combo's with the casual assurance of a long time pro.
They have either read enough posts to consider themselves experts, or have entered enough numbers into desktop dyno to assure themselves they are right.
So, who do you trust?
Yourself, of course. It's your motor. You are modifyiing it from it's original configuration. You are the mechanic and engineer in charge.
I personally think you should have flat sealing surfaces and verify through claying the piston or whatever your favorite method is of measuring the clearance at TDC whenever changing heads on an engine. Of course, I tend to take the time to cc and match my chambers on my vw heads and adjust them to meet my target compression ratio while maintaining a tight deck. Many do not. Their engines run well enough for them.
I outlined an issue I have found, and my solution. I have found that very few engine parts in life are truly ready to install out of the box. The time you take measuring, correcting, and improving the pieces as well as rejecting outright some of the unusable out of spec parts sold as new is what separates an engine assembler from and engine builder.
Hopefully that clears things up, and assures everyone that I was not in any way attempting to single anyone out but simply offering my experiences and opinions.
Anyway the real question about the slant heads is ??????
To make a long story short alot of things affect how the head is gonna act.
Most of theses motors are quite different from brand to brand.
Performance yes it will increase it.
#1 if you have the right piston.
#2 if the squish is set right.
The round raised circle is intended to give a better seal at the gasket.
The stacked gaskets arent there to give a better seal.
I have milled the raised circle off and i have left it there.
Either way works the same if the sealing surfaces are flat.
If there not flat the ring creates a better seal.
BTw better true up the jug wile your at it.
To make a long story short alot of things affect how the head is gonna act.
Most of theses motors are quite different from brand to brand.
Performance yes it will increase it.
#1 if you have the right piston.
#2 if the squish is set right.
The round raised circle is intended to give a better seal at the gasket.
The stacked gaskets arent there to give a better seal.
I have milled the raised circle off and i have left it there.
Either way works the same if the sealing surfaces are flat.
If there not flat the ring creates a better seal.
BTw better true up the jug wile your at it.
After about 2,000 miles on my old motor I found an engine on ebay called the H2 Slant head with my usual upgrades after market carb tuned expansion chamber and of course a nice jakshaft assembly I pulled 42 mph on flat road. Also I was told it was 68.5cc over the traditional 66cc. I Love it!
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i didnt take offense its just the way things come out in text i guess. I've been a motorcycle mechanic for 15 yrs now all hands on. text and books can only take you so far i guess. I just dont fix it if it aint broke i like to tinker with theese engines alot and have never had a head fail me or any seepage out of my gaskets.I also retorque them every ride 10 ft lbs and they never spin it clicks so they arent lossening up either. I have gotten theese motors up to 350 degrees f no issues i just think i have good luck or something lol. but I agree on the know it alls a few months after reading posts lol its funny. cant wait to start using some good ole usa equipment on my motors.