ascott 500 head swap onto a 350x.... with pics

[SWIGIN]

ok i finally i got my hands on a ft 500 head (ascott street bike) i got the stock 350x valve cover to fit with alot of tig welding and mill work. (you need to use the 350x valve cover since the only way for the oil to get to the head is the external oil line witch the 500 cover dont have)

the only problem im going to have is the 350x rocker arms are only about 1/2 on the valve stems. 1 out of the 4 ajusters is close to being dead on but the other 3 are off about 1/2 way.

i did a search but it brought up nothing usefull. what i need to know is if xr500 or ft500 (ascott) rockers will fit into the 350x valve cover and do the 350x rocker shafts have the same diameter as the 350x.

if anyone has a xr500 or ft500 i would love to see pics of the rockers and shafts and maybe get some measurements from you.

thanks

[SWIGIN]

i just checked my 350x rocker shaft and it is .471 which should be 12mm.

does anyone know if a late 70s - 82 xr500 or ascot ft500 has that size rocker shaft?

[4cylinders]

hey, why not use the 500 valve cover, and just drill it?

[SWIGIN]

well for one, there is no just drilling it.....the speedo stuff is there on the ft500 cover. (which i dont have anyway)

the ft dont get oil to the top end from a external line... it pumps it up one of the motor studs..... kinda hard to drill a oil passage if there is nothing there to drill.

plus i need the 350x head mount and its just the easyest way to go.


your idea was a thought till i found out its not worth the bother... if it can be done at all

[Jason Hall]

Here Is a picture of a 82 XR500 rocker cover. I also have the stock cam for this engine.

[SWIGIN]

perfect!!! thanks



yeah if the xr 500 had a external oil line that cover would be the way to go.

just looking at the rockers they look like what i need..... do you know the diameter of the rocker shafts?

the 350x rocker shafts are .471 or i beleive thats 12mm.... if you could please measure those it would help a ton.

honda wants over $100 for each rocker for the 500..... id like to know this inside diameter (or shaft size) before i lay the cash down.
thanks

[Jason Hall]

I will measure the shaft for ya. It might be an hour or so.

[SWIGIN]

iv heard about this head swap way back in the late 80s or real early 90s when dirt wheels did it or talked about it. iv also always heard rumors about this swap but never talked to anyone who ever did it.

from what iv read every one says you throw the ft500 head on and bolt a 350x valve cover to it........ its not that easy.

first the head does not go right on but all it needs is the 4 motor stud holes drilled to 10mm..... then it goes right on

plus the ft and the xr500 head gets oil pumped up the one motor stud and the oil fills the little cam lobe area to be splashed around i guess. well a 350x gets oil from a external oil line that feeds right on the cam journals..... so you can see in this pic that i had to fill the ft500 oil feed hole with jb weld so the oil dosn't run right back into the case.

plus you can see one of the motor stud holes i had to drill to 10mm

[SWIGIN]

so far the biggest thing was getting the 350x valve cover to ''bolt right on'' its not so easy....the black line shows where the ft500 head/valve cover ares was stock.

i had HREATV weld the top fin and we milled it off then shaped it some.

we also taped the new holes to 6mm for the valve cover bolts but the aluminum is thinner then i like but if they strip out you could get a nut under the fin and just tighten it that way

i also have a pic of the stock 35mm ft500 intake valve next to the stock 350x valve

in the second pic you can see how the 350x uses 2 large bolts just behind and between the valve springs and the ft head dont.

the ft has 2 studs sticking out of the bottom of the head ( no room up top for the 2 bolts) more on this later

[SWIGIN]

last night i got a junk 350x cly to play with.... heres what the ft head looks like on a 350x cly.

every bolt lines right up except for the 2 bolts that (on a 350x) go down right between the valve springs.

the ft uses 2 studs that go out of the head gasket surface down into the cly and then a nut is used to tighten them. so i have to machine the cly to accept these nuts.

the studs dont line up with the 350x bolt holes but they are close and can be machined to work.

now looking down the sleeve you can see the valves are going to hit the cly since the 350x is 81mm and the 500 is 89mm...... but this is perfect for a 89mm big bore and you get to use a basicly un modified ft500 head gasket (the xr500 has a different case stud pattern and thats why the xr500 gaskets or even the head are not used)

the last 2 pics are the timming chain area, you can that from the top looking down the ft head is almost a perfect match to the 350x cly. but looking up from the bottom of the cly its not as close but i dont hink i will run into a problem....... but if it look like a problem it will be no big deal to match them up perfect

[Jason Hall]

Yes the XR500 has the same size rocker shafts .471. Looks like a pretty complicated swap. Good luck with It, and let us know how she runs.

[SWIGIN]

perfect... thanks jason

yeah theres more to it then all the rumors led me to beleive but i was looking at some ft500 forums and they say 50hp is no problem with this head.

now thats also a 500cc motor but with a 6mm stroker and a 89mm big bore ill be at 460cc.

could be fun!!!

thanks again

[SWIGIN]

today i went to HRE and we moved one of the head studs that the ascot ft500 uses so it would line up with the 350x cly.

the hole with the arrow is the one we moved, it was real close ( like 2mm) so we moved it and threaded it for a 10mm stud (like a 350x) instead of the 8mm stud the ascot uses.

the odd looking stud showed on the other side of the head will be harder to deal with since it dont line up at all with the 350x gasket. it has a 12mm base and a 8mm shaft.

im thinking i'll just rethread it to 14mm and then thread my insert to 8 or 10mm since the new studs im useing are 95mm long.

this stud hole is just inside of the 350x hole in the cly so i will just have to make a new hole.

the last 2 pics you can see where im going to mill the cly so i can use nuts on these 2 long studs...... the factory ascot studs are short and only go to the first fin and i wanted more meat.

im going to mill out where the tape is and thats where the nut goes.

[SWIGIN]

2 more pics tonight

i threw it together to see how long the top end studs would be...... the inner 2 look fine but the outer 2 will need spacers made.

with a brass washer at each end of the spacer it should work fine.

hmmmmm.......i wonder if the ft studs would work

[SWIGIN]

145 views and no one has any questions or opinions?

i was hopeing for some insight from you guys but i guess this swap is to old school.

i read a artical in dirtwheels years ago.... maybe the late 80s about this swap and was kinda hopeing someone would throw it on here.

maybe this is the kind of thing only top motor builders at the time did ( TC, micky dunlop)

any way if you have some info id like to hear it.... it would be nice to see how other guys did this.