turbominivan
New member
- Joined
- May 5, 2013
- Messages
- 108
while i have the head on my diesel rat rod due to a broken top ring land, i figured i might as well cut my factory bowls bigger.
im lazy and cheap so im doing it in frame while thy are still in the block.
i assume i broke it because fuel was spraying outside the bowl due to my increased timing and compression ratio, so this is my cheap 'hold my beer and watch this' solution.
i used an old worn piston from Tate and cut the top off at the first ring grove to begin making my 'jig'. i chopped it off with a grinder.
i then chucked it up in my mini lathe and opened up the hole to my desired diameter. basically just to get rid of the lip that hangs over the top of the bowl. to about 58mm. i probably could have gone as far as 59.5mm before cutting too much into the walls of the bowl.
after the lathe work i cleaned up the bore to be smooth with a piece of sand paper by hand.
i then put it in my brothers lathe and cleaned it up to be flat and true. it ended up about 5/16" thick. because i needed the 'jig' tight in the cylinder i took up the slack/play by wrapping the 'jig' with 2 layers of electrical tape so it would press fit or tap tightly into each cylinder.
i then taped off the other cylinders and openings in the deck and brought the piston i was working on up to about 1/4" from TDC. i aligned my 'jig' with the hole and taped it in with a rubber mallet.
i had to modify my top bearing router bit by cutting the cutter edge down in length. my grinder had a hard time with its carbide.
once i had the depth set as i needed it, i moved the router carefully around the bore in a counter clockwise rotation cutting in slowly to avoid getting things too hot and making an ugly cut from melted aluminum chips. you really have to hold on and keep control of it or it will grab and run away on you and you risk chewing into the center cone. once i got most of the meat taken down, i gave it a few clockwise rotations to clean it up nicely. i used a touch of WD-40 on the router base so it didn't drag.
once i was satisfied i brought the piston up to TDC expelling the tightly fitting jig and cleaned away the chips with compressed air. it made a great cut and it was now opened to 58mm. i used a piece of 180 grit sand paper to carefully smooth the newly routered edge and get it ready for the next cut.
perhaps this next step was unnecessary or even dumb but i decided to put a slight bevel on the edge.... because i saw someone else do that to theirs. haha. no other reason.
i used another smaller router and set it up with what i believe is a 10* or 15* bottom bearing bit.
i set it up to cut about 5mm deep and to a 60.5mm diameter. it cut beautifully!
.
i then used a small piece of 180 grit sand paper to smooth/bevel the sharp top edge.
i have no idea what kind of compression to expect, or what cc the bowls are now, but as for looks and from what ive read, they should work good enough for my cheap back yard style of hot rodding!
i guess we shall see!
im lazy and cheap so im doing it in frame while thy are still in the block.
i assume i broke it because fuel was spraying outside the bowl due to my increased timing and compression ratio, so this is my cheap 'hold my beer and watch this' solution.
i used an old worn piston from Tate and cut the top off at the first ring grove to begin making my 'jig'. i chopped it off with a grinder.
i then chucked it up in my mini lathe and opened up the hole to my desired diameter. basically just to get rid of the lip that hangs over the top of the bowl. to about 58mm. i probably could have gone as far as 59.5mm before cutting too much into the walls of the bowl.
after the lathe work i cleaned up the bore to be smooth with a piece of sand paper by hand.
i then put it in my brothers lathe and cleaned it up to be flat and true. it ended up about 5/16" thick. because i needed the 'jig' tight in the cylinder i took up the slack/play by wrapping the 'jig' with 2 layers of electrical tape so it would press fit or tap tightly into each cylinder.
i then taped off the other cylinders and openings in the deck and brought the piston i was working on up to about 1/4" from TDC. i aligned my 'jig' with the hole and taped it in with a rubber mallet.
i had to modify my top bearing router bit by cutting the cutter edge down in length. my grinder had a hard time with its carbide.
once i had the depth set as i needed it, i moved the router carefully around the bore in a counter clockwise rotation cutting in slowly to avoid getting things too hot and making an ugly cut from melted aluminum chips. you really have to hold on and keep control of it or it will grab and run away on you and you risk chewing into the center cone. once i got most of the meat taken down, i gave it a few clockwise rotations to clean it up nicely. i used a touch of WD-40 on the router base so it didn't drag.
once i was satisfied i brought the piston up to TDC expelling the tightly fitting jig and cleaned away the chips with compressed air. it made a great cut and it was now opened to 58mm. i used a piece of 180 grit sand paper to carefully smooth the newly routered edge and get it ready for the next cut.
perhaps this next step was unnecessary or even dumb but i decided to put a slight bevel on the edge.... because i saw someone else do that to theirs. haha. no other reason.
i used another smaller router and set it up with what i believe is a 10* or 15* bottom bearing bit.
i set it up to cut about 5mm deep and to a 60.5mm diameter. it cut beautifully!
i then used a small piece of 180 grit sand paper to smooth/bevel the sharp top edge.
i have no idea what kind of compression to expect, or what cc the bowls are now, but as for looks and from what ive read, they should work good enough for my cheap back yard style of hot rodding!
i guess we shall see!
