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70bs Fastwin 20

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uk_vintage

Contributing Member
"Hello,

I got some serious

"Hello,

I got some serious scored bores on my fastwin, big black scores in the same place on each bore and pretty much all the way down, looks like thrust marks, I think it's had the wrong head on it but I'm open to opinions! Anyways, I would like to remove the liners and replace with new ones so has anyone ever done this. I just need to know the best way of removing them really. Overboring is not an option as the oversize pistons and rings are prohibitively costly.


Cheers"
 
if you think over size pistons

if you think over size pistons are expensive wait until you start pricing sleeves and the cost of having a reputable "marine" machine shop put them in.

oversize is the cheapest way to rebuild.

i would consider another eng entirely or another block...... it depends on your attachment to the eng.
 
"Hello David,

Who said anyt

"Hello David,

Who said anything about a shop doing the work, I was going to do that myself with the help of my friends equipment. Found a cheap place to get liners, not originals but a liner's a liner is it not? All I gotta do is get the old ones out, which may have to be a butcher job! Not overly attached to the engine but when they run right they're pretty good."
 
"thats pretty have cool that

"thats pretty have cool that you have usage of all that machining equipment....... i have to say im a little jealous lol.

i am no machinist for sure but have been involved in a little of it. it will take a while but if all else fails just bore the liner out...... i dont know any tricks or advice to give you, sorry.

the best part is you will have a brand new engine when you get done........ which properly maintained will out live you.


let us know how it turns out.

good luck."
 
"Hi, I have heard that the lin

"Hi, I have heard that the liners are cast in and can only be bored out so I think you're spot on with that. I am no machinist either but I'll give anything a shot, especially as I have nothing to lose on this engine, it's already knackered! Yeah it would be a very nice engine if I can put new bores in. I'll keep y'all posted.

Cheers"
 
"Hi, Tim here. You would have

"Hi, Tim here. You would have to rebore the liners to proper clearance to fit the pistons which you have to buy those too. Standard size pistons are same price as .010 or .020 oversize in my book. Re-sleeving the small engine is very careful work. I would advise against it unless you have severely damaged bores. Did you mic. it? What is your wear at the most damaged area above the exhaust ports? You need a small inside mic that comes to a point. I could send you a nice block for a reasonable price and you could just hone and re-ring it. There are maybe some locally to you as well. The sleeves are thin on these motors and overboring is not always a sure thing. I've played with lots of these and simple is good....time spent might be waisted. Good luck, Tim"
 
"Hi Tim,

I have found a com

"Hi Tim,

I have found a company that specialise in liners for the automotive trade and they have the exact size liners I need, 2.500 I.D so the old pistons will be fine with a new set of rings, which I have. The existing bores are knackered, big black thrust marks on each bore, maybe .005 - .010 deep, haven't officially measured yet but they're deep enough to notice when running your finger over them, and all the way through the travel of the piston, well beyond repair unless I got the oversize pistons and rings. Only prob with you sendin a block is that I live in U.K so if you're in the U.S then postage may be costly. I will post actual wear figures sometime in the next few days so watch this space. Thanks for your input."
 
"How could the pistons have su

"How could the pistons have survived? Check our machine shop site pdqengine.com we created the Italipino race and performance engine line. We run mostly dirt track and GM's, but build all including the old Chrysler Hemi's to 7000 hp. Check it out, I will check on shipping to UK, you can have the block for free. Good luck, mate."
 
"Hi Tim,

Yeah I'm still

"Hi Tim,

Yeah I'm still here, in fact I've literally just finished dismantling the engine, and you're right, the pistons are fudged, fortunately I have another set that are only slightly fudged. The centre bearing was also fudged along with labyrinth seal so I think that's the end of that one! Mmm free block sounds like a very generous offer, thanks, you must feel as sorry for me as I do for myself! Hemi's eh, nice! Can you make me an outboard with one of those please?! Actually on second thoughts that would snap my boat in half!"
 
"Ha! Well, I will check on the

"Ha! Well, I will check on the shipping then and let you know, probably tomorrow, take care."
 
"ok thanks man, I checked that

"ok thanks man, I checked that site out by the way, very interesting, think I missed my calling as a machinist. There's not many machine shops over here(hardly any near me) that can do that sort of stuff, certainly none I know of can build engines from scratch, I'm impressed. speak to you soon."
 
"Got caught up today trucking

"Got caught up today trucking engine parts from PDQ, will check tomorrow for you. I dug out an old 20 hp powerhead in the meantime.....Johnson green, I should pull the head to check it out before I weigh it. Take care, Tim"
 
"Hi Tim,

Thats fine, take a

"Hi Tim,

Thats fine, take as long as you need, the weather over here at the moment is not what you'd call ideal boating weather!"
 
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