Cam options for ATC 90

[turbowrenchhead]

DrATV is out of them for the next few weeks. I was wondering if their are any other suppliers for a performance cam. One guy contacted me and said he had one for $57. I feel that is a bit to high for just a 2 lobe cam.

[shortline10]

My price is not bad at fifty bucks for a NOS part . Try powroll or web and you will really pay . I might have a lightly used race cam or one not in the box but NOS for a bit less .

[SWIGIN]

Megacycle cam

Thats what I run in all my motors, even my 110.

[Mr_RPM]

Megacycle cam

Thats what I run in all my motors, even my 110.

there are 2 cams for the atc110, which do you run? the mild or race? for the race they say run race piston, what piston would this be?

[shortline10]

there are 2 cams for the atc110, which do you run? the mild or race? for the race they say run race piston, what piston would this be?

Race pistons like these .

[Mr_RPM]

Race pistons like these .

i just wondered if it was a specific piston made by that company to assure proper valve clearance, must be for compression reasons then. i already got a race piston so thanks for the info SWIGIN looks like im going to get one

[turbowrenchhead]

My price is not bad at fifty bucks for a NOS part . Try powroll or web and you will really pay . I might have a lightly used race cam or one not in the box but NOS for a bit less .

What is the lift, duration and price?

[shortline10]

What is the lift, duration and price?

I have 2 NOS #98 grinds made by Web 35.00 each + shipping .
Here is their website for the for details .

http://www.webcamshafts.com/404.html

[turbowrenchhead]

Would you say this cam is a good mid range to high range cam? I want to match the cam to the 56mm piston at 10.5:1 ratio.
Would you happen to know what the stock cam lift and durations are?

[shortline10]

Would you say this cam is a good mid range to high range cam? I want to match the cam to the 56mm piston at 10.5:1 ratio.
Would you happen to know what the stock cam lift and durations are?

Yes it will improve mid range and top end and if you use the 55mm big bore kit it will really wake it up . I have never seen a big bore kit for a atc90 in 56mm and the atc110 56mm is not interchangable they have different wrist pin sizes . wrist pin on a 110 is 15mm and the 90 is 14mm . You could get a atc110 crank from a 1979-80 atc110 and put it in your 90 cases and use the atc110 cylinder and it will be like adding a small stroker to your 90 set up making it 125cc .

[turbowrenchhead]

Good to know. That is something I have not learned yet. Thanks. I can get a crank and rod off of ebay. Are they pretty much a drop-in into the case? Or will there have to be some modification to make it fit?
I would like to get that cam from you then. Take paypal?

[shortline10]

Good to know. That is something I have not learned yet. Thanks. I can get a crank and rod off of ebay. Are they pretty much a drop-in into the case? Or will there have to be some modification to make it fit?
I would like to get that cam from you then. Take paypal?

Yes the atc110 crank is a bolt in deal but only a 1979/80 points model motor and you have to use the 110 cylinder and timing chain because the stroke is longer . I will pm you the paypal info .

[turbowrenchhead]

Do you think it is worth doing? I do have concerns over the cylinder wall being to thin. But I like the idea of higher compression. I could go with the 54mm and have a thicker cylinder but have less compression and hp too. I was planning on replacing the chain, the valve springs, piston/rings and replace all the gaskets and seals while I'm at it. I will go through the head and port and polish what I can and lap the valves if they are in good condition.

[shortline10]

Do you think it is worth doing? I do have concerns over the cylinder wall being to thin. But I like the idea of higher compression. I could go with the 54mm and have a thicker cylinder but have less compression and hp too. I was planning on replacing the chain, the valve springs, piston/rings and replace all the gaskets and seals while I'm at it. I will go through the head and port and polish what I can and lap the valves if they are in good condition.

Yes I believe its worth doing just shop around ebay for a deal on atc110 crank and cylinder . A 54mm piston in a atc90 will give you 104cc which is good but with the atc110 stock crank and a 55mm piston the atc110 will be a 123cc power house . or if you want to go big I have a 61.5mm stroker that will really make it BARK LOL .

[greenhuman]

Don't forget the 90 cases will have to be bored to accept the 110 cylinder.

[shortline10]

Don't forget the 90 cases will have to be bored to accept the 110 cylinder.

Yes I forgot about boring the cases on the atc90 bottom end . The other option is to use the atc90 cylinder bored to 54mm and a spacer under the cylinder to compensate the length of the longer 110 stroke .

[turbowrenchhead]

Ok just to let me get this straight. If I go with the 54mm DrATV piston at 9:1. I can use my stock cylinder. All I have to do is bore the stock one and no modifications to the case. Puts me at 104cc
Cost:
54mm piston $60.00.
Bore cylinder $40.00

If I go with the 56mm 10.5:1. I need to get a 110 cylinder, bore it. Bore the case and change the crank and rod. Also install a 110 timing chain. Puts me at 125cc? Also how thin with the cylinder wall be? I have seen opposing opinions on the 56mm piston. Some say its safe others disagree.

Cost:
56mm piston $30
Crank&rod $60
110 cylinder $50
Boring $40
Plus modifications to the case. Can this be done by hand with a die grinder? I am assuming that the opening has to be large enough so the rod doesn't hit it.

I have not seen a 55mm piston anywhere.

I want to understand all the in's and out's of these mods before I decide to start buying parts. I have the funds available but first I need to know what processes I must go through.

Thanks for all the input, its greatly appreciated.

[shortline10]

Sounds like you got it . The 56mm piston does make the cylinder pretty thin but your not making a 10,000 RPM monster so I wouldnt worry to much and the 55/54mm atc110 pistons are very hard to find . Not exactly sure how much material has to be removed from the 90 cases but I dont think its much , prob 1 to 2 mm .