huunz

Blowby in 650 Sand Spider

11 posts in this topic

Hi, I have the 650 Sand Spider 2 cylinder I've written about here before. I put in the Fast Freddie weber kit, Fox AirShox with limit straps and long travel, modified/built a better header, fixed the lighting (including flashing blue and amber rear safety lights), put on paddles in the back and made my own front runners from worn-out stock tires, and tore up the dunes at Dumont. Well, I couldn't get clear to the top, not enough power, which I'll be working on. Anyway, after a particularly gnarly high speed run, it started missing a little. I cleaned the carb jets (gotta love a Weber) and made sure everything was as it should be externally, but when it idles, the valve cover breather is blowing out a lot of blowby.

Is this normal? Do others have a lot of blowby? Did I break a ring?

Is there a list of ring sizes to possibly cross reference a set of Zero Gap Second rings?

Has anyone tried a crankcase evacuation system using drag race car evac setups?

Is there a hotter cam for this motor? Are overbore pistons available?

Has anyone run this motor at sustained high speeds?

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Hi, I have the 650 Sand Spider 2 cylinder I've written about here before. I put in the Fast Freddie weber kit, Fox AirShox with limit straps and long travel, modified/built a better header, fixed the lighting (including flashing blue and amber rear safety lights), put on paddles in the back and made my own front runners from worn-out stock tires, and tore up the dunes at Dumont. Well, I couldn't get clear to the top, not enough power, which I'll be working on. Anyway, after a particularly gnarly high speed run, it started missing a little. I cleaned the carb jets (gotta love a Weber) and made sure everything was as it should be externally, but when it idles, the valve cover breather is blowing out a lot of blowby.

Is this normal? Do others have a lot of blowby? Did I break a ring?

Is there a list of ring sizes to possibly cross reference a set of Zero Gap Second rings?

Has anyone tried a crankcase evacuation system using drag race car evac setups?

Is there a hotter cam for this motor? Are overbore pistons available?

Has anyone run this motor at sustained high speeds?

Silverbullet

You need to due a compression test dry and wet with a littel oil in it should be about 125 psi. on both cylinder1) we due carry all the parts you need forged pistons total seal rings standard and oversize.Custom camshaft

Do a cylinder leak down test this will help you to determine whats up rings or guides

650 do have some blow but you should have a catch can with a hose from valve cover to can

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The top of the valve cover has a hose that goes to a little filter, that's it. There's no oil dripping, but I can hear the "huffing" in the filter.

Can you up the compression with those pistons?

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I went to your website, found the kit. Are those rings ZGS type? How much increase in compression do you get with the pistons?

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The top of the valve cover has a hose that goes to a little filter, that's it. There's no oil dripping, but I can hear the "huffing" in the filter.

Can you up the compression with those pistons?

Silverbullet

Compression is 12.1 These are forged pistons made in the usa with floating pin and clips.The Rings Are total seal no loss of compression

Stock is 9.1

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So I still need to do a full rebuild for your kit? Grind crank, bore the cylinders, etc?

What is a "cam card"?

What size will the engine be after the overbore at 0.020"? Can I go bigger after this?

How much "bigger" is the cam? Will a two cylinder "lope"?

Will a head porting job help with this kit?

Do I need to run race gas, or can I get by with 91 octane?

I still need to do a compression check, but i like the kit....

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I tried to do the math, it appears that 0.020" over won't do a lot for the CCs. It is about 1/2 MM, on a 76 MM bore would be 76.5 MM. That would give me a 653 afterwards vice a 644 CC stock, a 1.4% increase in displacement.

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Silverbullet

It not the cc but the high compression forged pistons and the Total seal rings.Joyner use vary poor rings and pistons.We floot the wrist pins on the rods this helps.The quality is vary importment and these pistons are the best you can get the Total seal rings stop the lose of compression.Ad a custom cam and rejet carb.

Thanks Rick

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Silverbullet

It not the cc but the high compression forged pistons and the Total seal rings.Joyner use vary poor rings and pistons.We floot the wrist pins on the rods this helps.The quality is vary importment and these pistons are the best you can get the Total seal rings stop the lose of compression.Ad a custom cam and rejet carb.

Thanks Rick

Which way would I rejet? I put the Weber 45 DCOE on it, and it was jetted by Fast Freddie for the Joyner. Would I have to drill the throttle plates for idle with that cam?

I'm going to guess that I need to tear it down first and see if it needs an overbore to clean it up, or if I can go stock size. How long would it take for the kit to get assembled and out once I figure out if I need stock or 0.020" over?

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I finally got around to the compression check, 150 PSI in each cylinder. I guess the motor is still ok, for now.

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