Title says it all. I got my 91 block machined up, with the align bore that was needed the centerline of the crank dropped .015. ANYBODY know where to find a .015 shorter timing set? It can be double or true roller. I can find .010 short all day long for my app but no .015".

 

never herd of this one before. If im wrong then so be it but i think some one screwed up some place

 

I never knew you could buy a shorter timing chain. .015" of slop I figured was not enough to write home about (let alone .010" !)
Tagging along to find out more about this.

 

You can run the 0.010" chain, it will work, tho isn't ideal, or you can get another block. What dumba$$ align-honed it more than 0.003" anyway? I've align-honed at least 50 SBCs in the last 9 years, and I've never needed to remove more than that. I know the ten chain will work because this one guy had us put aftermarket 4-bolt caps on his 2-bolt LT1 (dumba$$), then it had to be align-bored , ended up 0.017". But he drove it that way.

 

I'm being told a .010 under will work but the chain will be tight and could possibly end up wiping out the bottom of the front cam bearing. New block is out of the question. This was a 4bolt 4.000 bore to a fully machined / worked over block. 4.030, squared, decked, etc, etc, etc.

Well, needless to say I have an update: YES, I agree that the .015 was a sh*tload to take during the machining. On a good note. Cloyes used to offer 9-3145-15 which was a .015 shorter timing kit. They discontinued a number of years ago due to lack of demand. I talked to them, they are willing to make one for me for a VERY small upcharge to the 9-3145-10 kit (.010" under). SWEET beans. Everything will be good to go once again.

 

The chain won't be tight, it will be loose.

 

The chain would be tight. Think about it. Say the crank is 9.00" away from the cam, center to center. I know it's not 9 even, just an even number for the example. The caps have material taken off the bottom, the crank journals have been moved closer to the cam center by 0.015". New center to center distance is 8.985", that requires a SHORTER chain. If I were only to use a 0.010" shorter chain, I would be higher than the true center line by 0.005", resulting in more tension. Am I completely backwards here?

 

yes, you have it backwards. I'm a professional automotive machinist for 9 years now, who has been there and done that. The chain WILL be LOOSE.

 

Atilla, thanks. I'm not trying to be combative. I know you guys in the engine building trade know your sh*t. I was just trying to educate myself in this. I've been in the tool&die industry for over 14 years, working in tenths up to millionths of an inch. Typically my machining tolerances were in microns (.001 millimeters). Anyhow, with this debacle I'll now have to keep an eye on the timing cover front seal, inspect my 1pc seal out back and certainly have to use offset / adjustable bellhousing dowels when I dial indicate the bellhousing.


BTW, as soon as I posted this, I pictured what a standard length chain would be like at my centerline dimension. You're 200% right, take a 9.000 chain say, or even a .010 under chain would still be too long. Further away from center = longer chain so anything going closer to a standard dimension requires a longer chain than what I need now. WOW, its funny once you can see it in your head. Hopefully this post helps others out in the future.

 

I wasn't trying to be combative either. Peace.

 

I got one BBC block that's been line bored too many times. I can't remember how much shorter the chain is that I have for it but there comes a time when you need to say enough and scrap the block or sell it to be someone else's problem. If your crank sits .015" higher in the block, how much clearance will the rods have going past the camshaft?

Cloyes makes shorter chains but I only see listings for .005 and .010" under. They say some applications are available .015" under. I'd suspect SBC would fall into that category.

9-3100-5
9-3100-10
Try ordering a 9-3100-15

SBC crank to cam centerline is 4.521". There are different ways of measuring the centerlines but use whatever works for you. If you do a measurement and get 4.511" then a .010" under chain would be snug. I wouldn't put a .015" under chain on until the measurement dropped to 4.506" or less.

Here you go
http://www.centralhp.com/viewitem.ph...=CLO-9-3100-15

 

Steve, thanks man. The measurement was 4.5065". Summit still lists the Cloyes 9-3145-15 (.015 under) chain but I personally called Cloyes and they said they stopped making a few years back but they'd make one for me. I agree with walking away from this block but I'm in too deep if you know what I mean. Cam clearance is the next thing I'll check if that's F'd up bad, then I'm going to have a deep personal chat with this machinist. This guy came by the recommendation of my buddys father who's used him over the past for his mopar apps. My engine guys is almost 6 hours away from where I moved to now so I didn't go back to him. Hindsite is 20/20. This engine only has to last the next 2 or 3 season MAX, then its Dart 434 time.

The cost for this Cloyes .015 under chain they "don't" make anylonger was only about 20bux more than the 10 under chain they still mfg.

 

I think that .0005" should be close enough to use a .015" under chain. It will be very snug. The part number I quoted was a high end chain. Glad you were able to find a cheaper version.

I gave up trying to use factory blocks. Too much was being invested into old, worn blocks. I finally broke down and bought a Big M block. It was well worth the money.

oops. I had some numbers backwards in the above message. fixed.

 

Steve, I hear you on the blocks. The next engine I put money into will definetly be a Lil M block. The 434 shortblocks are under 4500 right now which is a great price IMO. I looked at the chain you quoted for part #, its not for a factory roller, mines a hydraulic roller so thats why I whent with the 9-3145 instead of the 9-3100. The chain I'm getting me like I said is costing me $115 instead of ~$95. Either way, thanks everyone for the help. This engine probably won't go 50k miles, who knows. I just need it to last me the next 2 or 3 seasons.

 

I thought they'd been discontinued. I didn't think they'd whip one up, but that's great!