.005 or .010 shorter cam chain needed?
 

Measuring my 455 cam to crank cl. I know it's been line bored twice at least. My CL comes out at 5.18525". I read stock is 5.192. So .00675 closer. Are chains measured in distance closer or overall chain length shorter? Ie. A .005 shorter is for .0025" cl closer distance?

And, I got a new comp cams double roller set. Had lots of play. Why I checked. Can I just get shorter chain or do I need to buy a whole new set?

Brand new the cc chain has over 3/8" slack

I don't think it's a "shorter chain" when you're buying that type of timing set. At least that's how it is with Rollmaster. With those .005 and .010 sets, the chain is the same as in the standard length set....it's the gears that are different.

Ok. But since I am 6 thou closer. I'd it 5 or 10 thou shorter set I need?

My rollmaster chain was very loose i went with a cloyes and its alot tighter. my motor was align bored this last go around,

Call Cloyes and give them your dimensions. They have -.005 and -.010 in stock for Pontiac. Let us know what they say.

I'm in a similar boat and curious what you end up going with. Thanks

As was mentioned above, it isn't just simply a shorter chain, it is the gears that are different, in the -.005 and -.010 sets, that are for align bored engines ....

My last build the chain was very loose and I tried a Rollmaster -.010 short I couldn't even get it installed. I exchanged it for a -.005 set and it fit tight with almost no slop. Sometimes a test fit is the best you can do. I would try a .005 first a -.010 is usually not required except in extreme cases.

Might not want the chain to be too tight. Here's a test of one that lost 11 HP:
https://youtu.be/xk12lbg6SNI?si=ey5BCJLj-iX0Sx08

Mine felt about right with about 5/16" of total slack

I saw that video last year. It made me think I ran a -.005 set with this current shortblock. it was tight hard to put on. Late last year I swapped my looser standard set on..see what happens I'm always looking for horsepower.

I am not so sure its the gears.
With Cloyes they offer a "Z" series chain. The best on earth, but only in std. The .005 and .010 short sets get the IWIS chain. A good chain, just not as good as a" Z" chain.
Rollermaster BTW uses IWIS on all of their sets but do not offer a "Z" chain. The short Cloyes chains are IWIS, a step down from the "Z" chain. I called up Cloyes myself about this issue.
So, if it was the gears you could buy a Cloyes .005 short timing set with the "Z" chain. But you can not.
So it must be the chain, not the gears.

My understanding at least with Cloyes is the timing sets are "graded" Each set is mounted on a test fixture and tested for center to center distance with a dial indicator. Sets that measure in the STD range and boxed and sold as such. Sets that fall in at +.005 and less than +.010 and boxed and so forth. Tiny variations in axles and clearance between them and the ground rollers do stack up as well as tiny variations in the sprocket tooth cuts. The Z chains are so accurate, they don't measure outside the standard dimension range so no shorter Z chain sets are offered. The Z chain is an IWIS chain as well. Just a more precise, higher grade chain. Rollmaster either does not have access to this high grade chain or they choose not to use it due to higher cost. As far as I know, only Cloyes offers this chain for automotive use. FWIW, the "Rolon" brand chain is one to avoid if avoiding stretch and retarded timing is the goal. They are made in India and have very spotty quality. They seem to stretch excessively in stock/near stock applications. Many aftermarket cam companies use Rolon chains in their double roller sets and put them in a fancy camshaft manufacturers box. I strongly recommend NOT USING any roller chain that has no manufacturer marks on the links. They are almost guaranteed to be some Chinese knock-off or other low grade chain. IWIS or Renold are high quality chains.

So, you guys are saying Cloyes is the best timing set to use? Better than Rollmaster and whatever Butler is selling as their own, or Comp, or BOP is selling?

So, if you need a .005 one, it would be this? https://www.summitracing.com/parts/c...5/make/pontiac

I think you need to make your own decision. I feel the Cloyes premium sets with the billet sprockets and Z chain are the best available period. This is based on 11 years of running these sets in a blown nitro application at over 8000 RPM's with no harmonic balancer and a 44 amp magneto, a fuel pump, an 200 lb. oil pump all driving directly off the cam/sprocket putting incredible stress into the timing set. This is in addition to 450 lb. seat pressures and 1100 lb. open spring pressures on the valvetrain. If that didn't stretch these chains, I would consider them to be very high quality. We never had a timing set related failure even with a blower explosion, stripped/sheared off woodruff keys, broken lifters, broken rocker arms and a host of other chaos. Other people I respect on the forum have different opinions on the timing sets. Some like the Rollmaster sets because they can receive the SIMS torrington bearing modification. Cliff Ruggles and a few others like the flat link, non-roller chains for smoother running and better harmonic control. Also a claimed less stretch over time. That may be true vs a Chinese roller chain. In the end, quality parts will give you the best service.

Well, I just ordered the Rollmaster -.010 from Butler last night. New stock chain had just under 1/2" slack 1/4" each way. And Crank to Cam CL has been measured to .00675" closer than stock. Prev machinist had messed up more than the line bore on my HO Block. Not happy for sure. But that's where it lies and FAIK there no way to regain cam to crank spacing. If this undersize is a little snug, she will break in quickly I'm sure.

The 400 block I'm currently building was line bored amd fitted with arp studs. I used a roll master. 005 under timing set and it fit perfectly. Probably one of those situations where you will need to try them to determine which is best.

Align bored TWICE? WHY? I’ve align bored around 3,000 blocks. You only align bore when replacing main caps, repairing the main saddle after a spun bearing or you have an unusually out of alignment main saddle.

had a nasty Hydrolock once, filled bottom end with coolant then split no 7 cyl. Had it sleeved. Then a few years later, Exh lobe on No 5 went flat and basically locked motor with combustion pressure that couldnt exhale. that one threw the mains out .003 shop said.

BUT, I also had very bad work done from that shop on that rebuild. ie, SCAT crank was made with 455 journals, but thrust was 400 width. Instead of opening up crank, some yahoo there ground my thrust bearings down to steel to fit the narrower 400 width. I did not know this till 3000KM later when the metal dust took out yet another cam.

I can NOT have any shop work on my stuff. They ALWAYS mess crap up. Do it yourself if ya want it done right. It's a 1970 455HO Block. 455s are rare here in Canada as it is, let alone a HO Block and heads.