The honeymoon is over – Broken timing chain?

How do you know that from this info? (Just trying to learn.)

I bought the car knowing very little about the drivetrain other than what I could see. I assumed the worst, and was still very happy with the purchase. The more I discover about this car the happier I’m getting.

 

Never mind. I just read a Hot Rod Mag. article on offset grinding and how BBC rods are often used. Very interesting.

 

Why wouldn't this just use the stock type timing set? Am I missing something?

 

Your existing timing set should be stamped with something to indicate other than stock if it's not stock

 

Larry - Thanks for the link ... very informative.

Super - I previously checked the gears and I didn’t see any markings other than Rollmaster’s name. I’ll double check when I get home tonight. The receipt I posted above indicates the block was line honed. Is it possible to line hone a block without changing the crank’s centerline? Or perhaps line hone the block, but the movement of the crank centerline is small enough that you don’t need an oversized timing chain set?

 

I just read the caption of the picture Larry posted. That answers my questions.

 

The proper way the line hone the mains are to trim the caps, then hone, that way the center doesn’t move. If they cut the block then for sure you will need a shorter chain. As far as the cam is concerned, you could map each lobe and figure out the LSA and go from there. Or install as it was. Based on the stated performance if the cam was improperly degreed it’s probably not off by a lot.

I forgot to mention that I’d do a leak down test before anything else.

 

I would start with a standard chain. A line bore would likely require a shorter chain but not normally just a hone.

 

My block has been line honed twice and takes a standard chain still

 

When I had my block at the machine shop I asked if it was align bored or honed. My machinist said that they cut the caps and align honed it. I talked with him a great deal about it and brought up the undesized chains from TA and he assured me that the amount was so miniscule that a standard size chain will be fine. Not sure if that helps any but when my chain arrives and I get around to putting everything together we'll see how it fits I guess lol

 

I can say mine was honed by AMP about 10 years ago, after a basic refresh, no block machining.....we lost the center 3 main bearing and the center 3 main caps. FINISHLINE in Michigan installed new Program billet caps. These caps require a decent amount of work to fit the register and the both line bore followed by line hone. I was in Bob's shop when we finish honed it, then the block went through several hours of hand washing in the middle of Jan outside in Michigan......ill never forget how froze my fingers were..........we went to assembly the next day only to find out after cooling our clearances settled.....and required more honing.......and it didn't require a different length timing set up. I know finishline took extreme care to do most of the line bore so it cut off the caps........but given the biklet steel caps were so much harder than the cast block , this cause issue and was a slow process. We assume the size variant came from the expansion difference of 2 types of metal as the heat of friction from honing, tanking, the hand washing.....

 

Thanks for all the input! It's extremely helpful.

I ended up ordering a standard size timing set since it doesn't appear line honing significantly affect the crank-to-cam distance and my current timing set doesn't have any markings on it that would indicate it's oversized. I'll check how tight the chain is when I install it and go from there, but I'm anticipating it will be fine.

My plan is to install the cam at 6* advanced. That's were it was installed prior to the chain failure. Then I'll map the cam so I know what the specs are for future engine mod decisions. I would degree the cam, but I feel like I need the cam card to do so, and I don't have that. For example, I thought one of the points of degreeing the cam is to verify the cam is install with the amount of advance the manufacture intended (i.e., the amount of advance ground into the cam), so If I don't know what the manufacture intended to grind into the cam how do I compare my measured number to that? I'm just now learning about degreeing cams so I may be misunderstanding something.

Also, I plan on pulling the rockers and doing a leak down test while I'm waiting for the chain to arrive. One question: is there a specific procedure for installing the rocker arms other than tightening the bolts evenly and torqueing to 25 ft lbs.? I'm assuming some of the lifters will be on the base circle and others will be on the ramp, so it seems the torque may not be accurate (or a rocker may not seat properly) since some bolts will see more force from the springs than others (i.e., some rockers will have to compress the springs more than others).

Thanks!

 

Some places have a cam dr. They can map your cam and read it.

You can physically measure once you have a chain. And get the @50 numbers, the intake center line the exhaust center line and do the math and figure out lsa and all that. It takes some time and very careful measuring but can be done

 

Just got done doing a leak down test.

I didn't hear any air escaping through the intake or exhaust, so it sounds like I may have dodged a bullet.

 

Good news!

 

I just finished degreeing the cam. It was my first time, so it was a learning experience.

A little bit about the setup … I used a threaded rod and several bolts and washers to connect the degree wheel to the crank. (See pictures below.) This enabled me to rotate the degree wheel when I was finding TDC without the concern of inadvertently moving the piston. I may have over thought this, but it was cheap and worked great. My biggest struggle was trying to line up the gauge with the push rods. I’m sure it would have been much easier if I had extension rods for the gauge and just removed the push rods. I guess that will be on the list of things to buy. Anyway, after the setup things went smoothly.

Below is a table of my measured and calculated values. I’d greatly appreciated it if someone could let me know if the data makes sense. (I’m considering degreeing the cam again once I put the rocker arms on so I can compare the data. I’m not sure if setting the gauge on the spring retainer will provide more accurate data.)

Thanks!

 

I forgot to mention I installed the cam at 6* advanced. That's where it was when I disassembled everything.

 

Easiest method after you find true TDC is to zero the indicator at max lift, back up 0.100”, then in the direction or engine rotation, rotate until you’re 0.050” before max lift, record the number, keep going in the direction of rotation, you’ll hit max lift and stop at 0.050” (you’re on the backside of the lobe now). Record that number, add both together and divide by 2, that is your intake centerline. If you try to do w opening and closing your lobe must be right, most are missing 0.5*-2*.