Piper Fast Road Cam Installation

[dmorris1]

We are having trouble with the installation of a piper fast road cam. What is the starting point for the crankshaft and camshaft. Right now we have the crankshaft install 105 degrees out and the camshaft is dead top center? Is that correct, any help would be greatly appreciated.
Thanks,
David

 

[Bob Claffie]

I don't know squat about AH's but where did that 105* number come from ? Most cams whether modified or stock get installed straight up, that is, with the dots lined up. With some testing and experimentation it can be suggested the cam be advanced or retarded a FEW degrees from stock. Bob C

After reading the posts below that confirmed that I really don't know anything about AH's. Sorry for the useless, uninformed non-information. My bad.

 

[dmorris1]

It comes from the piper cam website in the section technical advice regarding cam timing .
David

 

[vette]

David, do you have a shop manual. Section A.25. I will try to attach the two pages that address this but to get them small enough to attach you may not be able to read them. But the gist of the proceedure is that on the Big Healey engine, you do not line up the dots. You will put the KEYWAYS of each gear in approx TDC postion. then as stated in the 1st paragraph of page 47 you hold the chain with it doubled over bringing both " BRIGHT" links together. This then shows a long and short portion of the chain on either side of the BRIGHT links. the shorter portion of the chain on the right. "Engage the spot marks on the camshaft sprocket tooth with the top bright link and the crankshaft marked tooth coinciding with the other bright link. With the sprockets in this respective position with the chain, push the assembly home. " With this done, you will note that the top bright link which is engaged on the cam sprocket where the marked tooth is, is in the straight up position. nearly vertical. And the other bright link which is engaged on the crank sprocket where the marked tooth is, is nearly straight down in the vertical on the crank. As seen in figure A.21 on page 46. It my pics come thru. Dave C.

 

[BoyRacer]

Well...... there are no "bright links" in any chain manufactured in the last 40 or 50 years. Get a factory or Bentley manual and look very closely at the picture. You can see the dimples on the cam and crank sprockets ( the keyways of both cam and crank should be in the 12 o'clock position). Carefully count the links in between the dimples and install your chain accordingly. However, that will only install your cam "straight up". A competition or performance reground cam usually requires that you advance the cam. If you install that cam straight up you have effectively retarded the cam, which is exactly the opposite of what you should do. You either need an offset cam key or a vernier cam sprocket in order to obtain the correct cam timing. If you do not understand what I am talking about, you should take your engine to an engine builder that does. And, lastly, the "cam card" (that should come with your reground cam) contains the necessary info that your engine builder needs to properly install your cam.

 

[bob hughes]

I have a Racer Brown cam in the car which is slightly hot and not having an offset cam key or a vernier cam sprocket I set it up as per the book.

You need to count the links on the chain, I make - 15 including the both 'silver' links on side A which is on the right hand side looking at the engine from the front. I marked my chosen 'silver' links with a blob of white paint to ensure that I got it right. I am probably not getting the best out of the cam but it does work fine. As BoyRacer has previously said the cam and the crank shaft key ways should be in the twelve o'clock position when you assemble the chain and sprockets on to them.



Bob

 

[Chris_Masucci]

Why not just degree it in and then you'll know for sure? Tolerances can stack up to be several degrees either way if you install it "straight up" anyway.

 

[EV2239]

It's dead easy. Just put cylinders 1 & 6 to TDC then rotate the camshaft until the two lobes for no 1 are pointing down (the firing stroke) and up for No 6. Rock the camshaft backwards to find the point at which the exhaust is closing and the inlet opening. At the exact change over point, stick the cam wheels and chain on and you're done.

Now put a degree plate on the car and check the timing against Piper's spec having used the tappet clearance they suggest. You'll be very close indeed and close enough.

Next follow workshop manual for inserting the distributor.

Works every time.

 

[mwagon]

Original message doesn't say which engine you're working on. The 4 cyl & 6 cyl cams get dots lined up different, as shown in both shop manuals. The 105 deg is for Inlets fully open per the Piper website for either engine

 

[EV2239]

Original message doesn't say which engine you're working on. The 4 cyl & 6 cyl cams get dots lined up different, as shown in both shop manuals. The 105 deg is for Inlets fully open per the Piper website for either engine

The method I've explained give you re-assurance that you're right. I recommend that timing this way to be sure the marks are correct if there are any. No 1 cylinder on the firing stroke and No 6 on the change over or rock point. You can see the two rocker arms swapping over. Rolls-Royce give the most elaborate valve timing instructions, especial for the 12 cylinder engines, so we always do it as I described and then test it with their suggestions.

If it's a 4 cylinder the same applies. Just like SU carbs, they're very easy once you know the tricks.