Camshaft degreeing 101

:beer

 

Any cam dyne results?

 

Hi there,
I have a 3 key timing chain set. Wondering how big a deal it is to use that and not the 9 key one. Also, I don't have any of the tool he uses on this. What is the bare minimum that I will need, because, wow, that's a lot of expensive stuff he uses.

Thanks,

Clint

 

How much difference does 3* make?
i understand cam timing moves the power curve but how much HP is lost or gained?
Cheers!

 

The mechanic rebuilding my engine showed me the camshaft this afternoon and it was
obvious even to my uneducated eyes that there is scoring on several areas.

So... add a new camshaft, timing chain and lifters to the list of items being replaced....

What would be a good street cam for a 1970 455?

I am/was pretty happy with the performance of the stock cam (it's a cruiser, not a racer)
but I wouldn't mind something slightly more aggressive - a bit more rumble at idle perhaps,
without sacrificing driveability or worsening the already abysmal fuel economy.

I would welcome any suggestions.

Thanks
Jim M

 

Thanks Larry. :TU:

I will educate myself this weekend and hopefully have a plan by next week.

 

In my opinion the best cam on the list you posted is the C118. This is an old KB grind but it works great in a 70 455. It has a slight lobe at idle, it idles at 800 rpm and pulls strong to 5500 rpm. The C118 camshaft is very easy on the valve train. We use to use this cam in many muscle car shoot outs where it had to retain somewhat of a stock idle and produce 15 plus inches of vacuum. We dynoed this cam in a 70 GS Stg1 engine and it picked up 25 hp over the factory stage 1 cam. Dave Knutson and I used this cam in the Car Craft Real Street Eliminator shoot out some time back in mid 80's I cannot remember the exact year. The car had to be pretty much stock including the Qjet carb and exhaust manifolds, the car turned consist 13.30's at 105 mph in the quarter mile.

 

Thanks Jim excellent reading

 

im so glad , on one can hit me !! ive installed several cams . they said , STRAIGHT UP , 2_, 2+, ive never degreeded , always set for low speed torqe. in the real world , how much variation is there , normally? are they EVER right ? im sure when built NONE were deg.!! so are they all off a little , or more ? OR , am I wrong , and all new mtrs. are deg,. and , remans.. WHAT ARE THE CHANCES OF IT BEING RIGHT , OUT OF THE BOX ????

 

Having degreed over a hundred cams in BBB's in the last 20 years, I would say the odds are no better than 1 in 10 that the cam is within 4* of where it should be, if you just line the dots up. I have degreed cams from virtually every manufacturer, reseller and grinder.. and there is really no advantage in any of them, they ALL have to be checked, to get the engine to run it's best.

The bigger the cam is, the more critical it is to have it installed correctly, and it is the number one reason that new engines don't run correctly.

JW

 

Consider the $ spent, and the hours spent on a build.

The last thing you want to leave to chance, is/are the thing(s), that you cannot go back and do over or fix after assembly and/or stuffing the engine/transmission/what not into a build.

In this case, the time spent degreeing the cam, vs loss over the lifetime of the build of horsepower, mileage, reliability or what not is just not worth the "time saved" skipping that step. And it is "free" performance.

If you feel that you are not savvy enough, then ask for help. Piss on the naysayers and those who ridicule you, and listen to the old heads that have BTDT and have the closet full of nasty T shirts.

For some, you may only have the blessing (of the wife) and money once to do this. And for the rest of us, not a lot of time left to do it wrong.

Cheap, Easy, or Fast. Pick two.

 

For the first cam that was degreed (the Lunati) and the .006 and .050 valve event numbers were given, it's interesting to see that in that example both lobes are non-symmetric: that is, the rise from 6 to 50 is shorter (in degrees) on the opening side than it is on the closing side (intake: 22 open 28.5 close)

 

Just venting a little - I recently purchased a new Crower cam for a 455 I am building. The engine is going to be around 10.4:1. The p/n on the cam is 52241, grind number 284HDP. Anyway, I just installed it last night and had some confusion about some of the notes on the cam card that came with it. The cam card itself was pretty vague I thought. It was missing data that I would normally expect to see on a cam card. There was a spot for the valve spring requirement, but it was blank - then the only other data on it was valve opening and closing info @ .050". The cam is advertised as having a 112* lobe separation. What confused me was a note at the bottom that said: There is 4* advance ground into this cam. If degreeing using the lobe center process, install at 108*. After reading that I assumed that meant I could install the chain at the factory (straight-up) position and it would be about in the right spot - with 4* advance. This was not the case. I ended up having to install it 4* advanced (per the timing set) in order to get it in spec with the cam card. What am I not understanding here? I've built hundreds of engines over the past 35 years, degreed plenty of cams - the card that came with this one really threw me for a loop.

 

This is true on every camshaft I have ever had a dial on. The valve should always open as quickly as possible and then close in a more graceful manner - it helps with the charge velocity.

 

There is a write up about timing sets in the TA catalog. OEM Buick timing sets had 4 deg built in. There was some confusion about which aftermarket manufacturers of timing sets had or did not have the 4 deg bult into the set. It could be that or just manufacturing tolerance stack up

 

The timing set I'm using is an SA Gear 78540R double roller set with a 3 keyway crank gear. It supports 0*, -4* or +4*.

 

Sorry to bump an older thread, however I have a question regarding timing chains that seems pertinent to this thread. I have seen many recommendations for running shorter chains especially after main honing or cam tunnel work. Why is this recommended? Is the stock length too long? I don’t really understand this relationship to the machining work, it doesn’t seem to me that the center lines would be changed so the chain length should be consistent. What am I missing?