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Old 04-29-2007, 11:02 PM
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Setting up cams

There was a lot of interest and holy war of words regarding setting up cams and degreeing cams. I have my engine out for its annual service so I wrote up some cam setup and cam timing issues and instructions. Here is a sample. Are you interested in my going further?

This is not the only way but it is my way and I have doen it like this for 20+ years on many Ferraris.

Setting up 348 base timing and cam belt:

This general technique works for any motor but specifically is being done on a 348. You will need to make a chart like this to find all the valve tappet clearances. Note it is laid out just like the engine and tells me which tappets I must change. The range is intake 0.20-0.25mm, exhaust 0.30-0.35 non cat cars. If I have a valve with 0.40mm measured clearance and I want 0.30mm per Ferrari spec and I pull out a 3.50mm shim out of the valve bucket then I need to change to a 3.40 shim.
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Last edited by fatbillybob; 04-29-2007 at 11:04 PM.
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Old 04-29-2007, 11:05 PM
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Once the tappets have been set to proper lash you can set the engine to top dead center in compression. This means that in TDC the cam marks all just about line up with the cam cap marks. You set the engine to this general specification based on the old timing marks for TDC and the cam marks which should be very close to perfect so you know your general point of referrence. The first thing we need to do is get real precise so You will need these items:
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Old 04-29-2007, 11:10 PM
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This is a homemade TDC plate of just ¼”x6”x2” steel bar stock with a hole for the threaded rod to touch the piston top and holes the dimension of the cam cover studs to anchor the bar. Here you can see the TDC plate and three large nusts on each cam cover stud to raise the plate high enough so it will not be hit by the cam lobes as they rotate.
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Old 04-29-2007, 11:56 PM
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This is great!
Many thanks!!!!
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Old 04-30-2007, 12:03 AM
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This is great, keep going.
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Old 04-30-2007, 01:30 AM
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You've got my attention
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Old 04-30-2007, 08:34 AM
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Having realized we set the cams up wrong (per the other threads discussing the difference between the "early" 308 cams and the '78-'79 cams), we are doing this all over again, this time with the engine in the car. The rear bank seems to be no biggie, but the front bank looks to be a PITA. As I'm going up to Watkins Glen this week and family stuff next weekend, the project is on hold for a while. I'm interested to see how you take care of degreeing the cams.

Very nice so far. Looking forward to seeing the rest.

Steve
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Old 04-30-2007, 03:32 PM
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If you really try to degree your cams accurately, the front belt sprocket on a 308 can be difficult. I think it took me an hour or better, because you just cant see up in there very good and put the sprocket pin in the right hole at the same time. Place the pin, let go of the tensioner, crank the motor and watch your dial indicator while you reference the degree wheel, and darn it, to far the "other" way. Loosen the tensioner, unscrew the bolt, pull out the pin, take the sprocket away and rotate it for a different belt tooth to realign different pin holes, replace the pin, put in the bolt, let go the tensioner and recheck. Darn, to far the "other" way again. Probably the next time it will be much easier. Lots of things are harder the first few times.

I think someone calculated that there is a potential difference of 3 degrees between cam and sprocket pin holes.
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Old 04-30-2007, 10:40 PM
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Quote:
Originally Posted by Artvonne View Post
If you really try to degree your cams accurately, the front belt sprocket on a 308 can be difficult. .
It takes time and precision but is doable. This way is just one way not the only way. This first thread is devoted to basetiming set-up not degreeing. The follow-up thread will be on the two ways to degree a 4 cam motor if interest seems to hold.
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Old 04-30-2007, 10:43 PM
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You will need a 1” travel dial guage that should be inline with the pushrod not crooked like my picture here. Two pictures down is what you want
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Old 04-30-2007, 10:47 PM
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You need a pointer for your degree wheel. I use brass brazing or welding rod cut to length and held by a 1” clamp. Sorry computer is acting up.....
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Old 04-30-2007, 10:53 PM
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You need a degree wheel. Summitracing.com makes their own and it fits the 348 crank snout without modification. Remove the damper and bolt the degree wheel right on the end of the snout. I have already found approximate TDC within 5 degrees or so. My pointer is at 9 o’clock out of convenience so my wheel O* TDC is at 9 o’clock too. If you hold the wheel here and impact wrench the crank bolt tight with 2 quick pulses of the air gun it is tight enough to not move and tight enough to move the crank clockwise and counter clockwise with no issue. If this comes loose on you during the process you need to start all over again. This needs to be tight.


When turning the crank try to stay in the driven direction which is clockwise. If you go counter clockwise it is o.k. but it creates slack in the timing system that needs to be taken up as you work to keep results accurate. Your engine should be set-up for TDC by a degree wheel and dial guage even if you time the motor with just the cam marks on cam caps. This should be set-up already. So you should know your TDC if you are starting to degree cams.

Finding TDC: You start at general TDC and Turn motor clockwise and watch the piston rod move and effect the dial guage. Eventually the rod will rise on the dial guage and you can see the cam marks starting to line up then you know you have piston back in the compression stroke. If you do not see the cam marks coming you are off one cycle keep turning. When you see the rise “peeking”… stop. Zero your dial guage. Crank the motor CW so the dial guage reads .050” Lets say it says 12* on the pointer/ degree wheel. Crank the motor CCW so the dial guage reads say .090 the other way. You need to overshoot in the CCW direction because you need to take up the timing slack. Now crank CW to .050 again. Lets say it says –10* on the pointer/ degree wheel. –10 + 12 = 2. You have just taken two measurements on either side of zero at approximate TDC.
2/1= positive 1*. True TDC is at 1 on the degree wheel. Now crank the motor CW until 1 shows at TDC on the degree wheel and the cam timing marks should be nearly spot on. You can now bend the pointer to read 0* TDC and from here on this will be your most important TDC referrence point.
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Old 04-30-2007, 10:55 PM
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Next you can lock or pin the cams with matchbook covers under a cam journal cap gently. Then remove the cam belt and change water pump and tensioners if so inclined. One at a time loosen each cam and use the old belt with vice grips to help position the cam perfectly on the marks. Tighten the cam journal with matchbook cover to lock the camshaft. You need to do it this way because the cam is under pressure and will move unpredictably. Do this for each cam. Next loosen all the cam cogs and remove the cam locking pins but put the cam bolt in loosely
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Old 04-30-2007, 10:57 PM
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Replace new timing belt and allow belt to move where it wants and cogs to turn freely. Set up the cogs so the most number of holes overlap the most number of holes on the cam snout so you have lots of adjustment either way. With the belt all the way on everywhere except the last cog pull off the last unbelted cog so that the cog can be placed on the belt and position this belted cog over and index it on the camshaft nose. You need to do this because even with a compressed tensioner you need the slack to place the belt. Replace this cogs bolt. Now the cogs are on and the belt is free to move the cogs but it won’t because you are at TDC and that is fixed. Tension the belt by releasing the tensioner nut and pull belt slack away from the crank cog to the 5-8 exhaust cog to the 5-8 intake then the 1-4 intake and the the 1-4 exhaust and lock the tensioner down.
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Old 04-30-2007, 10:58 PM
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This is my homemade pin wrench tool to help me pressure the cog one at a time by pressuring counter clockwise to take slack out of the belt to be taken up by the tensioner. Now you can slide in the cam cog locks to the most passive lined up holes and hand tight the cam bolts. You only had the cams locked with one matchbook cover. Place 3-4 matchbook covers in 3-4 journal caps and lock the cams down good. More matchbook covers with light force on the journal caps equal lots of locking power on the camshaft
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Old 04-30-2007, 11:01 PM
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Do not kill the journal covers. Use an impact wrench to put the cam cog nuts back to torque or use a torque wrench to about 70ft-lbs. I like a couple pulses of the impact wrench because it puts the least pressure on the cam for movement. Then I’ll gently apply a torque wrench to make sure I’ve reached 70 ft/lbs but watching timing marks to make sure I am not putting pressure on the timing belt or need more locking on my camshaft. Before anyone gets their undies in a bunch about this torquing method realize that wrenchs are typically +/-15% on torque spec, oil or no oil effect torque, the size ot the fastener allows a wide range of torque. I do not do this without thought. I’m at a minimum 70ft/lb on the wrench but I’m not at 200 either. Next remove all matchbook covers and test rotate the engine a few revolutions bringing all marks back to perfect position and to TDC. Engine is now ready to run or you can confirm engine timing or alter engine timing by degreeing cams with a degree wheel and dial guage.
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Old 04-30-2007, 11:03 PM
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So there you have it. The base timing on a 348 is complete. You can run the car no problem. Do you want to see two ways to "degree" cams for more precision? If yes I'll take it to a new technical thread called Degreeing your cams
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Old 05-01-2007, 08:02 AM
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Fatbillybob, thank you. Yes I would like to see your method to degree the cams with more precision than the factory marks. Did my last major 4 years ago. Plan to pull the motor at the end of the season here in MA. Your tutorial will be put to good use. John.
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Old 05-01-2007, 01:19 PM
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Quote:
Originally Posted by Artvonne View Post
Place the pin, let go of the tensioner, crank the motor and watch your dial indicator while you reference the degree wheel, and darn it, to far the "other" way.
Do you have a picture of the dial indicator for the front bank with the engine in the car? I had a really tough time with this. I'd like to see what you did. I must be missing an easier way to do this!
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Old 05-01-2007, 05:13 PM
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Quote:
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Do you have a picture of the dial indicator for the front bank with the engine in the car? I had a really tough time with this. I'd like to see what you did. I must be missing an easier way to do this!

Unfortunately I dont have a pic. I have a magnetic stand, and so I bolted a piece of bar stock to the head and stuck the stand to it. Its quite hard to find the right point for the rod to press against the follower so the cam lobe wont interfere with it, take's a bit of trial and error. .

FBB, I think its great that your showing people that this stuff isnt really rocket science. You guys dont need $10K worth of tools in a 3000 square foot garage with granite floors and a megabuck hoist. Sure, we all want one, and its wonderful to have, but its not required. I bought a nice $60 degree wheel and its so large I cant use it without fabricating more tooling. I copied a degree wheel off the internet, resized it, and printed it. Then I cut out a circle in aluminum, and scribed degree lines into it using the copy as my pattern. It works. FBB's TDC tool works. Verells cam locking tool works. I wont say much about my chain wrench deal but that works too. If you can visualise how stuff is supposed to be, and how its supposed to function, you can figure it out, its all actually pretty simple once you look at it.

As long as the last thing you do is rotate it twice around for one final check to verify your marks, clearances, indexes, and all your work, and that you fully understand what it is your doing, you will be okay. Whether you use a soda straw, a threaded bolt through a home made plate, or a $400 TDC tool, as long as your sure of your work, nothing else really matters a whole lot.
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