In this case Robbe has removed the old belts already. The best way to hold the crank nut and use an impact gun to loosen the cam bolts. You don't care about the old belts. If this is not an easy procedure it is possible that the former mechanic used the impact gun to put the bolts in after the last service and that they are way over torqued. Remember that after timing procedure and or other procedures you will need to torque the cam bolts back down. This is where you need to think about the method. While a pro says you can tighten against the new belts just fine I prefer to pin cams then tighten. Others like a cam lock tool is fine if the tool indexes the cogs like dave's vs. friction lock tools that bend cogs. Others wack the bolt on with an impact gun but I don't like the unknown torque.
On the 355 the center intake valve runs 10 degrees behind the outside two valves. It opens 10 degrees later and closes 10 degrees later. So you have to add 10 degrees to the total duration. = 248. I wish you lusk.
If the "fifth valve" both opens and closes 10 degrees later how is its total duration any different than the other two intake valves?
Duration is the time the intake or exhaust valves are open. Does not have to be all the valves. Individual cam duration is not changed, but the duration intake can occur increases.
Hello FatBillyBob, I see this thread goes back some ways! Its good stuff, thanks for the effort even these years later from me. Can you explain the 2nd paragraph above where you state the 508 bank requires its own TDC determination? I am confused by that statement. Thanks 348Steve
Ah, now I get it FatBillyBob ! The reason why you need to get TDC on the #8 cylinder is for decreeing the cams on that bank. You mentioned the need to do this a page ago, but didn't reference this action as the need at the time. Its all obvious now! You da man! Thanks!
this is why I just get it exactly on the manufacturers scribe marks barring a modification if the original cams are in it, just changing timing belts? why bother with all the science. just get the timing belts at exactly TDC with the gears on and with each cam just remove the timing gear bolt, turn the cam to line up the mark and find the sweet spot for the pin.
Those are not timing marks, they are assembly marks. They are there to ensure a tech does not bend a valve during assembly when tightening down the cam bearing caps. The engine will run using those marks, but they are nowhere near good enough for timing cams.
Yes, there are separate scribe marks, but that is an awful small circle you are working with. They are a good check after timing the cams, though, and there have been errors noted in some of the scribe marks.
It depends on what you are after, if you are going for absolute or are just getting the job done. for a worn cam you may be better off using the scribe marks because it will wear on the lift side so if you go for the center you actually end up a little advanced. If you are replacing the cam you have no factory scribe marks and need a degree wheel anyway. If you are just reassembling a stock engine and just want it to run well the scribe marks are wonderful if you make them line up perfectly.
What are these 'seperate scribe marks?' The cams in my 308 only have ONE Mark on each. And it took a helluva 'WACK' to put them on/in these cams. And one cam 'WACK' isn't accurate enough, measured against the cam cap mark, to be used in a Bobbie Car let alone a Street Car, let alone Again, in a Performance Street Car.
There are 2 marks on the cam. One at the rear of the front bearing cap which is your typical timing mark, it is approx 1mm thick. this is the mark used for assembly to put the cam in the correct position. After that the cam must be dialed in perfectly with a degree wheel. This is done using the pin position in the holes on the timing gear. At the factory somebody had to degree the cams and find the right position for the pin. The worker who did this then put a scribe mark at the back of the second to rear bearing cap, it is a very thin line literally scratched into the bearing cap and the cam. This was done to save the trouble of degreeing the cams during timing belt service or other service, you simply line up that fine etch mark and you have a factory setting AFTER the cams were degreeed. This only works on the original cam for that engine. Some say these marks are not accurate but if the cam is worn how can you tell? I can understand the factory has a certain degree of tolerence also, for speed they may say within one degree where you may want it within 1/4 degree but if you are not near those etch marks you are off from the factory setting.
Reid, Ill check for those little 'extra' marks. Never noticed or saw them before. I have a BETA Version Spreadsheet that all you have to do to time your cams/valves, is Start EXCEL, 'Plug-In:' 1) Which event on which cam you want to evaluate from the Drop-Down Menus, 2) Observe when, reading off the degreewheel/pointer, that event actually occurs, 3) Plug-In that number into the SS ... And the Spreadsheet then does its voodoo .... and graphically shows you IF you should make adjustments and: 1) Which hole in the cam to move/reinsert the pin, 2) Which hole in the pulley to move/reinsert the pin, and 3) How many if any, belt teeth to rotate the cam/pully, now a 'pinned,' singular unit, clock or counter-clockwise under the cam belt, to achieve (near)perfect cam timing. Using this EXCEL SS should allow a pure novice to time the 4 cams on their 3x8 in under/about an hour, first time ever trying.
This is interesting. In 17 years on F-Chat reading every thread on timing, this is the first time I have heard of this. Also please see attached factory bulletin. What the hell is this?????
I believe that SB is only for easily checking if something really terrible happened (without needing to remove the camcover) -- like skipping a couple of teeth (not for fine adjustment). On later models, they put (approximate) marks on the plastic belt covers and on the back of the cam sprockets for the same purpose.
I wrote this thread a dozen years ago as a companion thread to "setting up cams". These 2 threads go together. This thread is a good start at a time when only us racers and top Ferrari techs were degreeing cams. Much has been learned in the years since. Most important is that much accuracy can be gained in the more cryptic translations from italian to english from the WSMs of later cars like around late '90s+. Pete's 550 maranello sorting mega thread is an example of this. Once you start to understand this you will understand why this thread is a good start and as posted in my original post...there are other ways in cam timing. The Ferrari way is my prefered method and I do it every time I change belts. Second is the concept of consumer acceptable. There are Ferrari owners who cannot tell if their ferrari is running on 4 or 8 cylinders! The slowdown ecu is for this exact reason to protect the car from a clueless owner. 95% will not feel a few degrees of cam timing and thus you have most ferraris set to the assembly marks and called good. There are countless techs fixing these cars who do not cam time and may or may not own the equipment to cam time. Third, extra scrib marks are pretty useless. There are all kinds of reasons for this that I will not go into. At best they are a way to co-witness a reasonable camshaft position. At worst they are just plain wrong. Fourth, The most critical reference point is the cam assembly positions. NEVER lose sight of them.
sounds good, it is good to know what all of the different marks are so that when you are confident that the cams are set you can see how far off it is from the other marks and make sure it at least makes sense. I would only add to your list that a check of the timing reference marks BEFORE disassembly is also very valuable that is, if it is a running engine.
I have one of those tools too. My Dad made a wood copy from an ACTUAL tool a TECH was kind enough to lend me. He said he almost never used it and was in 'No Rush' to get it back. IIRC they are ONLY for the 308s, as the 328 doesn't have the space to make use of this 'Quick-Check' tool or technique.
