Cam Timing help needed
Discussion
I fitted a new cam earlier this year and at the time I really didn't know that much about the rv8 engine ((still don't but learning more and more). Anyway the cam i ended up with came with a non adjustable old style morse chain and pullys. I fitted this and never thought anything about it the car ran well plenty low end power. It achieved 269bhp at the growl but after 4500rpm the power just died litterally like someone turning the car off.
So I ordered a JP timing kit from V8D and according to the spec sheet of the cam it should be set up to .050" Lift @ 2deg BTDC.Is there any way of working out from this what deg ATDC the cam should be at full lift?
Just for a ref before I removed the morse chain set I checked what the setting was and the follower reached full lift at 107deg ATDC and stayed there until 112deg so timing was 109.5deg ATDC.I then removed the timing chain and cogs and fitted the JP multikey lining the sprocket at 0 and point to point (yes I used the marks on the outer edge not the key marks to line up the cam) and checked to see what the timing was It now reached full lift at 114deg and stayed there til 119deg making the timing 116.5 ATDC so to get the timing where it was before I need to use the max +6deg adjustent and still the cam is 1 deg higher than before. so I checked the timing as stated on the spec sheet and with the max adjustment the closest I could get was .050" lift at 1deg BTDC. Any Ideas what I am doing wrong?
Chris
So I ordered a JP timing kit from V8D and according to the spec sheet of the cam it should be set up to .050" Lift @ 2deg BTDC.Is there any way of working out from this what deg ATDC the cam should be at full lift?
Just for a ref before I removed the morse chain set I checked what the setting was and the follower reached full lift at 107deg ATDC and stayed there until 112deg so timing was 109.5deg ATDC.I then removed the timing chain and cogs and fitted the JP multikey lining the sprocket at 0 and point to point (yes I used the marks on the outer edge not the key marks to line up the cam) and checked to see what the timing was It now reached full lift at 114deg and stayed there til 119deg making the timing 116.5 ATDC so to get the timing where it was before I need to use the max +6deg adjustent and still the cam is 1 deg higher than before. so I checked the timing as stated on the spec sheet and with the max adjustment the closest I could get was .050" lift at 1deg BTDC. Any Ideas what I am doing wrong?
Chris
What cam is it? 110deg isn't untypical on the bigger cams.... 119 is way too retarded and Id imagine yr exhaust valves would be in danger of contacting the pistons. Assuming the right marks are being used, I'd guess the cam sprocket is a tooth or so back from where it needs to be ont he chain. When locating it, remember to keep the chain tight on the right and if you have a choice of slightly too advanced or slightly too retarded on the keyways, then advanced is the one to go for. After timing it up, rotate the engine clockwise to recheck with the chain tight.
Cheers for the info guys. Had another go at it tonight and have managed to get it set up. Spoke to Dave and he advised that the timing should be 110deg ATDC at full lift on no1 inlet.It is now set at 110.5deg which was the closest I could get as the multikey JP timing kit only has increments of +/-2deg.
I did this fistly by finding TDC using the DTI The piston stayed at Its max lift for 4deg so I set pointer on the deg wheel at TDC in the middle of this. Then I wound the engine clockwise to 100deg ATDC set the dti to 0 and turned the engine over again til the dti read the max lift and then returned to 0 I took a reading from the deg wheel wich was 117deg ATDC 1/2 way between these "100 and 117" was where the max lift was (108.5) I needed 110deg so I removed Jp timing chain moved the keyway to -2deg refitted it rechecked TDC and did the same again I now had the difference between 100 and 121 so the timing was set to 110.5deg ATDC I then rechecked it about 20 times then recheccked the TDC and again the cam timing basically untill my arm was that tired of turning over the engine I had to give up lol. I know this aint no massive mechanical achievment but I must say I feel pretty chuffed with myself for doing it.
Now to check the pre-load, Is It correct that I should empty all the oil from the followers before I check the gaps??
Chris
I did this fistly by finding TDC using the DTI The piston stayed at Its max lift for 4deg so I set pointer on the deg wheel at TDC in the middle of this. Then I wound the engine clockwise to 100deg ATDC set the dti to 0 and turned the engine over again til the dti read the max lift and then returned to 0 I took a reading from the deg wheel wich was 117deg ATDC 1/2 way between these "100 and 117" was where the max lift was (108.5) I needed 110deg so I removed Jp timing chain moved the keyway to -2deg refitted it rechecked TDC and did the same again I now had the difference between 100 and 121 so the timing was set to 110.5deg ATDC I then rechecked it about 20 times then recheccked the TDC and again the cam timing basically untill my arm was that tired of turning over the engine I had to give up lol. I know this aint no massive mechanical achievment but I must say I feel pretty chuffed with myself for doing it.
Now to check the pre-load, Is It correct that I should empty all the oil from the followers before I check the gaps??
Chris
in for a while at least, as I wont be racing but do like the low end kick in your back when its working well. Gassing Station | Griffith | Top of Page | What's New | My Stuff