Don't ask why, but my dad had his Olds Delta 88 307 rebuilt a few years ago and it has never ran right. I think it has been the carb, but a guy at the oil change place he goes to, put the idea in his head the the cam was off. Anyways, since I took it apart to check to make sure the dots lined up on the cam gears, I went ahead an installed a slightly larger cam. To make sure that there isn't anything wrong with the cam gears or something else, I decided to try to degree the cam. It's my first attempt doing this. I've watched countless videos and read many how to's. I'm doing this with the heads on and I'm 99.9% I've got TDC figured out correctly. I am measuring off of the valve retainer and pretty sure I've got the dial indicator inline with the valve. I made solid lifters out of hydraulic lifters and with a mixture of washers and a cut up feeler gauge, I've got it right at zero lash. I also took into consideration the 1.6 rocker ratio by taking my measurements at .080 of valve lift instead of .050 of cam lift. It's an Elgin E976P cam and the specs are supposed to be as follows: @.050 cam lift Intake opens 5 ATDC Close 29 ABDC Exhaust opens 44 BBDC Close 10 BTDC Intake centerline 107 Exhaust centerline 117 Duration Intake 204 Exhaust 214 My measurements at .080" of valve lift(1.6 rocker ratio) Intake Open 9 ATDC Close 28ABDC Exhaust Open 38 BBDC 14 BTDC Doing calculations found online I came up with these numbers Intake centerline 108.5 Exhaust centerline 116 Duration Intake 208 Exhaust 204 I'm not sure if I'm just doing something wrong or is it possible the cam is this far off. Any insight would be appreciated.
It's about 4-6* difference between your numbers and the cam specs. Off one tooth? Cam and timing sprocket compatible? You might want to run through your calculations again.
But the intake close measurement is practically spot on. I spoke to a buddy who's built a bunch of engines and he told me he doesn't like to degree a cam off of the valve because there are other variables added to the equation that can throw your numbers off. He said the most important part was measuring the centerline. So, I found max lift on both lobes. Intake was right at spec and exhaust was .006 short. Max lift occurred at right at 107 for intake and 117 for the exhaust, so I'm happy enough with those numbers to button this polished turd back up.
If he gives his Ave Maria, then I won't argue. As long as there's been no physical contact between the pistons and valves, that's all that would matter here.
The only reason to degree a cam is to make the valve timing perfect, you can be off way more than the stack up of tolerances degreeing is meant to correct and it will still run fine.. If the marks aligned on the timing set you should be good to go. Changing the camshaft on a car that isn't running right is a bit like shooting yourself in the foot. You need to have a solid baseline for diagnosis and this is just adding another variable. What does "never ran right" mean?
I've read a few experiences on the net, of people who have found cams that weren't manufactured properly and were way off, Not just minor tolerance issues and I just wanted to make sure an rule it out. It just didn't have the power it used to have before the rebuild and lately, it was running really bad. I've changed most of the ignition components and did a compression and leak down test and it looked good, A new Edlebrock Carb was put on it at the time of the rebuild, but I have a feeling there was something wrong with that carb from the beginning. A new Summit 500 CFM carb is going on it when I put it back together. He's 83 and it's his backup vehicle and I just want it to run properly if he needs it since his main car has just turned over 200k miles.
If your compression is good then I'd not worry about the cam, especially since the marks line up. Also since the loss of rower is concurrent with the rebuild which included alterations to the original set up(Edelbrock carb) I'd be checking things like the throttle linkage for WOT. Factory timing specs are probably not going to be correct if you've changed the cam so perhaps this is just asking for some more timing.
Well, I got it back together a couple weeks ago. I did need help figuring out the darn accessory brackets. What were they smoking when they designed those? Luckily, a neighbor has a low mileage 86 Buick Rivera with the 307 and I was able to get the brackets figured out. After, getting it together, I cranked it and it started right up and I let it run at about 2000 rpm for quite a while to break in the cam. I blipped the throttle and it started running like crap and popping through the carb and would barely run. I was pissed. After doing some thinking, I realized the gas in the tank was at minimum 6 months old and thought that had to be the problem since I filled the carb with fresh gas before installing it. So I pulled the carb off, dumped out the fuel, reinstalled it and ran the fuel line to a gas can. It fired right up and ran great. I thought I found my problem, until I blipped the throttle and it started doing the same thing. Only thing that wasn't changed in all this was the distributor. I took it out and noticed the mechanical advance was real sloppy and the weights would get hung up. I ordered a new distributor and finally it's running great. Sucks that I did all that work because of a bad distributor, but my dad is happy his car is running the best it has in a long time. Once the old gas is ran through and fresh gas is in it, I'll mess with fine tuning it, but I don't know if it really needs it. Looks better in the pic. Neighbor's Riviera with 63k original miles. He just sold it a couple days ago,
