I am sorry but the vacuum leaks do take away power, this is just one of the many reasons your 350 never ran right.
Like Devon says it is best to use a tach to find out when the mechanical advance is coming in, and use a timing light to find to find how much mechanical advance is coming in. You can either make a 30 degree mark on the balancer (as seen in the power timing thread) or use a dial back timing light, make sure the vacuum advance is disconnected and plugged when you do this so that the only extra timing above the initial is the mechanical advance. Lets say for example that your mechanical advance is giving you 26 degrees of timing and the stock springs that control this allow it all in by 3400 rpms. This means you are limited to about 8 degrees initial timing setting so that do not over-time the engine. The main problem with this is that the acceleration and fuel economy will suffer because the engine wants more timing early in the rpm range. Now if a person wants to run a higher initial timing setting then they need to limit the mechanical advance so that they end up at the same total advance. When you fine tune the rate of how quick the mechanical comes in using different weights and or springs then you change how quick or slow the timing will come in the rpm range. A general quideline for a 350 is to get about 32-34 degrees of total timing plus 10 degrees of vacuum advance. If you do not modify the dist. then just set the initial timing to get the total timing that you desire. Remember initial timing + mechanical timing = total timing. Under light load the vacuum advance is added on top of that which increases fuel economy and reduces engine temps.
I dont know about many problems, I fixed the vacuum leak before I had it dyno'd, yes it could have used a much bigger carb, but thats not going to make it accelerate like it's got a ton of bricks in the back, THE problem was the transmission, it made between 126-130 and less hp at the wheels in third, and did 153 in second, so something tells me the trans has some issues, second was obviously the strongest gear, first was pretty bad and third was awful but the whole trans was definately on the way out, too bad I can't pop my wicked new one in to re dyno and show you how much power I was missing, I could have told you this info about less power in different gears without the dyno but it needed to be validated. The dyno operator sure loved the half liter of trans fluid and oil that puked out of the motor and trans during deceleration on each run I dont know about you but that motor sounded pretty healthy and well tuned to me and chris at zensport.:TU: http://www.youtube.com/watch?v=WO_PxW3Vwp0
OK I have set my initial timing at 10* and that gave me 30* mechanical. I don't know when that is all in by until I get my tach. but that did provide more power. It still isn't right. I had quit a bit more torque still before the upgrades. I have a small vacuum leak around my carb. so I am going to replace the gasket tomorrow. Thanks to everyone for being patient with me and my learning curve. I will do better next time. I will keep you posted. My uncle is coming over today and he is going to give me a hand. Chevy guy but very willing to help.
Good, get that vacuum leak fixed, Breaking in the cam correctly is the single most important part of a cam install, right from the second that motor fires with the new cam, you cannot let it idle, it needs to be held at atleast 2000 rpm and revved slowly between 2000-3000 for 30 minutes to be safe, if the engine is allowed to idle you risk wiping the cam out, which can happen within a very short amount of time, did you break in the cam?
Great, glad to hear you are making progress. After the cam is broken in take the car out for a ride and with the vacuum advance disconnected and plugged drive the car at various speeds (on the highway and in the city). If you hear no ping or knocking from the engine then you can try raising the timing to 12 initial which should give you 32 degrees total. 2 degees can make a huge difference in how the car performs and 32-34 degrees is usually the best for most 350s.
I'm concerned that you "may" have a problem with the cam. I think you said earlier that you didn't get to finish breaking it in. I don't know how forgiving the cams are with slight break-ins so it might be a non-issue. But is it possible that you lost a lobe or two (or few) off of the cam? That could lead to very poor performance, and no amount of tuning could correct that. You may want to consider pulling the valve covers and verifying that all of the rockers are opening the valves. If all is good it would at least be peace of mind that yes the cam is still good. If you find out that the cam is flat; at least then you know it and can go from there. Like I said though, it may be a non-issue. How much time at 2000+ rpm were you able to get? 15-20 minutes, it's probably okay. One minute at 1000 rpm, maybe (probably) not.
OK just returned from my fathers. We did a compression test and I have zero compression on #1 cylinder. Took the valve covers off and the valves are all working. Took the rocker assembly off and still no comp. Looked at the push rods and they are straight. I think that I have a valve stuck open. I need advice.
If the valves are working (opening & closing), one shouldn't be stuck open. Maybe not closing totally? Are any of the valve springs broken? With the rocker arms off, push down on each valve with your hand, one at a time. You should be able to feel the resistance of the valve spring, and they should all feel pretty strong (hard to open the valves). Blown head gasket? Check if there is antifreeze in your oil. Or oil in your antifreeze? What else would cause no compression on #1? Hole in the piston? Broken valve or valvespring, bound valvespring holding valve open? I can't think of any other possibilites (maybe cracked head?), again unless there is a cam problem. But I'm thinking it wouldn't run at all if the cam was installed wrong somehow. And since #1 is the only cyl with no compression it makes me think it's valves, head gasket, or piston problem. It looking like you have a rebuild/engine swap at some point in the future?
I pushed on the valves and they were tight the springs don't seem to be broken. I am going to take the head off today and check the valves.
How was the compression test of the other cylinders? Hopefully fairly consistant. Before I'd pull anything apart I'd do a leakdown test on all cylinders to make sure you're not just going after one of many problems. However if the compression test was consistant for all the other cylinders I'd proceed. Actual numbers don't matter, just that there were none way out of line. A leakdown test is just a more precise way of determining what is leaking. Monday morning quarterbacking here but unless you did a 3 angle valvejob with backcut the headwork was probably worth nothing performancewise and apparently has just given you headaches.(Assuming that there were no burnt valves, which would have been found by doing a compression/leakdown diagnostic before doing anything.) I've got no problem with the cam change because you picked a good cam for your use again assuming the engine was up to snuff in the first place. Looking at what you did in the first place I'd go for head gasket or a poor machining job on the valves. Just for fun with the rockers and intake off I'd pour a couple of ounces of lacquer thinner into the intake port and see if it stays there. It should not drain off. Some thinner won't bother the oil and will just evaporate off when the engine gets hot. When you get the head off if you determine that it is a valve seal problem I'd check all valves for seal with some thinner poured onto each chamber with plugs in and the head upside down. As far as the head gasket goes if that is the problem then you have to look at installation problems. Were both head and deck surfaces cleaned and degreased completely? Did you get the car going and immediately go out and wail on it? If so that may have popped the gasket the first time. I'd give it a few heat cycles with light driving and then do a retorque of the head gaskets. Can I assume the heads were torqued according to spec and in the correct pattern? Get a service manual if not because it is imperative. It is doubtful that there would be any piston or ring problem this soon after startup assuming that they were decent before you did the repair.
I was going for just a basic valve job and replace any burnt valves and bad seats. Just a basic clean up and replace bad parts. I will check the other cylinders compression before I go any farther. When we put the engine back together we fired it up and let it idle at about 2000 RPM for probably 15-20 minutes. The carb started leaking. The housing was stripped out so I bought another carb and installed it. I started the car again. Let it idle and tried to get the timing right. This is when we started noticing a miss. So after quite a few sessions adjusting the carb and timing I decided to give it a test run. The car had been running in the garage several times at this point. Once the snow melted and the roads were clear and dry I ran it up and down the road and got on it some. The miss just got worse so I parked it and ran a compression test. Other than a slight miss the car sounded strong.
So a leakdown test on that cylinder would be the best way to determine what your issue is as we keep suggesting.
Thanks for being persistant. I get it. I was just answering the question the man had. End result was a bent valve. Caused by the valve stciking open and hiting the piston. The Piston thankfully was not damaged bad. A little nick, I sanded the burr and I think I may reuse.
Good, so the bottom end might be fine. Are the other valves ok? Do you know if the head is damaged at all? Hopefully you can get a new valve and be on your way. Oh, do you know why the valve stuck open? When you changed the cam did you use new valve springs? I don't know the specs on your cam, the stock springs could be alright for it.
Were valve guides replaced? If so, I'd check valve guide clearance on the others to see if this is could potentally be a future problem. I was thinking of asking about oversized stems being used on stock guides, but I don't know if oversized stemmed valves are even available for Buicks. Devon
Well unfortunately I am unsure of the problem. This cam should be fine for a stock build. The guide may have been a little snug but it feels fine now. I am going to try and just replace the valve and go on knowing full well of what could happen. Thanks to everyone for your help!
Sounds like you found your problem. I'd pop the springs off all the valves on that head while it is off and check for no tightness of the remaining guides. I wouldn't worry about the piston. I just bent an intake valve on my engine last year. I had just replaced the rockers arms and was tapping the engine around with a remote starter button to adjust the pushrods and I heard a slight crack and pop. It turns out I didn't check ALL the pushrods to see if they were seated. One wasn't in the cup of the lifter and actually broke the rim of the lifter and bent an intake valve. After all these years of working on Buick engines and having changed at least a hundred sets of rocker shafts I end up doing something like that. I'm getting old. I'm going to be turning the engine over by hand a couple of revolutions whenever I do something like that from now on. Double check that your pushrods are seated. Do as I say, not as I do.
