ok, here's the problem.........'72 350 does'nt seem to have the grunt it should. The engine details that I know of are these: Approx. 18k to 20k on rebuild, bore .040, mains .030, rods .010, pistons Zollner 9.5:1, heads #145 cast #, Poston intake, Performer 600cfm(Iknow), Pertonix conversion (again, I know but no problems with it so far), TA headers 1-5/8", stock converter, stock cam?, 308 open rearend, TH350 (very strong). I did a compression check but I did'nt have the throttle wide open and only had 125-130 across all cylinders. As for the carb, I'm a flatlander originally, but now just outside of Denver (almost 6000' above sea level) so the argument is, do I need more or less cfm? Any help would be greatly appreciated because right now I'm so :stmad: I'm ready to SELL it!
A Buick 350 should have at least a 750 cfm carb. The original Q-Jet was 750 cfm. Try that for starters. Does the car bog off the line? Will it light em up from a dead stop? The cranking pressure sounds about right for an 8 to 1 motor, which is proabably what you have even tho the pistons are suppose to be 9.5 to1. Buick sinks the piston pretty far in the hole, about .055 deep. My pistons are rated at 9.25 to 1 with a deck height of .020, I had my block decked to achieve a deck height of.005 Your compression is good and best of all its consistent. Any more details would help. Mark
Thanks Mark, I had a Q-Jet 750 & the car ran like dog poop, and since I moved out to altitude I went with the 600. (my bad) Wish I still had it! No it does not bog off the line, and no it won't light em up from a stop, but I just attributed that to the rearend. I don't have a dial-in timing light, so I set the timing & carb with a vaccuum gauge. (12 degrees initial) Other than that, what other details can I give?
With the 3.08 rear, that car should still light 'em up from a standing start, and even a 10mph roll with the open rear end. Iv'e set max initial timing with a vacuum guage also, keep advancing it till the idle vacuum maxes out, then back it off a tad, it seems to work. Are you sure the timing is advancing when its suppose to? Is it the original distributor that you converted to the Pertronix? If it is, try an HEI from a 75 to 80 350 Buick. When I first did my 350 years ago, I put in a Kenne Bell MK2 cam, I still had the crappy points ignition, the car surged when cruising, and wouldnt take any more than 8 deg. initial timing, the car wouldnt even brake torque, it just bogged. I later switched to HEI that I had laying around, WOHOOOOOOOOOOOO:Brow: What a difference, instant starts, no surging, and awesome wheelspin, that was when I still had the 3.08 open rear. Try takin a closer look at your distributor, see if you come up with anything. Mark
What brand and type of carb.? No bog is good, but the secondary my be opening to late, or not at all? and I'm with Mark, you might need more initial timing? Lars
All normally aspirated engines will have much less excess horsepower over what it takes to cruise (which is what tranlates into acceleration) at 6000 feet relative to mean sea level. There is less air pressure and therefore less air available to the engine as you go up in altitude. To keep the fuel air mixture optimized at altitude you require less fuel and overall you will make less power at full throttle. So if you comparing the feel of the car to when you were a "flatlander" my question to you is have you tried again at sea level?
Thanks for all the input fella's. First off I'm having a Q-Jet redone & then it's going back on. Next I need to locate a distributor so I can send it off to Ignitionman. To answer some of the other questions in the prior posts, here goes, no I have not tried it at sea level again, I believe the cam is stock, the distributor is OEM converted with Pertronix Ignitor, as for the timing, how do I know when the advance is full in? uzzled:
Pat, I'm assuming you have a timing light and a tach. If you measure exactly 1 3/4" clockwise around the balancer from the main timing mark, and paint another mark, this corresponds to 30* of timing. Now dissconnect your vacuum advance and plug the line. Shine your timing light on the balancer, and slowly bring the revs up. As you do so, you will notice your 30* mark moving up. This is the mechanical advance working. As you increase the revs, at some point, the mark will move no higher. This is the point when all your timing is in. Have a helper read the tach. That is the RPM where your timing is all in. For a strong street car, aim for 2500 RPM or less. The only way to change how fast your timing comes in is by changing the weight springs under the rotor(very easy) There are spring kits available, but the best in my opinion is the springs that come with the Crane adjustable vacuum advance unit. You will also be able to read your total timing like this. If your new mark stops at 2 on the timing tab, you have 32* total, if it stops at 0, you have 30*, 4, 34* total. Of course the ignitionman will set it up for you like this, but in the mean time you can check what you have now. Keep in mind that the factory used stiff springs in the distributor that would not allow all timing in until 4600 RPM. So if you see the mark keeps going up at high RPM, stop. I don't think you want to freewheel the engine up that high. Hope that helps.
0+13/4'' = 30* Larry is ok! :beer Zero mark +13/4'' IS 30* on a 350. (but you might want to check that zero mark rely is at zero, mine was not.) Lars :TU:
When your at high altitude you can set up your car with a much higher compression than for a sea level type set up. This will help to offset a bit of the loss from the lack of air... Often more timing can help too compared with a sea level state of tune. Jason
At 4,500'+ Altitude, you Will loose alot of H.P., even your Cylinder Compression will drop. Advance your Initial timing...at least 2 Deg. up to 5 Deg. over Sea-level. I, "Lost" at least , 100 Horses at 5'500 Feet. On my 11.5:1 Comp. Pontiac! Before the move..."Wheels off the Ground" in first and second gears. Now, Barely...in First! (Stinks!!!) No, other changes. Altitude. Lean the carb. out 2-4 jet sizes on the Primary side and at least 2 on the Secondaries. You can get, "Some" Back. As a Friend in IL. told me: "It's like your car is tied to a tree" (Altitude). Aircraft engines are Turbo-charged to allow for the density variance in Altitude. (Less Oxygen.)
