I have a 71 Gransport with a 350 in it. The motor developed an oil pressure problem so I rebuilt it. Should have went with a BB, but I wanted to keep it original. Now I think I have made a mistake, because there are a whole lot of other things that aren't quite stock anymore . I did a total rebuild about a year ago and have tried and tried and tried to get this thing tuned. I am in desperate need of some help before I just blow the thing up and start all over with a BB. Here is everything that is not bone stock: Stock Bore - 10:1 pistons Drilled oil passage in block and used the bigger 5/8" oil pickup tube Double roller chain High volume - high pressure oil pump Typical head work - Ported, bowl job, removed excess flash from exhaust runners Crower cam P.N. 50258: - Intake - Dur. 276 Degrees - Lift .446 - Exhaust - Dur. 281 Degrees - Lift .468 Poston Stage 1 Aluminum Intake Holley 750 - Mechanical secondaries - Jets: 70 Primary - 74 Secondary Stock Distributor with Petronics Electronic Ignition Petronic coil Hooker Super Comp Headers 2400 Stall Transmission Specialties Converter - Non Lockup Holley NOS 125 HP Powershot Nitrous - Haven't pushed the button yet Holley Electric Blue Pump Custom fuel tank pick-up fabricated that is 1/2" dia stainless to accept an AN Fitting -08 Russell Braided Fuel Line from the tank to the Pump, from the pump to the regulator, from the regulator to the HPG-1 Fram Racing fuel filter, from the filter to a moroso fuel spliiter. -06 Russell from the splitter to the Dual line feed -06 Russell from the spliiter to the fuel solenoid for Nitrous system Fuel pressure set a 6 psi through regulator Installed Air/Fuel ratio gauges at the end of both headers. Gauge reads 11. Slightly rich for the nitrous, so as not to damage the engine. More to come......
Now for the problem. This thing will not stay tuned. One time it will run great... no stumble... no stall... Drives like a dream! The next time I fire it up it idles fine, but when you put it in gear (r) or (d) it dies. Given enough gas it will run but will not idle in gear, in (P)ark it runs fine, 850 RPM. When it does idle in gear, it idles at about 650RPM. The timing does not change when it runs good and when it runs bad. I had a 670 Holley Street Avenger (new) on the car right after the rebuild. It was vacuum secondaries and electric choke. However, no matter how much I jetted or adjusted it, it stumbled just off of idle when driving. I switched to a 750 Holley with mechanical secondaries and manual choke thinking the other carb was too small. It doesn't stumble anymore off idle. In fact I have notice a tremedous power gain between the two carbs. I know for a fact that the 750 carb is in good working order since I took it off of my '57 chevy to try on the Gran Sport. I have recently noticed a slight puddling of oil on the intake between the # 1 and # 3 cylinder. Oil is also being pushed around the vent tube that goes to the air cleaner (Oil showing up on the valve cover). Not sure if this was happening before the carb change or not . The only vacuum line, other than the Brake booster is the line that runs to the tranny (rubber) and the vacuum advance line (which is Russell braided stainless). HMMMM.... What exactly does the line that runs to the tranny do? Maybe this is the problem... (thinking out loud) Anyone had any problems with Petronics?... and does this sound like the ignition is the problem?.... (thinking aloud again!) Any help would be greatly appreciated!
What is your initial timing set at? -- if your initial timing is too low then your primary throttle blades have to be open excessively to get the car to idle in park. This will also cause the erratic tuning because you are creating a vacuum leak through the carburetor. Increase your initial timing and the idle speed will increase, then close up the throttle blades to bring the idle speed back to the appropriate rpm. Note the RPM in park then put into gear, the RPM drop should be approx. 100 RPM. If it is more then repeat until you get it around 100 RPM difference. Once you determine what is the best initial timing, have the distributor re-curved. Note re-curving is not just changing springs and weights, it has to be done by a shop with a distributor machine, they will have to completely disassemble the distributor and physically modify it. -- Side notes: Perform all tuning with the vacuum advance disconnected and plugged. There are usually two small vacuum ports on the carb, one that has vacuum at all times and one after the throttle blades are open. When setting the initial timing you can spot check your results by getting the throttle blades closed so the one port reads 0 at idle. Use a dial back timing light so that you can read timing settings greater than what is on the timing tab. Also works great for checking total timing. Do you have the PCV valve installed and hooked up correctly? -- If the PCV is not installed and/or hooked up correctly, the excessive crankcase pressure will cause all sorts of oil leaks. There is no oil flowing in the intake so it is either getting pushed out at the valve covers or up past the intake to head gasket, either way that is excessive crankcase pressure. -- p.s. If you don't have a baffle or stock valley pan gasket under the intake and you get the PCV working, you will suck the oil out of the engine and into the plenum thus fouling you plugs (usually). Dave
It does have the valley pan under the intake, and oil pressure are as follows: At cold start-up 90psi at idle. After the motor gets good and warm the pressure is approx. 23-25 at idle. Off of idle (above 2000 RPM) the pressure runs about 60 psi. The rule of thumb I go by is 10 lb per 1000 RPM. Would you say that is correct? Thus when running between 5500 and 6000 RPM I have plenty of pressure to satisfy the engine. I will check the timing and PVC right away to see what I get. I think I only have the timing set at 10 BTC. I believe factory is supposed to be set at 6 BTC. Anything over 10 BTC seems to make the engine knock on hard acceleration. Maybe I just need to go a little further. As far as the PVC..... This is a dumb question ..... but where is this line supposed to go? To the tranny somewhere? Temperature-wise this thing usually runs between 190 and 200. Everything I have read indicates that up to 200 is good. After that the excessive heat starts to affect horsepower. If any of these statements are wrong please let me know, As I am a self taught bookworm mechanic!!! Ha Ha Ha. I think I will take out the distributor and send it to "Ignition Man" while this car is down for the winter. Everything I have read about him seems to be good! Keep those suggestions comingp
Why do you have to hook the vaccum gauge to the intake instead of the vacuum advance port on the carb? (I know not to hook it to the constant pressure port on the carb) Somewhat confused..... Seems the vacuum port on the carb would be better since that is where the distibutor advance connects to.
Try this for your stalling problem. Disconnect your vacuum advance completely and plug off the carb port and throw the hose in your tool box for now. As Dave described earlier you may be creating some of your own problems with the idle speed and butterfly angles. Holley carbs have a real touchy ported vacuum port and it doesnt require much throttle angle to start vacuum on them. So if you are running your vac advance and it starts to get vac at lets just say 800 rpm in neutral and it pulls your initial timing up to about 10 degrees indicated as you state but then the car is put into gear slowing the idle speed and then your vacuum signal decreases dropping the timing back down around to maybe 4 degrees retarded then the idles drops and the car dies. Sound familiar? My 350 with a little cam and compression loves about 16 to 18 degrees initial and no vacuum advance at all. The mecahnical advance in your distributor will probably need to be limited to around 16 degrees at the crank (a job for ignition man) but it'll solve most of your tuning probs. Do yourself a favor and drill about an eighth inch hole in the front of each primary butterfly about half way between the shaft and the edge directly inline with the idle discharge ports and then reset your idle mixture screws, Your nose will love you for it as holleys have a real rich idle circuit. That mod alone will let you set the butterflies closed as they were designed to be and cover up most of the off idle discharge/transition port. I've never done any of this myself but I did stay at an holliday inn express last night!
idle thoughts.. I agree it sounds like the problem may be with the idle setting. Isn't the 650 rpm idle in gear a bit slow? (just my opinion). Also, you may wish to check whether or not your vacuum advance diaphragm is functional. I had a similar problem a while back. I think you're on the right track...stick with it! :TU:
Your oil pressure is fine (above average actually) but oil pressure will not cause leaks, unless at the sending unit or the pump area. It's not stock anymore so factory timing recomendations don't pertain. Having the distributor re-curved will solve the knocking issue. You will be having the distributor modified so you can run the extra initial timing but so your total is limited to approx. 34 degrees. Dave The PCV valve is in the back of the intake and the hose is routed to a 3/8 fitting on the carburetor. If you do not have that type of connection on the carb, you will have to use an spacer with one or if possible add one on the intake so it enters the plenum. Do not connect it to one of the vacuum ports in the runners.
This is all great information. I will be working on this tomorrow so I will be getting back you guys on the results. One quick point about the valve covers I forgot to mention. These are the poston Cast Aluminum ones. I drilled two holes in the driver side one. One hole is for the line that runs to the air cleaner. The other is the oil fill. However, the oil fill hole is a tapped hole and I fabricated a nice little fill cap. Now mind you this is threaded, so there is no breather for pressure with the exception of the air cleaner line. Is this a problem? A fellow hot rodder I work with at the machine shop said I needed an additional breather in the valve cover itself..... What do you guys think????
First off Pertronix units are junk. I am on my 2nd one now. Go with an HEI for bulletproof operation. Try running about 15* of timing and lose the vacumn advance until you get it figured out. A cam of that size will probrably need to idle at 800RPM or so in gear. Your convertor should be loose enough to support a relatively low idle speed.
I agree with Chris, ditch the Pertronix and go with a good factory HEI. Make sure you supply the HEI with a full 12 volts from the ignition switch. Disassemble the advance weights, clean 'em, and put a bit if distrbutor lube on the plastic bushings that the weights ride on. Line everything back up timing wise, set initial timing around 12 to 15 deg. and go from there. Basically points suck, and any conversion from points to electronic using the same distributor doesnt work well, there fine for the car show circuit to fool people, but who do you want to impress, you or the guy looking at your car:beer I had the original points in my car years ago when I had the KB MK 2 cam in it and the thing ran like crap till I swapped the HEI in it. man what a difference!! Good luck to yah, Mark
So anyone have any specific recommendations for the distributor. I'm thinking MSD distibutor and a MSD 6AL Ignition box. I have the MSD system on my 57 Chevy. But that car is strictly a strip car and gets trailered to area shows. Do you think I need that much for a street machine that sees the track occasionally? That would also eliminate the need for having by stock distributor recurved.
Ryan - You had the right idea several posts above....go with one of IgnitionMan's conversions!! Dave has converted quite a few distributors for guys on this board. Everyone has been MORE than satisfied with his work!!!:Smarty: I've personally met Dave and was given the $.05 tour of his shop. He does incredible work and stands behind everything he does!! On top of that...his prices are easy on the wallet!!:TU: He can either do the MSD electronic conversion to use the MSD or Crane box ($135) or he can do a stand-alone small body Hei($175). An adjustable vacuum advance will be installed and he will recurve the dist. to match your combination. He will want you to use full manifold vacuum. If you haven't done so already, do a search on this board for 'vacuum advance' and 'ping'....that should bring you up to speed on what works and why!!:Smarty: Dave's site. Either call him or send him a direct email (not from the board).
Well I set the timing at 15 and it runs a whole lot better. I did myself a favor and bought a vacuum gauge. This thing is money well spent. Anyway the car runs a ton better, So I took it to the track! The car ran 9.30 @ 75.4 MPH in the 1/8, and 14.50 @ 94 MPH in the 1/4. The 60' time was 2.10 So, What do you guys think of the numbers? This is the first time for this car running at the track. Personally, I am a little dissapointed. This is not terrible for the 350 but I really thought this would at least get into the high 13's with this set-up. I didn't use the nitrous since my tank was empty and area race shops have ran out for the season. Thanks for all your help with this, hopefully it will stay running well. Stay Tuned
14.50 aint so bad. I assume you are moving a full weight GS and these things aint exactly featherweights. What size gear do you have? 60' seems a little soggy, but could be from traction or small gearing.
Only using a 3.73 w/ Auburn Posi unit. I want this car to be VERY streetable. I am of the understanding that anything you can shave off of your 60' time will double off of your total 1/4 ET. At least that's what I have always found with the '57 anyway. But it's a Big Block Strip Car... maybe that doesn't apply here. Anyway the car hooks great off the line, granted I am not using slicks, but those BFG 60's really work well. I not sure what the car weighs, but I will find out Monday at the local Livery. Actually the transmission is the weak link here. It hasn't been rebuilt for 17 years. EVERYTHING else mechanical is new including all suspension parts with the exception of the power steering components... next on the list! Any suggestions on shortening the time without changing to slicks? This is my twice a week driver as long as the weather permits it. (Usually on Monday so I can make myself go to work... and Friday so I can get home as quick as possible) :Brow: :Brow: :Brow: By the way, other than the slight tuning done today, I found the major problem with the motor dying/running bad. Believe it or not it was the battery. It was put in service back in July of 1995. It was really a fluke that I found it. I would start the car and it would run great for 10 minutes or so. Then it would start running bad. So I took it for a spin. With in a couple of minutes it was running like a top again. I repeated this cycle about 3 times. It was a little chilly this morning, so as I pulled in the driveway for the 3rd time time I flipped on the blower switch and the car died. So I checked the alternator output.... 13.8 volts. I checked the battery..... 10.8 volts. To make a long story a little longer, I guess the new blue holley fuel pump that I installed for the new fuel line and nitrous fuel solenoid just put the battery over the edge. Anyway, I changed the battery and the car has ran good all day.
