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1965buickspecial4dr

please help new to the forum 310 wildcat motor, runs great at idle but stumbles upon acceleration

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hey guys my names anthony im in the ridley township delaware county area, im 21 and relatively well rounded but im not a mechanic ive been learning as i go an im having alot of trouble, i set the timing on my 65 cause it was at 12.5 on the scale an i believe its supposed to be at 2.5 an i believe its right but im having a hell of a time getting the car above 25 she chokes an stumbles an sometimes wants to stall, i rebuilt the carb myself and the distributor plugs an plug wires were replaced by the original owner an i think its alright but the caps on wrong an i cant get to the dwell an also dont know how to check it anyway, im so lost an i traded my rebuilt 84 wagon that ran great when i was done a few months ago for this cause i love it but im pulling my hair out, any ideas please let me know cause im so confused now i dont know what to do thanks alot an i hope to hear back from you guys

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You say the cap is on wrong? A couple things, are you sure you are using the #1 cylinder? You would need a dwell meter to check the dwell, but can use a feeler gauge. Pop the cap off, ensure the points are fully open, and check and adjust for a .016 gap in the points. Did you do the carb and the timing at the same time? In other words, has it ever run fine since you've had it?

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You say the cap is on wrong? A couple things, are you sure you are using the #1 cylinder? You would need a dwell meter to check the dwell, but can use a feeler gauge. Pop the cap off, ensure the points are fully open, and check and adjust for a .016 gap in the points. Did you do the carb and the timing at the same time? In other words, has it ever run fine since you've had it?

hey man thanks for the response, when i first got it the car it was having pretty much the same problem but he said the carb needed rebuilt, im using the foremost cylinder on the driverside i believe is number 1, the caps position is strange you cant get to the dwell because of it location so i dont know if he ever actually set it because i dont know how he could of accessed it, he was a mechanic i believe though so i thought it would of been done right but the timing was registering at 12.5 which is wrong everyone says it should be 2.5, tomorrow im going to pull the cap off and try what you said and check the points, i did the carb an put it on but i dont have a tach so i cant check the idle, and considering it runs differently when adjusting different things i dont even know where to start now, i dont know if i should adjust the idle before i adjust the adjustment screws on the carb or do i time it before i try adjusting the adjustment screws on the carb, lol im so confused at this point im ready to put it in the shop but i wanna learn and fix it myself

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You need to borrow/rent/buy a timing light and dwell tach meter. Some auto stores loan or rent tools. Set the points first then the ignition timing both at a slow idle with the vacuum advance disconnected. Number 1 cylinder is on drivers side front. I don't know why the points adjustment is not in the window. The cap has a locator tooth on it and can normally only go on one way. Look for the tooth and the notch it fits in the distributor body. 2 1/2 degrees is right. After all that set the idle speed then the two mixture screws.

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Guest my3buicks

For your info when and if you need to find parts, your engine is a 300, the 310 on the air cleaner is not the engine size

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You need to borrow/rent/buy a timing light and dwell tach meter. Some auto stores loan or rent tools. Set the points first then the ignition timing both at a slow idle with the vacuum advance disconnected. Number 1 cylinder is on drivers side front. I don't know why the points adjustment is not in the window. The cap has a locator tooth on it and can normally only go on one way. Look for the tooth and the notch it fits in the distributor body. 2 1/2 degrees is right. After all that set the idle speed then the two mixture screws.

Thanks for the response, today i tried putting a new set of points in the car, i then adjusted the gap to .016 with a feeler gauge and reassembled the distributor, after this i installed a tach so i could check the rpms, i then set the idle with the choke off, vacuum advance disconnected and plugged up to prevent vacuum leak to 550 rpms with the screw connected to the throttle, after this i put the timing gun on and adjusted the timing to 2.5 degrees on the scale with vacuum advance still disconnected and plugged, after all this i tightened the distributor down plugged the vacuum line back into the vacuum advance and took it for a spin and needless to say she still feels about the same, i haven't adjusted the mixture screws yet because it was getting dark on me but i dont think they single handedly would make it run the way it is although i could be wrong, when setting the ignition timing do i do that at the 550 rpms or lower then set it to 550 afterwords? and what should the idle speed be set at after all this is that the 550 rpms?

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First off.......sure is fun to see a "youngster" who likes to get his hands dirty....... :D .......and isn't afraid of tackling something you've never done before.

Can you more accurately define "stumble"?

The problem with what I think yours is is that crap ignition and carburetor symptoms are almost identical so you can't fix one without ruling out the other........which you seem to have done with the ignition.

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For your info when and if you need to find parts, your engine is a 300, the 310 on the air cleaner is not the engine size

That's right.

The 310 refers to the torque rating

300 cubic inches is the engine size.

Welcome to the forum and to old Buicks.

You're getting the best advice here.

Be patient and take one thing at a time.

Good luck to you,

You're off to a good start.

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Your post in the Reatta forum that is now deleted got my attention. The guys in this forum probably know these cars better than me but I came over to this forum to see if I might be able to offer some help.

I've read your previous posts. For me it's not clear exactly what the symptoms are. It seems you are saying the engine is idling OK and runs smoothly except it hesitates and stumbles when you try to accelerate. Is that correct? If that is the case you should look down into the carburetor (with the engine off) to see if the accelerator pump is spraying gas as you open the throttle. If the pump isn't spraying correctly (a smooth and steady spray) as you open the throttle the engine will stumble and hesitate while accelerating under load due to a lean fuel mixture. You did install a new accelerator pump when you rebuilt the carburetor didn't you?

I think from reading your posts that you have the timing and the points gap set properly although you may need to fine tune the points adjustment with a dwell meter. Did you install a new condenser when you installed the points? If not you should install a new one.

You should check carefully to make sure the spark plug wires are connected in the proper order. The firing order for your engine is: 18436572 just like a Chevy small block. To get the opening in the distributor back to a position where you can adjust the dwell - you could move all the spark plug wires back one hole (terminal) on the cap - then rotate the distributor forward to compensate for the plug wires being moved - then set the timing again to 2.5 degrees. Only do that if you fully understand what I'm talking about because it could cause you a lot of headaches if not done properly.

The idle speed should be 550 rpm but I don't think the idle speed will cause the engine to hesitate and stumble as you describe.

Edited by Ronnie (see edit history)

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Two possibilities I have run into in the past one on a 49 Mercury but very similar problem. The carb was the culprit. I rebuilt it. I actually did it twice and it still had such a stumble or hesitation that it would about throw you through the windshield if you didn't feather it to take off. It would then miss on random cylinders running down the road. I eventually bought an NOS carb and it solved the problem. There was either a plugged passage I could never find (I blew out every passage with shop air and carb cleaner several times.) or the accelerator pump shaft had a seal / disc missing in the original carb that affected the way the shaft and pump overall functioned. I still think it was a plugged passage because of the missing at speed.

The other problem I ran into was a bad coil. The car would Idle wonderfully and you could accelerate it in Neutral fine but try to take off with it or even climb out of the steep driveway at our house and it would die out. I gave up on that car and put it in the Garage. When I needed a coil in a hurry one day, I grabbed it off that car and surprise surprise it gave the same problem to the car I put it on.

Yours could be neither of these problems but it is something to check. You may even beable to borrow the coil from a buddy's car to check yours or get an Ohm meter and check yours.

Good luck and don't give up. It's rewarding once you finally figure out what's wrong, to have won the battle.

Edited by auburnseeker (see edit history)

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Great to hear a young guy in this great hobby!

If you think the timming is to far advanced disconect the vac advance and plug it up and see if the problem changes with the vac advance disconnected.

I am leaning toward the accelerator pump in the carb as the culprit. It is a real common problem with today's fuels the alcohol in the fuel causes all kinds of problems to the rubber components in the fuel system. I had a problem many years ago with a 63 Chevy that was very similar this was about 30 years ago. I could not find it for weeks! I made a phone call to the local AACA region and two guys came over that afternoon and found the problem. A cracked rubber hose from the fuel tank to the main fuel line... I could not thank them enough and one of the guys said "this is what it is all about, one day you might be able to help us"

I would also look into any local regions of the AACA or the BCA in your area. I know if you were in my area there would be a least 5 guys coming over eager to offer some help.

Just keep narrowing it down, you will get it, trust me. We all become our own best teachers

Good luck!

Edited by Biscayne John (see edit history)

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It's a little tougher when your young and just starting out. If you think you are going to stick with one car make, 60's GM for example, it's always nice to have a carb that you KNOW is good laying around. I always had a few somewhat universal things here and there, that would save some time. Of course back then, I often bought cars just for the engines. Then I'd save a few of the common things.

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I have seen two guys plug the vacuum advance on the distributor and not the vacuum line, both were in their 40's, a little funny a little sad.

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You can test your vacuum advance. It works either by manifold vacuum (idle vacuum) or carburator (high speed vacuum). Make sure the hose has vacuum then plug it in. The engine should speed up and you should see the breaker plate in the distributor move as you connect and disconnect the hose. If not get a piece of hose put it on the advance and suck on the hose .The plate in the distributor should move and you should feel resistance sucking on the hose. No resistance means the diaphragm has a hole in it and is no good. If you replace the advance or reset the points you will have to check/reset the timing.

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A Buick 401's #1 plug is on the front plug on the right bank, not the left. I don't know if the 300 is the same.

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hey man thanks for the response, when i first got it the car it was having pretty much the same problem but he said the carb needed rebuilt, im using the foremost cylinder on the driverside i believe is number 1, the caps position is strange you cant get to the dwell because of it location so i dont know if he ever actually set it because i dont know how he could of accessed it, he was a mechanic i believe though so i thought it would of been done right but the timing was registering at 12.5 which is wrong everyone says it should be 2.5, tomorrow im going to pull the cap off and try what you said and check the points, i did the carb an put it on but i dont have a tach so i cant check the idle, and considering it runs differently when adjusting different things i dont even know where to start now, i dont know if i should adjust the idle before i adjust the adjustment screws on the carb or do i time it before i try adjusting the adjustment screws on the carb, lol im so confused at this point im ready to put it in the shop but i wanna learn and fix it myself
A Buick 401's #1 plug is on the front plug on the right bank, not the left. I don't know if the 300 is the same.

300 is closer kin to the 350 and 455, than to Nailhead

Nailhead's #1 is on the right because the right bank is forward ​of the left

300's left bank is forward. #1 is left

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300 is closer kin to the 350 and 455, than to Nailhead

Nailhead's #1 is on the right because the right bank is forward ​of the left

300's left bank is forward. #1 is left

Thanks for clearing that up. Just threw that out as a possible remedy.

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