1978 Small Block Chev/260/timing problem

[RandyJ]

I have two boats (1978)with 260 engines. Both came to me with major engine problems. One got a new block the other got new heads, both have new manifolds & risers. When I got ready to tune up both had this problem with the timing mark showing way down low towards the bottom of the boat rather than on the timing mark gauge where it should be reading somewhere near BTDC. I can't figure this out. When I checked the position according to the distributor and plug wires it pretty much corresponds to the position of the #8 firing position when #1 is at 0 degrees. I do not know if this is an advance problem or what the deal is. I don't know how to disable any advance in the Mallory distributor as there seems to be nothing connected to the distributor. Both engines seem to run fine (when running)and start up easy but both also run hot above 3/4 throttle. Any help will be appreciated....

 

[Haut Medoc]

Re: 1978 Small Block Chev/260/timing problem

You sure you have the wires in the right position? With the #1 cylinder @TDC, the rotor should be pointing at #1 on the dist. cap....Mallorys are funny that way... You might need to move it a "click" or re-position your wires....JK

 

[Laddies]

Re: 1978 Small Block Chev/260/timing problem

If the engines start and run, you are either confused with the position of number 1 cyl. or on the wrong wire or the enines have a problem with the harmonic balancer, some times they slip, but with the same problem on both engines I would think it could be the first problem. Till you ck everything don't start adjusting things

 

[RandyJ]

Re: 1978 Small Block Chev/260/timing problem

I've been working on small block chevy's for 30-40 years and never had this problem till I started tinkering with boats. I'm thinking the advance is causing it to move too far too fast. Heck, I don't even know how these Mallory distributors advance the timing... I just know that I've pulled the harmonic balancer to make sure it is correct...key way is right! Everything checks out but when piston is at TDC and #1 wire is at point of rotor button it doesn't want to run...neither of them... just ain't kosher... I'm missing something somewhere.

 

[Don S]

Re: 1978 Small Block Chev/260/timing problem

Everything checks out but when piston is at TDC and #1 wire is at point of rotor button it doesn't want to run

No rotor points directly at the terminal when it fires, it fires before it gets to the wire. Set the distributor so the rotor is pointing between 2 and 1. Then start the engine (you may have to move the distributor to get it to run), then set the timing to the proper degree at the proper idle rpm.<br />Then rev the engine (in neutral) to around 3000 or 3500 and see how much advance you are getting, so you can verify the advance is working.<br />The Mallory distributor have mechanical weights below the plate.

 

[KaGee]

Re: 1978 Small Block Chev/260/timing problem

Does your timing mark on the balancer align to 0* when #1 cyl is TDC ?

 

[RandyJ]

Re: 1978 Small Block Chev/260/timing problem

NO...I finally remembered how I figured out that the timing mark is not corresponding to the firing position. When the piston is at TDC the timing mark on the balancer is at about 120 degree position on the balancer which corresponds to about where the #8 plug wire position in the distributor is according to the rotor button... I can get it to run fine but the timing mark is simply like the 120 degree position rather than the 45-60 degree position of the timing gauge which is mounted on the timing chain cover... this is the same on both 260 motors I have in boats. So, apparently it is something weird with the balancer,crankshaft, or I'm looking at the engine wrong...but I'm looking at #1 the same as if it were in a vehicle. If I were looking at it backwards (#8 being #1) then this thing might have a different numbering order.

 

[Haut Medoc]

Re: 1978 Small Block Chev/260/timing problem

How about finding the plug wire closest to where it falls on the timing timing tab & using that to make final adjustments?.....JK

 

[Don S]

Re: 1978 Small Block Chev/260/timing problem

Sounds to me like you are doing something wrong. I can't see the problem happening on 2 engines side by side because something is broken.<br />Look at the picture below for the numbeing of the cylinders on 350 Chevy engines.<br />You may have the #1 wire in a different location on the distributor, but that shouldn't make any difference, the firing order is still 1-8-4-3-6-5-7-2 <br />I suppose if you had your timing light on #2 (where #1 is on a Ford) you could end up with the timing mark that far off.<br /><br />

 

[Haut Medoc]

Re: 1978 Small Block Chev/260/timing problem

Don wouldn't what I said work?....I know it it's not really right, but with both doing the same thing?.....JK

 

[Don S]

Re: 1978 Small Block Chev/260/timing problem

JK, I don't know, never tried it.

 

[Haut Medoc]

Re: 1978 Small Block Chev/260/timing problem

I'm not suprised you never tried it....It's just not right....JK

 

[lowshovel1]

Re: 1978 Small Block Chev/260/timing problem

Are you sure you have correct harmonic ballancer for your timing cover---theres two covers that fit---difference is location of timing marks on cover.

 

[rodbolt]

Re: 1978 Small Block Chev/260/timing problem

bring the piston up to TDC on COMPRESSION stroke and check the timing marks to the tabs. if the balancer mark is not on the 0 mark you either have the wrong balancers,wrong tabs or the balancer has spun. while its at TDC COMPRESSION stroke you can set the dist in correctly, turn the key on, hook a spark tester to #1 plug wire and rotate the dist back and forth. leave it at the position it makes spark which will be about the time the points open. now it will start and run without backfireing, everytime time after time.<br /> also check the advance weights are not stuck to the full advance position.

 

[rbezdon]

Re: 1978 Small Block Chev/260/timing problem

I'll bet you are looking at the wrong side of the engine for number 1. You are counting #2 as number 1. It just happens that number 2 is the last in the SBC firing order (and the next one to fire is number one on the next rotation - 1,8,4,3,6,5,7,2,1,8,4,3 etc.) and that makes it about 120 degrees from number one when it fires.

 

[RandyJ]

Re: 1978 Small Block Chev/260/timing problem

I'm definitely looking at it right. I've considered alot of scenarios but still, when the position of the piston is at the top of its stroke (regardless of whether it is the compression stroke or not) the balancer falls in the same place (at about 4 or 5 o'clock position rather than near the 2 o'clock position)...I've got a couple of old blocks out back that came out of chevy vans and I'm going to check them today to see if they do the same... distributor shouldn't matter since I can move firing position of the rotor fairly easily. However, I don't think I can do much worse than have firing position of the distributor shaft any way other than correct or 180 degrees off.....

 

[KaGee]

Re: 1978 Small Block Chev/260/timing problem

It's very simple Randy. Just like Rod said.