View Full Version : 425 Timing help

08-20-04, 07:33 PM
Hi all I'm new here and also new to the V8 scene. I'm in England and I just bought my first 425 V8 . The thing is I think my firing order may be incorrect as it sounds like I'm missing a cylinder or two. So my questions are. What is the firing order? How and in which order are the cylinders counted on the block? and what sort of advance should I be running? I tried timing it from what I thought was no1 cylinder but the timing mark doesn't even line up in the 0-24 deg range ?!? Maybe the front pully has been put on wrong? If I wind the distributor back to about 18o it runs extremly retarded. Sorry for all the questions ... Oh I got a casting number of 1609551 off of the manifold if this helps

08-22-04, 04:43 AM
Come on guys someone must know this info. I've now found my firing order 1-5-6-3-4-2-7-8 but I still don't know which is number one on the distributor cap ... or how to count the cylinders... is number 1 at the front passenger side of the engine? please help if you can...

lux hauler
08-22-04, 09:16 AM
The number one cylinder is at the front, passenger side.
Number one on the distributor can actually be anywhere you want it to be depending on how the dizzy is set. Drop the distributor in with the number one cylinder at top dead center on the compression stroke and note the position of the rotor. Where ever the rotor is pointing can be number one. If you don't like where it is, lift it out, turn it and drop it in again.....just follow the firing order clockwise around the distributor. As far as where it was from the factory......If I'm not mistaken, number one pointed at around 10 o'clock.

08-22-04, 02:50 PM
Thanks Lux..... that gives me something to go by... I tried timing from this cylinder and for some reason my timing mark is sitting right at the top at 12 o'clock.... I think the front pully may be bolted on in the wrong place... is this possible? or is the shaft keyed?

lux hauler
08-22-04, 03:09 PM
The pully isn't keyed but the bolt pattern should allow it to only be bolted on one way.

08-22-04, 04:38 PM
ahhhh ok.... I need to look into this then... thats why I was asking for the info before because when I set the timing back the car ran awful and kept firing up through the carb... almost like a backfire. What sort if advance should I be running? it doesn't sound too advanced at the moment..

lux hauler
08-22-04, 06:04 PM
Not all engines like to run at the exact specs the factory recomends. I'd just set it where you have the best over-all performance. Take it out and run it in different situations to make sure you don't have any pinging, heating problems, etc.

08-23-04, 05:40 PM
Thanks Lux.... you've been a real help. I sorted out my firing order today. I'll try advancing it up a bit tomorrow... I think I'll advance it until it starts pinging then back it off a bit.
Thanks again..

Cygnus x-1
08-24-04, 09:13 PM
Backfiring thru the carb usually means either seriosly retarded ignition timing (you need to turn distributor opposite normal rotation to correct) or severe vacuum leak. For vaccum leak, check the obvious (pcv line, carb gasket,brake booster, etc.) on 425 cadillac engine, itis also important to note that the bolts which attach air cond compressor to intake manifold go all the way through. Loose or missing bolts will cause severe vacuum leaks.

08-25-04, 02:06 PM
Thanks Cygnus.... your right it was seriously retarded..... I had to give it a good turn to get it running right... now I'm having trouble with my quadrajet though... lol... If I hit the throttle from standstill the car pulls well... but if I'm traveling along and I step on the pedal the engine dies at about 90% throttle... then it picks up again.... it's more like over fueling than running lean... :hmm:
Parts for this carb are hard to find in the UK

08-26-04, 09:29 PM
just thought I'd let you know that there is a rebuilt quadrajet on ebay its from a 425 only $80.

09-10-04, 12:44 AM
Mine was like that too. It detonated in the carb. Usually the cylinder number is stamped right on the intake manifold. It takes some cleaning to see though. I had re-seated the distributor wrong, and in order to fix the problem iI had to rotate the dist as far as it would go(till the vaccum advance hit the inside of the valve covers) and even then I had to put the spark plug wires on one off to get it right. Now its fine as far as timing goes. If you cant see the #'s on the intake manifold then your engine is probably dirty. Make sure you paint or mark the timing mark before you try to time it or else its impossible to see.

09-23-04, 01:18 AM
about the stalling of the Q-jet i think that is just the nature of the beast. every car that i have had or driven w/a q-jet has always hesitated when you mash the gas when your rolling. I'm sure if you wanted to get into it you could change out the secondary metering rods and lever arms but if it runs fine other than that i wouldn't mess with it, if your going to keep the q-jet. And it is a over fueling problem, atleast mine is because if i mash the gas once the engine picks up again ther is a giant black cloud of smoke behind me. which black smoke is a sign of the engine running rich. I don't know how avaliable parts for holley carbs are in the UK but if performance is what you want Holley's are a little more user frindly. However to put a holley on the stock 425 you would have to get a spread bore holley or a new manifold or atleast an adapter plate for a square bore holley.

by the way at what degrees did you end up stting the timing at? i was just corious.

09-23-04, 06:30 PM
Thanks Bryan, I've actually just finished rebuilding my q jet. I bought a rebuild kit... totally striped the the carb. Cleaned it, checked clearances, epoxied the plugs etc. I found that the hesitation was because the power piston holding the primary rods had siezed in its bore. The car runs much much better now. I still haven't managed to time it right though. The timing mark is way off for some reason. I'm thinking the crank pully has been fitted wrong. I haven't really looked into it. I just wound the advance up until it stared pinging then backed it off a little.