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Old 04-29-2010, 09:22 AM
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installing distributor/timing on sbc 350

I have searched and read many of the posts on this and there are many variations and I'm still a bit confused.

I did a search on the web and found this information from CarCraft magazine online:

http://www.carcraft.com/howto/ccrp_0..._pictures.html

I wanted to make sure what I got out of this is correct because it seems too simple:

1. Basically, if I'm at TDC for the 1 cylinder compression stroke (which I am), I roll it back to 10 degree BTDC (which I've read is the correct place for a SBC 350 mild build).
2. After lubing end of distributor, install in hole and jiggle it around until it goes down all of the way not worrying about the oil pump shaft in terms of where it is pointing but do make sure that the vacuum advance tank is pointing to the front right of the car.
3. Take cap off (mine has the coil built into it) and see where the rotor is pointing.
4. Make a mark on the cap/post where the rotor is pointing which becomes the post where you connect the wire that goes to the number one cylinder.
5. Reinstall cap and wire the rest of the way around the distributor as required for a SBC 350.

This should at least allow me to start the car and break-in the cam. After that, full timing and carb adjustments.

As always, I appreciate everyones assistance with a newbie.

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Old 04-29-2010, 09:41 AM
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Quote:
Originally Posted by 075turbo
I have searched and read many of the posts on this and there are many variations and I'm still a bit confused.

I did a search on the web and found this information from CarCraft magazine online:

http://www.carcraft.com/howto/ccrp_0..._pictures.html

I wanted to make sure what I got out of this is correct because it seems too simple:

1. Basically, if I'm at TDC for the 1 cylinder compression stroke (which I am), I roll it back to 10 degree BTDC (which I've read is the correct place for a SBC 350 mild build).
2. After lubing end of distributor, install in hole and jiggle it around until it goes down all of the way not worrying about the oil pump shaft in terms of where it is pointing but do make sure that the vacuum advance tank is pointing to the front right of the car.
3. Take cap off (mine has the coil built into it) and see where the rotor is pointing.
4. Make a mark on the cap/post where the rotor is pointing which becomes the post where you connect the wire that goes to the number one cylinder.
5. Reinstall cap and wire the rest of the way around the distributor as required for a SBC 350.

This should at least allow me to start the car and break-in the cam. After that, full timing and carb adjustments.

As always, I appreciate everyones assistance with a newbie.
Sounds OK to me. Remember to wire it 1-8-4-3-6-5-7-2, going in a CW direction from #1. #1 is front driver side, alternating from side to side, front to rear.
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Old 04-29-2010, 09:49 AM
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Hi,
That's all there is to it, start at #1 8436572
Rich
To make dist installation easer, use a long flat head screwdriver to turn the oil pump slot, close to where the dist. slot/pin will line up with it

http://www.boxwrench.net/specs/chevy_sb.htm
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Old 04-29-2010, 09:58 AM
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Distributor install vid.

http://www.youtube.com/watch?v=YdIGZ-tVuZA


Wiring vid.

http://www.youtube.com/watch?v=3ixfDRbAr2E
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Old 04-29-2010, 10:01 AM
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Quote:
Originally Posted by 075turbo
I have searched and read many of the posts on this and there are many variations and I'm still a bit confused.

I did a search on the web and found this information from CarCraft magazine online:

http://www.carcraft.com/howto/ccrp_0..._pictures.html

I wanted to make sure what I got out of this is correct because it seems too simple:

1. Basically, if I'm at TDC for the 1 cylinder compression stroke (which I am), I roll it back to 10 degree BTDC (which I've read is the correct place for a SBC 350 mild build).
Do NOT "roll it back" (as you posted). When rotating the engine (clockwise direction when standing in front of the engine looking towards the rear) over to get the #1 cylinder on the compression stroke, continue until the timing mark lines up fairly close to the '0' mark.


Quote:
Originally Posted by 075turbo
2. After lubing end of distributor, install in hole and jiggle it around until it goes down all of the way not worrying about the oil pump shaft in terms of where it is pointing but do make sure that the vacuum advance tank is pointing to the front right of the car.
The vacuum advance unit should be 'pointing' more towards the passenger side of the vehicle. You want to be able to rotate the distributor body in both a clockwise and a counter-clockwise direction without hitting the intake manifold or the firewall. This is so that you will have a full range of motion when adjusting the timing.

While you can drop the distributor in at any position and then arrange the plug wires in the correct firing order, it is best to set it up closer to the 'factory' positioning. You may have to rotate the oil pump drive shaft with a long screwdriver to enable you to get the distributor to fully drop in. You want the rotor to be pointing about the five o'clock position when viewed from above and from the front of the engine. This is also where the #1 sparkplug wire will be located in the cap. See drawing below.

NOTE:

Always check/set the timing with the vacuum advance hose dis-connected from the vacuum advance cannister and plugged off. Re-connect AFTER checking/setting the timing. I recommend and suggest using the full manifold source for the vacuum advance. You will have to re-adjust the idle speed after re-connecting the vacuum advance hose.

Best performance timing specs for a small block Chevy V-8 engine will be with the initial timing in the 12-18 degree BTDC range. Total Mechanical Timing (with vacuum advance dis-connected and plugged) in the 32-38 degree range 'All in' around 2500-3000 RPM.

For Vortec heads the Total Mechanical timing should be in the 32-34 degree range.
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Old 04-29-2010, 12:41 PM
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Frisco,

Please help me to understand a few of your comments.

Why shouldn't I "roll back" to 10 degrees BTDC? I thought this was how you set the initial timing (which you are suggesting should be 12-18).

Also, you mention that the vacuum advance hose should be disconnected and plugged off when I set the timing. Should I plug BOTH the vacuum advance canister and the carb?

Finally, you recommend connecting to a full manifold source for the distributor vacuum advance hose. Why do the instructions for the carb I purchased (Holley Street Avenger 670) show the vaccum line from the distributor connecting to the timed spark vacuum connection point?

I appreciate everyones quick responses.

Craig
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Old 04-29-2010, 07:11 PM
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Quote:
Originally Posted by 075turbo
Should I plug BOTH the vacuum advance canister and the carb?
Just the carb, or the hose coming from the carb.

Quote:
Why do the instructions for the carb I purchased (Holley Street Avenger 670) show the vaccum line from the distributor connecting to the timed spark vacuum connection point?
If the carb has street legal status, this is how the OEM would have routed the vacuum supply. In practice, using manifold vacuum will often give a better idle when using a non-OE camshaft that has less vacuum signal to the carb.

AFA not setting the timing to 10º BTDC (or where ever), maybe its a reluctance to rotate the engine "backwards"- in which case, it's easy enough to either just stop short of TDC with #1 firing, or to simply go 'round twice more, stopping shy of TDC by how-many-ever degrees that you want to set the engine at, to start it up.
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Old 04-29-2010, 07:49 PM
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That makes sense.

Ok, so installed the distributor at 10 BDTC. Put about 4-6 ounces of fuel in vent hole by primaries. When we turned it over, the carb puffed and backfired a few times then there was some smoke around the firewall. The first time we turned it over I thought it was residual smoke from the carb. Turned it over again and same thing with the carb. Went to investigate smoke and it was the ground strap that is running from backside of passenger head (where I scrapped off the paint to make sure it is contacting well) to the firewall. It was so hot I could barely touch it.

I called a friend and he thinks I'm 180 degrees out on the distributor even though I'm 99.99% sure I'm not.

In terms of my battery connections, I have the ground from the battery going to a bare metal spot on the firewall held by a bolt and nowhere else. I have the positive cable from the battery going to the starter. Both are new cables and have small wires coming off where they attach at the battery but I don't have them attached to anything.

Thanks again.
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Old 04-29-2010, 08:09 PM
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Quote:
Originally Posted by 075turbo
I called a friend and he thinks I'm 180 degrees out on the distributor even though I'm 99.99% sure I'm not.
Was the engine sluggish to turn over? It might be hard to actually tell with the ground wrong to the engine, but if it was, you're too far advanced, and you'll want to turn the distributor CW about 10º worth and try it again- provided that you're sure that you're not out 180º. Conversely, if the engine spins over freely, w/o acting as if the battery wasn't fully charged, the ignition could be retarded, and you'd want to go CCW with the distributor adjustment.

Quote:
In terms of my battery connections, I have the ground from the battery going to a bare metal spot on the firewall held by a bolt and nowhere else.
Thanks again.
You want that heavy cable going from the battery negative to the alternator bracket or a spot on the engine block. No paint, just like you did w/the firewall.

Then you want another heavy cable from the engine to the firewall as well as the front subframe or chassis. I currently (haha) have a dual-terminal battery that I use both negative battery terminals- one to the alt. bracket, the other to the chassis. Then I also use a cable from the engine to the firewall (that was there OE) and another from the engine to the radiator support.

Last edited by cobalt327; 04-29-2010 at 08:31 PM. Reason: Typo.
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Old 04-29-2010, 08:54 PM
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You also want to double check the plug wires and firing order. You’ll notice there are a pair of wires- 5 and 7- that fire right one after the other in the firing order, that are also right next to each other physically. Check them carefully. For that matter, recheck them all.

How are you determining that you’ve got the engine set to #1 firing? The finger in the plug hole works fine, but sometimes a guy can be fooled by the exhaust stroke- which also pumps out air but not nearly as much as when the cylinder is on compression.

The valves have to be lashed (adjusted) correctly. If they are too tight, the valves will not seal and the result can be a no start condition with popping through the carb and/or exhaust, depending on what valve(s) were adjusted incorrectly.

What procedure did you use to set the valves? Some guys will twist the push rod between a thumb and fingers to feel when the lash is at "zero". For someone not used to doing this, jiggling the p-rod up and down will be a better indicator.
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Old 04-30-2010, 08:00 AM
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Quote:
Originally Posted by 075turbo
Frisco,

Please help me to understand a few of your comments.

Why shouldn't I "roll back" to 10 degrees BTDC? I thought this was how you set the initial timing (which you are suggesting should be 12-18).
"Roll back" sounds to me like you are rotating the engine clockwise and then rolling back (reversing the rotation) because you rotated it too far. You do not want to roll it back because of the built in slack in the timing chain and other internal components. This will cause you to 'think' you have the crank in the correct spot when it actually will be off several degrees (depending on how much slack there is in the chain and other components). When rotating the engine, if you go too far, then just continue rotating in the same direction until you get to where you want it to be. Best to rotate using a manual source (breaker bar) than the starter motor to have better control. Remove the sparkplugs to rotate the engine manually.

Quote:
Originally Posted by 075turbo
Also, you mention that the vacuum advance hose should be disconnected and plugged off when I set the timing. Should I plug BOTH the vacuum advance canister and the carb?
Just remove the hose from the vacuum cannister and plug that end. A golf 'T' or a #10 cap screw works well for this.

Quote:
Originally Posted by 075turbo
Finally, you recommend connecting to a full manifold source for the distributor vacuum advance hose. Why do the instructions for the carb I purchased (Holley Street Avenger 670) show the vacuum line from the distributor connecting to the timed spark vacuum connection point?
Edelbrock and Holly both suggest using the ported source. Probably due to original factory specs from the manufacturers. My personal tests have resulted in my finding that the full manifold source works much better than when using the ported source. Most if not all automobile manufacturers went to using the ported vacuum source around the 1960's in an attempt to meet Federal Guidelines for emissions. They also reduced the initial timing at that time. Both of these 'fixes' resulted in the coolant temps to be much higher at idle and did lower the emissions at idle. That is when they switched from 180 degree thermostats to 195 degree and also began to run 14-16 lb. radiator caps. This was to compensate for the higher temps. Before that radiator caps either had no pressure feature or up to about 6 lb. They also caused a big loss in performance and fuel economy. Prior to those changes mandated by the Feds, when vacuum advance was originally introduced it was to a full manifold source. Today, on a non-computer controlled ignition and a carbureted engine, you will find that by using the full manifold source for the vacuum advance and increasing the timing will result in much better (very noticeable) overall performance and drive-ability as well as an increase in fuel economy. You will also have an increase in emissions and may not be able to pass a smog test. Many states no longer require that test on vehicles that are more than 35 years old. Some at 25 years old.

Some folks today, still think that running the vacuum to a ported source is best. While I have found in my own tests that the full manifold source performs best, I can only offer that you should try both. See which one works best for you and your combo.


Since I usually only come online in the mornings, I see that COBALT327 has answered many of your concerns. He has given you very good answers.

I have answered here so that everyone can benefit. I did receive your PM with the same questions you asked here.

Your 'popping' thru the carb sounds like the distributor is 180 degrees out.

Remove the sparkplugs.

Either place your thumb (or someone else's) over (not in it) the #1 sparkplug hole, or loosely plug the hole with some soft tissue. Toilet paper works.

Rotate the engine in its normal direction of rotation by hand slowly until the compression pushes your thumb away from the hole (or blows the tissue out of the hole).

Continue to slowly rotate the engine until the timing mark is lined up with the '0' mark.

That will be TDC on the compression (firing) stroke.

Do not rotate the engine any further at this time.

Pull the distributor cap and look at where the rotor is pointing. If it is not pointing at the location where the #1 sparkplug wire is located in the cap you will have to pull the distributor up and rotate the distributor shaft to get the rotor lined up correctly when the distributor has been lowered back down and fully seated.

Last edited by Frisco; 04-30-2010 at 08:05 AM.
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Old 05-03-2010, 12:22 PM
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I appreciate all of the help. I had a couple of guys come over to the house Saturday and they confirmed that I was in fact 180 degrees out. Once that change was made it fired in a half second.

Before they arrived though, I thought I would check all of the valves again as was suggested. Thank goodness I did because when I got about half way through, I noticed that the way the pushrod was engaging on the rocker arm was a bit in a bind. When I took off the rocker arm the pushrod didn't have full movement within the space in the head. I couldn't figure out what it was and left it out and decided to finish out the rest. Same problem again on one other one only this time I couldn't even get the rod out by hand. After a gentle tug with vise grips, it came out. I took a bright light and shined it in the hole and, yes, you guessed it, one of the manifold bolts was just barely contacting the rod. Went to the other side and it was the same thing. I checked the rods and they were still straight with just barely perceptible marks on them. Thank goodness the motor didn't fire before this or I can only assume it would have been ugly. I switched out to shorter bolts and everything was fine.

I post this for other newbies out there as something else to watch for.

Thanx again.
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Old 05-03-2010, 12:25 PM
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also, wanted to note that I followed the advice on how to properly ground the motor and all "smoke" issues were gone after that.

Guys that helped the other day also agreed that full manifold for the distributor was the best route as well.

Thanx again.
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Old 05-03-2010, 12:54 PM
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Quote:
Originally Posted by 075turbo
Before they arrived though, I thought I would check all of the valves again as was suggested. Thank goodness I did because when I got about half way through, I noticed that the way the pushrod was engaging on the rocker arm was a bit in a bind. When I took off the rocker arm the pushrod didn't have full movement within the space in the head. I couldn't figure out what it was and left it out and decided to finish out the rest. Same problem again on one other one only this time I couldn't even get the rod out by hand. After a gentle tug with vise grips, it came out. I took a bright light and shined it in the hole and, yes, you guessed it, one of the manifold bolts was just barely contacting the rod. Went to the other side and it was the same thing. I checked the rods and they were still straight with just barely perceptible marks on them. Thank goodness the motor didn't fire before this or I can only assume it would have been ugly. I switched out to shorter bolts and everything was fine.

I post this for other newbies out there as something else to watch for.

Thanx again.
Thank YOU for getting back to the forum w/the results- and especially the reminder about the too-long intake manifold bolts being able to contact the push rods! I hadn't thought of that in Years!

Good tip and good job!
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Old 05-11-2010, 08:59 PM
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After melting a few plug wires during cam break-in (duh) and replacing with Taylor Spiro-Pros, I'm now ready to set the timing and the carb. Based on my limited experience, it seems to idle and accelerate smoothly. Should I do the timing first and then carb or vice vesa? Also, do I need a vacuum gage?

I've searched a few times and although I'm sure I missed it, I would sure appreciate a detailed step by step explanation of what I do next for someone that has never used a timing light or worked on carb setups.
For background:
1977 Camaro
350 standbard bore
333882 head with screw in studs and heavier springs that machine shop said could handle up to 0.500 lift safely. Had them checked for cracks and a valve job performed.
Compression is only about 8.5:1 due to dished pistons with 4 valve reliefs. Did try to optimize what I had with FelPro 1094 head gasket though.
Edelbrock Performer RPM intake
Holley Street Avenger 670
1 5/8" headers with 3" collectors
Comp Cams XE262H-10 - Duration @ 0.05 is 218 In and 224 Ex, Lobe separation is 110, Gross valve lift is 0.462 In adn 0.469 Ex
GM distributor with Accel HEI Super Coil
Freshly rebuilt Turbo 350 with mild shift kit and stock converter
Lower end only had a couple thousand miles on after last rebuild as previous owner didn't find it fast enough.

Goal was to end up around 300hp with a reliable motor and tranny for my daughter.

Went to look at timing lights at the stores today and they have a basic model for about 40 and a super model for about 100. For what I'm doing, will the basic suffice?

Again, obviously a real newbie but wanting to learn as much as I can on my own.

Thanx as always.
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