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How do i time my 400 SBC?

44K views 27 replies 5 participants last post by  levisnteeshirt 
#1 ·
I finally put my engine back in my car and i need to time it with the timing light. What number of degrees am i looking for at idle? This is my first time timing an engine. I read somewhere that 14* at idle was close to factory specs. I have a SBC 400 with stock heads and internals and a edelbrock carb, intake manifold and a mild cam.

Thanks-Blake
 
#4 · (Edited)
advance kit

Your timing comes from 3 sources, initial set at idle with a timing light , vacume from the engine and centrifigal from the advance system in the distributor.

If you really want to nail down the timing on your car, this is what i'd do.
1st) i'd go get a advance curve kit that fits your distributor (moroso or mr gasket , or accel is where i'd look ) since the new cam will have different advance needs than the cam you removed.

2nd) I'd get a timing tape that fits the harmonic balancers diameter of your engine ( mr gasket has them ) , clean your balancer up very good then put it on

3rd ) decide if you want to keep the vacume advance feature in your distributor , fuel mileage might suffer without it , but it will be easier to set the distributor up without it. Your call. But i'd buy an adjustable vacume advance canister for your distributor if you want to make the oil cartel nervous and install it while your putting in the advance curve kit

4 ) re-install your self made hi-po distributor

Most advance curve kits come with a bushing to limit total centrifigal advance to 20 degrees. Check into this , this might be a good time to change distributors. IMO , i like the early chevy point distributor because you can convert it to electronics or use the points with an MSD box and I like the centrifigal advance system better. Accel makes a great kit for this distributor to convert to dual points that comes with a vacume advance lock out bracket and it has the bushing to lock the centrifigal advance to 20 degrees if i'm not mistaken , and also includes an advance kit as well. If you want to use points with the MSD , remove one set of points and the condensor and adjust the set of points just so they open and close and your done there. The MSD box will only send 5 volts to the points at a low current so a set of points will last a long time. I ran this set up for years and it was mis-fire free to 7200 where I wound my engine to. An MSD tech at a national event turned me on to this set up and it worked great for me. I have found that even this combo provides better starting than an electronic trigger from a HEI but thats me.
Might seem old fashioned but I like stuff that works.

With the car at idle , set it for 14 degrees at idle , with the vacume advance disconnected , watch the timing mark with the light and raise RPM at see where the timing tape is now telling you your timing is advancing to. Hopefully it should be close to 34 total with the advance kit installed.
This is a good time to decide if you want to continue to use the vacume advance. Since the new cam will defunct the stock settings, IMO , i'd connect it to manifold vacume instead of "ported " and set the new adjustable canister to add about 10 degrees timing checking what its doing with a timing light on the timing tape. Drive the car like this , do a full power run and listen for detonation. If you hear it , back the timing down 2 degrees and try again, back it down 2 more degrees until detonation goes away. If you want to go down a spring size on the centrifigal advance, listen again for detonation and adjust from there. A chassis dyno would be a great help but testing at a track is prolly the best place to set centrifigal advance.

If you decided to keep the vacume advance , do some driving up hills and listen for detonation using as smooth of throttle aplication as possible so you can ensure its the vacume advance thats doing anything with the timing at this point. You might slow the centrifigal advance down with a heavier spring and keep all the vacume advance as u can but you'd have to do some back to back testing to decide which way was working best. You might instal a vacume gage to tell how well your engine is staying at a steady speed without applying more throttle while increasing engine load going up inclines. This will give a more precise indication of what you just changed is doing. You could go back to the " ported " vacume source and see which way your engine likes best, but i bet it will like manifold vacume better

You could disconnect the vacume advance and see if it is helping your fuel mileage and lock it out if it isn't. This will give you certain numbers what your timing is doing but might be more intended if you step up in performance later on

I hope this helps you.
 
#9 ·
I looked at my cam specs sheet and it says the following-

CAM TIMING-
Intake
opens- 7*BTDC
Closes-31*ABDC
Max lift-102*ATDC
Duration 218*


Exhaust -
opens-39*BBDC
closes- (1*)
max lift- 110* BTDC
duration-218*

So i have the timing but how do i go about setting it. My harmonic balancer has numbers as well as my timing cover tab. Sorry for the newb questions as this is my first time.
 
#10 ·
You guys are confusing cam timing with ignition timing. Though they interplay a little they're totally different animals.

Ignition timing has everything to do with spark events compared to piston location in the stroke.

The cam timing relates more to valve events during the strokes.

Yes a different cam will change ignition timing characteristics, but trying to decide how much initial timing a motor will handle from a cam card is impossible.
 
#12 ·
16° is probably fine if that's it's was before your cam change. If you want to see just how much initial it can take overall there is a way. With the motor not running move the dizzy counterclockwise advancing the initial a few degrees at a time. Try to crank it, do this until you hear the starter do that rhythmic groaning against the motor's compression. You've hear it before rrrrrr.......rrrrr......rrrrr......rrrrrr....vroooom. Back off a few degrees until it cranks smoothly again and that's a pretty good place to start with initial.

People that have that rhythmic groaning when trying to start their cars are using too much initial timing or have locked out so much advance they have to start with a ton of initial timing to get full advance of 32-36° centrifugal. Not really the way to tune your motor IMHO.

Most of the time they'll just tell you "it's just THAT race" :rolleyes:
 
#15 · (Edited)
BLake,

Don't let them scare you off, all you need is a wrench to losen you dizzy and the timing light to do a decent job. The 400 will time just like a 350 or 283 your cam is going to make any measurable difference if any at all.

Lets not re-invent the f-n wheel here.

Go to the BEST OF TECH thread its located at the top of drivetrain & performance, open the thread about basic vacum advance timming that Johnny wrote and follow it.

If you don't have a vacum can on the side of your dizzy with a black tube going to the carb then its mechancical and its a bit different, let us know if thats the case and we may have to give you a bit more info.
this should be the link to the thread
http://www.stevesnovasite.com/forums/showthread.php?t=11689
Chuck
ps
Johnny is a very helpfull guy (nphnp)
 
#16 ·
lol thanks chuck. Like i said im only seventeen and im still not familiar with all the terms and what not but i am DETERMINED TO LEARN! :yes: I don't think i have a vacuum can but i can double check for you. What i do know that my carb has a hose thats hooked up too it and it goes into this black circle thing about a 3-4 inches in diameter and that then goes onto my distributor.

Heres a pic( The circle thing right next to my trans fluid dipstick) dont know if thats the vacumm can your talking about.



I will look into the thread you mentioned about.
 
#17 ·
Yes, thats the vacumm advance can, there should be a vacumm line that runs from it the carburetor. Don't make the mistake of not using it thinking it is just for reducing smog, the distributor is designed for it to be used. The distributor is the pointless HEI? that includes the coil in the cap, this is an upgrade over the original point distributors, so you don't have to worry about adjusting any points, nice set up.

We all started up at the beggining learning the basics I always learn something new when checking out this site.

Chuck
 
#18 ·
The distributor is the pointless HEI? that includes the coil in the cap, this is an upgrade over the original point distributors, so you don't have to worry about adjusting any points, nice set up.
Chuck
So Chuck, Are you saying that my distributor has been upgraded already and this is not the stock one? Oh and theirs a vacuum hose hooked up to the vacuum can its just that when i took this photo i was replacing all of my hoses.
 
#19 ·
Blake,
I'm not sure what year that distributor started, I didn't realize the year of your car until just now. If you wanted to find out you could start a new specific thread and someone would know.
That distributor is a common junkyard find upgrade from the point type distributor and the inside components can be upgraded further but not necessary for the cam and intake that's on your motor now or gears that are probably on your car.


Chuck
 
#20 ·
look at the red terminal lug

look at the red terminal lug going into the distributor , i'd say its been converted over. HEI's are ok i guess , but I like the centrifigal advance system better on the earlier distributor. But if your just getting started with this stuff , the HEI will prolly do fine.
 
#22 ·
If your getting good spark now, I would put the money in a good set of spark plug wires if they haven't been changed in a while - dress it up some with a nice wire loom, I really don't think your motor would run much different with a different coil - a 400 is not a high reving motor and the HEI will do the job if its working properly. The 400 is a strong motor in stock form, a monster when modified, your at the stock side now - Nice wires will work fine on a monster motor later down the road the Hei with a better coil not so much - probably a better distributor will be needed for a monster motor.
Just trying to save you a buck.
 
#24 ·
mallory makes ,,

mallory makes a nice cap for the HEI distributor so you can use most any aftermarket coil ,, looks good too on the engine

http://www.mr-gasket.com/pdf/29049_29050.pdf

there is the directions to hook it up

Here is a link to see the pic

http://www.malloryperformance.com/pdf/Coils_&_Accessories.pdf

you'll have to scroll down to see it its part number 29050, I had one , it looks alot better than the HEI cap , and you can use something like the big yellow Accel super coil. But remember , you'll need an extra wire in your spark pulg wire set to go over to the remote coil since now the coil won't be in the distributor, a good parts counter man should be able to match something up for ya . Then if you want , you could get you a MSD 6a box to go with this and you'd have a nice ignition
 
#25 ·
mallory makes a nice cap for the HEI distributor so you can use most any aftermarket coil ,, looks good too on the engine

http://www.mr-gasket.com/pdf/29049_29050.pdf

there is the directions to hook it up

Here is a link to see the pic

http://www.malloryperformance.com/pdf/Coils_&_Accessories.pdf

you'll have to scroll down to see it its part number 29050, I had one , it looks alot better than the HEI cap , and you can use something like the big yellow Accel super coil. But remember , you'll need an extra wire in your spark pulg wire set to go over to the remote coil since now the coil won't be in the distributor, a good parts counter man should be able to match something up for ya . Then if you want , you could get you a MSD 6a box to go with this and you'd have a nice ignition
Thanks for the info... One question though.... What is the purpose of the MSD 6a box?
 
#26 ·
MSD6A box

An MSD6a box , ( multiple spark discharge ) will send multiple charges through the ignition to the plugs instead of one , and it will be at a greater electrical value to enhance combustion. MSD has a list of coils they recommend to use with their products. I used the Accel Super Coil and it worked fine. An MSD box is one item that will do what its advertised to do. You should be able to feel and notice a difference how your car performs. Using that cap for an HEI i showed you Mallory sells, a good remote coil , good curve kit in the advance when your ready to tackle that, and an MSD6a , your ignition system would be support up to IMO 550-600 hp. Watch ebay , sometimes a MSD6A box will go for under 70 bucks. A MSD6AL will be higher , because it has a built in rev limiter , but MSD can convert a 6A to a 6AL when your ready for a rev limiter. One thing I had to do, was to turn on the ignition after the engine was cranking because of the added power to the ignition was making the engine drag like it had too much advance in the timing.

How did you get so lucky to start out with a Nova with a 400 small block ?? Talk about being born under a lucky star.
 
#27 ·
An MSD6a box , ( multiple spark discharge ) will send multiple charges through the ignition to the plugs instead of one , and it will be at a greater electrical value to enhance combustion. MSD has a list of coils they recommend to use with their products. I used the Accel Super Coil and it worked fine. An MSD box is one item that will do what its advertised to do. You should be able to feel and notice a difference how your car performs. Using that cap for an HEI i showed you Mallory sells, a good remote coil , good curve kit in the advance when your ready to tackle that, and an MSD6a , your ignition system would be support up to IMO 550-600 hp. Watch ebay , sometimes a MSD6A box will go for under 70 bucks. A MSD6AL will be higher , because it has a built in rev limiter , but MSD can convert a 6A to a 6AL when your ready for a rev limiter. One thing I had to do, was to turn on the ignition after the engine was cranking because of the added power to the ignition was making the engine drag like it had too much advance in the timing.

How did you get so lucky to start out with a Nova with a 400 small block ?? Talk about being born under a lucky star.
Well i think when i have enough money and i start focusing on the ignition I will choose the setup you mentioned. Thanks! And i picked up this nova in Austin Texas from a kid that was in college for 5500. Is the 400 a rare block? It is a stock block with stock internals. Only changed the stuff on the outside like carb and intake and headers oh and the cam.....This is my first car and the only way your going to take it from me is if i die in it. :D:devil:
 
#28 ·
I doubt ,,

I don't think they put a 400 in a Nova factory , but thats cool in my book , I like 'em to run better than look myself. 400's are getting rare around here , which they never were as easy to find as a 350 anyway. I had a 73 ss that was similar to yours with a factory 4 speed , bucket seats with the center console and gauges. Way back in 1982. Traded it for a 68 ss396 chevelle with a 4 speed.
 
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