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I've got a 427 sbc in my 75 set up for a high performance street car, may take it to the track the odd time but mostly city and highway driving. Was timing the engine and it runs good with 12 degrees initial timing and 30 total, but feel that it could be a little better with a few more degrees in timing. Problem is at 12 degrees, the vacuum advance is hitting the intake runner. Edelbrock performer rpm air gap intake. I've tried moving the plug wires over 1 post and repositioning etc, and can get it to run good by ear, but then timing light is showing 40 degrees timing at idle. Put the plug wires back to where they were and again 12 degrees against the intake. Lifted the distributor up and moved it 1 tooth over and timing was saying 68 degrees at idle. So once again set TDC and got it back to 12 degrees against the intake. Any suggestions? I've heard some say to delete the vacuum advance and some say not too.
Take it back out and restab it. That distributor should be square to the firewall, more or less. The vac can hose should be pointing roughly at the rear valve cover bolt. I'll look to see if I have a photo with the covers off.
From: At my Bar drinking and wrenching in Lafayette Colorado
Your distributor is installed at least one tooth off, and is clocked incorrectly in the block. Pull it out and install it correctly.When correctly installed, the distributor and the top coil pack is "square" in the engine compartment. E-mail me for my distributor installation paper if you need to see how to install it correcrtly.
As stated....restab the distributor.....one tooth clockwise will get you where you want to be......just loosen, lift it up and rotate one tooth clockwise then roll the engine around to get it to line up with the oil pump driveshaft....just keep turning the crank until it falls in. Bring it up on #1 TDC......now find #1 on the cap and mark a line on the distributor base straight down from that lead.....remove cap, line up rotor with the line you made on the base....now turn it 1/2" counterclockwise from that mark and snug it down.....repalce cap and start the engine.....you should be at about 15 degrees initial......modern fast burn chambers in aftermarket heads like about 33-34 degrees total.....
that photo was taken years ago while working on it. Pretty common to remove and plug the vacuum hose while setting timing. It was the only photo I could find with the shielding cover removed. Here's my engine as of yesterday.
Note vacuum hose to vac can. And covers over the distributor. Hard to get a good look at the distributor orientation with the covers on. And this thread is about the orientation of the distributor. The only time my covers are off is when it's being worked on.
From: At my Bar drinking and wrenching in Lafayette Colorado
It's a new HEI distributor that the OP bought for the new engine. Whether it's rebuilt, new, or not is irrelevant to the clocking and orientation that the OP is concerned about. He just needs to re-clock it 1 tooth to get it right.
Lars
I need to reclock mine but I moved all the wires over counterclockwise one post instead and everything seemed to workout fine... is there a reason that might effect performance negatively?
It's a new HEI distributor that the OP bought for the new engine. Whether it's rebuilt, new, or not is irrelevant to the clocking and orientation that the OP is concerned about. He just needs to re-clock it 1 tooth to get it right.
Lars
Lars
If rebuilt, it is possible to reinstall distributor gear 180 degrees off. This will often generate OP's problem.
You want "dimple" on gear and rotor tip to be on same side of shaft.
Left distributor gear has large "dimple" - just below "Pin" in "Spring Pin". Right distributor gear has quite small "dimple" up 45 degrees from "?" in "Dowel Pin?".
Right distributor is from an early SBC around 1957 - pin was swedged in place.
I'm gonna ELI5 this because I don't know the level of ALL possible readers, not just OP. Don't take it as condescension!
Any distributor can be clocked in any position the owner (or OP) wants, PROVIDED the plug wires correctly line up with that clocking.
Distributor/engine don't care.
CONVENTION is to "make it square" in the engine bay as in reply #1. Electrical plug 90 degrees from the front of the car, vacuum pot facing maybe 7 o'clock
Which puts the #1 plug tower at ABOUT a 5 O'clock position.
This avoids the problem you've got of the HEI disty hitting things. Yours appears to be clocked one plug /tower counter-clockwise.
Start with a piece of chalk by marking 0 degrees on your harmonic balancer -- just to make it easier to see. You don't need a timing light, a flashlight will do.
Pull spark plug #1 (driver's side, front), put your thumb over the hole, and crank until compression begins to blow your finger off the hole.
That's how you know you're on the compression stroke, and not 180 out. On some engines you can put a drinking straw in the plug hole and watch the piston push it up.
Well, before they made straws illegal, you could /s
You can crank or you can simply turn the crankshaft using a long wrench and the bolt on the front of the motor. It's easy to go past TDC if you
do it by cranking, and you can't (or don't want to back up).
Confirm you're at or near TDC by looking for the mark on the harmonic balancer. Go around again if necessary.
Take the cap off the HEI rotate the rotor as necessary, and stab the distributor so the rotor lines up with the #1 tower on the HEI cap. Disty will usually sit about 1/4" above its base.
Firing order is 1 8 4 3 6 5 7 2
Gently push the disty down as you crank a little more until the oil pump drive seats and the disty goes all the way down .
Replace the plug, gently tighten the disty hold down, see if it starts. If it doesn't, you're probably 180 out. Or failed to hook up power to the distributor (sheepish grin...)
On the other hand, if it starts right up, get out the timing light and set yer base timing, with the vacuum line disconnected from the disty and plugged. (so no vacuum leak!)
I just got done doing this, stabbing a HEI to replace a decrepit Mallory distributor. Want me to tell you all the WRONG ways you can do it? LOL I hadn't stabbed a disty in...DECADES!
The one GOOD thing about stabbing a distributor 180 degrees out is that NO cylinder will fire. You crank and get absolutely NOTHING. That's when .... YOU KNOW!
It' doesn't do that horrible thing like when you've got a couple of plug wires reversed, backfiring through the manifold, etc.
One other thing. If you've got a disty with a mechanical tachometer drive, you do not ABSOLUTELY have to buy a HEI with a mechanical drive.
You can buy a doo-dad that converts your tachometer to electronic. Now would be a good time! Great! Just another project, pull the dash, AMIRIGHT???
If you set the engine at exactly top dead center, and then line up rotor to plug 1…..then when you set initial timing to 20 degrees like on my engine….the distributor will be out of position again. Is it not better, if you want to get the distributor correctly oriented to firewall, vacuum canister clearance, etc to set engine at 20 degrees BTC…..THEN position rotor to point at No 1 plug?
If you set the engine at exactly top dead center, and then line up rotor to plug 1…..then when you set initial timing to 20 degrees like on my engine….the distributor will be out of position again. Is it not better, if you want to get the distributor correctly oriented to firewall, vacuum canister clearance, etc to set engine at 20 degrees BTC…..THEN position rotor to point at No 1 plug?
Let's say there's 10 teeth on the bottom of the distributor shaft. 360 degrees / 10 = 36 degrees PER tooth.
You can easily twist the distributor body 20 degrees to obtain your desired timing.
But yes, you could stab it on the NEXT tooth (position, alignment, whatever) , and twist it 16 degrees the OTHER way.
I "ran out of twist" on my old distributor because the tachometer drive hit something. Couldn't advance the timing as much as I wanted. The solution was, as you suggest, to restab it one tooth off and twist the other way.
When I purchased the car the timing was horribly retarded. What a pleasant surprise to get it where it should have been and instantly get another 30-40 horsepower (or more) , FREE!
Saw the EXACT SAME THING on some TV show about restoring classic cars, '68 with poor performance due to retarded timing. I'm sure someone remembers the show and the episode. I was like.... are these guys reading my mind? Same color car as mine, too!
Replacing an old Mallory with a "generic" HEI disty in a few days ago, WHAT AN IMPROVEMENT! Starts instantly, idles much lower/ smoother, and.. I could swear it's making more power than ever. It sounds different, especially at cruise The Mallory did NOT have vacuum advance.
Last edited by wadenelson; Jul 14, 2023 at 02:36 PM.
Let's say there's 10 teeth on the bottom of the distributor shaft. 360 degrees / 10 = 36 degrees PER tooth.
You can easily twist the distributor body 20 degrees to obtain your desired timing.
But yes, you could stab it on the NEXT tooth (position, alignment, whatever) , and twist it 16 degrees the OTHER way.
I "ran out of twist" on my old distributor because the tachometer drive hit something. Couldn't advance the timing as much as I wanted. The solution was, as you suggest, to restab it one tooth off and twist the other way.
When I purchased the car the timing was horribly retarded. What a pleasant surprise to get it where it should have been and instantly get another 30-40 horsepower (or more) , FREE!
Saw the EXACT SAME THING on some TV show about restoring classic cars, '68 with poor performance due to retarded timing. I'm sure someone remembers the show and the episode. I was like.... are these guys reading my mind? Same color car as mine, too!
Replacing an old Mallory with a "generic" HEI disty in a few days ago, WHAT AN IMPROVEMENT! Starts instantly, idles much lower/ smoother, and.. I could swear it's making more power than ever. It sounds different, especially at cruise The Mallory did NOT have vacuum advance.
This was my issue my tach drive cable ws coming in contact with my oil pressure sender.. so I had to reclock but then I had the issue of the vac can hitting intake.. took some finagling but I found the happy medium with a 45 degree fitting in my oil pressure sender.
HEI distributor hits intake
