L24 High RPM Popping

[Onion]

I'm running a Holley 390 with the Arizona Z car single plane manifold. I don't own a timing light, so I adjust my timing by ear. The engine is an L24 running the late model E88 head.

 

The issue I had was when I took it to a shop, they told me my timing was too far advanced, and they pulled it back. The distributor was advanced one mark from center. On high rpm, especially in first gear, I would start getting a popping sound from the engine bay, and it would keep going until I hit an RPM wall and the car would Rev anymore. This would happen around 5k-6k rpm (not sure, still don't have a working tachometer).

 

I've adjusted my floats. My secondary is on point, and my primary is a little high, but it's on the to-do list. The idle mixture is perfect and the car pulls about 18 inhg of manifold pressure. I tuned it again this morning, got it to 19 inhg. I have an in-line tee fuel pressure gauge which reads 4 psi. When I adjusted the mixture again this morning, I decided to mess with the timing and see how it affects the vacuum. I advanced it about two more notches, which bumped me up to a hair over 20 of manifold pressure. I took it out for a spin and was able to wring it out all the way in first gear with no popping.

 

My questions are as follows.

 

1. Was the popping a lean condition at high revs?

 

2. If so, how does advancing the timing affect the lean condition?

 

3. Does the combustion happen sooner, requiring less gas? (I don't really understand how this would happen, I'm still learning and reading a lot.) Or was this just a timing issue that would cause the popping?

 

4. Is my timing being too advanced really rough on the bottom end? I heard if it's too far, it'll shorten the life of the engine and eat the crankshaft bearings. I had my timing all the way advanced at one point.

 

Pardon me if this post is poorly structured, I typed the entire thing from my phone.

[Onion]

I forgot to mention this...

 

The car uses to bog down when I was accelerating from a stop and letting the clutch out too fast. I'd have to kick the clutch in quickly and give it a bit of gas to save it from stalling. This started happening after the shop poorly tuned my carb and adjusted my timing. It no longer happens now that I've advanced my timing.

 

Also, my fuel filter is probably in need of being replaced, but would this contribute to the issue at hand?

Edited October 24, 2013 by Onion

[GeeZ]

Get a timing light!

[Onion]

Get a timing light!

I don't have the money to spare at the moment, college is expensive. I asked autozone if they can loan one out, but they don't loan timing lights.

[NewZed]

I took it to a shop,

 

I don't have the money to spare at the moment, college is expensive.

Pardon me if this post is poorly structured, I typed the entire thing from my phone.

How much did the "shop" cost, and what did you get for the money (besides an engine that doesn't run right)?

 

Curious - what are you studying in college?

 

 

Left the phone part in just because it's amusing.

[Onion]

$50, got 10% better gas mileage. I realized it was stupid, bought a vacuum gauge, and learned how to do it myself.

 

Studying international business law.

[NewZed]

10% better gas mileage from retarding timing seems odd.  Tuning your engine with a vacuum gauge is not common, you only see what's happening at idle.  Popping from the intake can be a sign of a lean mixture.  You should be able to make it run smoothly within a pretty wide range of initial timing settings, like 5 to 20 degrees, so using the shop's setting and focusing on carb tuning might be your best option.  Learn more about your distributor's advance characteristics - how much centrifugal advance (check the weight stamps,see if the springs have been messed with, make sure it works smoothly), and is the vacuum advance working (if it's used, some carb people don't like it).  Also, are you using a stock cam or performance-modified?  If the head's been swapped,who knows what's up there.

 

If you're short on money, troll the used book stores for books on tuning Holley carburetors (they exist), and basic internal combustion engine principles.  Or do the same on the internet.  You're missing a lot of basic knowledge, in addition to the tools you need for tuning.

 

Did the Holley 390 come with the Arizona Z Car package or were the two parts pieced together?  Here's some text from the AZC site - maybe you're in this boat -

 

"The recommended carb is a Holley 390CFM (model 4160 part# 8007) , normally NO rejetting is required on these.
Use a brand new one (about $300) as a rebuilt one will NEVER run right, cause nothing but aggrevation, and cost you many many times the $100 you thought you were going to save in trying to trouble shoot it."

 

Just some basic thoughts.  You're starting from way down the knowledge ladder.  I've been there and you can do damage if you're not careful.

Edited October 24, 2013 by NewZed

[beermanpete]

You did not mention what type of ignition you have. If it is still the stock breaker point system you can "dead time" it using a test light or other simple test equipment you might happen to have.

[Onion]

10% better gas mileage from retarding timing seems odd.  Tuning your engine with a vacuum gauge is not common, you only see what's happening at idle.  Popping from the intake can be a sign of a lean mixture.  You should be able to make it run smoothly within a pretty wide range of initial timing settings, like 5 to 20 degrees, so using the shop's setting and focusing on carb tuning might be your best option.  Learn more about your distributor's advance characteristics - how much centrifugal advance (check the weight stamps,see if the springs have been messed with, make sure it works smoothly), and is the vacuum advance working (if it's used, some carb people don't like it).  Also, are you using a stock cam or performance-modified?  If the head's been swapped,who knows what's up there.

 

If you're short on money, troll the used book stores for books on tuning Holley carburetors (they exist), and basic internal combustion engine principles.  Or do the same on the internet.  You're missing a lot of basic knowledge, in addition to the tools you need for tuning.

 

Did the Holley 390 come with the Arizona Z Car package or were the two parts pieced together?  Here's some text from the AZC site - maybe you're in this boat -

 

"The recommended carb is a Holley 390CFM (model 4160 part# 8007) , normally NO rejetting is required on these.

Use a brand new one (about $300) as a rebuilt one will NEVER run right, cause nothing but aggrevation, and cost you many many times the $100 you thought you were going to save in trying to trouble shoot it."

 

Just some basic thoughts.  You're starting from way down the knowledge ladder.  I've been there and you can do damage if you're not careful.

 

I got the vacuum gauge to tune the idle mixture after watching all the Holley videos on how to tune the carb properly. They say that the a bad idle mixture will make it run poorly throughout the rev range. 

 

I'll definitely get a timing light. I know I need one, but I read that you can get pretty close by ear, which is what I did in the meantime. I'll do some reading on distributors and poke around. The vacuum advance on mine doesn't work, so I'm running mechanical advance. I'm not sure what the cam is, but based on the characteristics, I believe it to be a Stage 3 MSA cam, or something similar. The head is the original E88 head, but the previous owner claims it has been ported. Who knows, maybe he even shaved it. I'm trying to get my hands on a different head (more details on that when I meet up with the guy). 

 

That's the reason I don't post very much... I pretty much just read and read and read. I've learned a whole lot, but I've got a long ways to go. 

 

I've read that from AZC, my carb and intake were sold separately, but both pieces were brand new. 

 

You did not mention what type of ignition you have. If it is still the stock breaker point system you can "dead time" it using a test light or other simple test equipment you might happen to have.

 

Slipped my mind... Pertronix Ignitor and Pertronix Flamethrower 3 ohm coil. 

 

I'm thinking of getting this timing light... Not the cream of the crop, but I can afford it and it (probably) does the job well enough for me to use it a couple times. Any thoughts?

 

http://www.amazon.com/INNOVA-3551-Inductive-Timing-Light/dp/B000EVYH72/ref=sr_1_1?ie=UTF8&qid=1382647805&sr=8-1&keywords=timing+light

Edited October 24, 2013 by Onion

[Chris83zxt]

The harbor freight adjustable timing gun works fine and is cheap.

[HowlerMonkey]

Yep.....bought one after having my second snap on digital display timing light stolen in a 13 year period.

 

One thing to do with the harbor freight gun is to test it against a couple of other "advance timing lights" to see if it's close as I had to pull off the knob and move it over one slot to get it perfect.

[Onion]

I don't have a light to compare it to, so I'm going to cross my fingers and hope that it works properly...

 

I bought the $30 HF one and used the 25% off coupon. Seems like a decent light, and the price was good. 

[Onion]

Just to update this... I did a rough timing and primary float adjustment. Primary is a hair too low, timing is 10 advanced on idle and about 30 at speed. It doesn't bog down anymore or hesitate when I go WOT, but only when it's earn warm out. I'll finish my tune in between school and work today, hopefully that cures it.