A little timing help ??

Guys,

My first Chevy engine build and I seem to have an issue with the timing. After setting the initial timing at 12 degress BTDC (it seems to settle in best here with about 17 lbs. of vacuum) and adjusting the idle at 800 RPM, when I go off idle (rev it with no load) I get some pretty serious popping out the exhaust. Almost sounds like a backfire from the passenger side cylinder bank.

I went through, using a write-up from this board, and lashed all the valves turning the dampener 90 degrees at a time and taking all the slop out of the push-rods + 1/2 turn.

For the record, engine and cam specs are as follows:

Chevrolet Gen 1- 5.7L
Stock bore 4.00
Stock Stroke
Edelbrock RPM intake
Holley Commander 950-700 CFM Fuel Injection
MSD ignition box and billet distributor
Cam: Intake: .420 (at Valve)
Exhaust .443
The cam card is showing "Max Lift" at Intake: 109 ATDC, Duration 204 and Exhaust 117 BTDC and Duration 204.

I've put this engine into a '94 Jeep Wrangler with an SM465/Dana 300 Transmission/Transfer Case combination. It almost seems I have too much timing immediately off idle. The distributor is mechaniocal advance and I'm not sure which springs are in there for timing advance nor do I know what total timing is at a specific RPM.

Any advice on what to look for with this engine. I've built a number of Ford FE blocks over the years and I know they like a lot of timing early. Not sure what this engine/cam combination is looking for, if indeed, that is the issue.

Thanks for any and all help/ideas you guys might have in terms of what to look for or experiment with.

Mike

A few things come to mind for you to check.
Is there a vacuum advance on the distributor and is it hooked up to a vacuum source - should be.
Are the plug wires installed correctly? Firing order is 18436572. Sounds like you have the #1 wire installed correctly. Driver side plugs are 1357 and the passenger side is 2468. The wires on top of the distributor should match 18436572 in a clockwise direction viewed from the top.
If all is correct, re-check the valve lash. Warm the engine and have everything ready to go. Pop the covers off and back off the valves 2 full revolutions. Place the engine at the #1 TDC and check the distributor rotor pointing at the #1 wire. Adust the following valves:

Intake: 1, 2, 5, 7
Exhaust: 1, 3, 4, 8

Rotate the crank one revolution until #6 TDC. Adjust the following valves:

Intake: 3, 4, 6, 8
Exhaust: 2, 5, 6, 7

Finger roll the push rod until zero lash (NO movement) and go one half turn. Once set - leave it alone because the lifter will start to bleed down. If you do then the valves will be open at ignition and causing that popping noise.
Should fix that popping problem.

you probably should have a dist without any advance for a fuel injection system

18436752,

Thanks for the reply. I'll walk back through the firing order and will re-lash the valves. My distributor is mechanical advance, so the vaccum is a non-issue for me. I'll let you know of that fixes it.

Jerry,

Not sure what you're trying to tell me about not needing any advance with fuel injection. I'm using an MSD to control spark, not the FI-ECM. Can you clarify what you mean ?? Thanks.

Mike

yes---all the electronic fi systems control fuel and spark---they do not use mech advance----lock out the advance in your dist and it will run

Jerry,

I understand now. Don't I need to give the EFI some sort of reference as to where the engine is in in it rotational pattern ?? The reason I ask, the engine does not have a crank trigger and I'm not sure where it would get that signal. I realize I'm showing my ignorance here but this is, also, my first foray into EFI on an engine I've built.

I'm assuming, I'd need to lock out the ignition box as well ?? I think I understand conceptually, what needs to happen. Not sure of the reality. Can you give me an idea as to what needs to happen ?? Thanks.

Mike

Call Holley or read your directions

Jerry,

I was reading through it last night. I'm checking with Holley and MSD but it looks as though I'll need a different distributor to be able to control timing. No worries. Thanks for the help guys. Mike

you should be able to lock out your MSD distributor... I don't know the specific dist you are running but here is mine (p/n 85551) they have instruction manuals for all their products at Welcome to MSD Ignition

good luck,

-Chris

Guys,

Thanks for everyone's help !!! I'm going to eat a little crow on this one. Feel free to have some fun with it.

Went back through and re-set the valve lash on everything. Restarted, same popping noise. Played with idle timing and still the same issue. Was taking the distributor cap off and the plug wires looked weird. Long story short: I had wires 2 and 7 flipped and firing in reverse order. So I had it firing 18346527. Swapped the wires, fired right up and accelerated smoothly off idle to half throttle.

Target is currently on my back. LOL. Thanks again guys. sometimes it's the little details you overlook, even after someone points it out in the first response.

Mike

Also, the Holley manual has this info:

Installation Notes
The programmable timing feature of this system is available either by: 1. Using one of the following distributors: 1980–1/2 through 1990 GM 7–pin (coil–in–cap); 1984–96 GM (external coil); 1984 – later Ford 7–wire TFI. Use wiring harness adapter P/N 534–47 for GM istributors and P/N 534–48 for the Ford distributor.

You are certainly truthful and a real man for saying it. We have all made mistakes. I am glad you are running smooth.