Visit our Popular Forums

PeterH-350LE · 04-19-2003, 09:08 PM

here is a good one:
I had to use cylinder #5 to set my timing.
Why?
Hint: Could have used #8, but was to hard to reach.

wb13798 · 04-19-2003, 09:14 PM

why bother with cylinders. a friend of mine uses a glass of water sitting on the breather cover. dont understand it but the silver weenie likes it. lol
al

thenewkid64 · 04-20-2003, 07:35 AM

My guess is that #5 TDC is within 2-3 degrees of TDC on #8 So it would work to use it and set the timing according to the strobe at 0 degrees of advance?

Or that #5 TDC is 180 degrees opposed from #8TDC so you can check the timing from underneath?

I do not have a big block manual, so I am guessing at firing order. I am more than likely wrong on both of them...............

My question is how in the heck do you get the strobe on the flywheel so you can check the timing in the first place.

jim8860 · 04-20-2003, 07:54 AM

I just had the same thing on my MH. The reason you have to use #5 spark plug or #8 is because the motor is time at "top dead center" or TDC . Every motor has a spec and is varries from year to year and motor size plays a factor as well.My 95 LY was a spec of 4 deg BTDC and I have to "pull" a wire to set the motor in a "service mode" . Back to the reason of the #5 plug wire. Normaly you use the #1 wire but when you do you need to read a point that on top of the motor but on the MH there is no way you can see it. The factory mark is now move off the the lower sides on the bottom of the moter no longer the top of the motor. Now you are on the bottom now you have to make a "false #1" cylinder so you can time it to the factory specs.To sum it up in a nut shell every motor has to be set a mark , so from what I now every one uses the #1 cylinder at TDC (that means the piston is at the top of its stroke and all the valve on the #1 cylinder are closed) so the distribtor can be deg. (ex. 12 deg.) to the opening and closeing of the valves so the spark plus can fire at the right time.Hope I made some sence . Jim

jim8860 · 04-20-2003, 08:05 AM

The # 5 is not 180 deg out. and the #5 and # 8 share the "stroke"in the motor so the motor runned "balanced" . The B.B. and the S.B. Chevy motors share the same firing order. 1-8-4-3-6-5-7-2. and the odd are on the driver side 1-3-5-7 and the evens are on the pass side 2-4-6-8. To do timming is a two person job. One on top to move the distibtor and one to use the light. Also what year MH do you have?. If its F.I. you need to pull a wire to set the timming. Also the mark is on the harmoic balancer not the flywheel.

PeterH-350LE · 04-20-2003, 08:09 AM

Jim got it.
The timing marks for #1 TDC are present but inaccessible, so they added another timing mark on bottom.
Since that timing mark is 90 degrees from the factory one and the firing order is 1-8-4-3-6-5-7-2, cylinder #8 or #5 have to be used for timing.
The best way to time a big block is to drive it under load and have a second person adjust the distributor and stop short of pinging.

59toaster · 04-20-2003, 12:37 PM

Quote:

Originally posted by PeterH-79MH
Jim got it.
The timing marks for #1 TDC are present but inaccessible, so they added another timing mark on bottom.
Since that timing mark is 90 degrees from the factory one and the firing order is 1-8-4-3-6-5-7-2, cylinder #8 or #5 have to be used for timing.
The best way to time a big block is to drive it under load and have a second person adjust the distributor and stop short of pinging.

I agree with this up to a point. The point is mid 80's when GM started using the HEI with a Knock sensor. I know that on the small blocks it had it in 85 maybe earlier. Not sure if it kicked in at the same time on the big blocks. If it has FI it has it for sure.

Now you can bypass it and do it that way I would guess. Just be sure it has freash gas when you do it or you may end up with it to far retard once you run through the stal gas.

If you do this with a knock sensor then the timing may always be retarding on it's own and if you get a bad tank of gas with unusualy low octane it can't do it's thing properly.

87MH · 04-20-2003, 05:30 PM

Just checked the timing on the '87 454 last weekend., it was dead on at 4 degrees BTDC with the vaccuum advance device on the distributor disabled. The No. 5 plug is a little more difficult to get to than the No. 8 due to the air baffle and the brake master pump assembly on the drivers side, but the access to the timing mark is easier off of the #5 cylinder. The absence of points makes the requirement of constantly adjusting timing obsolete. (Praise the Maker.)

Mine is the year just prior to FI, and the SMOG equipment is a fairly intricate array of intake controls and blowers adding pressurized air to the exhaust manifold., so I feel that, as long as all of the engine jewelry is working, Iwill leave it at spec settings instead of a more high performance tune job.

The removal of the drivers side wheel makes everything MUCH more accessable, also, don't pass up the opportunity to check the level of the brake fluid as long as the wheel is removed.

59toaster · 04-20-2003, 07:00 PM

Quote:

Originally posted by 87airstream345
Just checked the timing on the '87 454 last weekend., it was dead on at 4 degrees BTDC with the vaccuum advance device on the distributor disabled. The No. 5 plug is a little more difficult to get to than the No. 8 due to the air baffle and the brake master pump assembly on the drivers side, but the access to the timing mark is easier off of the #5 cylinder. The absence of points makes the requirement of constantly adjusting timing obsolete. (Praise the Maker.)

Mine is the year just prior to FI, and the SMOG equipment is a fairly intricate array of intake controls and blowers adding pressurized air to the exhaust manifold., so I feel that, as long as all of the engine jewelry is working, Iwill leave it at spec settings instead of a more high performance tune job.

The removal of the drivers side wheel makes everything MUCH more accessable, also, don't pass up the opportunity to check the level of the brake fluid as long as the wheel is removed.

You chassis is probably 86 production then. The chassis was proably at the plant several months before it was completed. Since it was an incomplete chassis it get's the year of completion on the title. 87 Is the first year of FI on GM Trucks.

They really cleaned up that vacume hose nightmare with the FI. I litteraly have 4 Vac hoses, the plumbing from the air pump, Control valve for the Air pump, intake for the air pump and a couple Vac control valves on my 88 454 Burb. It looks barren compaired to my 79 350 Blazer that didn't have the Air pump at all.