Guys,

While at the track this past weekend I caught wind that there was a change made to the 400 block with regards to the keyway locating the balancer.

If compared to a 350 balancer, is there a difference in location? Or after a certain year did they change the 400 keyway location?

Sorry for being so vague in the question. But any information about the similarities or the likeness would be appreciated.

Here is the reason for my question: My car likes TONS of timing. 40+ degrees! While Corkys car is down at 28* total timing. The cars run nearly identical on any given day, so the power is equal, but why would mine want sooooo much more timing? I gave it what it wants and from dyno results also verified its at its sweet spot. So I know its dialed in.

At the track this weekend it was brought to my attention that there was a design change to the 400s over a certain year that moved the keyway ~12* retarded. That would make perfect sence then with my car. The keyway being off 12* or so would put me at a true 30* of total advance. Much more reasonable.

I have to believe that something is screwy that is making my car want so much timing.

Thanks. :cheers:

 

I don't know about advance, but the balancer should be weighted to account for the 400sbc crank... it may have something to do with that as well?

:lurk:

 

My entire assembly was balanced with the balancer (which I thought was the stock balancer) to less than 1/2 gram.

I am thinking maybe the balancer was picked from a different year motor, and the keyway to 0* mark is off by the alluded to 12* mark. The guy that mentioned it to me was not 100% sure of the date changes and the specifics.
:lurk:

YOU KNOW what else.....a friend of mine is having a problem with his new 400 block and gllowing headers, a key sign that there is too much retard in the timing, and fuel is burning in the headers. Maybe his base timing is really off from what he thinks due to this also. I was just fortune enough I guess to move the timing that far forward and achieve the best timing mark, since its way further than I would normally recommmend someone to advance the timing, with everything normal.

Thoughts? :cheers: :confused:


[Modified by ski_dwn_it, 2:11 PM 7/28/2003]

 

Can you remove N0. 1, plug rotate the engine by hand, and by poking a stick in the plug hole estimate TDC. Then look at your timing marks. It won't be all that accurate, but it will tell you if you're on the right track.

 

Yeah....Thanks. I am going to do that as a last resort, but turning this critter over at 11.8:1 compression is easier said than done, and confimation of this information would be much easier tahn pulling all the plugs to make the before mentioned easier to do. But yeah I will also do that. Unfortunately the car is in NJ getting the roll bar installed, so it will have to wait till later for the verifying.

I figured a few here might have a clue.

 

I understand.
:)

 

jesse when we degreed the cam we would have caught that :cheers:

 

This isn't much help - but it confirms the possibility:

Years ago I read a magazine article or some service manual indicating that the timing mark on the balancer isn't necessarily set at TDC. It was set up so that the tune up guy just sets it to that mark at idle. It kept any thought from entering the equation. So what year or motor? Don't know. The only positive fact is that it related to GM products.

 

But the balancer wasn't on it then. I agree that the cam is degreed in properly, and the car is running perfect, but if the keyway was off 12* inside the balancer, its possible the shown 0* mark for that balancer could be off 12* with the true TDC of the crank.

Remember I bought that motor, crank, balancer used. That balancer might not have even been the original for that motor.

This is the only logical explination for the difference we have in timing. Unless my balancer slipped on the inner part. But I inspected the balancer and it was not in bad enough shape for that to have happen.

I think the keyway on the crank is OK. But not on the balancer. It our cars were not such SOBS to pull that on. I would just take it off and line it up against the 350s to see if there was a difference.

When I adjust the RRs I will take the needed time to verify that the 0 mark is truely 0* on the balancer. I suspect its off about 10-12*. As there is no way I am running 42* of timing. 36* or 38* maybe but not 42*
:lurk:

 

I can't help but think would have noticed a 10* plus shift.

Pull the dist cap, line up the bug with number one and look at the timing tab...

Is the line on the 0* mark?

Add a timing tape to the balancer(available at any speed shop) put Zero on the line on the balancer and and then fire it up and look at the numbers with a timing light...

What number on the tape lines up with the zero mark on the tab; at idle, at 2500rpm?

 

metalsphere,

It would be real easy to miss. When you set your base timing you really have nothing else to go by. If the keyway in the balancer is off 12* your base timing about be off by 12* then. There is really nothing to reference it to. Sure you can pull off the cap, but that is really just a judgement call when eyeballing it.

The best way to know for sure, and something I will do if no-one can offer a good source of information on the question. Is get a piston stop. Put some tape on the balancer, rotate the engine forward till it stops, note the degrees. Rerotate the engine back the other way, and again record the degrees. Divide the difference in 1/2 and bingo you have TDC. Now if that is at 12* then the keyway for the balancer or something is off. If its at 0* then I have a freak of a car that likes a bunch of timing, and I can't explain it LOL.

Its something I would like to learn if the keyway is possible off from the factory. As it could screw a bunch of other people up, as I mentioned my other friend that was having the glowing headers.

When degreeing the cam, as corky said would have been the best time to identify the problem. But the balancer was not installed at that point and hence the reason it could have been missed. Hind site always is 20/20.

I am just fortunate enough to have advanced the timing enough to have found the sweet spot, regardless of the number. If I had this timing back 12* more, It would be like a turd going down the strip. At the dyno I turned it back 2* and it lost all sorts of power.

:lurk:

 

All 350 and 400 cranks have the keyway in the same place and it is the same with balancers.

Jay

 

The cranks ARE the same, but how do you tell if the damper keyways are in the same spot? I DO know that different dampers are marked with their timing marks in different positions (relative to their keyway). Why do you think they (even Chevy) sell different timing tabs? The damper mark- timing tab orientation, could be the whole difference between the amounts of advance Corkie's and Jessie's engines, seem to prefer. Good luck, and...

RACE ON!!!


[Modified by CFI-EFI, 8:59 PM 7/28/2003]

 

CFI_EFI.

Exactly what I am trying to point out. How do you know that the keyway to the mark on the balancers are the same? Unless you pull off each balancer, you really have no clue.

Unless of course you do what I am going to do when it gets back home from having the bar installed. I searched the net for the past day and found nothing that was valuable.

I am betting its either the keyway inside the balancer was off, or the timing tab I bought was off (but I know I held it up to the stock timing cover and it was dead nuts the same. So I think I can, with confidence, eliminate that possibility.

Man I can't believe I did not look at that balancer closer! :rolleyes:

 

Jesse, the only way to do this accurately is to do what you described above with the piston stop. Even if all dampers are the same, you dont know if the one you have has shifted or not. Really can't tell buy looking it.

 

You cant change where TDC is on the crank so the Balancer is allways going to have TDC mark at the same place, it can be off -1* or +1* that is why they make taps that you can movie, but it can never bee 12* off.
If you can get your engine on TDC then you will see that the Ballancer is going to be on TDC too or 0*.

Jay

 

Jessie,

Get or make yourself a piston stop that you can thread through the spark plug hole. Rotate the eggine until it hits the stop. Mark the damper at the zero indicater on the timing tab. Reverse rotate the engine until it hits the stop, again. Again, mark the damper at the zero mark on the tab. The TDC mark on the damper SHOULD be exactly half way between the marks. If not, the outer ring of your damper has rotated. In any case compare the half way point between the marks, to the zero on the tab. If the half way point isn't at zero on the tab, the tab is either wrong for the application or needs adjusting. This method of checking, checks for BOTH potential problems. You may have, one, both, or neither. Have Corkie do the same. For consistancy, each of you should assist the other. I suspect both of you have a problem to one degree (pun intended) or another. The need for 40*, total indicates some combustion inefficiency. A lot of Chevy engines "like" this kind of advance, but a good combustion chamber and squish area, should yield best power with less advance. While 28*, total can be good, it's awfully low. Good luck, and...

RACE ON!!!

 

Thanks CFI.

I will try that as soon as I get my engine/car back from neverlift :D

I will let you know what I find.

I agee with your statement about cylinder ineffieciency = 40* timing, but I highly doubt that is the case with my motor, as far as being ineffiencient. That is why I am questioning the accuracy of the timing method.

I will definately post results when I get the car back this weekend or next week, depending on how much time I have.

:cheers:

 

Whenever I degreed a cam, I always degreed the balancer afterwords. The small block is notorious for spinning the outer ring. I have found the tdc mark as far as 8 degrees off one one of my engines. I then remark the tdc and 38 degree position. Plus it's a lot nicer to do it while still on the engine stand.




[Modified by jimtreber, 5:35 PM 7/30/2003]

 

Jim,

I hear you. Wish we would have done it to mine as well.

Engine stand work is much much better than over the fender sweat in the eyes, trouble light burning your arm, wrench slipping, knuckle busting, back breaking, hard seeing, trailer talk generating work that in the car work affords.

But at the end of the day you learn from mistakes and another balancer will not be installed on any engine without first checking this out.

Its really not a big deal for me at this point, but rather its just a question in the back of my mind that I want to answer. I know the cam is degreed correctly and the timing for performance is where it needs to be.

:thumbs: :lurk: