454 vs 8.1 BBC firing orders...

[wayne petty]

i ran across this..i know that this odd knowledge will save somebody's weekend sometime in the future...

waynes question... for discussion .. i wonder if this cam when installed in earlier motors.. as it seems to fit.. might be like the cylinder swap used on small blocks to pick up a few horsepower..  hmm???



http://www.enginebuildermag.com/Article/74136/big_block_chevy_cam_identification.aspx

text from short article...


Big Block Chevy Cam Identification

Imagine getting a call from a customer who has just received a meticulously remanufactured 454 Chevrolet engine but who claims it only runs on four cylinders.

By Roy Berndt

While turning the distributor during diagnosis process your customer noticed the other four cylinders would start running and the original four go dead. Now, since it is a big block I truly understood a phrase that my brother always used: "There is no substitute for cubic inches," because it did actually run on either of the four cylinder sets.

In your mind you're thinking "Great, I'm dealing with another guy who is certainly not the sharpest tool in the work shed," but in the interest of customer service you entertain the bizarre possibility that there is something wrong with the engine and not the ignition system. Finally after what seemed like enough time to grow a beard on the phone with the customer you agree to take the engine back into your facility and provide the customer with another one, certainly expecting him to have the same problem as the original.

A few days and hundreds of tasks later your customer calls and says the new engine runs great. You wonder how that can be possible and realize that it is time to get the returned engine on the bench and pull out the CSI tools and find out what happened. Heads are perfect, cylinders good, pistons and rings fine, all the  bearings look great, the timing gear's in time - there is absolutely nothing wrong! You see the camshaft lying on the bench and know there's nothing wrong there...or is there? You pull out another new camshaft and lay it next to the one you just removed and scratch your head, because the two are very different. First thought, this is simple. Somehow a reverse rotation marine camshaft was incorrectly packaged, right? Wrong! Finally you just walk away and right it off to a bizarre anomaly. Then weeks later you read a short blurb about how the firing order on 8.1L big block engines is different than a normal big block. The 8.1L FO is 1-8-7-2-6-5-4-3 where a 454/7.4L is 1-8-4-3-6-5-7-2 as seen in Figure 1.

Despite the differences, however, an 8.1L camshaft will drop right into a 454 like it belongs there - but it will only run four cylinders.

So guess who had the elevator that didn't get to the top floor? It wasn't the guy who called up saying that his engine only ran on four cylinders, that's for certain. If you're in the engine business long enough you'll have those days when you feel like one of those suckers that you used to get after a shot at the doctor's office – I think they were called Dum-Dums.

[Bruce Dorsi]

Thanks, Wayne!

Hopefully, I can remember that info when I need it!

[wayne petty]

i woke up this morning.. got to thinking about this..

the 8.1 cam will work in a non sequential fuel injected motor.


1 8 4 3 6 5 7 2    454
1 7 8 2 6 5 4 3     8.1
6 5 4 3

so it would just be the swap in the firing order to make it work..

its' just a shame that gm closed the big block assembly line forever..

the companies that use them new ordered 2 years worth before the line closed..    they are still building other motors at the same plant..

[tomslik]

i woke up this morning.. got to thinking about this..

the 8.1 cam will work in a non sequential fuel injected motor.


1 8 4 3 6 5 7 2    454
1 7 8 2 6 5 4 3     8.1
6 5 4 3

so it would just be the swap in the firing order to make it work..

its' just a shame that gm closed the big block assembly line forever..

the companies that use them new ordered 2 years worth before the line closed..    they are still building other motors at the same plant..

it STILL could work in a sequential injected eng.
just change the injector wiring to the same as the ignition...