I tow a 40' tripple axle trailer with a 33' 9000 lb boat on it with 2 150 gal fuel tanks in it. Figure max load around 14000lbs. Been towing it for over 3 years. Never seen any black specks, silver or gray deposits on my plugs. 20 years ago I would have run a totally different curve. Empty I use 3 gears now 3, 4 and 5 th.
I have gotten as good as 12 MPG towing the boat. I just got started lots to modify yet still stock duraspark II ignition box, stock exhaust manifolds. Truck has original 82K on it.

 

Have to agree with Bear 45/70. 20 deg is way, way, waaaaaayyy to much initial timing. You may be seeing 20 deg with the vac advance hooked up, but static should be 8-10 deg, maybe 12 if you run good gas.

I'm guessing you either have a timing chain that's installed on an offset or a cam with a ton of overlap to bleed off cylinder pressure. Otherwise, that much initial timing is a sure bet for inevitable 'dynamic dissassembly' of your powerplant.

*Edited to add* Just looked at your sig and saw you have an 86 vintage truck. Now the pic becomes clearer. You have the 8 deg retarded timing set. No wonder you can get away with that much initial timing! If you had the straigh-up timing set you would have already grenaded the engine.

Brad

 

Havent got vacuum advance. If I did it would be timed port. Vacuum adv is the last thing I will mess with. What inital advance do you thik most of todays FI engines run once the spout is connected. The SBCs in my boat now run 20 inital total of 34. gets me up to 65 in rough water.

 

The SBC's in your boat are also tuned for constant RPM marine running and have a totally different timing curve than is recommended for the street. Marine tune leans more towards constant speeds in a fairly narrow RPM range. It might very well get you to 65 in rought water, but the last time I checked the engine demands on boat are totally different that a truck towing a boat.

Brad

 

A boat and a truck towing are a lot closer timing wise than a car. A boat runs higher RPM constantly than either and if timing was going to burn up an engine it would do it in a boat much quicker than either a car or a truck.


Basicly old school gas started burning fast then slowed down requiring less inital advance and more in the distributor.
Todays gas starts out slow then speeds up requiring more inital and less in the distributor.

Both my truck and boat were timed much as you sugest when purchased. The truck got 6 MPG at best towing a 4000 lbs boat. Now does 12 at 14000lbs. I bet you bairly get that empty. Not trying to be offensive here just trying to make a point. I an not any kid either been building engines for 40 some years. Also have spent the last 16 designing heads, blocks, cams, cranks, pistons, rods ,feads, intakes, exhaust manifolds, oil coolers, oiling systerms, turbochargers, ballance shafts, rocker arms, valve trains and more.

 

Gotcha! your "old school" gas was higher octane due to the addition of tetraethyl lead. Higher octane equals higher ignition point. Harder to ignite. After ignition the flame front propagation speed of "old" gas vs "new" gas is, for the purposes of this thread, the same. And today's "new" gas, being rated a lower rating and thus being easier to ignite, requires less advance at a given compression or you get into preignition problems.


That's an awfully big claim. Care to back it up? And by the way, a real automotive powertrain design engineer would not have felt the need to dream up such a specific list. That's what benchracers do.

And balance only has one "L", mr engineer.

Try again.

Brad

 

Harder to ignite requires a hotter ignition not advance. I will be the first to admit I cant type or spell. I am not an engineer I am a designer.

 

BBF250:
have you looked at Crane's Street/Strip distributor? It has multiple mechanical and vacuum advance curves. I agree with Brad on the timing thing for towing. I run 12 initial and a total of 34 on all in around 3500 when towing. With the Crane dist though I can change my all in to 3000 for running around when the truck is empty. Anything steeper (advance) and I start getting pinging on pump gas.

 

The rate of advance is a different issue. I could change my rate of advance and have the same problem with pinging.I have looked at the marine Crane distributors and didnt like there curves. Was there one though that could be modified by a computer. Dont remember now. In my boat I have two Mallorys converted to Petronics electronic although both have YL tags one has a YT advance system the other is a YL. The YL has a set up the YT cant duplicate. Its given me headaches. They are set up with the same amount of advance but I cant duplicate the same advance curve in both. Because of this engine with the YL is a bit stronger than the other. The YL hasa compound curve the YT has a liner curve and cheeper guts.

 

I worked on recreational boats for a living and was also a paid mechanic on several offshore and tunnel boats plus own my own tunnel and did all my own work and have forgotten more about boat engines than you will ever know and you are wrong. I've built and maintained race motors for others and myself and have several speed records and championships to my name. You have just been lucky to not fry your boat motor is you cruise with it at all. Under pure race conditions where you idle or run WOT an engine will live with what you say. But for a recreational boat, no way will they live with you recommendations. The only marine engine that ever ran 20° initial were the OMC 2.3 Ford motors and they ran 20° in the car motors too. Your claims of designing engines doesn't fly if you use your timing specs as even EFI motors don't go there with computer controlled timing. Oh yeah, and "bairly" is spelled barely. I never heard of a non-degreed designer for engines. Your degree has got to be in EGO as it sure didn't have a spelling requirement.

 

Sir, after reading your post several times could you restructure and puncuate it better as I find portions of it more difficult to understand than my poor spelling and typing.

 

Bear, I notice he still hasn't backed up his design claim with any verifiable data. Want to just call this thread done and stop wasting our time with him?

Brad

 

Works for me.

 

Neither have either of you. Bear's posts measured on Brad's ratings makes him a bench racer too. I dont see were you have proven any of your claims either. I saw the brick wall you have built around your limited comprension on your first attack on my person. LOL
At least my first inovative design (the drawings for wich sit 2 feet from me) was a major reason Dan Gurney won the Indianapolis 500. Not a boat race were you spend thousands and win no real money.

 

Our claims are based on several decades of proven automotive performance tuning.

Yours...?

Brad

p.s. - It's spelled "comprehension" and "innovative" and "which".

p.p.s - If your drawing is so innovative, scan it in and let's see it.