Charging System for Big Block

LURCH

I bought a couple of the 990 Generac engines that were sold on this forum several months ago. The big question is they don't have charging systems on them and I was wondering if anyone had ever put a car alternator on any big block and made it work. I can buy the parts to change them over so they will charge a battery but it will cost about 550.00 for parts.
I though about using the factory starter/generator but with 9.8 to 1 compression I don't know it that would work. If anyone has any info or ideas please post or P/M. Thanks again for any help.

LURCH!!!!!!!

BGW

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pachanga90

You can use a GM 10SI(1970? thru 1986) Either get one with a 1-wire conversion,or get one from an auto-parts store and wire it yourself.I can't remember which terminals of the 2 on top get connected to which source(been 15yrs.since stock-car racing)but we would hook one to key-power,the other ran to the back of the alt.to the batt.stud..Then run 10ga. wire from the batt.stud to batt.positive.The standard is 37amp,the better was 63amp.The one-wire units run about $100 or so,the reman stockers are anywhere from $40-up.I think a 37amp will be fine unless you have a bunch of extras on the cart.Hope this helps.

sho305

Yep that is the ticket for low buck car alternator. Far as the stock gen it will turn over a V twin because they have a compression release. It works fine on my milled head 15hp clone single, and a single should turn over harder because the cylinder is larger. If you put a perf cam in the engine without the comp release, then you can run into problems. If you put a light alum flywheel on the engine that will also cause problems. If you advance the timing a lot that can also cause issues, but if you turn the ignition off until it is spinning over then on it seems to work ok. You can also just use the stock gen to charge and not start with.

LURCH

I have a mid 90's alt. off of a V-6 S10 would that work?

I didn't know the Generac's or any of them had the compression release and just didn't think with that kind of compression the stock unit would start it.

Thanks again guys I'll decide which route will be the easiest and hopefully get started in a couple of weeks. I still have to buy the intake, carb, clutch and the stuff to build the header. At least this saved me about 550 bucks.

LURCH!!!!!!

sdub1

Lurch, I also am setting up these generac engines. I would like to run the Yamaha starter/gen, however I too do not think it will spin these large 990cc Generacs as they do DO NOT have a compression release. My simple math says FAT CHANCE! Factory engine approx 300cc with 1 piston firing per cycle VS 2 fat 495cc holes firing. I have looked into electric compression release system but they are way to much$$$. So for now I have bolted the generic starter back to the engine. I have found a used stater and flywheel for charging and I will idle the engine.

sho305

Some generator or special use engines may not have compression release, most lawn equipment does though with electric start only it may not. My single 420cc spins over just like the stock 285cc or whatever it was. Incidentally the stock G9 does not have a compression release I know of, it has zero ignition timing at idle to help. Usually you can look at the rocker when you turn it over by hand and see it bump up, or feel it turn pretty easily by hand or have a really short compression stroke. Another issue is they don't like to idle really slow as the release kicks in, but you can enlarge the valve lash to lower the rpm it works at. I've only seen external comp release on motorcycles they have a valve on the the cylinder.

sdub1

My g9 starter/gen seems a little weak when starting but charges fine . Sometimes it will not spin the yami engine if its up against the compression stroke, I must re press the pedal to get it spinning. As for this Generac, I can barley turn it by hand at the clutch when it is up against the compression stroke. When starting, it seem to fire off violently on the first few hits and is fairly smooth at a some what low idle through to the top end.

sdub1

Here is a link to the only compression release that I can think to use automaticly when starting.

http://www.ebay.com/itm/S-S-Electric...e0fe44&vxp=mtr

pachanga90

You can wire in a switch for ignition-kill,get it turning-over then hit the switch.I did that on my Opposed,but it was so I could shift it faster in bad situations on hills(change direction on the shifter,hit the switch,soon as the engine starts to drop off,it shifts and hit the switch again quickly,it will refire with the trans in the opposite direction).The mid-90s' alt won't work,its' computer-controlled.It needs to be the early 70s' thru 86'.Look up one for a 84' Chevy C-10 Silverado w/V8 and A/C for the 63amp,look up same truck in a lower trim level w/V8 and No A/C for 37amp.Most of the Big-Blocks such as Briggs run 20amp or less from the factory so the 37 should be more than enough.Hope this helps.

LURCH

Thats good on the Alt. I was just thinking its a lot smaller.

LURCH!!!!!