They were marine 8.1 motors set up by a company to run with a carb and distributor and ran on natural gas. Have a 4 barrel aluminum intake and use the same distributor as a 350/454. I'm not sure what all has been changed to make this work. From the research I've done they are there own engine based off the 6.0 and nothing off the 454/502 motors. Seems they have cast internals and no longer made after 2010. I have 4 of them and trying to decide if I should try a build a high HP motor out of them or not. Seems most people throw them away and go to 502s

I can't add much to this, but I do believe the 8.1 has a gear on the cam. I seem to remember having one out when working at a GM dealership and wondering why they bothered, but that was many moons ago.

Dart makes a carb intake, also has provisions for distibutor. http://www.dartheads.com/products/in...-manifold.html

The 8.1 uses same cam type as earlier engines but has a firing order swap.

That's when the aftermarket got more into firing order swaps as the cam cores where more available and cheaper since, again, the 8.1 used it in production.

DArt intake:
http://www.dartheads.com/products/me...manifold_1.jpg

I know you are a mechanic so think about what you are saying and picture the 496/8.1 - at first, I agreed with you in my head than thought, WAIT thats what the little ball bearing reinforced carrier that bolts in for the oil pump is for...

How would you drive the oil pump?

Its all there you just need to take out the oil pump drive gear assembly and swap for a distributor and you are back to a distributor type ignition.

I did a lot of research and talked to a lot of people before repowering the Donzi. Everyone except Ray at Raylar (he was a little biased) said to lose the 496 and go with a 502 based engine. I'm sure glad I took their advice. Those are some unique engines you have there. I'm not sure why someone would think that a carburetor and distributor would be an upgrade though.

It is possible that a carb/intake combo will make more power than a FI setup. On LS motors with the same internals a carb setup will make more power. It is your call, if already have everything 8.1 you need to do the math on parts, combos and costs.

I believe the 8100's were tall decks and had 4.375 stroke cranks GM introduced into the truck line. Which Merc marinized.

Yep Keith Atlanta I remember now since you brought it up. Its been about 3 or 4 years ago to have completely torn down a 496 to the last rod bolt.. I do remember the OIL PUMP DRIVE and one screw / bolt holding it down. Yes it does have to be removed for the distributor placement. You are 100 % correct and I was 100 % wrong about possible no gear on the cam for a distributor app.

One of these days I will tell a story about the biggest lunch eater Mercruiser 496 / 8.1 that showed up back about 6 or 8 years ago. Cam sensor code and ran like a distributor motor 180 out. What a F' in lunch eater.

Next I took the 2 hour seminar from Dart University in person about the all new Gen VII stuff back in Dec 2010 before it hit the market in April 2011. I know Dart has the carb intake manifold with distributor hole mount if needed. That same class should be on youtube as well. They tape the whole seminar and said it was going on Power TV and youtube just incase any wants to look for it.

I personally think it would be cool if someone build up a 8100 Vortec engine, with the intake SB posted, and an overall custom combination.

I say lets start a thread on building up what you have. Maybe Raylar can chime in. Lets keep it old school carbed....throw some cam at it, and have some fun. Please, lets not do another "stroker 454" build....theres already about 100 threads on that topic.

I'm not super familiar with the 8100 engines, but , I think they had many technology advancements over the old big block engines. Like the intake runner design for starters. Isnt it sort of like a giant LS engine??????