thinking of exploring another option

[Carlb]

I just checked the specs. 4 inch bore, same as a 350 or 302 chevy. I havent time to check if the piston pin height is the same yet but it sure would be easy to find high compression pistons if...   And the way GM 'parts box engineered' stuff I think it's likely that we can fit 350 pistons  12 1/2 to one, anybody?

Why stop at 12.5:1  when 15:1 are available.

[TimSR2]

OK I found it. It's half of a Pontiac 301.  So the  151 Tech4 is actually a Pontiac, and is NOT the GM 153 Iron Duke that is used in Marine outdrives. The original Iron Duke was a Chevy II engine, based on the early stovebolt 6 design.    Back to the drawing board guys, there are no off the shelf marine manifolds for the 151. 

[mobile_bob]

i don't want a marine manifold, in my opinion they are not efficient enough,
all they were made to do was cool the exhaust enough to keep the boat safe from fire hazards

bob g

[Tom T]

The Iron Duke was used in boats they used a different cam than an auto but they were the same block I know of more than one that has been used out of boats and the other way.Tom T

[Henry W]

Another engine that is often overlooked is the Engine 2.3 four cylinder engine that is used in the 240 Volvo.It is the B230F. My wife and I both have 1993 240 Volvo's and they have been the most reliable cars period.
My sedan has over 286,000 miles and my wifes wagon has over 310,000 miles. Both engines have lots of life left. These engines have been known to last 600,000 miles. The reason the engines last so long is the high nickel content in the block and the oiling system. The compression ratio is 9.8 to 1 so this might be a good engine for LP and natural gas for engines in the 2.3 L. class. another thing is there is lots of them becoming available in the bone yards. They are a very easy engine to work on also. Another thing is the timing belts last a long time I replaced my wifes belt over 170,000 miles ago and it only takes 30 min. to replace. If the timing belt ever breaks the valve train will not get wiped out because it is a free running engine design. This engine has a taller deck height than most compareable engines and the crank to rod angle is also better than most. This will mean longer burn time near TDC than some engines well known engines. These engines never needed an EGR valve to pass emissions so the only smog control was a catalist. They were pretty clean and efficent running engines.

Henry

[TimSR2]

Natural gas is 130 octane, I just checked. Wow! We can push the comp way beyond propane engine territory here.

The ideal donor engine will be something small that had some aftermarket racing support at one time, and cheap and common.  But better if it has small displacement, so we can get better control on the rpm. Even better if hydraulic lifters and pushrods   Cross flow design preferred for ease of getting at the exhaust manifold to build a heatex. Anything that had or has a any use in a racing class that will give us access to the high top pistons that we will need to make an efficient engine on NG.  130 octane should support 13 to one compression ratio easily.

Datsun in the 60's and 70's had a little pushrod job that was based on a British design. Used in 60's trucks, Datsun 1000,, Datsun 1200,   B210 . That was a good little engine, very tiny in size too. Still in production as an industrial engine. Might be a good prospect.

[Henry W]

That Datsun/Nissan pushrod Austin designed engine was built up to 2009 over seas. I know lots about that nice engine. I built one engine using Nissan performance parts I purchased from Bob Sharp Racing back in the early 80's. Any one that wants a 9000 RPM screamer pushrod 1400 cc engine that is a good one to start out with. The engine had to be wound up to 5500 to get the car moving.

Even stock they lacked torque.

Henry

[Henry W]

http://www.datsunhistory.com/Sharp.html

I did meet Paul Newman and talked briefly. He was a very down to earth guy. He brought a lot to racing and he is missed.

Henry

[Tom T]

The Datsun engine is the about the same as used in the MG I know the rocker shafts and some other parts will interchange not sure about all parts but the shafts will.It started out as a tractor engine.  Tom T

[TimSR2]

I rebuilt one in a 66 truck for my buddy in about 84 , it was 3 main bearing design. Datsun dealer wasn't any help so I crossed over the pistons and rings from a Spitfire. That's how I know it's really a british engine. By the way that truck had crank start and was super easy to hand start. Now that might be useful!

There's one on ebay right now, they always turn up in power sweepers,, or apu's for tour buses, always   on propane.  Just search propane engine, there's usually at least 1 nissan 1A on offer

[mobile_bob]

the volvo looks good

so does the mercury topaz 2.3hso engine

http://www.tempotopaz.com/main/index.php?name=Sections&req=viewarticle&artid=35&page=1

iron head, pushrod enigne, looks like a contender to me
they seem to be readily available and don't bring much likely because no one in their right mind is going to repower
a 20 year old dead topaz.

having both manifolds on the same side is a minor issue

there is one here in tacoma for 250 bucks with 46k miles, i think i will go have a look at it.

it looks like the 88-91 engine's had their peak torque at 2200rpm, that makes it close enough for a direct drive generator application.

bob g

[BioHazard]

they seem to be readily available and don't bring much likely because no one in their right mind is going to repower a 20 year old dead topaz.

You haven't met my russian neighbor. I still haven't ruled out removing 4 pistons from the old 350 I have in the corner...

How does increasing the compression ratio effect the overall durability of the engine? I would think low compression engines would be under less stress and therefore last longer...then again diesel engines kinda blow that theory away. I wonder why the Olympian 2.4L LP/NG generator I posted only has 8.5:1 compression?

Let's get one thing straight here though: There is only one Iron Duke. That's the 151 Pontiac. All the 'others' are just random chevy motors that have similar displacements. I don't think any of the others are cross flow.

Edit: I just looked up the specs on the Mercruiser 3.0L engine, which I think is based on the iron duke but never used in cars. They list a 4" bore by 3.6" stroke with 9.1 compression...looks like a stroked 2.5. More torque....

[BioHazard]

Another consideration might be the AMC/Jeep 2.5L engine. It's basically a shortened Jeep 4.0L, which is known for it's amazing reliability and tractor like qualities. 3.875 bore by 3.1875 stroke makes more torque than the Iron Duke, and it's got the same bellhousing. Both the iron duke and the AMC 2.5 have five main bearings.
http://en.wikipedia.org/wiki/AMC_Straight-4_engine

I have an old Cherokee with the 4L inline six version and it's only parked because the CPS sensor went out at 230k. Everything else is original. If I averaged 35mph, that's just over 6500 hours, though I'm sure it's much higher than that.(and I'm certain I could double that with a new CPS) My cousin has one that she's wrecked 3 times and the engine is still going past 300k. I wrecked one myself and pushed the engine back about 3 inches into the firewall. It was still running, though spewing coolant, ATF, oil, and freon. I still remember having to climb back in the wreckage and pull out the key. 24mpg on the highway in an automatic 3500lb vehicle with the aerodynamics of a barn and the A/C on. You guys are making me want to convert my old Jeep to propane....

[Henry W]

the volvo looks good

so does the mercury topaz 2.3hso engine

http://www.tempotopaz.com/main/index.php?name=Sections&req=viewarticle&artid=35&page=1

iron head, pushrod enigne, looks like a contender to me
they seem to be readily available and don't bring much likely because no one in their right mind is going to repower
a 20 year old dead topaz.

having both manifolds on the same side is a minor issue

there is one here in tacoma for 250 bucks with 46k miles, i think i will go have a look at it.

it looks like the 88-91 engine's had their peak torque at 2200rpm, that makes it close enough for a direct drive generator application.

bob g

The mercury topaz 2.3 HSO might look like a nice engine but they are known to crack heads. And I am talking about more than a few. We had a company car that cracked a head. and it took three trips to the bone yard to find a good one. They crack in the exhaust valve seat and up in the exhaust port. Not a very reliable engine in my opinion.

Henry

[Henry W]

I rebuilt one in a 66 truck for my buddy in about 84 , it was 3 main bearing design. Datsun dealer wasn't any help so I crossed over the pistons and rings from a Spitfire. That's how I know it's really a british engine. By the way that truck had crank start and was super easy to hand start. Now that might be useful!

There's one on ebay right now, they always turn up in power sweepers,, or apu's for tour buses, always   on propane.  Just search propane engine, there's usually at least 1 nissan 1A on offer

That engine was and early version. They all changed to a 5 main block after that.

Henry