Tecumseh V-twin talk

So today I finally got my hands on a tecumseh 18 horse v twin and can’t find much information on them online as far as durability and weak points? I know they make a lot of torque and some use them for racing and pulling, but can’t find anything about how strong the bottom ends are and how tolerant they are to Governor deletes.

What I do know, they’re factory dual carbs. Which is super cool. Mine is an 18 horse, 691cc (42 cubic inches). As far as I’m aware, the 18, 20, and 22 hp twins all have the same displacement. And if we’re bench racing, an 18 horse vanguard is only 35 cubic inches….35 cubes and a single barrel carb vs a 42 cubic inch dual carb…hmm

Seems like the tecumseh should make more than it does. But I’m so happy with how the slide carb woke up the 16 horse vanguard (30 cubic inch) on the haspin build, I’m fully planning on dual sliders on this. But don’t wanna push my luck on the stock rods.

Sorry for the long post that’s a little bit of everywhere, but I’m trying to collect the infinity vtwins (think thanos’ infinity stones but with engines). Next on the list, Kohler and Kawasaki. I’m jacking my own thread. Ramble over.

CraftsmanQuad19 wrote:

I’m jacking my own thread. Ramble over.

It's your thread so no harm, no foul!

I know nothing about them but it sounds like you scored yourself a gooder one and I love engines so I'm intrigued!

Anyone have any info on their durability? Or am I venturing into unknown territory?

Unknown territory here...

From what I understand finding parts for these newer teccys is a pain and a half. Can’t speak for durability though, maybe you’ll have to open yours up and educate us

Just had a gander around and just looking from a mechanics point if view.

Looks like the valves and ports are on the small side.
Crank looks like a decent size and plenty strong, also looks like the crank is fairly large.
Head shape looks pretty good, not flat or hemi but very nicely directed to the spark plug.

Seems like decent castings aswell, I like it.

Any engine above 16 hp that isn't Briggs usually is a pita to source go fast bits for.
Kawasaki is my favourite brand and I have an infinite amount of them lying around but the lack of parts is what always stops me

I was thinking I’d do a port job on it for sure, and the dual slide carbs. Some guys race these things with good success, some pull with them. I’m looking forward to tinkering with it and I think I know what chassis I’m putting it in

If I had one I'd definitely tinker with it!

Hey guys haven’t been on in a LONG time, but recently I’ve been messing with one of these tecumseh v twins with the twin carbs, and here’s my experience with it. Incredibly tough, I have mine set to turn almost 7000 rpm, I found that’s where the ignition fails at. Can’t keep up with the engine rpm. As far as sourcing parts Amazon will have almost everything you need. It was 40$ for a set of new carbs. Brand new. Can’t complain about that LOL. I’ve also taken and decked my heads quite a bit, can’t remember the exact amount off the top of my head. I tried carb swapping but I didn’t have anything that was small enough to allow for a proper Venturi effect. So with that I opened up the stock carb throat 1/16” per carb and opened the main jets up slightly with a torch tip cleaner. I then took and advanced the timing roughly 8-10 degrees. Needs premium to not detonate, but it runs damn strong so it’s worth it. The only real problem I’ve been facing is keeping it cool, haven’t figured that one out yet so any input is appreciated. This engine is in a ~1999 or so craftsman lt1000 with an mst-206 trans that has been oil filled. So far I’ve been nothing but impressed with this engine, in my opinion it completely outperforms the vanguard I had in the last lt1000 with similar engine modification. Also I built a 2-1 header and side pipe with muffler insert, it seemingly runs smoother with a header versus true duals, not sure what’s up with that.

I think that has to do with scavenging.

I wouldn’t be too suprised, it’s pretty primitive but should flow decent

Increasing compression increases the heat, run it as rich as possible that it will still run clean to the help keep the temp down as much as possible.

Yeah that should help, I’m also thinking of somehow adding an oil cooler, shouldn’t be too difficult as it’s a pressure lube engine

AWESOME input ZSMachines! Haven’t seen you on here in awhile lol. I’m concerned with the Venturi effect with twin carbs as well. The vanguard single barrel intake is 28mm, so I matched the port with a 28mm slide carb. Runs awesome. I have no idea what the tecumseh carb port size is, but peeking in they looked pretty big. Might do twin 21’s? Roughly 1mm per cubic inch? I’d like to match to the factory intake size but I also don’t want to over carb it.

Found an old thread from guys that raced with these engines and I guess they have small ports for their displacement. That’s why I was wanting to see port the heads. There’s a lot of displacement, so I know the bottom end can move air. Figured if the heads were sized better to the cylinder volume, it might move enough air to put slide carbs on that actually match the intake manifold and not be over carbed.

I love bench racing!

If I remember right the carbs were tiny, like 5/8” bore at the Venturi. Im unfamiliar, what is bench racing? I’m sure porting would do a ton also, I don’t feel like I’ve been necessarily restricted by them though. It makes rpm incredibly quick.

Bench racing, basically meaning to compare hypothetical builds. An unproven this vs that.

Maybe I’ll get time to pull the carbs off mine this weekend and actually start putting some hard numbers on here, but 5/8 would put us at 16 mm, which is definitely on the small side. I thought they looked bigger at the opening of the carb, but the deflector was in the way so I couldn’t see straight through.

The carbs on these are surprisingly small, I know mine felt better after opening them up

Well that’s good to hear. You haven’t had any bottom end issues out of yours though? Stock rods and all?

Yep stock rods, I do change the oil often and run a straight 30 weight if that means anything to ya

I run AMSOIL in all mine

ZSmachines wrote:

Yep stock rods, I do change the oil often and run a straight 30 weight if that means anything to ya

Don't mean to be that guy but running SAE 30 in any climate where it drops below freezing is a no Bueno.

Looked in the manual and while Tecumseh isn't as liberal in oil weights as Briggs they do recommend a 10w-30 or 5w-30 around or under freezing temps.

But then again iam rather A. Nal (that's a normal word in English lit. guys come on) about oil weights.
Especially in Israel where we go from below freezing in the northern areas to scorching desert temps in the south and we tend to service the entire country.
I guess same goes for a forum where the same does not apply to everyone

Apparently tecumseh recommended 5w30 or 10 weight oil below 32 degrees. Source here.

Hmm I wonder if I have the wrong oil cap it’s stamped sae 30 wt right on the cap lol but everyone knows that doesn’t necessarily mean that’s the cap that came on it lol

Well the engine only dictates the oil up to a certain Point until outside factors come in to play.

30w simply can't stand freezing

That’s a picture right on the back of the shroud, and I’m up in nw WA, temperatures get down to freezing during the winter but not for too long normally, I’m not too worried, especially since the oil will only be freezing for about 30 seconds once it starts