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I'm a new user here and having trouble finding the torques specs for a Toro V-Twin 24.5HP engine. It is a Toro model 74790 engine Serial number above 315xxxxxx and below 316xxxxxx Specs I have found says 38 FT Lbs but I know that cannot be correct. Looking at the similar Briggs specs they say 220ft lbs which sounds more like it.

Has anyone out there got any experience with this engine? Thanks for any help!

I see 38 pound feet too.

MParr said:

I see 38 pound feet too.

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When I went to remove the head bolts with a 1/2 impact wrench set at 150 PSI, they wouldn't budge. Had to use a breaker bar to loosen them. They had to be above 180 ft lbs. Does anyone have the head bolt torque specs for a v-twin 24-25hp Briggs, Kawasaki and Kohler? I figure they will all be similar and I will get them to that range. I'm afraid if I only go to 38Ft lbs I will blow the head gaskets

Reverett said:

When I went to remove the head bolts with a 1/2 impact wrench set at 150 PSI, they wouldn't budge. Had to use a breaker bar to loosen them. They had to be above 180 ft lbs. Does anyone have the head bolt torque specs for a v-twin 24-25hp Briggs, Kawasaki and Kohler? I figure they will all be similar and I will get them to that range. I'm afraid if I only go to 38Ft lbs I will blow the head gaskets

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So, 38 pound feet is probably correct for the Loncin engine. It lists 10mm x 1.25 bolts so, it cannot be 180 pound feet.
I hope that you are using new bolts of the correct grade.

180 ft lb in an aluminum block???

Hammermechanicman said:

180 ft lb in an aluminum block???

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I know! 150 ft.lb. is the torque spec on the lug nuts of my F-150.
The book says 38 ft.lb.
A 10mm bolt is about the same size as a 5/16” bolt.

That Briggs torque head torque would be 220 in/lbs not 220 ft/lbs.

Thanks guys! I wasn't taking into consideration the aluminum block and bolt size and only what it took to remove the bolts. But the bolts were probably oxidized to the block making them seem tighter than they were. I'll use the 38 Ft lbs and see what happens. Just didn't seem right! And yes, replacing the bolts with factory part numbers.

38Nm is 28ft lb which is on the high side for a coarse thread zinc plated bolt into aluminium castings
38 ft lbs will strip the thread out of the hole
So I will guess that the translator forgot to convert the Nm figure as used in China to Ft lbs as used in the USA.
Break away torque is not a reliable measure of original bolt tension and this is very much the case with steel into aluminium as a very tiny amount of galvanic corrosion massivly increases the friction between the bolt & the hole unless the bolt is lubricated with a seizure preventative .
There are thousands of torque charts on the web that list torques per bolt diameter & thread profile in different materials

And anything over 50 ft lbs into an Al-Si castingwill strip the threads out of the hole for any bolt under 3/4" diameter
The B & S specs are INCH POUNDS and are used to imply a very accurate calibrated tension wrench is required because a 220inlb would be +/- 0.5 inlbs and that is the sort ot torque you caouls apply with your fishing tackle ( to be polite )

@Reverett listen to @bertsmobile1 .

Here’s the ARP bolt torque specifications.
I see 24 ft.lb.

Thanks to all! I've worked on 100's of small and large engines but always able to get good specs that I can trust. But getting info on this engine model has been difficult and somewhat not reliable. ALL of you have pointed me in the right direction and is much appreciated! (BTW.... I use a calibrated snap-on torque wrench that is checked every year) But if manufacturer is putting out inaccurate specs, it doesn't matter how accurate it is if your not applying the correct spec! With the new bolts, I'll put them at 33 ft Lb and use anti-seize compound.

Also, a local Toro dealer told me to just tighten them equally and go 1/4 turn further! I knew better!

MParr said:

Here’s the ARP bolt torque specifications.

The Official ARP Web Site | Metric Bolts

arp-bolts.com

I see 24 ft.lb.

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Thanks for posting that
I have rubbish internet so searching for a good clear chart was never going to happen
My guess it is a bad translation
Thread shear on a 10 x 1.5 mm bolt is 42 ft lbs but the alloy will yeild way before that 30 to 35 ft lbs depnding upon composition & temper .Considering that very few mowers run anything like high compression those published figures have to be wrong .

bertsmobile1 said:

Thanks for posting that
I have rubbish internet so searching for a good clear chart was never going to happen
My guess it is a bad translation
Thread shear on a 10 x 1.5 mm bolt is 42 ft lbs but the alloy will yeild way before that 30 to 35 ft lbs depnding upon composition & temper .Considering that very few mowers run anything like high compression those published figures have to be wrong .

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You are welcome.
A 10mm bolt is pretty close to a 5/16” bolt. You certainly don’t want to booger up the threads in the block or break the bolt off. All that’s needed is proper clamping pressure on the head gasket.
Here is the SAE chart. 5/16” bolts also list 24 ft.lb.

Reverett said:

Thanks to all! I've worked on 100's of small and large engines but always able to get good specs that I can trust. But getting info on this engine model has been difficult and somewhat not reliable. ALL of you have pointed me in the right direction and is much appreciated! (BTW.... I use a calibrated snap-on torque wrench that is checked every year) But if manufacturer is putting out inaccurate specs, it doesn't matter how accurate it is if your not applying the correct spec! With the new bolts, I'll put them at 33 ft Lb and use anti-seize compound.

Also, a local Toro dealer told me to just tighten them equally and go 1/4 turn further! I knew better!

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Naw, you are supposed to zip them down with the impact and give it 4 ugga duggas.

It is some thing I have tried to get through peoples heads for ages
The actual numbers are not as important as them all being the same
I play with vintage & veteran motorcycles and it is a daily refrain "What is the torque ona 19xy ABC ?"
Well prior to the 60's a tension wrench would only be found in race mechanics tool kits, air craft hangers and military establishments
Cast iron heads it is till the bolt head is home on the surface then 1/2 turn
For alloy it is the same story but only + 2 flats or 1/3 turn .
And as for tensions wrenches, unless they are calibrated and you are working in a temperature controlled environment then no 2 will ever be the same particularly if they are spring loaded .
Deflecting beams are good for several thousand tensions provided you only use the middle 80% of the scale and never go past the upper limit .