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21HP V-Twin Head Gasket Repair

#1

GasGuzler

GasGuzler

I just picked up a Craftsman LT1000 with a 21HP Briggs V-Twin, model number 407577-0283-E1. I believe it needs new head gaskets, I have ordered the gasket kits but I was just wondering if I need to order new head bolts too? In the past I have ran into issues reusing head bolts and them snapping in the block while torquing them down. I was also wondering what the torque specs are for the head bolts, and how many stages I should torque them down and how many foot pounds for each stage. I’m 18 and fairly new to this, so any help would be appreciated.


#2

Craftsman Garage

Craftsman Garage

So, I have reused head bolts many times and never had any lssues. I also didn't torque them down and didn't have issues lol. I would pull out a bolt or two and if they're really Rusty or corroded, etc, then replace them. Otherwise, I wouldn't replace them. BTW, Welcome to the forum!


#3

GasGuzler

GasGuzler

Craftsman Garage said:
So, I have reused head bolts many times and never had any lssues. I also didn't torque them down and didn't have issues lol. I would pull out a bolt or two and if they're really Rusty or corroded, etc, then replace them. Otherwise, I wouldn't replace them. BTW, Welcome to the forum!
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Oh alright, I’m used to rebuilding truck engines and torquing everything down in stages and in a pattern. Guess I will tighten them down what I think is enough and hope for the best.


#4

Craftsman Garage

Craftsman Garage

Would you happen to be GasGuzler on YouTube?


#5

GasGuzler

GasGuzler

Craftsman Garage said:
Would you happen to be GasGuzler on YouTube?
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Lol yeah that’s me


#6

Craftsman Garage

Craftsman Garage

GasGuzler said:
That's awesome dude. Let me start by saying I enjoy watching your videos. I bought my 72 F100 at 13 years old after watching your video about your 76 back in 2022. Last year, I wanted an OBS so bad after seeing lots of Videos come up about them. I got a 92 f150 std cab shortbed 4x4 manual last August. Its not an inline 6 tho, its a 5.0. With the help of this forum, I fixed some riding mowers and bought those trucks. Long story short, love the content so Keep doing what you're doing brother!
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#7

GasGuzler

GasGuzler

Hell yeah man! I honestly never expect anyone to recognize me let alone on a lawn mower forum haha, but that’s awesome that you’ve got some trucks of your own! A buddy of mine convinced me to buy a cheap LT1000 off of marketplace, and I don’t know how but somehow I’ve become addicted to them and now I currently have 4 sitting in my garage, it’s becoming an issue lol. So chances are this won’t be the last post I make on this site, that’s for sure. Plan on turning this 21HP twin into a race mower just for fun, might even make a video series on it. Not sure how the community will enjoy mower videos instead of truck videos but we’ll see.


#8

Craftsman Garage

Craftsman Garage

GasGuzler said:
I know exactly how that is lol. I've got a channel with truck content and riding mower content, I think the link is in the about section of my profile. I would watch lawn mower content on your channel. Btw, if you make a racing mower, don't use hydrostatic-automatic transmissions. Only manuals can go fast because automatics have rev limiters and they're really weak.
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#9

GasGuzler

GasGuzler

I figured as much, unfortunately my V-Twin is a factory Hydro-Static. I was planning on swapping the 6 speed out of my other mower into it, but how would I go about bypassing the rev limiter?


#10

Craftsman Garage

Craftsman Garage

Manuals Don't have rev limiters. Post your mower's model no. It should start with 917.Xxxxx


#11

GasGuzler

GasGuzler

Craftsman Garage said:
Manuals Don't have rev limiters. Post your mower's model no. It should start with 917.Xxxxx
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Currently away at school but I’ll have to check. And is the limiter actually part of the transmission or is it like a CDI box on the engine? Because if it’s just the tranny I can just swap it.


#12

Craftsman Garage

Craftsman Garage

No, the engine could go up to 7k if you wanted it to. It's an internal part of the transmission. It would probably be easier to swap in a manual.


#13

GasGuzler

GasGuzler

Craftsman Garage said:
No, the engine could go up to 7k if you wanted it to. It's an internal part of the transmission. It would probably be easier to swap in a manual.
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Sounds like I’m doing that then, I already wanted to swap the rear fender since it’s nicer so this just gives me more reason to lol.


#14

Craftsman Garage

Craftsman Garage

Also, there's nothing wrong with Briggs v-twins, but if I was making a racing Mower, I would prefer a Briggs opposed twin. Basically the "indestructible inline 6" of mowers


#15

GasGuzler

GasGuzler

Craftsman Garage said:
Also, there's nothing wrong with Briggs v-twins, but if I was making a racing Mower, I would prefer a Briggs opposed twin. Basically the "indestructible inline 6" of mowers
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Haha my teacher at school has a 20HP opposed twin, he told me I could have the motor in the spring if I swap another motor onto his. I just like the sound of the V-Twins.


#16

Craftsman Garage

Craftsman Garage

IKR, the vtwins with open exhaust sound like motorcycles. IMO any engine is better than a single cylinder for a racing mower. Vtwins are also wildly reliable most of the time.


#17

ILENGINE

ILENGINE

Head bolt torque is 220 in/lb. I usually do a three step process.


#18

StarTech

StarTech

You could cripple the governor and rev the engine up until a rod goes thru the cylinder block. Note these Briggs are design to run safely at 3600 rpms max.


#19

Craftsman Garage

Craftsman Garage

Hey, that would make some good content... "Driving my racing mower until it throws a rod" Iol 😉


#20

Tiger Small Engine

Tiger Small Engine

GasGuzler said:
I just picked up a Craftsman LT1000 with a 21HP Briggs V-Twin, model number 407577-0283-E1. I believe it needs new head gaskets, I have ordered the gasket kits but I was just wondering if I need to order new head bolts too? In the past I have ran into issues reusing head bolts and them snapping in the block while torquing them down. I was also wondering what the torque specs are for the head bolts, and how many stages I should torque them down and how many foot pounds for each stage. I’m 18 and fairly new to this, so any help would be appreciated.
Click to expand...
Torque specs for this engine can be found online. Always look up correct specs for important parts such as head gaskets, and use a torque wrench. Gradually tightening head bolts in a pattern to correct torque is the right way. Reusing bolts will be no problem. Did you do a leak down test to determine bad head gaskets?


#21

StarTech

StarTech

Craftsman Garage said:
Hey, that would make some good content... "Driving my racing mower until it throws a rod" Iol 😉
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Well I had a go cart in the shop a few years ago that they putting it up on blocks to start it and rocking it off the blocks to ride it. They took a piece of field fence wire and had crippled the governor. It was the complaint that it in with the kid's father that it could be started without it taking off across the lawn.

The darn kid did it again but this time the governor part was not available. I have no idea has happen to it now.


#22

GasGuzler

GasGuzler

Tiger Small Engine said:
Torque specs for this engine can be found online. Always look up correct specs for important parts such as head gaskets, and use a torque wrench. Gradually tightening head bolts in a pattern to correct torque is the right way. Reusing bolts will be no problem. Did you do a leak down test to determine bad head gaskets?
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It had no oil in it and I believe it has a sticky valve, so heads will need to come off regardless. And once that happens, I’ll have to do head gaskets anyway.


#23

Craftsman Garage

Craftsman Garage

Was it ran without oil or just leaked out over time? You might wanna crack the sump open and check for damage.


#24

S

slomo

No oil in a Briggs, she will be fine if you can get her to spin over. Little polish on the crank and such. Good to go.


#25

GasGuzler

GasGuzler

Craftsman Garage said:
Was it ran without oil or just leaked out over time? You might wanna crack the sump open and check for damage.
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I’m not sure, the guy who I bought it from said it was in a storage unit he purchased. While spinning it over with the battery, one cylinder makes a loud popping sound through the intake and it feels like it’s pushing air back out through it. I don’t know if the oil was drained for while it was in the unit or if it was going to scrap.


#26

Craftsman Garage

Craftsman Garage

Hmm, are you going to take both heads off and adjust the valves?


#27

GasGuzler

GasGuzler

Craftsman Garage said:
Hmm, are you going to take both heads off and adjust the valves?
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Yes, that was the plan. I was going to rebuild the whole top end, and if it is really bad possibly rebuild the whole motor.


#28

Craftsman Garage

Craftsman Garage

Craftsman Garage said:
Sounds like a good plan!
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#29

Craftsman Garage

Craftsman Garage

You shouldn't have to rebuild it unless you have low compression on one side. It sounds like it could be a bent pushrod or valves need adjusted. A top end refresh is smart tho. Could only be a carb.


#30

Craftsman Garage

Craftsman Garage

I hope you get this on video :)


#31

Alan46

Alan46

You guys should get a room!😂😂😂😂😂☮️✌🏻


#32

Craftsman Garage

Craftsman Garage

Wdym?


#33

Alan46

Alan46

Just my sense of humor, don’t be offended!☮️✌🏻


#34

oldlawnguy

oldlawnguy

GasGuzler said:
I just picked up a Craftsman LT1000 with a 21HP Briggs V-Twin, model number 407577-0283-E1. I believe it needs new head gaskets, I have ordered the gasket kits but I was just wondering if I need to order new head bolts too? In the past I have ran into issues reusing head bolts and them snapping in the block while torquing them down. I was also wondering what the torque specs are for the head bolts, and how many stages I should torque them down and how many foot pounds for each stage. I’m 18 and fairly new to this, so any help would be appreciated.
Click to expand...
Search this forum for the thread:

B&S Valve Adjustment Hiccup (Murphy's law & not a pro)​

I replaced both head gaskets on a 24HP B&S V-Twin and the gang helped me through it with specs, tips and pointers. You probably want to get gaskets for muffler assembly, carb assembly as well. Torque the head in the suggested pattern.


#35

Hammermechanicman

Hammermechanicman

If it popping back through the carb after long storage probably was stored with the intake valve open and it rusted some so it is stuck open. Easy fix. Take the valve cover off and check.


#36

R

rhkraft

GasGuzler said:
I just picked up a Craftsman LT1000 with a 21HP Briggs V-Twin, model number 407577-0283-E1. I believe it needs new head gaskets, I have ordered the gasket kits but I was just wondering if I need to order new head bolts too? In the past I have ran into issues reusing head bolts and them snapping in the block while torquing them down. I was also wondering what the torque specs are for the head bolts, and how many stages I should torque them down and how many foot pounds for each stage. I’m 18 and fairly new to this, so any help would be appreciated.
Click to expand...
Probably over torqued if you broke them. On these little engines you set the torque in your elbow. Usually around 225 inch Lbs. Divide that by 12 to get ft lbs or 18.75 ft lbs. That becomes 18.75 lbs on a 12 inch lever. That is not much! estimate by picking up 2 1/2 gallons of water in a bucket ( Water is 8 lbs/gal). That's how pull you have to put on a 12 inch wrench handle. Use a criss/cross pattern a little at a time. On truck lug nuts that require 150 ft/lbs, use the lug nut wrench and step on the handle. If you weigh 150 lbs your on. If you weigh 200, add about 3/4 th of you weight.. Now, when you are done try to turn it a little more with you cross wrench. If you make it turn a little feel the force with your arms. You'll figure it out.


#37

Craftsman Garage

Craftsman Garage

@Alan46 did you mean a chat room?


#38

Alan46

Alan46

Craftsman Garage said:
@Alan46 did you mean a chat room?
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Yes!


#39

T

TobyU

I always clean up the heads and they block service very well with a scraper and some Scotch Brite pad sometimes and then I always tighten in the Briggs recommended tightening order in two or three steps and I always use an accurate inch pound torque wrench and tighten to the current Briggs & Stratton recommended torque.

I will say that sometimes you have to be a little careful when you get right near the end of that torque because sometimes one will feel like it's not quite going to make it unless it strips or snaps off so if the torque you're going for is 220 inch pounds let's say, you might have to back it off to 215 or 218 or something and then see if it'll click and maybe not push it all the way to 220.
I think I broke one off one time and that's made me a little leery after that but I've done a whole lot more after that and never had a problem but I do get very cautious near the final torque.

This is not something you should be guessing at and just using a 3/8 drive ratchet to tighten.
Sure, people have been doing it for years can just use a criss cross method and get them to what they know is tight enough but ideally it's better to use a torque wrench.


#40

G

Gym123

rhkraft said:
Probably over torqued if you broke them. On these little engines you set the torque in your elbow. Usually around 225 inch Lbs. Divide that by 12 to get ft lbs or 18.75 ft lbs. That becomes 18.75 lbs on a 12 inch lever. That is not much! estimate by picking up 2 1/2 gallons of water in a bucket ( Water is 8 lbs/gal). That's how pull you have to put on a 12 inch wrench handle. Use a criss/cross pattern a little at a time. On truck lug nuts that require 150 ft/lbs, use the lug nut wrench and step on the handle. If you weigh 150 lbs your on. If you weigh 200, add about 3/4 th of you weight.. Now, when you are done try to turn it a little more with you cross wrench. If you make it turn a little feel the force with your arms. You'll figure it out.
Click to expand...
Head bolts are often brittle after they become 'work hardened'- he's not inexperienced in general, just with these engines, which don't require much torque.


#41

T

TwinL

GasGuzler said:
I just picked up a Craftsman LT1000 with a 21HP Briggs V-Twin, model number 407577-0283-E1. I believe it needs new head gaskets, I have ordered the gasket kits but I was just wondering if I need to order new head bolts too? In the past I have ran into issues reusing head bolts and them snapping in the block while torquing them down. I was also wondering what the torque specs are for the head bolts, and how many stages I should torque them down and how many foot pounds for each stage. I’m 18 and fairly new to this, so any help would be appreciated.
Click to expand...
I know these engines are famous for the valve guides sliding up jamming the rockets and bending the push rods, usually the shroud over the fly wheel has gotten filled with crap, quite often caused by mice causing the engine to overheat, the head bolt torque is 220 Inch pounds, that's "Inch Pounds", I've done many and used the original bolts and never broken a bolt off.


#42

S

slomo

TwinL said:
I know these engines are famous for the valve guides sliding up
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Also famous for OWNERS not doing maintenance of any kind. That is the real problem these engines face.


#43

GasGuzler

GasGuzler

So bit of an update. Tore down the motor, it appears that the exhaust valve guides had began pulling out, and on one cylinder it had lifted enough that it didn't allow the exhaust valve to open all the way, consequently bending the pushrod. It had fallen out and ventured down into a passage right next to the lifter, I was able to pull it back out. Now the intake valve on that side was also bent, though no signs of a reason why... I can only wonder if it had let air into the engine, and right after the guide popped out and didn't allow it to exit the cylinder, and then when next intake stroke came around the compression forced the valve shut and bent the pushrod. It wasn't horribly bent like the exhaust one was, but definitely noticeably crooked. Other cylinder was perfect, valve guide had began pulling out on that side as well but hadn't gotten far enough to cause any damage. I pulled both heads, the headgaskets were both perfectly fine with no burn-through marks whatsoever, so those had survived. HOWEVER... the cylinder with the bent pushrods had a puddle of oil in the combustion chamber when I initially pulled off the head. The other cylinder did not, and that worries me a little bit. Both pistons have ever so slight side-to-side movement in the cylinders, but I was told that it is normal as the rings expand when the engine heats up and seals up better. Felt equal in both cylinders so one was not worse than the other, a hopeful sign. But that puddle of oil is definitely something I am worried about. Any ideas what the cause of that might've been? I'm just about ready to throw this motor back together, have new pushrods for it and every gasket needed. Just want to make sure there isn't something catastrophically wrong with it before I do so.


#44

Tiger Small Engine

Tiger Small Engine

GasGuzler said:
So bit of an update. Tore down the motor, it appears that the exhaust valve guides had began pulling out, and on one cylinder it had lifted enough that it didn't allow the exhaust valve to open all the way, consequently bending the pushrod. It had fallen out and ventured down into a passage right next to the lifter, I was able to pull it back out. Now the intake valve on that side was also bent, though no signs of a reason why... I can only wonder if it had let air into the engine, and right after the guide popped out and didn't allow it to exit the cylinder, and then when next intake stroke came around the compression forced the valve shut and bent the pushrod. It wasn't horribly bent like the exhaust one was, but definitely noticeably crooked. Other cylinder was perfect, valve guide had began pulling out on that side as well but hadn't gotten far enough to cause any damage. I pulled both heads, the headgaskets were both perfectly fine with no burn-through marks whatsoever, so those had survived. HOWEVER... the cylinder with the bent pushrods had a puddle of oil in the combustion chamber when I initially pulled off the head. The other cylinder did not, and that worries me a little bit. Both pistons have ever so slight side-to-side movement in the cylinders, but I was told that it is normal as the rings expand when the engine heats up and seals up better. Felt equal in both cylinders so one was not worse than the other, a hopeful sign. But that puddle of oil is definitely something I am worried about. Any ideas what the cause of that might've been? I'm just about ready to throw this motor back together, have new pushrods for it and every gasket needed. Just want to make sure there isn't something catastrophically wrong with it before I do so.
Click to expand...
If i
GasGuzler said:
So bit of an update. Tore down the motor, it appears that the exhaust valve guides had began pulling out, and on one cylinder it had lifted enough that it didn't allow the exhaust valve to open all the way, consequently bending the pushrod. It had fallen out and ventured down into a passage right next to the lifter, I was able to pull it back out. Now the intake valve on that side was also bent, though no signs of a reason why... I can only wonder if it had let air into the engine, and right after the guide popped out and didn't allow it to exit the cylinder, and then when next intake stroke came around the compression forced the valve shut and bent the pushrod. It wasn't horribly bent like the exhaust one was, but definitely noticeably crooked. Other cylinder was perfect, valve guide had began pulling out on that side as well but hadn't gotten far enough to cause any damage. I pulled both heads, the headgaskets were both perfectly fine with no burn-through marks whatsoever, so those had survived. HOWEVER... the cylinder with the bent pushrods had a puddle of oil in the combustion chamber when I initially pulled off the head. The other cylinder did not, and that worries me a little bit. Both pistons have ever so slight side-to-side movement in the cylinders, but I was told that it is normal as the rings expand when the engine heats up and seals up better. Felt equal in both cylinders so one was not worse than the other, a hopeful sign. But that puddle of oil is definitely something I am worried about. Any ideas what the cause of that might've been? I'm just about ready to throw this motor back together, have new pushrods for it and every gasket needed. Just want to make sure there isn't something catastrophically wrong with it before I do so.
Click to expand...
If you pushed a valve guide, you can’t simply tap it back down. It will work its way back out. Valve guides that have moved is usually caused by engine that overheated. Engine overheating is usually caused by cylinder head cooling fins and top of engine caked in dirt, oil, and grass. Long term you need a new cylinder head and gasket to fix the problem.


#45

GasGuzler

GasGuzler

Tiger Small Engine said:
If i

If you pushed a valve guide, you can’t simply tap it back down. It will work its way back out. Valve guides that have moved is usually caused by engine that overheated. Engine overheating is usually caused by cylinder head cooling fins and top of engine caked in dirt, oil, and grass. Long term you need a new cylinder head and gasket to fix the problem.
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I am aware of that, however I am on a budget here. I’m also not going to be using this mower to cut grass, the deck will be getting removed and I’ll most likely just be fooling around with the tractor. I’ll replace the heads in the future if needed, and will make sure to keep the block clean.


#46

ILENGINE

ILENGINE

GasGuzler said:
I am aware of that, however I am on a budget here. I’m also not going to be using this mower to cut grass, the deck will be getting removed and I’ll most likely just be fooling around with the tractor. I’ll replace the heads in the future if needed, and will make sure to keep the block clean.
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Need to keep in mind that even if the cooling fins are kept clean and you push the guide back down, it will migrate back up and bend another pushrod in about an hour.


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