OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Stripped Quantum head bolts

I recently changed the head gasket on a Briggs Quantum and while the bolts were out I gave them a good go on the wire wheel. Trouble is I think I ate into the thread because half of them don't want to tighten up. I may have damaged the thread on the block as well. Can anyone tell me what size and type of thread the head bolts are standard and also what size and thread type I should replace them with so I can tap a new thread. Also do I need to upsize all the bolts or just the ones that won't tighten.
Model 121702
Type 0191 01
Code 90121125

You don't use larger bolts, instead you put helicoils in the old holes and use the original size again.

Cheers,
BB.

Only problem in using helicoils is unless you already have a helicoil kit it will probably cost more that the Quantam is worth

I've just had a look on Ebay and they have 131 piece kits for about $40. Problem is not sure whether I need the Imperial Thread SAE or HSS Metric kit. Anyone know which type I need?

It certainly won't be Metric if I'm correct

Pretty sure without checking is that they will be UNC but for what it is doing you could get away with Whitworth. Before you go any further you need to work out what the problem is, have the threads stripped out, if not no need for helicoils. How far are the bolts threading into the head before stopping?

5/16" UNC

Hi Dave,
The holes may have already been bad, plenty of old quantums around, try tip shop. get some more head bolts and try again.
Reminds me of when my brother got a job with a mechanic. Had to change sparkplugs in a BMW, stripped all 4.....
speedy

Some of the little european Ford engines were also pretty bad for that speedy - or just getting stuck in altogether and snapping in half if left too long.

I have heard of a guy who was a real p.i.t.a. to his mechanic (numbering tyres to check if rotated, etc) - the mechanic retaliated by loctiting the plugs into his 626. Guy took mechanic to court and won.

This is what I don't understand with mechanics. You are entrusting them to take care of your car not to mention paying handsomely for it, but they resent the customer taking steps to try and make sure all work requested has been performed -something often difficult to do -and we get low mongrels like this. ExÍŸaÍŸcÍŸtÍŸlÍŸy why they need to be checked on in the first place.

5/16" UNC!!! Thats the answer I was looking for. Gonna stop off at the hardware store and grab me half a dozen and see where that gets me.

Where in Melb are you, I have plenty here

I get what your sayin' Speedy and it makes sense but I've put in a few hours on this little 5hp Briggs. Stripped and washed. Honed and painted. Lapped me the valves too. Given the intake and exhaust ports a bit of a grind and polish and given the Walbro carb a new wardrobe. Ha. I can see you shaking your head from here. I know. I know. I've got way too much time to spend on it...... Thanks again mate

Northern suburbs. Preston.

Hi All,

As mentioned above the bolts are 5/16 UNC 18 threads per inch with a 1/2 inch AF head.

The top 3 bolts are longer , length 2 and a 1/4 inches .

If the alloy threads are not too damaged you can re-cut them with a cheap eBay tap and
if the bolts aren't too damaged a cheap die nut will repair them but that will be just under $23.

Cheers
Max.

Ok we can forget the bolts I have here I'm in Hampton Park

Thanks for the offer NormK. I appreciate it but its a bit of a hike for a handful of bolts true?
And Max, you are a top bloke. Thanks for posting those files. Saves me time and mucking around. Just got a quick one for ya. Lets say i have perfectly good head bolts, perfect length and thread. 5/16" UNC 18. Now if the threads on the block are damaged and worn, and the original size is 5/16", I'm assuming I'm gonna need to tap the next size up and thats a 3/8 and she looks alot bigger.....

Hi Dave107,

3/8 should be ok it's only 1/16 bigger than 5/16 or 1.5875 mm bigger than 5/16. Some holes will be about point .75 mm closer
to the bore.


Cheers
Max.

That is when you have to go back to the helicoil idea

And there it is, it looks like we've gone full circle and as such you'll probably have to buy a full Helicoil kit, but it will be enough to do every 5/16th thread in that engine. The sad part is that the Imperial sizes are more so being sold from the USA and the UK where they seem to be far more expensive than metric counterparts that are commonly sourced from our new Mother country.............China.

Cheers,
BB.