8.5 hp tecumseh issues

[corvairbob]

sounds like the engine is already apart. Normally the head comes off, the valve spring gets compressed with your own tool or an inexpensive one you can buy, then the keeper comes off. The valve to tappet clearance gets measured, usually at a specific piston height past TDC then the tip end gets evenly ground on a fine cool grinder wheel until the clearance is in spec. If you gently rock the valve when it is about 1" high off the deck you can feel the guide play. These flat head engines are not worth the PITA to replace guides unless you already have the tool set to ream them out and press in new guides. It is not a car that you will drive 100.000 miles more. All you need is it to run well when blowing snow or whatever. If you want to rebuild it, do it because it is hobby, not to save money. You can buy a new engine for less than to properly re-manufacturer the old one. If you just do a new head gasket and valve adjustment your compression should be fine, unless the cylinder is scored.

yes i know but the guy that need this has no money to pay for a new or rebuilt engine. so i will get this going one way or the other. i measured the guides and the intake is good but the exhause is 5/16 so now i'm looking for a car valve that is the same or close for the head size and the stem is 5/16 .312 and the stem is 4" with the retainer ledge at 3.66" from the top of the head. i can grind the keeper to fit and regrind the valve thanks

 

[Hammermechanicman]

On these type engines i don't rely on compression tests. I use a leakdown tester. One of the benefits is that you can tell immediately if it is rings or valves.
The worn exhaust valve guide is a common problem Briggs and Tecumseh L head engines. Unless the guide and valve are badly worn if you just lap them in the engine will run fine but with some occasional popping in the exhaust. If the valve stem is worn you can fit a new OEM valve to help. Unless you have a reamer that matches a larger diameter stem i doubt if a different valve will work as the guide is not worn round or straight top to bottom.

 

[corvairbob]

ok i found out from my former son in law that has a repair shop that i can't get even the case for this engine. so he found me a nos oversize valve and so i will just rebuild this engine. i posted the dia gram just in case some here know of other valves that are similar. but for now i'm ordering rings a gasket set and seals and will work on this until i find a workable valve or at that time just get a nos valve. thanks

 

[corvairbob]

On these type engines i don't rely on compression tests. I use a leakdown tester. One of the benefits is that you can tell immediately if it is rings or valves.
The worn exhaust valve guide is a common problem Briggs and Tecumseh L head engines. Unless the guide and valve are badly worn if you just lap them in the engine will run fine but with some occasional popping in the exhaust. If the valve stem is worn you can fit a new OEM valve to help. Unless you have a reamer that matches a larger diameter stem i doubt if a different valve will work as the guide is not worn round or straight top to bottom.

thanks i can't tell if the guide is worn out equally all around but if i get a ne oversize valve i may be able to ream it out if not it will be better than the wobble i now have. thanks

 

[Hammermechanicman]

Hope you get it running. The main reason for the exhaust guide to wear is because the engine is not run hard enough. The engine needs to get hot enough to create an oil mist inside the engine which lubricates the valves. Since no oil pump and the oil slinger doesn't sling oil into the valve chamber the engine on snow blowers need to be run at full throttle and run hard to get the temp up to where it needs to be. Worn valve guides is a common problem on old snow blowers because it is hard to get them up to temp. Newer OHV engines do better on snow blowers.

 

[corvairbob]

if you look close at these valves you see the intake has a brighter ring on the face that is the seal but the exhaust is all full of crud that is not sealing. i could re grind it and lap it in but because of the wobble i believe it would become this way again real fast.

 

[corvairbob]

Hope you get it running. The main reason for the exhaust guide to wear is because the engine is not run hard enough. The engine needs to get hot enough to create an oil mist inside the engine which lubricates the valves. Since no oil pump and the oil slinger doesn't sling oil into the valve chamber the engine on snow blowers need to be run at full throttle and run hard to get the temp up to where it needs to be. Worn valve guides is a common problem on old snow blowers because it is hard to get them up to temp. Newer OHV engines do better on snow blowers.

your correct but what you going to do they run in the winter. but tecumseh might have made the guide hard and the valve to be the wear point so that you replace the valve and your done. it is far easier to change out a valve than to punch out the seat. but it is what it is. at this time i have a handle on a oversize valve but also still looking for a car type valve. i have an old corvair valve that i could regrind the stem and head and redo the keeper but the seal surface has a divit that is just to deep to make it work. if i could find a alve that was 4" long and had the 5/16" stem and the1 1/8 or a bit bigger head i would make that work. thanks

 

[sgkent]

the valves stretch. Once that happens the clearance goes away and they never shut. I glass beaded my valves with high quality fine beads like I used to do in the machine shop, or you can wire brush them. Use a little lapping compound and a hand lapping tool after you adjust them. Then check the adjustment again. I had to grind quite a bit more than I thought I might on mine to get the spec clearance. They the compression came right back up to normal. It is a lawn mower engine. They aren't made to be fully re-manufactured. The cost of a new engine makes re-manufacturing one uneconomic. The valve guides are crappy. Some engines you can get replacements that you bore the guide hole, then ream it then press in a false guide. Others as stated the guide simply gets reamed then an oversize stemed valve is used. These engines are old so parts are getting scarce, and in some cases expensive. Many times a replacement engine or snow blower is less expensive. And in states like California they want you to use an electric or battery powered one.

 

[sgkent]

if you look close at these valves you see the intake has a brighter ring on the face that is the seal but the exhaust is all full of crud that is not sealing. i could re grind it and lap it in but because of the wobble i believe it would become this way again real fast.

If you can get a replacement exhaust valve do so. If you have a real valve grinding machine put a lite resurface on it, then tip it to get the correct clearance, then hand lap it. It is a lawn mower engine and not worth buying the tooling to screw with the guides. If you decide to go that route then next you will want to bore the engine, go to an oversized piston, replace the rod and maybe crankshaft and when done the cost will be 3X what a new engine might have cost you. How many years old is the snow blower now? My pressure washer, was slightly better, I hand lapped the valve and it cleaned up enough to seal well although the guide was really worn, its power came back. It is 25 years old. I won't live that long for a new one.

 

[corvairbob]

the valves stretch. Once that happens the clearance goes away and they never shut. I glass beaded my valves with high quality fine beads like I used to do in the machine shop, or you can wire brush them. Use a little lapping compound and a hand lapping tool after you adjust them. Then check the adjustment again. I had to grind quite a bit more than I thought I might on mine to get the spec clearance. They the compression came right back up to normal. It is a lawn mower engine. They aren't made to be fully re-manufactured. The cost of a new engine makes re-manufacturing one uneconomic. The valve guides are crappy. Some engines you can get replacements that you bore the guide hole, then ream it then press in a false guide. Others as stated the guide simply gets reamed then an oversize stemed valve is used. These engines are old so parts are getting scarce, and in some cases expensive. Many times a replacement engine or snow blower is less expensive. And in states like California they want you to use an electric or battery powered one.

yep i know but i did have proper clearance on them so they did now stretch to much this time. but is you saw the seat there is a hairline area about halfway around the block seat that is there this valve was hitting. and because of the wobble it had i do not think the valve had time to completely seat before it had to open again plus if you notice the divit in the seat? but that might be just dirt i have to recheck it today to make sure. but notice the hailline sealing this did and it is only about halfway around the seat. there is not enough there to do a seal at all. plus i now theya re cheap for some folks but some people just can't afford new engines when they take a dump. this is for my brother and he just has no money to spend on engines. thanks