Compression Leak

[eavdic10]

Hi there guys,
Got a 1991 70 HP Force with low compression in middle cylinder. 120 top 120 bottom 70 middle. took the head gasket off no scarring or damage to the cylinder walls I am thinking its the head gasket. I got some gasket maker heat resistant in a tube and put some around waited about 4 hours and checked again and now as soon as I check it it looses that compression. On all 3 cylinders...Do you guys think it could be head gasket or how could I check if it is the rings?

 

[roscoe]

Re: Compression Leak

Can't tell without seeing it.

But it sounds like you re-used the head gasket, which won't work.
Nor will the gasket sealer.
You need a new head gasket, torqued in sequence, to factory specs.
Check the head and block to make sure the surfaces are flat.
If the rings are broken, they need to be replaced.

 

[eavdic10]

Re: Compression Leak

There is no scaring on the wall cylinder rings are on there and they look fine too. I took off the fuel pump which is on the side of the middle cylinder and could see the rings from the side and everything looks the same as the other two pistons. I am hoping is the head gasket and I just get one tomorrow and put it on. Is there a way of checking where it is leaking. I am thinking to push 100 psi through the spark plug hole and see where it goes but not sure if that works or if that would even work. What do you suggest first? Replace the head gasket? is there any other things I should look for before I take on the job of taking out that piston. Thank you.

 

[jerryjerry05]

Re: Compression Leak

Pictures of the head gasket?CLOSE UP"S
Pics of the head. CLOSE UP"S!!
NO silly cone and a new gasket.
Make sure the head and mounting areas are clean.
20# tourqe.J

 

[eavdic10]

Re: Compression Leak

I don't have any pictures but I will try to see if I can get a new head gasket and will not use any silly cone will see what it does but the head gasket looked good , no cracks no missing pieces there was nothing that would indicate that the headgasket was bad. I guess it could only be the head gasket or the rings right ???? OR is there something else where it could loose compression

 

[Frank Acampora]

Re: Compression Leak

At 70 psi you may have stuck rings (or a broken ring) on the center piston. They stick on the exhaust side where you can not see them unless you remove the cover (and possibly break a few bolts. After replacing the head gasket, TRY a decarbon treatment--it may not help and is a "Hail Mary" move but it can not hurt either.

New head gasket goes on dry at 225 INCH pounds torque. Use a spiral pattern from the center two bolts outward and approach 225 in three steps, say 150, 200, and 225. This will prevent warping the head. Since it has never been compressed, re-torque it after about 1/2 hour running time or after you come back from the boating day.

 

[eavdic10]

Re: Compression Leak

Well if the head gasket does not work, I will remove that exhaust side because it will have to come off anyways . I used a bit seafoam on it there is no gunk in there at all they all look pretty good. I use premix. But I got another question there is a 030 stamped on top of the engine on he side where the head gasket goes on does that mean that the head were already bored to 0.30 ? If I go with new rings I would have to get the oversize 0.30 if that were the case correct?

 

[Frank Acampora]

Re: Compression Leak

If you have calipers, measure the cylinder bore. Stock is 3.375 (3 3/8) an 030 overbore will measure 3.405 or 1/32 more than 3 3/8 or 3 13/32.

If you simply need to replace a ring and the engine is bored oversize, then yes, you need to buy oversized rings. If the engine IS bored .030 over practically speaking, that is the max. >040 pistons are sold but it is not recommended to bore .040 over because wall thickness may be compromised.

 

[jerryjerry05]

Re: Compression Leak

If it's been bored out?The top of the piston,it should have the .030 stammped on it,somewhere on the crown.
Once you get past .030 then it's recomended you change the jets.
The air screws what are they set at?
If it's carboning up then maybe you need to do that anyway.
Like Frank says do the Seafoam or Powertune de-carbon and see if it helps.
I've never really seen one recover from a stuck ring,but try anyway.J

 

[eavdic10]

Re: Compression Leak

Alright, today I took of the exhaust cover on the engine and it looked pretty gunky in there. From that side I could see scaring on the piston side itself, no damage to the ring. What I did next is I put a attachement for air into the spark plug hole, turned the cylinder past the exhaust hole towards the spark and gave it nice 100 psi and I could feel the air passing by the piston. I am sure I need a new piston with rings. So next step is honing and replacing that. I also took of the carb because the best way to get to that is through the carb it self .Now I am debating should I take off all three and replace the piston with rings on the middle and at least put new rings on the other two. and hone all 3 cylinders a bit. Also found out that the reed valve on the middle cylinder had a little hole in it so will be replacing that as well. Hopefully this thing will have 150 across all 3 by the time I am done with them. I have included pictures let me know what you guys think.
Thanks.

 

[pnwboat]

Re: Compression Leak

The reed valve for #2 cylinder has broken and may be the cause for the damage to #2 piston/cylinder.

 

[eavdic10]

Re: Compression Leak

Gents how do I remove the connecting rod from the piston there is no holes to I just knock one side out?

 

[eavdic10]

Re: Compression Leak

Just wanted to share if anyone is looking for standard or overbore size pistons for Force you can find them here. I ordered one should be here before the weekend
http://www.ebay.com/itm/32089151648...AX:IT&_trksid=p3984.m1423.l2649#ht_1324wt_860

 

[eavdic10]

Re: Compression Leak

Guys, the piston I purchased they are out of stock...I have 030 stamped on the block itself but I am not sure if it is bored or not. What is the best way to find out? How to measure? Where to measure? and where to get the piston? Thank You

 

[Frank Acampora]

Re: Compression Leak

Measure at the top of the block. I told you in my previous answer what sizes to look for in both decimal and fractional inches.

You need a press to remove the wrist pin. Do yourself a favor and buy Wiseco pistons because they have a wrist pin held in by circlips and no special tools are needed for installation.

 

[eavdic10]

Re: Compression Leak

I just found out Wiseco does not make them anymore in standard size. The piston measured 3 3/8 which would be the standard. there is nothing stamped on the piston itself. I could have napa take that out and put new one in. I just can't find them anywhere not in town and not online.

 

[eavdic10]

Re: Compression Leak

Guys anybody know where I can get standard size piston for this 70HP Force..????? Anyone???

 

[eavdic10]

Re: Compression Leak

Here is a stupid question what if I used 010 oversized piston and ring, would those fit in a standard size cylinder and if so what is the downside.

 

[Frank Acampora]

Re: Compression Leak

NO! Even if there was enough clearance to fit the piston, it will be too tight in the cylinder and eventually (sooner rather than later) seize and jam in the cylinder. Then your problem is solved because you will need to bore at least .020 oversized and replace with a piston that is available.

My Wiseco catalog is a year old and they show standard pistons--3151PS. This piston is used in Chrysler 115, 135, and 140 in addition to Force 70, 90, 120 and 150. Try calling 800-321-1364 or 440-851-6600 and ask for technical services or customer rep.

 

[eavdic10]

Re: Compression Leak

I called them and spoke with them they could not tell If I could use the 90 HP one. I found a guy on craigslist he has one in good shape according to him from the same exact engine he is about 1.5 hours away but I don't want to use an used piston but Id rather use that then put the wrong one in there I can't find anyone in town that would bore these engines either..