Piston tool for Chrysler 75 hp 757HB

ErSa

Cadet
Joined
Jan 23, 2022
Messages
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I have to change pistons on my conecting rods in my 75 hp chrysler. To do that you have to use tool T2990, se picture 1. I have do make such tool a need some measurements.
Questions 1: Can somebody give me the measurements A to H? Se picture 2.
Question 2. Is the piston pin fixed in piston or in the the spacers, se picture 3. It seems to differ in my motor???

Regards / Erik Salwén, Sweden
 

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Jiggz

Captain
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Oct 23, 2009
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Not familiar with Chrysler but I believe they are identical (though different sizing) with the Force pistons. I also just finished changing all my pistons on 89-125HP Force. But didn't have to use that T2990 tool. Not sure if you are replacing the pistons with original Chrysler pistons but in my case I upgraded to Wiseco Pistons.

Wiseco pistons come with newer and better rings and a easy to install pin, bearings and spacers. The only part you will re-use is the piston rod.

The original Force (maybe the same as Chrysler) piston wrist or pins are pressed in type while the newer Wiseco are slide in or floating with circ clips on both ends. On the old piston, the rod, spacers and bearings are NOT pressed in. So with a shop press and a solid round stock about 5" in length you should be able to pressed out the old pin.

Now putting it all back in with the original piston is a different story for me because like I said, I used the after market Wiseco pistons which are floating pins with circ clips. But I'm pretty sure the process is just reverse of the removal process except you have to be very mindful of the spacers and bearing being placed in as you press the pin back in.
 

Nordin

Commander
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Jun 12, 2010
Messages
2,081
Erik the spacers has press fitting that is why you need the tool so you get the right distance for the connecting rod to the piston.
One side of the tool is 0,295 in (7,49 mm) and the other side is 0,310 in (7,87mm). I do not have the OEM tool but I have made a tool with the rounded U to fit the spacer large diameter and the thickness of the tool is about 7,8-8,0 mm.
I think the important thing is to get the same distance for the spacer to the connecting rod at each side as the piston rod slide in the piston and the spacers has press fitting to the piston rod. The piston pin do not has to get out of the piston when the piston pin slide in the piston. The distance for the spacers has to be equal at each side to the piston pin end.
 

ErSa

Cadet
Joined
Jan 23, 2022
Messages
21
Thanks guys for priceless information.
Then you own a Chrysler outboard you are not alone .......
I think I want to trye old type of pistons after i have made the tools "aligment pin", "drive pin", and "shim bar".
ES
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,631
If it's not too late?? Change to Wiseco pistons.
Much easier to work with.
 

ct1762@gmail.com

Chief Petty Officer
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Jan 17, 2019
Messages
611
with Wisecos it needs to be bored a few thou over to make room for the larger expansion. can't just swap them in on old worn out stock bores!
 

stresspoint

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Sep 19, 2022
Messages
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with Wisecos it needs to be bored a few thou over to make room for the larger expansion. can't just swap them in on old worn out stock bores!
this is true , im not familiar with how it works on Chrysler 2 stroke in regards t AM wiseco , but fell for that with a 2 stroke jet ski motor , i was informed of this but i ignored the advice.(y) bad mistake.
 

racerone

Supreme Mariner
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Dec 28, 2013
Messages
32,218
With Wiseco pistons you bore to the size it says.-----If standard bore is 3.000" and you want 0.020" O/S piston you bore and hone to 3.020" nothing to it .----Easy as can be.
 

stresspoint

Petty Officer 1st Class
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Sep 19, 2022
Messages
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With Wiseco pistons you bore to the size it says.-----If standard bore is 3.000" and you want 0.020" O/S piston you bore and hone to 3.020" nothing to it .----Easy as can be.
:) i know that after seizing 3 cylinders at once on a fresh built Kawasaki 900 jet ski motor within 2 min run time under load .
:mad:warmed up fine on the hose.
lesson learned the expensive way using AM shyt wiseco.
i found WSM as an AM replacement was much easier if i was building a motor performance or otherwise.

OP use the formula race 1 provided "as said very easy" and you will be fine , don't attempt to use those pistons without clearance.

if you are using stock cylinders get WSM as AM replacement and all you need do is a quick hone for x hatching the bores .
 

racerone

Supreme Mariner
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Dec 28, 2013
Messages
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??----This is all easy.---Even new pistons ( Wiseco or factory ) are tapered.----You have to know where to measure them.----------A new Wiseco piston for a 3.020" bore would measure about 3.017" at the skirt.----Simple old time stuff.
 

Nordin

Commander
Joined
Jun 12, 2010
Messages
2,081
Erik the spacers has press fitting that is why you need the tool so you get the right distance for the connecting rod to the piston.
One side of the tool is 0,295 in (7,49 mm) and the other side is 0,310 in (7,87mm). I do not have the OEM tool but I have made a tool with the rounded U to fit the spacer large diameter and the thickness of the tool is about 7,8-8,0 mm.
I think the important thing is to get the same distance for the spacer to the connecting rod at each side as the piston rod slide in the piston and the spacers has press fitting to the piston rod. The piston pin do not has to get out of the piston when the piston pin slide in the piston. The distance for the spacers has to be equal at each side to the piston pin end.
Has to correct myself.
Piston pin has press fitting to the piston but not the spacers.
The difficult when assemble the new piston with the needles/bearings and spacers is to assemble the spacers so they will rest to the bosses at the piston.
That is why you need the tool T2900. You bring the tool to the small diameter of one of the spacer.
This will end up so the spacers rest at each bosses of the piston.
This will give the piston some space to move in horizontal (piston pin) direction.
When assembling I cool down the piston pin in a freez and heat up the piston to about 80-90 degrees Celsius.
It will make it much easier to press in the pin into the piston.
BUT the OEM pistons is a PITA compared with the Wiseco.
 

ErSa

Cadet
Joined
Jan 23, 2022
Messages
21
Thank you all for the advices concerning OEM pistons for Chrysler 75 hp.

After making tool T2900, aligment tool, driver pin and pillow block I have managed to asseble OEM pistons.
Now remains only to test run the motor IRL. Fingers crossed!
PS Help me with the forum question "Chrysler 75 hp 1975 Spacer plate?"
 
Last edited:

ct1762@gmail.com

Chief Petty Officer
Joined
Jan 17, 2019
Messages
611
With Wiseco pistons you bore to the size it says.-----If standard bore is 3.000" and you want 0.020" O/S piston you bore and hone to 3.020" nothing to it .----Easy as can be.
your saying wiseco builds in the extra .0003'' (per your example)? I always thought they needed extra clearance for the greater expansion than stock cast
 

Nordin

Commander
Joined
Jun 12, 2010
Messages
2,081
Yes it is as racerone says with the Wiseco pistons.
If you bore 020 over size just do that. The clearance is calculated, but you have to check the ring gap. That is what it is in the instruction for the Wiseco pistons.
 
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