Pressure washer maximum PSI?

[84prerunner]

Had another thread about unloader valve issues, got that sorted out. Now I'm wondering if anyone had an idea what the maximum PSI is on this old pump. It's stamped 1978, on an old Simpson pressure washer. I can't find any information, only info I have is "T80/5" stamped in the head.
I was steadily upping the PSI on the unloader with the red high pressure tip installed and pump spinning about 1100Rpm, got to almost 3000psi and blew an o-ring out of one of the cylinders at the head. Now I'm wondering if it was simply over pressure for this pump or if it's just old parts/seals.

Anyone seen one of these or have any information?

 

[84prerunner]

 

[EOC_Jason]

What size is the engine?

 

[84prerunner]

It didn't have an engine when I got it, I installed a 6.5hp HF engine.

 

[rpcraft]

Probably was too much power for the pump head if it is blowing o-rings Does the pump head have any details on it as to what the gph rating is?

 

[84prerunner]

Only writing on the entire pump is 1/78 (guessing year) and t80/5 on the head

 

[84prerunner]

After more research it appears I was way over pressure. This is a piston pump, not a plunger pump. Can't find any specs on this exact unit but by design/comparison it looks like it is a high-ish flow, low pressure pump. Something around 4gpm but sub 2000psi. Got the pump back together tonight, looks like I'll be setting the unloader for 1800ish psi and going to town with my surface cleaner

 

[OccupantRJ]

That looks like my style unit, and pump looks like my Cat pump. I bought my unit from a rental tool company 25 years ago and it was set of for 1200 psi when I got it. I clean my old machines, vinyl siding, and some concrete with it and it has done fine for me. I also installed the 6.5 Predator engine on mine, it starts like a Honda now. Careful of too much pressure around windows. It can blow the seals out of them.

 

[84prerunner]

Thanks for the reply! Turns out it's a giant pump, which may or may not be a rebranded cat. Did some concrete cleaning with it set at 1200psi but it was struggling to take the deep black and greeen algae off. Bumped the pressure up to 1700 and it came right off. This old pump/machine seems to do great! Hopefully it has a few hours left in it as I have a lot of plans for it.

 

[OccupantRJ]

Thanks for the reply! Turns out it's a giant pump, which may or may not be a rebranded cat. Did some concrete cleaning with it set at 1200psi but it was struggling to take the deep black and greeen algae off. Bumped the pressure up to 1700 and it came right off. This old pump/machine seems to do great! Hopefully it has a few hours left in it as I have a lot of plans for it.

Great, glad it worked out for you.