compression PSI for 361 ??
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Junior User
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From: Wenatchee, WA
compression PSI for 361 ??
Ford 1975 361 Compression??? acceptable range? .. psi from___ to ___. Can't seem to find any numbers for the psi...can only find the compression ratios. Anybody know?? Engine is in F600 but don't think that really matters.
Thanks
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Save the old ones
Joined: Dec 2002
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From: Boyne Mich
Totally from the hip here
145 and up would be good
125 and down, I would think is low
My dad always said its not so much the number, but more importantly are they all similar. Meaning there isn't one or two considerably lower. Say 6 or7 cylinders are in the 130-145 range and the other 1 or 2 n the 100 or lower range. = problems.
Does it burn any oil?
Weak on power?
Usually a good idea to check pressure when new and strong so you compare for later.
145 and up would be good
125 and down, I would think is low
My dad always said its not so much the number, but more importantly are they all similar. Meaning there isn't one or two considerably lower. Say 6 or7 cylinders are in the 130-145 range and the other 1 or 2 n the 100 or lower range. = problems.
Does it burn any oil?
Weak on power?
Usually a good idea to check pressure when new and strong so you compare for later.
Thread Starter
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Junior User
Joined: Jan 2014
Posts: 83
Likes: 2
From: Wenatchee, WA
Totally from the hip here
145 and up would be good
125 and down, I would think is low
My dad always said its not so much the number, but more importantly are they all similar. Meaning there isn't one or two considerably lower. Say 6 or7 cylinders are in the 130-145 range and the other 1 or 2 n the 100 or lower range. = problems.
Does it burn any oil?
Weak on power?
Usually a good idea to check pressure when new and strong so you compare for later.
145 and up would be good
125 and down, I would think is low
My dad always said its not so much the number, but more importantly are they all similar. Meaning there isn't one or two considerably lower. Say 6 or7 cylinders are in the 130-145 range and the other 1 or 2 n the 100 or lower range. = problems.
Does it burn any oil?
Weak on power?
Usually a good idea to check pressure when new and strong so you compare for later.
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Junior User
Joined: Jan 2014
Posts: 83
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From: Wenatchee, WA
Thanks for the figures.. I come up with 7.2 compression ratio too, this 361 has a 4 barrel holley.. think most had a 2 barrel?? so hp and torque figures may be slightly different?? don't know. The compression psi figures seem to be elusive....for some reason
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Save the old ones
Joined: Dec 2002
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From: Boyne Mich
Compression ratio for this engine is 7.2. Being a truck engine i'm not expecting the "when NEW" compression psi figures to be as high as car engine. this is a 38 year old used vehicle.. so just trying to establish current baseline and establish current "health" of engine. figures run: 4@125, 110, 117, 115 105. Have not done valve adjust yet.. so that may make a difference.. engine runs fine.. have not put many miles on it yet so no idea about oil consumption.. but don't see any smoke. at this point just sorting out this 'new to me vehicle" and making sure it is roadworthy.
I don't think you'll gain by adjusting valves. A looser valve train will surely allow the valve to seat. If the valve train was too tight I could see loosing pressure. But they don't wear tighter.
I know I'm not much help here for ya, as you're looking for actual expected numbers. And I'm just speaking in generalizations.
Something going on with the 105 cylinder seems out of line. Maybe a valve. Not like it would ever leave you stranded. Not sure if I'd do anything about it. Does it have a lot of miles on it?
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Junior User
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From: Wenatchee, WA
Being 7.2:1, I guess the 110-125 may be in order. The 145 I'm thinking is more in the 8.5-9.5 cr.
I don't think you'll gain by adjusting valves. A looser valve train will surely allow the valve to seat. If the valve train was too tight I could see loosing pressure. But they don't wear tighter.
I know I'm not much help here for ya, as you're looking for actual expected numbers. And I'm just speaking in generalizations.
Something going on with the 105 cylinder seems out of line. Maybe a valve. Not like it would ever leave you stranded. Not sure if I'd do anything about it. Does it have a lot of miles on it?
I don't think you'll gain by adjusting valves. A looser valve train will surely allow the valve to seat. If the valve train was too tight I could see loosing pressure. But they don't wear tighter.
I know I'm not much help here for ya, as you're looking for actual expected numbers. And I'm just speaking in generalizations.
Something going on with the 105 cylinder seems out of line. Maybe a valve. Not like it would ever leave you stranded. Not sure if I'd do anything about it. Does it have a lot of miles on it?
Car-nut motorhead friend says that psi compression test reading can be affected by valve adjustment as test measures closed overlap of psi when both valves are closed. Yep... looking for actual numbers..like psi when new or rebuilt-stock? don't know how many miles on the engine. an inquiring mind has been my curse..especially when it comes to numbers...not sure why a new/rebuilt psi number is so elusive. One would think that I would have better things to do than search after such things.
Save the old ones
Joined: Dec 2002
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From: Boyne Mich
Yeah I get it. Hunting down something that's not really going to matter. I too have the "Love those ford trucks" curse.
I like your truck. I have a 65 N-700 with a 331. If it ran at all I'd check the compression just to compare for you. It was my grandpa's truck and it hasn't ran it 15 years.
Be sure to post this in the FE / FT Engine forum. Someone on here knows
I like your truck. I have a 65 N-700 with a 331. If it ran at all I'd check the compression just to compare for you. It was my grandpa's truck and it hasn't ran it 15 years.
Be sure to post this in the FE / FT Engine forum. Someone on here knows
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Junior User
Joined: Jan 2014
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From: Wenatchee, WA
Yeah I get it. Hunting down something that's not really going to matter. I too have the "Love those ford trucks" curse.
I like your truck. I have a 65 N-700 with a 331. If it ran at all I'd check the compression just to compare for you. It was my grandpa's truck and it hasn't ran it 15 years.
Be sure to post this in the FE / FT Engine forum. Someone on here knows
I like your truck. I have a 65 N-700 with a 331. If it ran at all I'd check the compression just to compare for you. It was my grandpa's truck and it hasn't ran it 15 years.
Be sure to post this in the FE / FT Engine forum. Someone on here knows
What I find curious is that the used engine places reference compression test as well as the rebuild folks..maybe I'll just contact the folks that are offering a rebuilt FT-361 and ask what the compression is.. I'll look all day for a $2 tool i misplaced.. not saying it is logical. Actually would like to know.. kinda like blood pressure.. what is good? whats not? what it IS doesn't mean as much if you don't know what its supposed to be...If anybody has rebuilt a FT361 and knows the psi.. please share the info.
Fleet Mechanic
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From: peru kansas
IIRC your 361 should have only been available with a 2bbl but i may be wrong.... but are you 100% certain its not a 391? same way to test as a 360 vs 390, 3.5" is a 360/361 and 3.78" is 390/391.....
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Junior User
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From: Wenatchee, WA
Thread Starter
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Junior User
Joined: Jan 2014
Posts: 83
Likes: 2
From: Wenatchee, WA
Yep..not seeing any psi figures..they can't hide forever. Or even the 7.2 comp ratio. always thought that 10-15% max was allowed spread high to low.. bit surprised to see 25%.. thats a bunch.. like 30#