maximum safe RPMs
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Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
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From: Western Washington
maximum safe RPMs
What is the max RPMs on a stock 390? The motor is stock as a rock, 2v carb and intake, regular exhaust manifolds, factory cam. It's all got 100,000 to 150,000 miles on it.
Sam
Sam
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Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
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From: Western Washington
So if it made maximum power at 4000, it would probably go a few 100 past that before it would break something, I hope! The reason I ask is someone else was driving my pickup a few days ago, and they didn't bother to up shift and went down a steep hill at 30 MPH, in second. That poor thing was screaming at 4500 RPM. Then yesterday I fired it up and got steam blowing out the exhaust (one side only), and I'm not very happy. I've had a tough enough time keeping this thing alive, I don't need it to have it over revved!
Sam
Sam
Laughing Gas
Joined: Jul 2004
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I wouldn't worry much about it. 4500 isn't that high, and i wouldn't think they would have balanced your engine any better or worse than the higher output 390's and i think they peaked HP at 4800? The major thing to worry about would be valve float with weak springs.
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Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
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From: Western Washington
Well, I didn't loan it out, Dad wanted to drive it. He can drive this thing like a pro when he wants to, but he loves that v-8 through a glass pack sound a little too much. I've got a mind to trash the glass-packs and buy some stock mufflers for it, unless there's anything quieter!
Like you said, 4500 RPM for a new motor isn't that bad, the thing is, this engine is on it's last legs. A year ago I checked the compression and it's got 40 pounds in one cylinder, 80 in another and 110, 120 on the rest. And before I put some thicker oil it had all kinds of clunks and rattles coming from the valves and who knows what else....
I'm getting my license next month and this truck was going to get me and my tools to work! So if it dies, I'm in a bad spot.
Sam
Like you said, 4500 RPM for a new motor isn't that bad, the thing is, this engine is on it's last legs. A year ago I checked the compression and it's got 40 pounds in one cylinder, 80 in another and 110, 120 on the rest. And before I put some thicker oil it had all kinds of clunks and rattles coming from the valves and who knows what else....
I'm getting my license next month and this truck was going to get me and my tools to work! So if it dies, I'm in a bad spot.
Sam
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Fleet Mechanic
Joined: Jun 2007
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From: Ohio
Well, I didn't loan it out, Dad wanted to drive it. He can drive this thing like a pro when he wants to, but he loves that v-8 through a glass pack sound a little too much. I've got a mind to trash the glass-packs and buy some stock mufflers for it, unless there's anything quieter!
Like you said, 4500 RPM for a new motor isn't that bad, the thing is, this engine is on it's last legs. A year ago I checked the compression and it's got 40 pounds in one cylinder, 80 in another and 110, 120 on the rest. And before I put some thicker oil it had all kinds of clunks and rattles coming from the valves and who knows what else....
I'm getting my license next month and this truck was going to get me and my tools to work! So if it dies, I'm in a bad spot.
Sam
Like you said, 4500 RPM for a new motor isn't that bad, the thing is, this engine is on it's last legs. A year ago I checked the compression and it's got 40 pounds in one cylinder, 80 in another and 110, 120 on the rest. And before I put some thicker oil it had all kinds of clunks and rattles coming from the valves and who knows what else....
I'm getting my license next month and this truck was going to get me and my tools to work! So if it dies, I'm in a bad spot.
Sam
yea tell your pro driver dad he's no longer alowed to drive it lol
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Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
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From: Western Washington
Amazing that it still runs isn't it? Now I just have to make my dad understand that motors that run 4500 RPM are healthy, have even compression, and don't make bad noises. The FE is a tough motor, but I don't want to test out how long it'll live at 4500 RPMs! The motor's in a 3/4 ton pickup, not a mustang for goodness sake!
Sam
Sam
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Fleet Mechanic
Joined: Aug 2009
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From: Western Washington
And I appreciate the advice, this forum always points me in the right direction.
Sam
Laughing Gas
Joined: Jul 2004
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If you are going to rebuild it. Watch ebay for parts. There are a set of the 2291 TRW's on there now for a .030 over bore with stock rods. Says they were mounted and installed but never ran. I got lucky last fall i beleive and got a brand new in the box set for 200 shipped. If you have time and some money start watching and grabbing up some parts you will save a good amount. So that will save 200+ if you can get the pistons that way. Not sure what you are planning but thats how i build the last one.
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Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
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From: Western Washington
At this point, I don't know what I'll do with it. I've thought about swapping to a different motor, or maybe getting a used runner, but it's all up in the air right now.
I will definitely check ebay for parts, it has served me well in the past.
Sam
I will definitely check ebay for parts, it has served me well in the past.
Sam
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Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
Likes: 9
From: Western Washington
Well, some good news! I drove it for the first good long drive today, and it actually ran ok! It was blowing steam (out one side only) but it finally cleared itself up and quit! It still stinks like a wore-out old v8 with 7 working cylinders, but it actually might get me around once I get that license! I guess we'll just have to wait and see.
Sam
Sam