Engine question with 81f150 4x4 351w
Thread Starter
|
Freshman User
Joined: Nov 2000
Posts: 29
Likes: 0
Engine question with 81f150 4x4 351w
The question is this.
I recently relace and rebuilt the lower end on my 351-w (the top end was fine)and replaced the oil pump at the same time. Now there seems to be an increase in crank case presure.(i.e. blowing a little oil out of the dipstick tube) so I went and sealed the tube just to see what would happen.
Well my oil presure increased about 5-9lbs and it no longer leaks. No other places appear to be leaking at this point.
The oil pump I put in is "high volume" . Is it possible that the "high-volume(presure)" oil pump is making to much presure there bypassing into the crank case? All bearing are new along with the crank itself. I check all the tolerances on the top end, and they are well with specs. All oil ports are clear and there is maybe 1% blow by at the rings maybe not even that much.
The engine is tight, and runs like a raped ape.
Any help would be appriciated
1981 f-150 4x4 351W /4in lift/short bed/baby blue
33-12.50-15 bfg mudder tires
RUDEDOG
I recently relace and rebuilt the lower end on my 351-w (the top end was fine)and replaced the oil pump at the same time. Now there seems to be an increase in crank case presure.(i.e. blowing a little oil out of the dipstick tube) so I went and sealed the tube just to see what would happen.
Well my oil presure increased about 5-9lbs and it no longer leaks. No other places appear to be leaking at this point.
The oil pump I put in is "high volume" . Is it possible that the "high-volume(presure)" oil pump is making to much presure there bypassing into the crank case? All bearing are new along with the crank itself. I check all the tolerances on the top end, and they are well with specs. All oil ports are clear and there is maybe 1% blow by at the rings maybe not even that much.
The engine is tight, and runs like a raped ape.
Any help would be appriciated
1981 f-150 4x4 351W /4in lift/short bed/baby blue
33-12.50-15 bfg mudder tires
RUDEDOG
Elder User
Joined: Jan 2000
Posts: 656
Likes: 0
From: Gravel Switch, KY
Engine question with 81f150 4x4 351w
Check your PCV valve to be sure it is operating correctly. Also, some blow-by will be normal until the engine is broken in, especially if you used chrome-moly rings.
DannyP
89 F-150 4x4 former EFI I-6 now carbed 351W, Edelbrock heads,cam,intake,carb.
MSD 6A, ZF, Sterling 10.25 with 3.55L's.
DannyP
89 F-150 4x4 former EFI I-6 now carbed 351W, Edelbrock heads,cam,intake,carb.
MSD 6A, ZF, Sterling 10.25 with 3.55L's.
Moderator
Joined: Jan 2001
Posts: 56,984
Likes: 2,738
From: Virginia
Engine question with 81f150 4x4 351w
I agree with DannyP. Never had a problem with blow-by on
any of the engines I've rebuilt, but everytime I put Moly
rings in, It seems to use a little oil for about the first
month of daily driving. Then it goes away. When I use cast
iron rings they don't do this. I figure I am putting the wrong
finish on the bores or something.
any of the engines I've rebuilt, but everytime I put Moly
rings in, It seems to use a little oil for about the first
month of daily driving. Then it goes away. When I use cast
iron rings they don't do this. I figure I am putting the wrong
finish on the bores or something.
Thread Starter
|
Freshman User
Joined: Nov 2000
Posts: 29
Likes: 0
Engine question with 81f150 4x4 351w
PCV is new and did not use crome moly rings.
I check the cylinder leak down by compresion and don't have but maybe a pound loss in 15 minuets.
I beleive that I can eliminate blow by. The only place I can think that this is comming from is the oil pump, Just never heard of a problem like this one. Then again all ford trucks are unique. Anyway thanks for the help, I anyone can think of anything else just let me know.
L8TR
RUDEDOG
I check the cylinder leak down by compresion and don't have but maybe a pound loss in 15 minuets.
I beleive that I can eliminate blow by. The only place I can think that this is comming from is the oil pump, Just never heard of a problem like this one. Then again all ford trucks are unique. Anyway thanks for the help, I anyone can think of anything else just let me know.
L8TR
RUDEDOG
Thread Starter
|
Freshman User
Joined: Nov 2000
Posts: 29
Likes: 0
Engine question with 81f150 4x4 351w
O.K.
hears the seal.
I found after droping my oil pan that the oil pump presure relief valve spring was bad and was venting more presure into the crank case. It seems that when you put a high volume oil pump on this perticular motor 351-W, It makes to much presure and vents by going thru the presure relief system. I don't exactly know why this happens, but it did.
I replaced the pump with a standard oil pump from FORD and the overpresurization of the crank has been eliminated.
This is just a fllow up and is for people that might have the same problem. I would hate to keep this info to myself seeing that this group has helped me out in the past.
Good luck and happy FORDING.
RUDEDOG
1981 F150 4X4 351-W BABY BLUE SHORTBED
33-12.50.-15 BFG MUDDER T/A 4IN LIFT
hears the seal.
I found after droping my oil pan that the oil pump presure relief valve spring was bad and was venting more presure into the crank case. It seems that when you put a high volume oil pump on this perticular motor 351-W, It makes to much presure and vents by going thru the presure relief system. I don't exactly know why this happens, but it did.
I replaced the pump with a standard oil pump from FORD and the overpresurization of the crank has been eliminated.
This is just a fllow up and is for people that might have the same problem. I would hate to keep this info to myself seeing that this group has helped me out in the past.
Good luck and happy FORDING.
RUDEDOG
1981 F150 4X4 351-W BABY BLUE SHORTBED
33-12.50.-15 BFG MUDDER T/A 4IN LIFT
Thread
Thread Starter
Forum
Replies
Last Post
Peavey1986
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
5
Jan 5, 2015 04:42 PM
CrazyMiracleMan
1987 - 1996 F150 & Larger F-Series Trucks
13
Oct 16, 2012 03:35 PM
884x4broncoII
1994.5 - 1997 7.3L Power Stroke Diesel
18
Dec 21, 2008 02:24 PM
blue oval blues
1987 - 1996 F150 & Larger F-Series Trucks
5
Feb 6, 2004 11:14 PM
martyf150
Ford Inline Six, 200, 250, 4.9L / 300
8
Feb 4, 2003 11:28 AM
