1991 351W compression
1991 351W compression
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Joined: Oct 2004
Posts: 32
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If you live in Denver, CO. a compression test would read lower than in say St. Louis, MO. Although I agree your readings seem low compared to my 1990 F250 4x4 w/5.8 litre w/250,000 miles.. The lowests cyl. was 160# the highest was 175#, this is well within the allowabe 20% difference between highest and lowest cyls., and I live in Wisconsin.
Although I was satisfied w/the results of the compression test and cylinder leakage test I pulled the motor to replace rear main seal, ring and replace bearings. (I have some blow-by). My desire is to swap in better breathing heads and install a new cam. Upon disassembly the cam is obviously worn and 2 lifters have knife sharp edges. The worn cam explains my loss of power.
What kind of problem are you trying to diagnose?
Although I was satisfied w/the results of the compression test and cylinder leakage test I pulled the motor to replace rear main seal, ring and replace bearings. (I have some blow-by). My desire is to swap in better breathing heads and install a new cam. Upon disassembly the cam is obviously worn and 2 lifters have knife sharp edges. The worn cam explains my loss of power.
What kind of problem are you trying to diagnose?
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Tuned
Joined: Mar 2007
Posts: 258
Likes: 1
Thanks everyone I appericate the fast response. I just picked up this truck, I had to rebuild the hubs and brakes already and I just felt the power was lacking. I also noticed the air filter box was full of oil, my 86 did this also it was caused by a bad ring on #8 but it was obvious as the cylinder was in the 70's and the others were up around 120. So when I ran a compression on this 5.8L and all the cylinders were around 100 or so, I just want a second opinon to my thinking. It only has a 115000 miles on the truck and I plan on this being my hunting truck which means it needs to be dependable in harsh country in the high country, my hunting camp is at 10600ft, as well as needing to tow my camper and gear over two passes and up and then up to my camp on snow,mud,rain or what ever comes along in the Colorado high country in the middle of October. I have pictures posted of this truck in my gallery.
FTE Legend
Joined: Jun 2006
Posts: 31,930
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From: Ottawa, Ontario
Originally Posted by rkymtnman30
Any suggestions for the cam and intake to maximize hp?
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Tuned
Joined: Mar 2007
Posts: 258
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I am in process of a full rebuild I will have the motor out by this weekend and am looking for a machine shop nearby for the heads and block. I agree that is exactly what I am looking for any suggestions as far as cams go?
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Joined: Jun 2006
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From: Ottawa, Ontario
Originally Posted by rkymtnman30
Will I need to make any modifications to my computer with a different cam?
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Tuned
Joined: Mar 2007
Posts: 258
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9:1 pistons and a Comp cams 35-255-5 is good with my 91 351 W EFI with no other modifications and will help with towing capabilities, correct? I am still trying to find a reasonable machine shop to take care of my block I wish I had a dip tank, lol. I am hoping the one I find can take care of my heads as well, with out costing me my first born.
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Tuned
Joined: Mar 2007
Posts: 258
Likes: 1
I found a machine shop to dip my block but get this they won't do it if they don't remove and install the cam bearings, lol. I have always done my own cam bearing so I had to tell them to forget it. I found another place though has anyone heard of jet wash vise dip for a block?
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1991, 351, 351w, 50, block, compression, cylinder, f150, ford, horsepower, low, small, specifications, specs, test
