. The engine runs SO darn good though, quiet and doesn't smoke at all!
Blow by?!
Thread Starter
|
Junior User
Joined: Jun 2015
Posts: 77
Likes: 0
Blow by?!
Just bought a clean "84 F150 with a 300/C5. Two owner truck with 161K miles. It runs really good,smooth and does not smoke. It does have blow by though...The guy hooked up a catch can, and always kept her full of oil. What should I be looking at? I have not done a compression check, but I find it hard to believe it would have a cylinder problem!
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
Hello Gahighrider,
I have some blowby on my engine too. Compression is only around 120 - 130 on all 6 cylinders. But, it runs really well, and is nice and smooth. I'm assuming worn rings or the like.
However, first things first, are you sure it's venting properly? Is the PCV system in working order? If it's not, that will cause the normal crank case pressure to come out wherever it can, which will make it seem like blowby. It would be a good thing to check first before jumping to bigger conclusions.
On a sidenote, the transmission is a C6 (not C5).
Best of luck!
I have some blowby on my engine too. Compression is only around 120 - 130 on all 6 cylinders. But, it runs really well, and is nice and smooth. I'm assuming worn rings or the like.
However, first things first, are you sure it's venting properly? Is the PCV system in working order? If it's not, that will cause the normal crank case pressure to come out wherever it can, which will make it seem like blowby. It would be a good thing to check first before jumping to bigger conclusions.
On a sidenote, the transmission is a C6 (not C5).
Best of luck!
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
Interesting, I've never heard of a C5 being in a full size truck. I always thought they were in Rangers, Bronco IIs, etc (smaller stuff). Especially in the 80s. So, if so, I stand corrected. Either way, that's a tangent. 
The smog pump doesn't factor into the PCV system. It's there to help the catalytic converter be more efficient.
As for the PCV system, have you ever changed out the PCV valve on the back of the valve cover?
When the engine's running, pull the PCV valve out and put your finger over the end. You should hear the checkball inside "snap" and it should suction on pretty well. You can also try pinching the vacuum line going to the PCV (some pliers can help) and you should hear the checkball snap closed too.
If there's little to no vacuum, check the vacuum source, the hose itself for plugs/damage. If the PCV valve constantly rattles, replace it.
Hopefully that's all it is.
The smog pump doesn't factor into the PCV system. It's there to help the catalytic converter be more efficient.
As for the PCV system, have you ever changed out the PCV valve on the back of the valve cover?
When the engine's running, pull the PCV valve out and put your finger over the end. You should hear the checkball inside "snap" and it should suction on pretty well. You can also try pinching the vacuum line going to the PCV (some pliers can help) and you should hear the checkball snap closed too.
If there's little to no vacuum, check the vacuum source, the hose itself for plugs/damage. If the PCV valve constantly rattles, replace it.
Hopefully that's all it is.
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
If your PCV system is working well, and you still have blowby, you may simply be in the same boat as me in that the rings are worn or broken. If it's venting well, and there's still blowby, there's more pressure coming out than the PCV can accommodate for.
Trending Topics
Thread Starter
|
Junior User
Joined: Jun 2015
Posts: 77
Likes: 0
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Thread
Thread Starter
Forum
Replies
Last Post
mrblottokid
1961 - 1966 F-100 & Larger F-Series Trucks
3
Mar 25, 2004 04:30 PM