Hi all, new member...

Considering purchase of a '69 Highboy with a 390 and need to know what is the stock compression ratio. Any help greatly appriciated. Thanks

Toddler19

 

First off, welcome aboard.

Secondly, "most" 4x4's did not come from the factory equiped with a 390. Your VIN on the door tag will tell which engine was in the truck when it was purchased. Is the motor factory or did you buy the truck and were told it's a 390? If it is a late model 390 truck motor, I think they came in around 8.5-8.9:1. Some of the experts will correct me if necessary

--Mike

 

Welcome Aboard!

I think your going to have to pull some #s off the block and heads and intake So some of the guys with the Numbers books can run them for ya!

I have some #s but by no means all...Most of the guys in here are pretty well verst of the FE motors..They can give all the skinney you want..But lets ID the Motor First!

Russ

 

Most stock truck FEs were in the low 8s for compression. Remove the stock steel head gasket and use a standard felpro and you are in the 7s!

 

Sean..If there were no 390s put in 4X4s he might have a car motor??

Transplant? or ? Truck motor of what year?

 

He could have anything. Hopefully he comes back and adds some more info.

 

Yep Sean... I think #s and a stroke test will prove to be the right wat to go!! IMO

 

390's were put in trucks, F-250's and up. I see loads of 'em in F-250's up at the junkyard. I just read the sticker on the valve cover.

A set of higher compression height pistons and you're good to go. Like Rat said, you're in the low 8's now. The stock compression height for that year is 1.680", and the compression height for *some* aftermarket pistons is 1.776". 360 pistons also have 1.776" compression height and are a cheap alternative if your block doesn't have to be bored.

 

Kurt were they put into that year of 4X4? were they put into any stock 4X4s?

 

No, the 360 was the biggest FE you could get in a 4X4. The 390 was only in the 2WD versions.

 

Thanks for all of the help with this guys! I have not purchased the truck and was not able to get in touch with the owner yesterday so, I was not able to obtain any more information. I am going to try to talk with the owner more today and I will post the information as soon as I get it. So, Mike G., I will be able to find out what motor it has by the VIN number?

 

One more piece of information.....it is an F250.

 

Maybe... You had indicated it was a highboy so I was working a F250 4x4 in my head. If the motor is the original and the door is too, the tag on there will tell what motor it should be. You should see the VIN start with F26x, where "x" is the engine code. I believe you will find a "Y" in this location, which is 360, but if you do see an "H", it would be a 390. I would definitly take along some goodies to do the "stroke check" to see what's inside for sure if you are serious about the truck. You can check out the sticky by Ratsmoker, I believe the how-to is there, if not, just ask.

--Mike

 

I finally spoke with the owner and here is the VIN Number: F26YRF10591.
He said that he was pretty sure it was the 390, so is he right? Where can I decipher the VIN number? Thanks again for all of you help.

 

Thanks Mike G, I guess that answers the question of what motor it has...the 360. So, the stock compression should be in the 8's? I will also check the sticky from Ratsmoker on stroke tests to make sure that it is the original motor.