I ran a compression check on my truck today. I warmed her up real good and then pulled all the plugs, and hot wire. I also opened the throttle all the way open. I had 6 cylinders with120 lbs or a little higher and two had 102-110. Now I will say I was using a $20 kit I got from China Freight so results could be iffy, however, I was wondering how can I tell if problem is rings or leaky valve? All spark plugs are free from oil and looked pretty good. Engine is running a little rich as I currently still have a 2 barrel intake with a 4 barrel carb. I will be pulling engine week after next and sending heads to shop for valve job and hardened seats so I hope I can pin point valve issue.

Also, read thread where 351m running 4 barrel intake on heads mfg for 2 barrel could cause problems. Is this an issue with FE motors as well?


Thanks for the help

 

No problem for an Fe switching intake with 2 or 4 barrel heads..

A few pumps of oil from a hand held oil can into the each cylinders seals the rings then compression goes up to it's max rating-+= good valves.

But if the compression fails to get but a small noticeable movement valves are leaking or burnt..
One thing that happens when redoing the valves if real bad it put extra force on the rings and then they start leaking more having the higher compression you end up with having a increased in blow-by that you did not have before going past the rings.
Now you'll wish you rebuilt the lower end..
orich

 

Off your subject; but I did not know you could do that. ??

 

Are the cylinders next to each other? If so that could point to a head gasket starting to go. A Mustang buddy of mine had the same issue in non-adjacent cylinders on his 390. Turns out it was stuck rings in those cylinders. They were carboned up really bad and each one had one stuck ring. He ended up rebuilding the motor but YMMV.
And Dee, Jegs and Summit sell adapters for that.

 

cylinders are number 4 and number 5 so not next to each other.

You can run a 4v on a 2v intake but have to buy an adapter. Not a real good situation cause now I have 4v's trying to empty into the 2v hole. I had a to good to pass up offer so I had to do this, a buddy of mine had someone wanting a motor craft 3v for restoration so he traded me for a quadrajet.

Orich, you are so right about this, I can't see myself having the motor out and not putting in new rings and bearings. I am going to pull the motor and clean up the engine bay now as I am pretty much caught up on my list of things to do.....

 

anyone know of a good place to get a decent priced rebuild kit? Can't seem to find one on Competitions site....

 

I got ss intake & exh valves off ebay and the manly seat. A comp cam kit 268H, Pistons,ring brand name from summit seal power or Jags Not the pressed pins tho!
H-rods from ebay who ? Cam bearing, rod & crank bearing ebay, New head & ss intake bolts ebay,.. A lot from speedway motors, A 428 crank from Engle's. I doped my compression down 8.7 so could run 87 octane gas when needed due to the high cost of gas in Calif. To make up for the lower compression added the 428 crank. For 30+ yrs had to run 91+ and time 2* no vacuum adv. too keep it pinging under load. All due to having a 1,800lb. over head camper on the already heavy High boy 5,700lb. Then $800 for labor for head work= 3 angle valve job install seats & new guides shaves 00.5ths refaced exh. port side.. Not counting block prep Squared block bored 0.30 and honed with torque plates for a straight cylinder walls. If you have pistons that all are all the same size then no need to fit each piston too a cylinder. So drop in any piston in any cyl. hole. for first install. Then theirs balancing.. Grand total about $4500 if you assemble it.

Take your time go slow, measure and double check every thing a shop has done the best you can. And what you do and you'll have a fine motor that will last for yrs, that is unless you race it..
orich

 

Engines kits - Discount Engine Rebuild Kits Manufacturers at Clegg Engine

I get all my parts from here for my engine. If you call them you can get a custom kit put together for you. Here is the best part of the deal, they will put the kit together, price match the individual parts against Jeggs, Summet Racing and a couple of others. Once the base price has been figured, they will give you a "kit" price further reducing the total cost. If your like me and have a wishlist as long as your arm and can't afford to purchase everything all at once, they will line item the kit out, spread your savings across some of the more expensive parts, then allow you to purchase your "kit" one piece at a time.

My kit had the following:
OE 390 Crank .020/.020
reconditioned Connecting Rods
Sealed power flat top pistons (CNC Machined)
Gasket set
Mallory Rings
Bearings
Freeze plugs
dual roller timing set
PRX Rocker Arm Assembly
Hardened Stainless steal push rods
High volume oil pump
7 quart oil pan
Dip Stick
Assembly lube
Total cost with shipping ----- $1800

I highly recommend them of anyone doing an engine overhaul

 

i use Mabbco motors myself...( MABBCO® MOTORS, USA - Short Block, Automotive Motors, Marine Motors, Engine Kits, Crank Kits, Long Block ) got the parts i wanted for around $500 and shipped to my door free of charge in the continental U.S.

 

All I need is rings and bearings for standard and they have for $95! I will definitely be in touch with them. May use other as 390 is in future plans.....

 

at the very least, replace your head bolts. This will help to prevent blown head gaskets in the future. I would also recommend replacing main bolts. If your going to reuse your rods and pistons, then replace your rod bolts and wrist pin bushing. These are high wear items, and will likely fail on you after you have restored your compression. The last thing you want if for a rod to go threw your block after you spent so much time rebuilding it.

 

Looking at the cam break in I am concerned about engine oil. I read where Castrol GTX, Rotella, and Valvoline still have enough zinc to protect (after break in) but I need to add a bottle of zinc during break in process. This wasn't the case last time I broke a cam in, I guess this is a relatively new change in oil? Anyway, I will probably run the Castrol GTX for now..... Hope everyone has a Merry Christmas!