thanks BEAR
Installd A 390 Need Help?
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Installd A 390 Need Help?
WELL I GOT A 390 COMPLETE MOTOR FORM A GUY AND THE TIMING CHAIN WAS STRETCHED I DONT KNOW MUCH ABOUT THE MOTOR. YOU COULD STILL SEE THE HONE MARKS IN THE CYLINDERS SO I MEASURED ALL THE BARRINGS IN THE BOTTOM END AND THEY WERE ABOUT 150 THOUSANDTHS. I GOT A TRUE ROLLER TIMING CHAIN FOR IT ALSO, IT HAD A MOTOR CRAFT 4 BARREL CARB I PUT A KIT IN IT BUT IT DIDNT RUN VERY GOOD, SO I PUT A HOLLY 670 4 BARREL ON IT AND IT RUNS GOOD. BUT THE PASSENGER SIDE IS BURNING OIL SO I CHEKED THE COMPRESSION ON IT AND IT WAS AROUND 100LBS. I PUT SOME MOTOR OIL IN EACH CYLINDER AND IT DIDNT COME UP. ALSO THERE IS NO CRANK PRESSURE, SO ARE THE RINGS OK ? IF I GET THE HEADS REBUILT DO YOU THINK THAT MIGHT FIX IT AND ALSO I WANT TO PUT A DIFFERENT CAM IN IT SO I HAVE A LITTLE MORE TORQ WHAT KIND DO I WANT?
Post Fiend
Joined: Mar 2004
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From: Union, Washington
If the compression doesn't increase with the oil, then the rings are good. Probably the valve seals are bad. But then again it the valve guides are bad enough new seals won't help much. With the right tools you can change the seals without pulling the heads.
Post Fiend
Joined: Mar 2004
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From: Union, Washington
If the compression is even thru out the motor, most likely. I have always prefered the RV cams for trucks with short durations and lots of lift. But then I have a big camper and have several trailers I tow alot. Even though I have used several different cams in light duty trucks that don't haul much. Something in the 270 to 290 degree region with about a .500 lift. To much duration kills gas mileage and streetability, extra lift does not.
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I Pull My 19' Boat It Only Is About 2500-3000 Lbs. With The Holly 670 And 350 Gears On The Hwy I Got 16+ Not Pulling But I Would Like A Little More Pwr Out Of My F150 Also Is The Holly 670 Street Avenger Ok Carb It Runs Good Just Need A Little More Torq
Post Fiend
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From: Union, Washington
For the average street engine anything bigger than a 600 CFM vacuum secondary carb is not a good choice. Dual exhaust and a recurved distributor will help more than a bigger carb. I ran a Holley 600 CFM on my '68 F250 with a 390 with the 390GT cam and 3.73 gears and the dual exhaust and the recurved dist. got me more mpg and preformance than the carb rework did. I also have a 600 CFM Holley on my '84 F250 with a 460 engine.
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help what is a recurved distributor? and is that the name of the cam that i need 390gt cam? thanks mike.
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Post Fiend
Joined: Mar 2004
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From: Union, Washington
Recurving a dist. refers to changing the advance curve. Usually meaning shortening the amount of advance(so you can run more intitial advance) and changing how fast the advance comes in. Most auto parts stores can get you a recurve kit with instructions if they handle hotrod parts. The 390GT cam was the factory cam that cam in the 1966 and on 390GT engines. If memory serves it had 270 degress of duration and .481" of lift. and after market cam with 270 to 290 degrees of duration and around .500" of lift would work well. Get a set of lifters with the cam if it doesn't come with them.
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Guys, advertised duration doesn't really tell you much, I always go by the duration @.050 lift. For a lower compression stocker, I wouldn't think you would want to have anymore than 212 duration @.050 and maybe even less. The cam I bought and haven't yet put in my 401 (.060 over 390) which should be at least 9.5:1 compression has 225/230 duration @.050 and 566 intake lift and 552 exhaust lift. I hope I like it. I don't know if it will be much on mileage but only time will tell.
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Post Fiend
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From: "Islander"
270 / 290 cam
Russ; that cam 270 / 290, is only 194 / 204 @ .050", .481-.490 with 1.76 rocker was the old 428 CJ cam. Been running one for years on the 410 with 3 degrees advance. Great low end torque, midrange and fuel mileage. Now at 14.2 mpg if running at 62 mph with 12.00 x 33 x 16.5, 3.54 with C-6. I've been (bashed, my thinking sorry) by why I used a 35 year old design or grind, there is better. This motor was built over 18 years ago and I installed a Performer cam once, what a failure and waste of money. The 270 / 290 has been the best cam so far until I build another motor.
Carl....=o&o>....
Carl....=o&o>....
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From: Grain Valley Mo.
Bear, did you mean the valve seats are bad? Not sure if valve seals would lower compression.
Beemer, am curious about your performer cam bad experience. Low power?
____________________
'fordman (retired)
1953 F100
if it was easy everybody would have one
Beemer, am curious about your performer cam bad experience. Low power?
____________________
'fordman (retired)
1953 F100
if it was easy everybody would have one
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I know what Beemer is talking about with his Performer (they are actually called a Performer-Plus) cam. I have used this cam in my now rebuilt again and mildly souped up 390 and I haven't been impressed with it at all in either incarnation of the 390's I have had it in. I really couldn't hardly tell a difference between it and the stock cam it replaced. They just are not an agressive profile and my engine does run pretty darn well but it just kills me to think I put that cam back in there because I really think my engine has a lot more potential and is being held back by it.
Post Fiend
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From: "Islander"
xfordman; the Performer cam caused solid detonation above 1/2 throttle. Compression check showed readings of 210 / 215 psi. With more overlap on the 270 / 290 cam, 38 degrees advance, 11 degrees initial, 9.10 cr on mid grade gas the 410 would just begin to have detectable detonation. This is when just getting off the highway and jumping on it when the heads and block are highway hot.
Carl....=o&o>....
Carl....=o&o>....