This past summer we rebuilt our 390. The block was done at 60 over, RV cam, everything else was gone through / or replaced. The only old items under the hood are the power steering unit and alternator. Timing is set at 6 BFTDC and I have a holley 600 cfm, the rest is stock.
We put about 2000 miles on her after the rebuild and the only problem has been a lack of power. Without a load on it, it appears to do fine. As soon as we put our trailer (about 5000 lbs) on it I can barely make average hills at 50. Our 01 4.7L Dodge Durango can do that.
I am about ready to look into the possible causes and need a little guidance.
Checks planned -
Compression
Timing - To include checking the advance -
Vacuum from the manifold - Any suggestions on where to get a descent gauge without killing the wallet? The 09 we just bought has successfully done that!
Suggestions and ideas would be appreciated!
Thanks
Dan
There could be a million reasons. Timing at 6 BTDC is a little conservative. FE's need timing advance. I keep mine at 10-12BTDC. Way back in my off road racing days I built a 390 with mostly stock Ford parts. I had used an interceptor manifold, 428CJ heads 12.1 TRW pistons and the cam was from a 63 427 dual 4V. I was disapointed on the initial test. We pulled the distributor and had it recurved. It was a totally different animal after that and one of the best engines I ever built. If there is nothing misbuilt mechanically I would look at timing and timing advance. Us old timers used to keep a hand vacuum pump in our tool box for checking advance. Some of the old distributors had an allen screw inside the advance port. You can adjust how much total vacuum advance you are allowing with this.
sgs
I should have added the Duraspark ignition system from a 76 was also installed before the rebuild...
From what I have learned here, the compression will check the pistons, the manifold vacuum will give me an idea how the top end is doing and last the timing advance...
When I get to the timing, we'll try 12 degrees BFTDC and then check what kind of advance we get, I read here I should see around 34 to 36 at a given RPM (I'll look for the thread). .
Last, about re-curving the distributor. Could someone briefly explain why and how??
Thanks!!
"RV" cam could mean anything... any chance of a brand and part number or specs?
in addition to the checks already suggested, It look at the cam timing as well, a stock replacement timing set may not install it "straight up".
Recurving a distributor involved changing the amount and rate at which advance is added by the centrifugal advance weights. Usually to reduce the amount of total advance (so that the initial can be set higher) and quicken the rate at which the advance is added.
I'll have to stop by the craft shop and ask which cam I received, they ordered the setup through EPWI. Is there a way to ID the cam without tearing the front off?
When I set this timing chain, we just aligned the points on the gears with the #1 cylinder at TDC. There were no other marks one the gears - a set I received from Summit appears to have three different settings. I still have that set in the box.
For the re-curve, is this done in a specialty shop? The distributor we have was a rebuild from NAPA for the Duraspark.
Dan
Checking compression Ford says the cylinders must be within 75% of the highest cylinder and a check checks head gaskets, heads, valves and Piston rings.
Vacuum gauge checks carb and ignition settings once you really learn the gauge. It also checks the intake valve for leaks and the exhaust valve if it does not open.
Old Fords Rule Was a Ford Service Tech
71 F250 with Shell Car 390 NP435 Dana 60 3.73s, PS, PB, 750 EC VS Holley Accel Points Eliminator.
98 Volvo S70 2.4T Auto 71 Service manuals Volumes 1,2,3 and 4 So ask away. My Gallery Spark test
Dragon wrote:Nope no real way with out fancy tools.
Checking compression Ford says the cylinders must be within 75% of the highest cylinder and a check checks head gaskets, heads, valves and Piston rings.
Vacuum gauge checks carb and ignition settings once you really learn the gauge. It also checks the intake valve for leaks and the exhaust valve if it does not open.
The 10% rule is what most companies/people go by. 75% is a waaaaays off in my book! There is no excuse for it to be over 10%. I don't use a Vac gauge. I use a timing light with the RPM built in. Vac gauges don't really work when you go to bigger cam shafts!
Personally, I would set you timing @ 10 to 12 Deg. And go from there. One thing at a time or otherwise you wont know what fixed the problem or you can cause more problems. Also did you dial in your camshaft??? If you didnt, you should of! JMHO
Wes Adams FORD428CJ
Built Ford Tuff With Good Ford Stuff
79 F-250 X-Cab 4x4 6.9 Turbo Diesel
64 Falcon X-Ram 428
55 FORD Truck 4-link Rides on air with X-Ram 428
67 Stang 351 C/J
2000 Yamaha V-MAX VMOA#4277
75% of the highest cylinder is on a 25% drop but that is Ford's GM's and Chrysler's guidelines. Forgive me for cussing.
Vacuum gauges work on any motor just not for stock they don't read at low vacuum in a lumpy cam motor but just above the lump they will tell you what is up.
Old Fords Rule Was a Ford Service Tech
71 F250 with Shell Car 390 NP435 Dana 60 3.73s, PS, PB, 750 EC VS Holley Accel Points Eliminator.
98 Volvo S70 2.4T Auto 71 Service manuals Volumes 1,2,3 and 4 So ask away. My Gallery Spark test
DuckRyder wrote:
in addition to the checks already suggested, It look at the cam timing as well, a stock replacement timing set may not install it "straight up".
DGrant09 wrote:When I set this timing chain, we just aligned the points on the gears with the #1 cylinder at TDC. There were no other marks one the gears - a set I received from Summit appears to have three different settings. I still have that set in the box.
Dan
The stock cam chain set up for 1972 probably has a factory 5 degree retard in it, a result of tighter emission controls beginning in 72. Your summit set has 3 positions- 5 degree advance, straight up (0 degrees), and 5 degree retard. That factory timing set really isn't helping anything! Also older vehicles draw off a direct vacuum port for the vacuum advance whereas 72-up draws from a timed vacuum port, resulting in less advance. It's something you may want to try; just don't cause so much advance that it results in spark knock.
Joe
1971 F100 flareside 8ft
1964 Chrysler New Yorker Town and Country wagon
2006 Dodge Ram 2500 cummins
2005 Ford Ranger
DuckRyder wrote:
in addition to the checks already suggested, It look at the cam timing as well, a stock replacement timing set may not install it "straight up".
DGrant09 wrote:When I set this timing chain, we just aligned the points on the gears with the #1 cylinder at TDC. There were no other marks one the gears - a set I received from Summit appears to have three different settings. I still have that set in the box.
Dan
The stock cam chain set up for 1972 probably has a factory 5 degree retard in it, a result of tighter emission controls beginning in 72. Your summit set has 3 positions- 5 degree advance, straight up (0 degrees), and 5 degree retard. That factory timing set really isn't helping anything! Also older vehicles draw off a direct vacuum port for the vacuum advance whereas 72-up draws from a timed vacuum port, resulting in less advance. It's something you may want to try; just don't cause so much advance that it results in spark knock.
I'm understanding it would be best to replace the stock timing chain setup with the Summit set and then set the gearing at 5 bftdc prior to timing? I'm hoping to get to the compression checks in the morning..
I think that it would be best to replace the oem style timing set with the summit one and install it at 0 degrees.
Before I tried advancing or retarding the cam I would definitely try all the simple stuff. When you change the cam timing you should check the piston to valve clearance (if it has stock pistons I'm sure it will be fine, but check) at least hand rotate the engine to be sure that there is no contact.
Ideally the cam should be degreed as the chain set of the cam itself could be ground a bit off spec.
Also older vehicles draw off a direct vacuum port for the vacuum advance whereas 72-up draws from a timed vacuum port, resulting in less advance. It's something you may want to try; just don't cause so much advance that it results in spark knock.