truck 390

[fastback 427]

A guy in our group bought a 390 from a local guy who is supposed to be the best fe guy around. It was put in his 76 f-250 4x4 4spd. Truck has 37" military oz tires. The motor was built for this truck. After driving it for a thousand miles he was complaining about power and mileage. After more break in he pulled my 18 ft trailer with 78 150  on a 100 mile trip. He came back furious. Said the truck was overheating and pinging like crazy. We pulled it in and checked timing which was 18 initial and 38 total. Turned it down and didn't help. Truck was missing also so we did compression test all 170. No bent push rods. Checked plugs and pretty black. Number 8 looks like antifreeze. New plugs then threw in 5 gal 110 VP and runs little better. After a falling out with his engine guy we finally found out engine specs. .30 over 390, flat tops, performer can and intake, 750 Carb, manifolds. I did the math and I'm thinking it's got about 10.7 to one. Can we bleed this off with bigger cam? Also might pull heads,d-2, and unshroud valves and smooth chamber, maybe try to take a little extra? He would like to leave bottom alone if possible as cost is an issue. We do have performer rpm to put on but he is worried about runner mismatch. The truck is mostly a driver but will pull occasionally. It has OK low end but no top end. You help would be much appreciated.

[jayb]

Yes, you can bleed off some compression by stepping the cam up in duration.  The Performer RPM is a much better manifold than the Performer, even down in the low speed ranges by most accounts.  There shouldn't be a big port mismatch.

Why are you seeing antifreeze on the #8 plug?  Are you suspecting a head gasket or intake gasket leak?  Also if the plugs are black I'd be looking at jetting in the carb...

[fastback 427]

I'm thinking the antifreeze is due to someone welding the crossover shut. Could be warped. Also if memory serves his rpm intake is medium riser runners and heads are lowriser. I have him talked into set of headers and we do have a distributor machine to curve it. Do you think the compression is still to much to bleed off?

[My427stang]

I'd check cam timing first.

Edelbrock claims the Performer cam is 272 advertised intake, 282 exhaust, 110 LSA on 115 intake centerline.  However, that HAS to be a misprint, because it doesn't make sense with the .050 timing.  Those events events put it at 105 intake centerline, which is logical for that cam

http://ecx.images-amazon.com/images/I/61g4h3-fjnS.pdf

So you could cam up, but in a big truck like that, you will lose low end and have all the expense of a new cam.

Assuming it is at 105 ICL like the numbers equate, a 10.7:1 390 is at 8.68 DCR at least, which with tall tires, probably poor quench, would ping or require so little timing that it'd be a turd and generate so much heat it'd probably STILL ping

You could go the cheap way and retard the cam 6-8 degrees, it basically would be somewhat similar to 428CJ cam timing and only cost you a timing set. I see it a pretty good match for the use

In the end, you'd have a 272/282 adv 194/204 @ .050 110 LSA on 111 or 112

Compare that to stock CJ cam specs,  270/280, 208/222, 115 LSA on 114.3 ICL


What I would do is:

1 - Retard the cam to 111-112 ICL (seems late but Ford used to install them as late as 114.5 in CJs, they sure didnt have a torque problem, as well as 4 barrel small blocks)
2 - Install your headers
3 - Recurve the distributor to 12 inital / 36 total all in by 2800
4 - Run a 185 degree thermostat
5 - Decide later on the intake, I like the RPM better, much better, but with the tall tires and towing, the Performer will do better part throttle despite giving up LOTS of WOT power so I am really on the fence on whether I would change it.  With that being said, I run an RPM in my truck

[fastback 427]

Yup, you're right it is a turd! We did degree cam, thought it was straight up. It replaced a worn out 360 and has less power. He would upgrade cam as well if it would help. He was just trying to save rebuilding it again with different pistons.

[My427stang]

When you say straight up, you put it at 110 ICL? or put it on the zero mark? If its on the zero mark, to make it less fussy you'd put it on the -6 on the lower gear, if you have a multiple keyway

More cam won't do anything different than retarding the current cam in terms of octane tolerance.  I'd say go cheap

However, I am amazed it has less power than a 360, must be more wrong than that

Also, 170 psi isn't a lot of cranking compression, my truck 445 and my car 489 are both 195 psi on the starter and run on 89 octane in normal driving, and 91 or 93 when I am going to horse it

[jayb]

I'm thinking the antifreeze is due to someone welding the crossover shut. Could be warped. Also if memory serves his rpm intake is medium riser runners and heads are lowriser. I have him talked into set of headers and we do have a distributor machine to curve it. Do you think the compression is still to much to bleed off?

A medium riser intake like the RPM will work fine on the low riser ports in the heads.  That's what Ford did with the 428CJ engine; big port mismatch at the bottom right from the factory.  Didn't matter there, and it won't matter on your friends truck either.

[fastback 427]

Thanks for the info on the mismatch jay. When we flowed our heads the probe showed no movement at the floor until short side radius. And thanks my 427 stang for info as well. We are thinking there might be something else wrong as well, we just don't know what yet.

[BH107]

Actually your D2 heads do not have LR intake ports, but the later MR style ports, so it should match up to the RPM intake just fine.

Also, what kind of gearing does it have with the 37" tires?

[fastback 427]

4.10. Thanks

[cjshaker]

That engine should have plenty of power. Sounds like something a little more serious going on here.

You really need to figure out where that anitfreeze came from, if in fact that's what it is. If you do have a blown head or intake gasket, that can play havoc with fuel distribution (intake) causing a lean cylinder and pinging. If it's a head gasket, a little bit of water will cause all sorts of problems also.

Before you spend money and start changing things, I think I'd give it a thorough physical. If you weren't the assembler, I'd go back to basics and check cam timing at the rocker using a degree wheel. Then double check the damper to make sure your numbers are correct. They can slip and that throws all your "data" out the window concerning timing. It can also cause overheating and other issues you mentioned. Does it backfire at any speed when the throttle is opened? Could be timing, or jetting....or both. But before you can proceed with confidence, you have to know the basics are right.

That 750 should be a good carb for it, assuming it was new and not something somebody has already fooled with. That's a big IF since the engine was bought complete. But you could easily throw on a smaller one and see what difference it makes. Even a 600 should work ok for diagnosing a carb issue.

[My427stang]

Actually your D2 heads do not have LR intake ports, but the later MR style ports, so it should match up to the RPM intake just fine.

Also, what kind of gearing does it have with the 37" tires?

That is not really true.  The port centerline is very close to med riser, but they are smaller sized in every direction and flow far less.  A typical D2 head flows max 220s a med riser is closer to 260s

FWIW - We copied a ported med riser port as close as we could on my D2s and it flows well, but takes a lot of grinding.

Regardless, port match isn't that critical, if the heads were off I'd probably blend to help low speed response on the port a little, but it's not critical

[mammyjammer]

I'm sure there are guys on this forum who can make a high compression FE a good towing engine, but this is my experience...

I had a 10.5 428 in MY 76 F-250 4X4 4speed truck with 4.10 gears and 35 inch tires. I initially used the same RV cam I used in the 8.5 to1 390 I took out of the truck. Horrible pinging under load and terrible towing manners.
I then put COMP Cams  Advertised Duration 275/285, Lift .515/.541 cam in it to "bleed" off some compression and the pinging problem was solved and the truck  flat hauled ass empty.
When pulling hills with a trailer in 3rd it had to turn 4000-4500 RPM to pull the same load the 390 pulled at 3000-3300 RPM.
 I was not comfortable winding a FE like that the looong grades we have around here...

[fastback 427]

Wow. So much info. We did not build or assemble the engine. The Carb is from jesse at bigs performance and made new for this truck. We feel like we're polishing someone else's turd. My 76 350 dually 390 4spd is worn out. Lots of blow by. It pulls circles around his truck. I pulled my equipment trailer with 10,000 lbs on it 230 miles one way and got 9 MPG. Only grabbed third twice. His barely pulls in fourth. It is honestly embarrassing. I think we'll start at square one and redegree cam and make sure dampner is right. Double check Carb and ignition and see where we're at. The truck idles like a kitten, does not bog, backfire, or hesitate. When you accelerate however it sounds angry like its fighting itself. Plugs aren't to bad and does not smell rich at all. Thanks for all the help guys.

[machoneman]

That angry sound and no pull in 4th.....interesting! I'd check the rate of ditzy advance (likely way too slow) and also if you're getting the total advance you think you are getting...as mentioned above already.

Sounds like an engine I ran into long ago and with a new ditzy (with a performance curve) it made a world of difference. But, one must fix the leaky gasket issue 1st and also determine why you have one black plug....blue Printo-o-Seal Fel-Pros?