74, f250, 4x4 High Boy, 4 speed, I took my 390, boarded it up to a 410 and put in a 428 crank. Stock heads and a RV cam. This was to make a great pulling machine. It has a stock 4b intake and a Edel 550 carb and Pertronix in a stock distributor and coil. Distributor has been rebiult, new vacuum advance in, several degrees taken out by the shop per their analysis on the bench... Ok, so there is a lot into this motor and yuck. The shop that built it has a great reputation, been around a long time, lots of success with the build... At 12 degrees it pre-ignites horribly when pulling a load, it clears up at 8 degrees, but has no getup-n-go and diesels on shut down, and gets 6 mpg... I have had it to two shops that are well known for quality work... They can't figure it out. They've suggested putting in a hi-rise intake, change carb (bigger), hotter ignition, all just kinda guessing at the out come. Any of you motor heads have an idea on a solution? The truck is used mostly on the road, will pull a heavy boat in summer, loads of wood in fall and mountain muddy roads for elk season. A catch all rig.

 

Just a quick comparison.
I've got a 441 (4.125 stroke and bore)
My timing is at 14 initial to 34 all in by 2800ish.
750 Holley vacuum secondary.
9.5 compression
Comp 270 roller cam.
No detonation probs at all.
There's an awful lot that can be wrong to take a WAG at it.
But just off the top of my head a 550 might be a bit small for the amount of cubes you're running. Prolly not the whole problem but maybe a part.
Assuming youve checked to make sure your dizzy is operating properly.
I know it can get maddening.
Good luck.

 

do you know what the actual compression is, i.e. actual combustion chamber size, deck height, volume of piston dome or dish, compressed head gasket volume, etc? what are the specs for the cam? It sounds like yourratio might be to high. If you can find those two sets of numbers, the you can use a DCR (dynamic compression ratio) calculator to see if the two numbers are compatible with each other.
Compression Ratio Calculator | Tools | Diamond Racing Pistons

Wallace Racing: Dynamic Compression Ratio Calculator

notice that some assumptions about what is pump gas compatible is NOT based on modern methanol laced gasoline. Also modern engine design has characteristics like swirl and fuel injection that enable the higher numbers in todays vehicles that the open chambers of our vehicles can not stand. Look at the dif between your heads and the Edlebrock or Survival Motorsports FElony heads

 

You have a new vacuum pot on your Dizzy? dialing those in is an art. If you are getting a ping at low RPM under heavy load, back the adjustment of the pot off an 1/8 of a turn counter clockwise until that pining stops under heavy load....( the adjustment, is an allen screw, inside the hose inlet on the pot... 1/8 inch allen wrench... the Dizzy springs might also be too light, and allowing it to advance too quickly.... FE's don't like a lot of ADVANCE...quickly... especially with a RV (High Torque) cam also a 550 cfm on that set up seems a bit small, it will be a ton happier with a 650-670, even up to a 750... but with the RV cam anything more will be a waste... with an RV cam initial timing is better at 12-14 deg. 8 is to low.. set the initial to 12, check it for ping and then adjust the vac pot counterclockwise until the ping stops. if your timing is going all in too quickly you will get the ping.... Good luck with it

 

Also stock heads need Stainless Steel valves with modern gas...

 

I have a 575 Holly . RV cam . RPM Preformer manifold .
My carb size is fine for me . It is a work truck .
Go do the Carb size calculations . Where is your timing chain set ?
Get someone to put your distributor on a Sun machine .
You can recurve it yourself if you feel capable . Go back a few posts and see the thread about recurving .
I ended up with an MSD , but there is nothing wrong with a Duraspark that is set up right .

 

Whats the deck height? Quench? I would not say it's the intake...carb seems a bit small. Was the cam degreed in?

 

we need to know what kind of compression he has now since if he has 10:1 compression pistons (or higher) with a short duration cam, band aids on the top-end just wont fix it

 

I would not put a high rise intake on if you tow with it. Your torque and horsepower curve will go up in RPM's. I would also put a bigger carb on it. I don't think either will fix your problem, but it is what I would do if it were my truck.

 

I think you mean hardened seats.

 

Is the harmonic balancer new? If not have you verified that it hasn't slipped making your ability to check timing all off? You may even want to verify TDC with a new ballancer just to make sure.

Do you know your total advance? Initial advance is fine for idel and just off idel but detonation (pinging) most often occures at full timing advance (or there abouts).

To start on this problem I would block off the vacuum advance. It helps with mileage but is one thing you can eliminate for now until you get it running right then after you have your mechanical advance dialed in you can then dial the vacuum advance in.

What gas are you running? 87? 92? You may have just ended up with too high of compression for regular gas or maybe even any pump gas.

That is a start to finding the pinging issue...

The 6mpg... have you verified that the carb is running correctly? What color are the spark plugs? 6 seems really low but it may all be due to timing. Do you know what cam you are running?

As for spark plugs... Are you running stock plugs? It is possible that running a cooler spark plug could help reduce your pinging.

 

I'd be checking mechanical advance and vacuum advance see what your total timing is at 2500rpm.You should be using ported vacuum to your vacuum advance ported should be coming off base of Carb.Also your Carbs a little on the small side from the factory I think 670 to 700 cfm was the norm for a 410 to 428. a minimum of 650 would be my choice.Your total timing should not be over 38 degrees.You can run more initial advance and mechanical but back off on your vacuum advance by using a allen wrench in vacuum advance port as another member said.

 

If you do a cfm calculation , the carb size is adequate unless he is running 6000 rpm all the time .Altitude is another factor . Have you tried another distributor . Also do you have any vacuum leaks .

 

I also have a 390 bored to a 410 with 428 crank and rv cam basically the same as you and also have the pertronics . My carb is edel 650 and mine pings like there's a midget with a hammer in there . I had 428 heads that were ported but kept burning valves so I put truck heads from an industrial engine like 352 and so on. You need hardend seats these trucks have a hell of a time running this new crappy gas. I run the highest octane I can find with octane boost and it's better but it still pings a little when loaded. It's all this junk gas new cars have no compression so they run . You have to get some rocket fuel

 

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If OP has D2TE heads, they do have induction hardened seats