PCA SDR

I am trying to get a fresh rebuilt 1986 Ford F250 with the 460 Gas and Carb engine running correctly. I need a Mechanic who knows old American Iron and Carbs, and CA Smog requirements/pluming.
Very Clean.. She's run's perfect at Ideal to 2400 where she starts detonating. I tested 1 cylinder at 130 PSI so I don't think over Compression. I tried running Premium. Timing is 8 BTDC with no-vac. Am getting around 55 deg with vac at 2500 rpms. Using new rebuilt 600 CFM Holley Carb. Tried using my 750 Holley. Tried running with out Distributor Vac Advance. Running and MSD 6A Ignition Module and stock distributor. Running out of ideas. I need a Pro that can come in and do a basic diagnostic in my driveway on a weekend. If she needs something serious, I can get the truck towed to a shop. Will pay normal hourly wages. Need it done.

I would appreciate any advise/referrals. This is my tow beast. Need her to get to the tracks!

Thanks

Jim

Dyno it and see what the air/fuel ratio is...that is the best place to start.

Hey Sean,

Don't know the Mustang Dyno Air Fuel Ratio, but my exhaust nose says it's more on the lean side and Not Rich! With a 600 CFM Carb on a 460+ beast, necessary for smog ;Timing Seems good. Compression a little low but OK. Not sure on this old beast? Need a Iron horse Mech.

Jim

JivenJim wrote:She's run's perfect at Ideal to 2400 where she starts detonating...Timing is 8 BTDC with no-vac. Am getting around 55 deg with vac at 2500 rpms.

55 degrees ignition advance at 2500 RPM? Is that right? It sounds like radically excessive advance to me and could cause pre-ignition or detonation. I looked up 460ci Ford specs quickly and even for a 525 hp race engine I could only find a spec of 36 degrees total advance. I would check the ignition advance curve again. Was the distributor rebuilt?

Don't know any good 'Murican iron mobile mechanics off hand--Sorry!

TT

I agree with tom 55 is too much advance

A few things seem out of place.
I agree that 55° seems too much. An MSD distributor is not too expensive, look into one, should meet CARB. If it does not, check the springs and weights in the stock one. Also check the vacuum advance.
A 600cfm seems a little small for a 460. It'll work, but remember that it needs lots more fuel and air at >2500rpm. Check the power valve in that Holly, they make different ones for more fuel and at a different vacuum. and make sure that the secondaries are opening on time. Also try checking the high rpm jets (I really don't remember if that Holly had changeable rods).

Check with the guys at MIT in El Cajon and see who they recommend for a mechanic.

If you can put on an ociliscope to check the firing, that would be prefered. If not and you have an extra coil and coil wire, see if it clears up.

He Guys thanks for all the input.

Agree 55Deg BTC at 2500 with vac seemed high to me. I did however read up a few posts and found that up 60 Deg can be found on these big blocks. so not sure? I tried running without Vac and it was closer to 35 Deg but still popping ;+( I too, was thinking it might be the sprung weights. This is a very low mile factory Dist. I have heard that the Those cool MSD Distributors and such are great for full throttle but not very good on street cars. Anyways, both good ideas.
I also have a new Blaster Coil and new MSD 8.5 plug wires.
I think I will pull the Spark plugs and see if the color shows me any stories. I was also thinking maybe its a cross fire issue between plug wires (like I think 7 and .
I've seen putting an O Scope on an injector to see firing but how would you do that on a high energy plug wire??
I have a Fresh 750 double pump that will go on after smog ;+)

Anybody know a good old Iron Mech?
Thanks for ideas and keep them coming.

I have built many of these engines as a Ford line mechanic. 36 degrees total is about right Ford used to have 10degree advance plates for their distributers. 10 degrees in the distributer is 20 degrees at the crank 10 or 12 initial will get it running about right. If it starts popping at 2500 rpm you might have a lean carb (small jets). A condition like this is hard to nail down you need to get some professional help, the frustration just ain't worth it. Feel free to give me a call 619 447 4353. Greg

Thanks so much for Stepping up Greg. Sent PM
After a good Saturday and some targeted testing on Electrical/spark, I found the the #2 plug (new) was not firing all the time. Tale signs; was the smell of gas stronger than others on the spark plug. Checked Impedance wires at 4-6K per ft. Replaced plug, and now the truck is not Detonating!!!! Yea....

Some people I talked with said that because I put in a none factory spec, Higher lift type RV CAM and springs to help, that this big 460 beast likes a lot of advance BTC. So, now that I got rid of the first problem; I am wondering if I should address the timing with new Distributor. Or if 55 BTC at 2500-3000 is OK?
Also got 135 ish on one of the compressions I ran last week. Isn't that low?? Only ran 1 but will recheck and test all sunday.

I know now this post is going more Technical side but wanted to keep in the General, since I started there.

34/36 degrees total is all you'll need or want. If you take the breaker plate out of the distrubuter you can see the advance cam it takes two springs a light & heavier one. Stamped in it is the total degrees available. 10/12/14 etc. you double this amount at the crank pulley. a 12degree plate would take 12 degrees initial and 12x2= 24 give you 36 degrees total. The total advance is relative to the maxium rpm the engine can turn and determined by such. That engine won't see much more than 6k rpm and 36 degrees is good to maybe 8k rpm. Connect your vacuum advance to PORTED vacuum. If the firing order has cylinders 7 & 8 firing after one another do not run these spark plug wires parralell to each other as 7 will induce voltage into 8 prematurely. Ford's were always Fastest On Race Day Greg

Would of replied awhile ago but just got my car..

anyway
Mission gorge auto in Santee...Dave Mchenry owner.619-562-2777
none better at this kinda stuff.