Author Topic: 351C Tuning Observations Long (Read 1204 times)

JBauer4363 · « **on:** August, 09, 2009, 09:28:38 AM »

After years of trying to find help getting my car to run right, always close but always bogged ran rough etc. Plus everyone local is sick of me asking stuff I decided to try to learn how to adjust timing/idle myself to try and get the buggs out. After messing with it I seem close to geting it to run pretty good but not being a mechanic I thought I would post some of the thing that it is doing after Ive messed with it and see if anything seems like it could be detrimental to the engine. I have a 351C automatic that is stock except non stock cam and heads with solid lifters and a Holley 600 carb. PO said cam,heads and lifters are for a 71 Boss 351 but I have no way to verify. Have been told that I might need the rockers adjusted but Im not sure that the person that told me that really has any idea. This probably seems kind of lame but Im just curious and dont want to hurt my engine.

After adjusting the timing and driving over and over It seems to run and drive the best timed 12 degrees.
Have idle set at 910 to 940 in park when put in gear its 640 to 660, any lower and it starts to want to die.
Temp gauge reads right in the middle at idle but goes down to about 1/4 at highway speeds. Doesnt overheat no matter how long it idles.
Oil presure reads in the middle at idle but goes to 3/4 at highway speeds.
Adusting carb with vac guage it reads 16bs of vac and turning screws up to 1 turn doesnt seem to affect vac or idle much much at all. No matter how much I turn them the vac doesnt get any higher than 16.

It seems to run pretty good set like it is and has hardly any hesitation and gets rubber when it hits 2nd. It loupes pretty good at idle but that would be the cam.

Opinions?

JBauer4363

Midlife · « **Reply #1 on:** August, 09, 2009, 01:15:22 PM »

I didn't notice anything about adjusting the points, condensor, or rotor. What kind of ignition are you running?

I believe solid lifters require the valves to be adjusted on a regular basis.

16 psi of vacuum is pretty good; I would be concerned that adjusting your idle air mixture screws doesn't affect your vacuum. I wonder if your idle speed is too high and bypassing your carb's idle circuitry.

No bog from a standing start?

JBauer4363 · « **Reply #2 on:** August, 09, 2009, 02:03:13 PM »

Im using Pertronix Igniter 2 with a flame thrower coil. If I turn the screws far enough either way they do affect the way it runs but turned out 1 1/2 turns turning them about 1 turn either way doesnt seem to affect it much. Idled any lower and it wants to die in gear. No bog from a standing start.
I just wondered about the temp staying in the middle of the gauge and it going down on the highway. Also I dont want to set the timing at a point where it could damage something. This is the first time in years that it has ran right. Must be dumb luck.

How do I tell if the valves need adjustment?

Thanks

Sluggo · « **Reply #3 on:** August, 09, 2009, 02:09:29 PM »

12 degrees base is not bad for a Clevey. Sounds like it might be pretty close at idle. 16 inches of vacuum is about all you'll ever get out of any engine. If you have a cam similar to a solid lifter Boss cam I'd expect a little less.

If your vacuum advance is bringin' 20 degrees more timing to the party you're right on the verge of where clevelands get pissy, if your mechanicals bring in ten more, you're pushing 42 degrees of total timing.

Most people I have talked to recommend 35 degrees total timing all in by 3500 rpm on a cleveland. When I did my 71, it ran like poo with any more than about 35-38 degrees total timing.

All the numbers you indicated in your post seem very acceptable. Does it ping or missfire at high rpm?

JBauer4363 · « **Reply #4 on:** August, 09, 2009, 02:41:38 PM »

It didnt notice any pinging and it doesnt misfire. It seems to run better that it ever has. I just dont really know what I did. Its a shaker car and its such a pain to remove the shaker, adjust put it back on drive it, take it back off, adjust, put back on etc. it was driving me nuts. I had the timing at 16 degrees and kept lowering it, adjusted the idle screws some and then it seemed to run great. I guess I need to double check to make sure its not pinging.

Thanks

Sluggo · « **Reply #5 on:** August, 09, 2009, 02:50:18 PM »

Sounds like you have it whipped.

Perseverance has just paid off for you my friend, you need to :tigg

daveSanborn · « **Reply #6 on:** August, 10, 2009, 07:00:47 AM »

Quote

heads and lifters are for a 71 Boss 351 but I have no way to verify.

Is there a "4" stamped on the upper front/rear corner of the cylinder head?

JBauer4363 · « **Reply #7 on:** August, 10, 2009, 05:15:14 PM »

Ya there is a 4 stamped in the corner. I dont think they are stock.

Cant see the 4 in this pic but its in the top corner:

Thanks

daveSanborn · « **Reply #8 on:** August, 10, 2009, 05:51:44 PM »

The "4" implies that the heads were original equipment on 4V 351C aka Boss 351 cars. 2.19 intake valves and 1.90 exhaust valves if I remember correctly. Any original 4V 351C should have had those heads, but it's safe to believe the original owner when he stated they were off of a Boss 351 car. The exhaust valves on those heads are bigger than most SBF intake valves. Those heads LOVE to breathe.... the higher RPMs, the better.... I'm not sure if they'd ever reach a point where they were processing too much air.