Thanks everyone for all the ideas, I did verify it is a 390 and it's the original 390 in the truck. I left the stock manifolds on when I had the exhaust re done, Some of the issues I found and corrected were timing, tire pressure in both the truck and the trailer tires and the weight distribution of the trailer, once I added my Polaris RZR into the rear of the toy hauler it took a lot of weight off the tongue and leveled out the trailer, it is now towing a lot better and I have to still install the carb and intake!

 

So let me get this right you have Polaris RZR in the bed of the truck plus a dual axle travel trailer all being towed by a F350 with a 390 with auto trans and air?

 

Think the RZR is in the trailer, its a toy hauler he stated. a camper with a garage in the back.

 

In the back of his trailer. A toy hauler

 

The point is the total weight including the truck on a stock 390 .. There's no bolt on parts that are going to get you there ..

 

The Polaris RZR is in the trailer which evened out the weight ratio as the trailer wheels are farther back to handle the load, thus when the trailer is empty it put to much tongue weight on the truck, so now with the load evenly distributed the truck is pulling the trailer instead of dragging the trailer. Between increasing the timing and adding more tire pressure to the truck and trailer tires, it is towing much better now!

 

Glad it's all coming together. Just a few more little changes and adjustments and you'll be set.

Nice looking "toy".

 

Is this a bone stock 390? if so, a few mods are needed to "uncork" the power...

1) straight up timing set, oem sets, after '72 are retarded 4 degrees

2) headers, the oem manifolds are a huge bottleneck in the exhaust flow

3) Advance the timing, oem timing specs are for warranty/emissions concerns, not performance

4) Up the compression ratio, oem (truck) FE's after '72 are low compression turds

 

them junky plastic razrs dont weigh that much,

 

Well I added an Edelbrock Performer 4bbl intake and a new Edelbrock 650 cfm carb along with a full tune up, I also found that the Vacuum advance was not working, a new vacuum advance is $29 and a rebuilt distributor is only $39 so I am on my way to the parts store now to pick one up! I will post the performance increase later on today!

 

Nice !! Be all you can be 390

 

That looks sharp!

 

Looks great

 

Them valvecovers are very nice looking

 

Aha! Well there's your problem, as the old saying goes, timing is everything. Glad you figured it out!

I'd check a few other things too, like make sure you tune the carb in right, make dead sure it isn't lean. A lean carb will kill power and shorten the engine life dramatically. Also check for vacuum leaks, the brake boosters can be an issue.

Also, high compression ratios are great for power, but when you put a big load on them they are much more prone to pinging. Yes you can run high ratios, but you need to be careful doing it and only run higher octane gas.

Sam