Some time ago I decided to swap out my tired 390, for a built inline 300.

I wanted to save fuel, but still have enough power to tow and cruise fully loaded. With larger sbc valves, higher compression from milled block and head, ported, cam, high power ignition, offy intake with an Autolite 4100 built by Pony Carbs, and an MSD 6a box, with a new, recurved DS11 dizzy, and hedman headers with dual exhaust, and a new HP HD C6, I wondered if anyone would be interested in the price of the built up/swap.

I should have about equal to the 390 in hp, and hope to get 50% better mpg.

 

Sorry, but are you asking how much it would cost to do such a thing, or if we are interested in how much it did cost?

 

I think he wanted to know if we were interested in how much his swap cost.

 

um.....sure

 

Not possible. You might have few friction losses with the six but not by much. 7 mains vs. 5, more cam bearings, offset by 2 fewer cylinders, but those pistons travel farther.

You may gain some advantage in fuel economy, but not 50% at the power levels you are talking about.

Also, which HP rating are you going after? 390s had ratings ranging from the low 200s for low compression net hp rated truck motors, to over 300 gross rated hp for GT models....

Cost will be a little less than rebuilding a mild 390 methinks. Summit and Jegs and many others publish their prices for engines, parts, kits, cams, etc, so a little pencil work will give you some hard numbers.

Trans swap costs will depend on what you want--used box or newly rebuilt, auto/manual etc.

 

but those pistons travel farther.

If I remember correctly, the 300 and 390 have almost the same stroke.

The figures I read regarding my engine, is that it produced 260 hp. With my build I should be close to that.

When you say the cost would be a little less than rebuilding a 390, you are not taking into account that ALL linkages, exhaust, etc, must be changed, as well as all the accesories.

With Summit and PAW, stated price is one thing, but then shipping is tacked on.

I have done the rebuild/swap. I know the true cost, right down to the spray paint and solvent cleaner.

To sit and argue here is flapping it in the wind. It is like building a house. An architect draws the plans, with all the specs etc. But those dimensions NEVER translate exactly into physical reality. Perfection has not been seen since the pyramides. It is the same when reading engine specs, costs, etc. vs. building it and driving it.

It sort of reminds me of the catholic church debating how many angels could dance on the head of a pin.

 

Its pointless trying to go by Gross HP. Gross is essentially the engine is dyno'd with headers and straight pipes, no accessories, wide open intake and no emissions controls at all. An engine rated for 300HP gross is only likely to put out around 220-240 NET (which is how it would be installed in the car itself).

That is one of the biggest things when people look at say a large V8 from 1968 vs. the same engine from 1972. They see a huge drop in power and assume emissions. It was actually the switch from SAE Gross to SAE Net measurement in HP.

I built 300-6 should have no problem hitting 220-250HP. The biggest thing is porting the crap out of the head, and sticking in the biggest valves you can find. It is a non cross-flow design, so by nature it doesn't flow that well.

 

There is difference of .196 inches in the stroke, with the 300 having 3.98", and the 390 having 3.784".

 

OK, I thought you were asking. Sounds like you know, and are just bursting to tell the rest of us.

Or is there another point here I don't see?

Good luck with it.

Correcting point on piston travel--even though the 300 sends them on a longer trip, the 390 sends more of them, so the piston friction award would go to the 390 here methinks. My bad....

 

Friction vs total mass vs who gives a ****?

The question is, how do you like it?

 

So far I have spent $5,156.98, and have yet to buy the tranny.

Keep in mind that about $360 of that went for the Clifford aluminum valve cover, the fee to have it professionally polished, and the fee to have the side cover chromed.

Unless there is an issue with the radiator, that should be about total for the swap/build.

It's been a lot of fun. I couldn't have done it without the help of some of the guys on this forum. Thanks.

 

Wow, you don't want just powerful. You want powerful and pretty. Can you post a pic? I'd like to see a 300 will a solid chrome plate lifter cover

 

hi; i just purchased a 72 ford camper special with 390 a/t and i have the same idea as you but as you probably know people tell you keep the truck stock 390 s are good engines but i am doing the swap for economical reasons.what can you tell me about your swap .i have a 81 econoline 300 6 a/t that i intend to swap into my camper special in the near future.both vehicles run good i can go either way with the camper special but for what its worth i am in the recycle business and instead of scrapping the van the body is wearing out fast and the 72 is in good condition body wise i am going with the swap when the time is about right in the near future.what was your cost assuming you have a used 300 6
what was the cost of your modification thanks Sandy

 

I love my 300, I just wonder what kind of mileage is gained after these $5000 conversions.
Can it possibly pan out? $5000 Buys a LOT of gas. ...?

Murph.

 

yeah lets see some pics of this beast! i love the sight of a built 300...