Hows it going all? I'll start with the info I have on my truck, the problem and see if I'm on the right track with a build plan after the hours of reading I have done.

The truck: '86 F150 2wd, 300 6cyl, 4spd, 8.8" rear, 3.08 gears. Its been on Propane since new, has about 371,680km on it, no oil burning, no blow by, it is spotless inside.

The problem: Since I bought it in the spring of last year there is been a deep thud off and on at idle that we figured was worn timing gears, as well as a higher pitched sound that kind of seemed like a wrist pin knock, it was most noticeable at around 2500rpm+ especially on decel. On Wednesday morning the came gear gave up, so that part has bee solved but how much chance is there that the other nose was also the gears?

My plan: Build the '86's I6 while running the '88's I6...

So far, my parts list includes...

Comps 268H Kit (the one with the springs and everything included)

Port and polish on the head, and larger valves

EFI Manifolds

Steel/steel Timing set, I know they are louder but also bullet proof...

352FE Pistons milled to allow 11:1 CR (To better make use of the higher octane rating of LPG)

As for the intake, I'm still very unsure on that part, probably an Offy DP as I hear the EFI intake really isn't much better then the older carb ones.

Sorry the post is so long, thanks for any info you might have.

 

You need to set a goal for hp, useage, mpg, etc., and work towards that goal. I found copy/paste into a file a great way to save useful info for my build. After reading your parts list I would point out a few things:

The 352 piston has to be milled off the dome, thereby weakening it?

If you use the Cloyes t.gears, you will not have any whining/noise.

The Comp 268 is a performance cam. It seems a shame to tether it to a DP intake. Those two parts conflict. If you are going to install the 'stallion' 268 cam, you have to let that horse runnnnnnn! The Offy C manifold will flow better and perform better, or the Clifford.

You might want to consider a turbo set up. Less compression, but much more hp.

 

The truck's main use is a daily driver, light off roading(read pulling ppl out of the mud) but it also needs the power band in a good position for highway driving/passing. I can't really set a hp goal due to the Propane but would like to pull hills without having it at W.O.T.

One thing I am keeping open is cam choice and the intake, I keep forgetting that with a gaseous fuel I can run a single plane intake and keep it streetable. I've been questioning the 268H cam already, leaning towards the 260H, slightly more tame. The 352 pistons, I have no idea just how much it would weaken them, meant to get ahould of a machine shop on that one.

 

You need to get over to Fordsix.com, and enter the forum. There you will find the God of Ford 300's, French Town Flyer, who was a ford engineer. There are too many backsides there for me, but he is a nice guy...one of the few. He recommends the 352 piston too. He is THE guy to speak to.

 

Yeah, I've seen some of his posts over there. I will for sure be checking in with those guys as well. In the research thus far this build is looking to cost me an arm and a leg just for the bottom end due to the machine work for the 11:1CR. Then there is the head.

 

My main point of the build I guess is just to get the power up where it is useable on the highway.As the truck sits with the 4speed, and 3.08 rear I have to have my foot on the floor on hills. I am swapping the chassis though, so having the 5speed and 3.55 gears in the 4x4 might make the difference too.

Part of me is saying to get a new timing set and a cheap cam to stuff in the engine just to see how bad it really was. If there was in fact a bad wrist pin etc.

 

You could always use 351W pistons - just need to have the rods bushed to use the smaller pin size. I'd wager there's a ton more options for 351w pistons vs. the 352 or 360 and cheaper too. Depending on your head volume, with some flat top hypereutectic pistons and .02" deck height you'd be right around 11:1.

Buy the right pistons and the machine work shouldn't be different than any other 300 rebuild. Be sure to budget for balancing the rods/pistons.

 

Thanks, I'll look into that as well. I guess talking to the machine shop will be a good place to start as far as cost.

 

If your truck is factory propane only then your distributor timing is probably calibrated to propane's peculiarities. This is what most accounts for people's loss of power when they switch to propane on their dual fuel systems. Old factory dual fuel systems were timed for gasoline and this caused loss of power when propane was used.

While there is less chemical potential energy per given measure of propane compared to gasoline, the superior carburetion of propane together with a correctly timed spark curve will yield about the same power as gasoline for a given compression. And the added benefit of no special fuel grade needed to bump the compression a full two points over factory.

Your engine feeling anemic was probably more of a mechanical issue, like your cam sprocket being extremely worn, then just because it's propane. 11:1 might be a little high though. LPG is not regulated nearly as well as gasoline is. Any given day the LPG you buy could be 95% propane to 80% propane, and any mixture of lighter and heavier hydrocarbons making up the difference. Depends of the crude and the refinery. Keeping the compression in the 10s might be a good buffer against inconsistent fuel.

What mixer is on it now? Bumping up to an IMPCO 425 on a 4BBL intake might give a nice performance boost. There was a good thread from a couple years ago of a canadian guy who built a high compression 300 to use with propane. I wish I would've kept the link but I didn't and can't find it now. He used milled 352 pistons. Said it was about 50 thou off the crown to get the pistons to zero with the deck. Left about 2cc of detent in each valve pocket too he said. I don't know if that makes the valve to pistons clearance really close or not. You could also bush your rods for windsor pistons. I don't think either way is better or worse, just whatever fits with your plans the easiest really.

BTW, the truck he put his propane 300 in was a 4x4 dentside with 38s and he said the the truck had good power

 

Before the cam gear went I was dealing with fuel system problems actually. I just recently replaced the worn out 225 mixer it had with another good one I had laying around.

The issue of timing also came up, the ICG conversion tag under the hood says it was set at 12 degrees base timing, and 40 degrees mechanical. On the alternative fuels section here, as well as on Frank Raso's Alternative fuels forum I have been told it has way too much timing into it. Locally, I am told that is fine. All agree that the 425 may just be a bit large/rich for this engine, while some say the 225 is too small. Now if I can manage to get this build done, it may be about right.

On the topic of 351W pistons... I haven't counted those out either, still reading and seeing what works and trying to figure out the most cost effective way of doing this. The 351W slugs are looking to be the way though.

 

After a bit of reading, I came across some pistons on the Flatlander Racing site. Can't seem to find much info on them, other then they come in flat or dome top.

Venolia Pistons

PART #

4630 F/T $331
4640 Dome $371




ENGINE Ford-240-300 6Cyl / 2600-2800 V6

Anyone have any experience with them?