4.6 & 5.9 Tuning Tips needed?

[davetfft]

I'm running 2 4.6 and a 5.9 and all have high end fuel starvation symptoms and tuning seems to have no affect so I'm wondering if my fuel type isn't correct. What % fuel do folks run with these larger engines?

It has great acceleration, pops easy wheelies, decent blue smoke (not a cloud, just a stream/trail) and sounds like it's running fine and then it sounds like it's starving out until you let up then it's fine again. The 5.9 is a brand new unit as is one of the 4.6, my other 4.6 is a little old but a good solid runner, all three exhibit the same behavior.

Am I just completely botching the tune or is something else up? It's consistent with ONLY my HPI engines. My MAC, OS and TRX engines all run great so I believe I understand basic tuning... or do I?

Any thoughts appreciated...

Dave

*Note- also checked head tightness, new hoses, hose routing (no pinching or near heat sources), exhaust seals, ,,,

 

[cwal1774]

Seal them up.

 

[davetfft]

Seal them up.

Thanks for the reply, I do have new exhaust gaskets, good pipes and everything is tight. Once I even went so far as to silicone seal most mating surfaces as I saw on a youtube video. No dice there either...

Is there anything special/different on an HPI engine? I've used the same break in procedure on all my engines and only the HPI have these odd tune issues.

 

[cwal1774]

I run Eliminator 20% nitro 14% oil with an LC4 glow plug in my Savage XL. But I'm running an Ofna Force .32. I don't much care for the stock HPI engines. They have three needles and sometimes the mid range needle can leak. Hell i've had 2 of them fall completely out in the middle of a run. Nothing like bringing your truck in and seeing a big gaping hole in the side of the carb. If you haven't already take it out put some loctite on the threads and scew it back in flush with the carb body. See if that helps.

 

[devo]

Have u checked for air leaks in gas tank you may need a ne o ring in the lid
I have also shortened fuel line to try and get more fuel pressure.