BHW Hard Starting With Stage 3 Colt Cam

My freshly-built BHW is running great, I've been driving it around everywhere and it's doing awesome in almost every situation.

There's only one thing that's been bugging me: sometimes the engine is hard to start when it's hot. It'll rattle on for a few seconds before finally catching. Even a cold start isn't terribly lively, but it's at least immediate. The hot starts are a little embarrassing in public Especially since all my friends know how much time, effort and money I sank into this project.

I tried making many small adjustments to the torsion value from -0.5 to +2.5, but it didn't seem to help. I'm running a Colt Cams stage 3 cam, so I wonder if that's contributing to hard starts? Is this just something I'll have to live with?

Make sure that whomever did the head work set the install height properly for a higher lift cam. The install height can be at one end of spec and be fine with
a stock cam...not with a higher lift cam..

Pretty heavy duty cam, can raise the fueling during warm starts a tad and that might do the trick.

mrchill said:

Make sure that whomever did the head work set the install height properly for a higher lift cam. The install height can be at one end of spec and be fine with a stock cam...not with a higher lift cam..

Click to expand...

Yep, I triple-confirmed the installed height during the head build. Got so anal about it that my machinist was getting annoyed with me It was spot on for the high lift springs I used with the cam.

Owain@malonetuning said:

Pretty heavy duty cam, can raise the fueling during warm starts a tad and that might do the trick.

Click to expand...

Is there ANYTHING that can't be fixed via software?

This brings up another question... are there any special considerations for the torsion value when using a high lift cam? I'm pretty sure the duration and timing aren't all that different from the OEM cam, so I guess it *shouldn't* affect the torsion value, but maybe I'm wrong. I never spec'ed the OEM cam before disassembling it, so I don't know how the timing and duration compare to the Colt Cams stage 3.

Torsion is important IRO the injector cam lobe and what the ECU expects in terms of fuel delivery. Owain is pointing out that your cranking compression may be lower than expected due to overlap. Hot start should be better unless it's the lower density of hot air dropping your compression even more. I'd zero the torsion and set the glow plugs to give you 5 pre-glow seconds regardless of ambient temps and a bit more in the areas below 9 deg C. along with the suggested fuel increase at start while you work this out.

Try to start it without coolant sensor connected and see what's happening.

Thanks for all the suggestions! Starting it with the coolant sensor disconnected didn't make any difference. Malone ended up retarding the start of injection for startups, and that helped a lot. It now only rattles for about 1 second before catching. I'm happy with that.