Thread: common problems with log manifolds

Don't forget you'll be rightly ridiculed on the Internet web car chat forum bulletin boards for running one. That may be the hardest thing to deal with.

Yep that's why it's not on there yet lol. It might say (WTB VVL Head) lol

I have think skin lol

Hope it's smart?

You might as well run a DET then, it comes with piston squirters by default. Or DET bottom with Lowport head if you really want that extra CFM.

^^ got the VE block for free, already have a full DE & a good set of 57c piston & rods.

Can't complain at free

so is there anyway to make the log manifold flow better? maybe a different placement of the flange or more porting perhaps?

Low overlap cams is the only way to successfully run a log manifold on any motor. Now Protech did redesign the manifold to flow better, Coheed ran it on his VET, but he still experienced the same powerloss issues due to reversion.

The problem is cylinder 1 bleeds into cylinder 2 instantly, 3 and 4 bleed into each other. Exhaust gases from another cylinder is forced into the cylinder that is in the overlap period. These are hot gasses that are polluting the fresh air/fuel charge. Since there is not much oxygen left, you are making your burn less efficient, but what's worse is the heat from them which leads to detonation.

Low overlap cams keep the valves closed so keeps the hot gasses at bay and out of the cylinder, when they do open they open for a few degrees which limits the amount of reversion.

To keep things in perspective some overlap numbers:
20VE cams have 48* of overlap on high cams, 0* overlap on low cams.
VET cams are 13* of overlap on high cams, 0* overlap on low cams
DE cams have 8-16* depending on the years

So the lower the degree the better the chances of choking the Turbo and minimizing the chance of detonation