I know ZZP sells front and rear power logs, but I'm entertaining the idea of fabricating my own. I'm having a lot of trouble finding what people usually use for custom manifold stuff like this, 90 degree elbows, in the correct diameter, which would be 1 5/8". I thought about using plain straight pipe in place of elbows, welded to the flange at an angle. My original concern with this plan was that using an appealing to the eye 45 degree angle off the flange would create an exhaust flow restriction. Like hitting a hard corner, instead of a smooth 90 degree elbow. But then I thought to use three 30 degree angles to create a 90. Math, duh. That should in theory create a smooth flowing transition from the head, to primary pipe, to collector pipe. The reason I don't quite like the ZZP plogs is the way the primaries enter the colloctor pipe. They're perpendicular. This I think would create a rough flowing exhaust path. What do you guys think?

 

The restriction youre worried about wont be an issue. If the primaries are 1 5/8", theres really no bend or turn that could counter the added flow.. (On these engines, at least)

BTW, I lost power when I added headers to a stock l67..

 

Yeah, ZZP claims that their plogs wont reduce low end torque, unlike the headers they also sell.

I've read in a few post from more experienced guys here on the forum about these 3800 engines can't make much power, don't make much power at this part of the rev range, etc. Particularly in the lovell factor thread i started a while back. Is there a certain factor that limits the power output of this engine? I'm still learning about the platform, and about engines in general, so I don't quite know what makes this engine less powerful than say an LS, besides the obvious two extra cylinders, and larger displacement. But a counter to that, is lots of 4 cylinder Hondas make loads of power.

 

Honestly, I dont think its worthwhile power wise. For a supercharged setup, I'd just wait until you have enough mods to need headers and just go that route. At the higher levels of SC power, down low power loss doesn't really matter and can actually be welcomed when you're struggling for traction due to how hard blower setups hit.

For a turbo setup, people have made 550++ whp on power logs, way more than the trans will hold built with currently available parts. Certainly custom headers could make more power, but if you cant put it down or keep the trans together, then it's not really a benefit.

If for whatever reason you were dead set on hand making headers, Jegs / Summit and other online retailers have a couple options:
-DIY header pipe sets that have all the bends needed for a pair of v8 RWD headers. There should be plenty of bends and pipe in these to make what you want
-whats probably more cost effective are individual bends / J tubes, etc. This would eliminate the excess parts of the kits above, but you'd have to be pretty sure about what bends yoid need.

ZZP sells 3800 flanges as well, so you'll need a pair of those either way unless you've got access to a local water jet / laser.

 

A few reasons why a NA LS can make gobs of power and a NA 3800 cant:
-Besides cylinder count, the displacement difference is HUGE. 3.8L vs the standard 6.2L LS in performance vehicles now - the v6 is only about 60% of the displacement. That alone is a primary factor. They also tend to spin a bit faster than 3800s at redline, so that consumes even more air.
-Compression ratio is very different. Most of the LS/LT stuff is high 10s to mid 11s. The NA 3800 - 9.4:1. Mid/low 9s is compression for boosted engines nowadays on the DI stuff.
-Cam size. Stock 3800 cam is 182/192 .413/.413. Stock LS3 is .204/.211 .551/.525. That's about as big as many of the mid level aftermarket 3800 cans (granted it's a much bigger engine, so it needs more flow). Certainly you can swap cans, but then you've got the issue below.
-Head flow. This is tough to A-B as you really need to do the heada back to back on the same bench. But for reference, at .600, some 3800 specs I found were 194/161 (int/exh), stock LS3 are 332/202. Again, not a great direct comparison tool, but gives you an idea of how magnitudes better the LS head is to the 3800.

The list goes on and on with every other part of the engine. The LS was designed to go in the highest performance cars Gm had, so it received the best of the best R&D and money and continues to grow into the gen 4 and now gen 5 engines. The 3800 on the other hand was designed to be a reliable commuter car engine and didn't need crazy high power to compete when it was released. As it was slated to be killed off anyways, there was minimal money put into it in the latter parts of its life.

You can also look to past history to see how well they've done historically. Plenty of results for NA FWD 3800 builds and generally theyve sat around the 200 whp mark. Certainly a few have made almost mid 200s, but when you've got a full blown build with $5k+ into it and you're struggling to keep up with 3.4/bolt on L67s, it sure makes it seem like a waste.

The upside is 3800 boost is (relatively) cheap and helps to overcome a lot of the deficiencies.

 

There's no doubt small engines can make big NA power, see all these crazy liter street bikes out there. But look at how they do it - by revving to the moon. That's one way to get around a displacement limitation, you spin the engine faster so it consumes more air+fuel, and makes more power. The other option is of course boost.

A stock K20 makes peak power at like 8000 rpm. A stock L36, not much over 5000 (and the stock dyno chart is barely climbing past 4500). The issue with the 3800 is you cant spin it to the moon. It doesn't have the head flow, cam flow, or engine design to be revved that high NA. Redline on that K20 is something like 8500 rpm (9000 on a F20) - nearly double a L36.

The other big thing the 4 cyldiners have going for them is tech. All kinds of high tech goodies (especially in the performance variants) that just aren't present on the old 3800. DI, cam phasing, variable lift, etc etc.


None of this is intended to make the 3800 sound useless, it's still a great, reliable commuter engine. It's still fun to mod cheap (with boost). Unfortunately there is probably more that could be extracted from the 3800 if people kept pushing its limits on boost, but IMO the trans was the Achilles heel that really curtailed further aftermarket development. People just flat out got tired of constantly breaking and refreshing transmissions and the power people were getting was pushed right up against those limits. It doesn't help being in a FWD setup as you'll almost always get out launched by a dialed in RWD or AWD setup.

 

Either you are very ambitious or just a lot of time on your hands. Cartuning makes exhaust manifolds for the 3800. From the image I found they looked angled. I heard that the ZZP pipes extend into the collector a bit, further causing more disruption on the air flow. Plus they are only rated for 300 whp. Think the Cartuning ones are rated for much more hp.

 

Curious where you had got that number, I did some poking around on their site. I now see where you're getting that on their web page, and IMO its poorly worded. That's intended to be a guideline for supercharged applications. That would basically exclude any turbo kit use, yet that's billed as one of the upgrades between the Z3 and stattama turbo kit options, so its clearly just not worded well.

To that last point, the normal stattama kit comes with front & rear powerlogs and has been proven capable of exceeding 500 whp. Not saying the cartuning manifolds are bad, they sure look nice. My point is more that if a 500++ whp setup isnt enough the OP and he's looking for mods like this for more power, I'd hold off until you could secure a GMR input shaft and drive chain/ sprockets and have the budget to put them in a fully built trans. Otherwise adding even more power will be useless.

 

I wanted to come back to this thread and share a basic 3D model I whipped up bassed on the drawings I shared at the begining. My design dumps the three 1 5/8" primaries into a 2.5" pipe that would then merge with the other side. I generally liked ZZP's plogs, except for the two hard 90 degreee turns. I kept the angled cap on the collecting pipe from ZZP's plogs. To simplify this, think of it as a 2D plane. The primaries essentially make a 60 degree turn out of the flange, and a 60 degree turn downward. I think this design would allow the exhaust gasses to flow smoother, and for example, spool a turbo faster.

 

Is this something youre seriously planning on doing or are you just getting ideas? I really would like to see how they turn out if so..

Good luck.