Thread: Calling All Header Experts!

OK, ready a billion posts on headers. I have a 2002 GP GTP 40th and ready to go down the header path. Who makes the best headers from a fitment and durability perspective. Stainless or Ceramic coated? I have looked at SLP, ZZP, and Speed Daddy. Heard a lot of fitment issues with Speed Daddy. What say you? What else is out there?

I've had the prototype version of the stainless Speed Daddy headers (SLP clone... previously called SSAC, DPP, etc.) since 2006, and couldn't be happier for spending under $200. Dyno tested with my XP/GenV/L36 block setup with a 25whp gain and ran down to 12.7 @ 111mph in street trim that year.

Speed Daddy Pro-Tips:
- Use the Torca-style clamps, and leave the flanges loose while you connect the crossover, starting with the rear header first.
- Replace the flex pipe with a ZZP one right away, and have a good welder use stainless TIG method to swap it, if you can. I actually moved the v-band clamp up to the collector, and the flex on the downpipe side of the v-band.
- wipe down before start so grime doesn't make them ugly, and re-wipe when cold occasionally to keep shiny (same for any bare Stainless header)

ZZP's are beautiful, but you'll pay 2-3x the price to have them, and they're inventory is a bit slower to restock lately. The diameter is a bit bigger, but only a big cam, 11sec/400+whp car is going to notice a tangible benefit (If I was putting my MP112 setup back in a GP/Regal/etc., I might go for them as I chased 11's/10's with it... otherwise I'd get SpeedDaddy's again in a heartbeat.)

I'd avoid mild steel ones, even coated, if possible. Coating is a nice bonus on stainless, as SLP, TOG, and some others may have offered years ago

All headers will require some tweaking of the trans dipstick, and all but ZZP's may require giving some firewall/swaybar clearance for the O2 sensor.

Good notes. Ya, I buried the firewall note in my last sentence with the dipstick and swaybar note (may need to flip it with most brands), oops.

Thanks for posting those ads, BTW.

The SD downpipe was copied directly from the original SLP design, which does scrape as you're about to scrape the other low points on the car. Mine ran ~75k over 10yrs before my GTP chassis rusted out from all the winters back home, so the headers sit ready in a tote for future projects.

I've only dealt with 1 set of PaceSetters. The design was promising, but non-coated mild steel was a little scary. I know the eBay stainless knock-offs had bad crossover fit issues, dunno about the black mild steel version. Good luck.

Here's some old pics of those 2 styles, including the mock-up of PaceSetters on a spare engine to weld the downpipe and avoid rear clamp issues.
(sorry for Photobucket, I need to get my stuff off there before that site gets even worse)

Torca clamps & ZZP flex (suggested for any type): LINK
SD custom downpipe "fix" (don't know source): LINK
SD (mine) w/ new flex after 5 NY/MI/MN winters: LINK
SD front after warm-up: LINK
PS mock-up: LINK
PS welded: LINK

@BillBoost37
I noticed ZZP is running out of stock on lots of items and they never have a good idea on restock. Also, ZPP headers are more expensive than SLP. I was leaning SLP, and I am glad to hear of no issues installing. I think I will go down the SLP path.

Thanks for the feedback everyone.

Originally Posted by BrandonHall10

The used parts market seems to have gone away also. That's especially depressing when you have a low mile rust free w-body you're looking to build for cheap.

have you looked on facebook?

3800 MARKETPLACE Public Group | Facebook

Ugh, I've been avoiding FB, but it might be worth dipping a toe for the sole purpose of the marketplace. Currently refreshing and upgrading the Regal, and it's 100x harder to source some items, or resort to paying ZZP/etc. retail. I couldn't imagine (or recommend) someone starting from scratch with one of these cars, both parts and experience are too scarce to comfortably mod in the dark like that. I'll hang onto mine simply because the build is already done, and I'm just tinkering.

I have noticed that Milzy Motorsports has a good selection of 3800 stuff too.

Originally Posted by FlynnZero

I have noticed that Milzy Motorsports has a good selection of 3800 stuff too.

lots of reports of dishonesty about milzy

Originally Posted by SgtMarshal

lots of reports of dishonesty about milzy

I've only had a few exchanges with him 10+ years ago, but I saw his site yesterday and it seems like he's working hard to offer various GM V6 products. He's at least showing transparency, it seems, with his Schedule page listing what is going on as projects are in his shop.

My hope is that Milzy is doing a decent job, because I may try getting some of the things he's listing.

Don't buy anything from Milzy. Search his name. He has about $40k of lawsuits against him right now for not completing work that he charged for up front.


As far as headers go, I didn't know slp still made them. Like others said though, that gooseneck in the downpipe sucks. The flex also has a bad reputation for leaking.

SD's are hit and miss anymore. They used to all fit decent, but quality has really fallen off in the last year or two. On the Dyno, they also show basically no gain in power.

Zzp's are probably the best available now. Tog also makes a very good set, but I'm not sure if you can still buy those new.

Sad to hear that he's dropping the ball.

SLP has been out of our market for a while now, like TOG, so anything out there is legacy parts from 10+ years ago.

I can tell there's slight changes in the SD's from my original SLO clones from 15yrs back, but there's definitely a gain to be had. I was tasked with dynoing the difference between manifolds and the headers.
LINK to chart
They better me the same ~25whp as SLP used to claim possible. (XP, 105", Gen3, 3.3") That made sense when the pipe diameters and layout were identical, and SD's are essentially the same, barring minor fit issues due to quality control.

ZZP has really the only new option outside eBay offerings, but it's up to what someone wants to pay, when they're in stock.

Spell check replaced a couple things, but you get the idea.
SLP, not SLO
"netted me" not "better me"
105# not 105"

That's a pretty good difference Dave. I'd be interested in seeing the differences between Dyno runs. Were they on the same day? Same pulley, tune, fuel, etc?

There are a few before and after Dyno results with SD's that show some pretty mediocre results.

Originally Posted by GTPpower

That's a pretty good difference Dave. I'd be interested in seeing the differences between Dyno runs. Were they on the same day? Same pulley, tune, fuel, etc?

There are a few before and after Dyno results with SD's that show some pretty mediocre results.

I ran them a month apart at the same shop outside Detroit we used to frequent with MCCGP. Only change was the pipes, and I may have had my tuner by then to add fueling, if necessary. The entire point of the runs was as direct of a comparison as possible.

Too bad it wasn't the same day. You easily could make 25 hp difference on these cars due to weather.