I have been battling an issue with my car. Recap: Swapped to hooker long tubes. Made NO other changes to the car. Car stopped pulling up top. Checked valve spring pressures, fuel pressure. Found pressure dropped to 31 psi in 3rd and 4th. (This was a coincidence wrt the header install) Installed a bigger pump to solve this issue. Car pulls better but still has an issue up top rpm. Last night I took wideband readings from each bank of cylinders. It looked slightly rich all around except for 6200 plus rpms on the passenger. After 6200 I usually shift but it looked lean. The driver side had a few blips of 20.8 A/F which I believe to be a miss.

Question: Does the fact that my #7 plug boot is touching the header matter?? The clearance there is horrible. I put a woven ceramic heat boot on it and the headers are jet hot coated. It is not melted, though.

Does anyone see blips of high a/f readings under wot?

WTF could be my issue? Thanks

 

If you have to take the header off, and dimple the area by the plug, then by all means do that. Would using some of those short plugs help?, I've never used them, but it's something you might try.

My AFRs wonder around a little, may .3 AFR, but not much more then that.

At 6,000 is also when on a single coil V8, the time you start running out of time for completely saturating the coil. If your not using a CD ignition system you might consider doing that.
HTH

 

Just my opinion bu t after shelling out the cash for my jet hott coated long tubes, I would not put a ding in them. I got the L98 angle heads, 90 degree boots, and shorty plugs. I think putting a ding in them is a bad solution.

 

I bought the long tubes knowing that I would have clearance probs. I dented the header where it needed it just to the point that the boot touched the header, then had them coated. I figured that would be enough.

*There are no shorty plugs available for AFR heads.

Here is my ignition system:

MSD Digital 6
MSD coil
Taylor 8mms
Delco FR3ls plugs
GM Module
Accel Cap on a stock distributor.

 

My AFR doesn't really move around much the times I have checked it at WOT with an LM1 or on a Dynojet.... Stays pretty flat when graphed and I have had people watch the LM1 screen when I pulled through a few gears and it would move around a few tenths but that is about it....

The 20+ AFR blip could be from an exhaust leak maybe???

Everything I know indicates that there is really no possible reason just changing to better and bigger headers would slow you down assuming you checked the tune and have the AFR where your engine likes it.... Putting massive headers on a stock 305 I can see robbing some power if the velocity drops off in the primaries and it loses some of the scavanging, but yours should love those LTs over any shorty....

So I take it you have logged data? What does it look like? Any knock?

 

yeah, i logged it on both cylinder banks with my wideband. The blip could of course be a miss or a cylinder leak. I just don't understand why the motor stops like a rock at 6100 when I changed nothing but headers. The a/f ratios look fine. Slightly rich at 12.0 usually. I'll lean it out when I get a chance. Maybe I should do the 1/16 rocker adjustment thing?

 

Definately back off the lifter preload if you have more than a 1/4 turn, IMO. It certainly helped mine a lot. It still kind of plateaus on the top end above 6k but before I adjusted the valves down to as little lash as possible it wouldn't even rev past 6k at all, so.....

12.0 is a bit rich.... Mine seems to like 12.8-ish and makes nearly the same HP as it does at 13.0 (445 versus 446) but a little better TQ (415 versus 412 and a little better throughout the curve). To make a fair comparison you should get everything dialed in with the AFR and double check the lash but it does kind of sound like something else is going on..... Could the valve springs be giving up the ghost? Which ones are they and are they new?

I have just about had it with my hydraulic setup... I mean I know something isn't quite right and it could be made to pull better above 6k if the valvetrain was matched better, but I really don't care to deal with it anymore. I got the HydraRev and had Brodix install Ti retainers and springs to TPIS' specs for the ZZX and it still doesn't do much above 6k. Doing valve adjustments here and there on a solid roller are really not that big of a deal. I mean I tinker with the GTA all the time anyways and pulling the valve covers isn't a big deal at all.... My engine is meant to rev with the lower end being built to take it and the heads and intake being so big and flowing so well and the solid roller will work better with it. Not to mention it is probably worth another 20 RWHP over the ZZX. Thanks BTW - that ZZX works pretty good!

It certainly sucks - been right where you are quite a few times myself - but sometimes parts just happen to fail when you are replacing other parts and make you chase your tail. I wouldn't blame the headers though....