So I am about to drop my newly rebuilt 428 into my 68 Firebird this weekend. My previous motor a nicely built 400 had a set of Hooker headers which were old and rusty but did the trick. Since I was doing a whole new motor, I decided to get rid of the Hookers and swap to a set of long branch manifolds. I found a set local to me and went to look at them. The seller also had a real nice set of ceramic coated Doug's headers for a 1st Gen Bird for the same price. Since my exhaust system is already set up for headers, I grabbed the Doug's headers instead of the LB manifolds.

The 428 is on my engine stand pretty much ready to go in so in the interest of curiosity I mocked up the Doug's headers on the motor and the header hits the oil filter. Now my 428 has a 110 degree filter housing and the 400 had the 90 degree housing but the header hits the filter both ways.

What the Hell am I missing?? I always thought Doug's headers were well known for their ease of install.

Can I run a different filter or is there an adapter to rotate my filter out of the way?

At this point I'm considering calling the seller and taking him up on his offer to take back the headers and sell me the manifolds if things didn't work out.

Any suggestions/feedback??

The long branch adapter rotates the filter 45 deg towards the firewall. Use the 90 deg firebird bracket with the adaptor.

I did some extensive research and it turns out that I can use a smaller filter. I scored a NAPA/Wix filter #1042 which fits the GM LS series engines and it also fits classic Pontiacs.

I threaded it onto my motor and mocked up my headers again and it fits perfectly.

check this thread here