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I have seen my exhaust headers red only one time about 35 years ago when I ran it hard one night with high octane airplane fuel.
The exhaust runs red hot for the first foot of pipe after the head ever time you have your foot near to or flat to the floor for more than a few seconds. Not as problamatic with stock 4-2 exhaust manifold, but I broke the 2-3 secondary on a dyno run. You will rarely see a red exhaust jumping out the car and diving under the bonnet, it's something you see on the dyno where you can watch your motor at full noise for extended periods.
Also, airplane fuel runs cooler and B18 140's had the highlight flasher/relay there and moved it to the inner mudguard. I'd move the MS relays to inside the car.
I am not sure why Volvo engineers selected this firewall location for the FPR, but it works for me. The rubber fuel line routing and metal fuel lines are all original. The metal fuel lines are not new, and so yes they must be cad plated.
I would change to Volvo's later version. 1st, that short length of hose from the injector rail to the firewall would be inlined to crack due to the inline 4 shaking left, right and especially up and down is going to become a fire hazard very fast. 2nd, the later injector rail was a leap foward because each firing injector has an equal supply of fuel. If your FPR is single entry, then you need a fuel rail that is 1/2" with 5/16" in, out and injector lines to give equal pressure to all injectors. You would have noticed that the modern versions which have the injectors attached directly to the rail have a BIG hole through them which functions as a plenum for the pressurized fuel.
With the stock exhaust, I would elongated the secondaries to the 2nd harmonic in length, thay then need to go in to a tuned length of 2.125", then that slides in to your 2.25" or 2.5" exhaust. OR, if you have a 2.5" exhaust, a megaphone might be worth the effort fron the secondaries to the 2.5" exhaust. Either the collector or the megaphone will fall into the 12" to 18" length depending on details.
4-1 Headers use to be for engines with a maximum head, HUGE cam, dual DCOE's or injection with dual DCOE injection throttle bodies. Now every NASCAR engine has a modern style of 4-2-1 as do the majority of NHRA Pro Stock, engines that run to 9500-10000 rpm.
I like the original exhaust manifold 1st, because it creates a unique sound and 2nd, it dampens out alot of the anoying treble frequencies. 3rd, as I said above, there is room for improvement on the secondaries and collector or megaphone.
There is only 2 brands of header that I like the look of, I is a Swedish 4-2-1 which had 1.5" primaries, the other is BHP's 4-1 which are 4-1 with 1.5" primaries stepping up tp 1.625". The BHP headers are intended for ITB racers, but I think they need an upgrade to a merge collector. The VPD headers look like something I made in 1991. The IPD 4-1 headers look like junk as do most of thier products.
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69 142S Overdrive + 69 164S Manual
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