Vicks vs. AR vs. Allison Headers

[justrhines]

Hi All,

Just finished installing and tuning up a pair of IDF's on my '75 1800. Sure sounds great- but sitting at about a 12 sec 0-60, in part due to my lack of flow downstream of the block. Wondering if any of you have experience with the above-listed 4-2-1 headers (or any other brand) and could recommend a set.

Thanks,
Justin

[jon8christine]

I'm in the middle of planning the performance mods to my '76 1800 as well and am interested in this topic. I like the Allison system, and it's reported to increase a stock motor HP by 10-15%, but only at really high rpm and it costs significantly more than what I'm used to paying for an exhaust.

[justrhines]

Thanks for the info Jon, didn't know Mark was claiming those gains. If I remember correctly the cost is almost double that of the AR headers.

What else are you planning on your '76? My tentative plan of action is the dual IDF's (done), headers/exhaust, and then start going in the block with cams and (one day) high comp pistons.

Justin

[jon8christine]

Doing suspension, wheels and brakes before I really go after going faster. Original exhaust is shot and planning a 32/26 DFEV carb upgrade and a lightweight flywheel.

Vicks exhaust looks good for the price, but I wish it had a center resonator (have heard that it's too loud).

AR isn't too much more $$, but the performance center w/ single resonator is out of stock.

Does anyone have experience with the Auto Ricambi performance 2" exhaust? How loud is it?

[justrhines]

I've heard the same on the Vick's exhaust. This video seems to prove it, albeit being a 2L car:

https://www.youtube.com/watch?v=bFhHzSa1Ge0

Also interested in the AR exhaust note.

Justin

[fishboy]

Late to the party but....I have the Allison headers and exhaust system on my 71 1608. Mine was sent with a Magnaflow muffler. Always get compliments about the sound and i also love the look of the header.

[18Fiatsandcounting]

https://www.youtube.com/watch?v=bFhHzSa1Ge0

What's with all the exhaust smoke? If I had a car that smoked like this, I would be seriously looking at a tuneup or a diagnosis to figure out why...

-Bryan

[jon8christine]

Any noticeable difference in performance with the header and exhaust?

[justrhines]

Finally slapped on a set of Vicks headers and a custom exhaust with a Lawson Insynerator Muffler. Sounds good, maybe a bit loud, with some resonance at multiples of 1500 RPM. As far as power goes, no huge difference I can tell. I probably need to tune the carbs a bit more, but no 0-60 change greater than 1 sec.

[Nut124]

Here's what I found out trying to squeeze HP out of my Fiat over the years:
- I had to install an AFR system. I have a narrow band now but looking at wide bands.
- The AFR showed I was going extra lean at sustained WOT, above 6200rpm. Dangerous, detonation hazard. No way to know w/o an AFR gauge.
- I had to get a bigger fuel pump and an adjustable regulator. The webers need a steady 2.5 to 3psi supply.
- Replace the fuel filter if old. Could be restricting flow.
- I mounted a a fuel pressure gauge at the carbs on a hose where I could see it while flooring it. You do not want to see fuel pressure go down to nothing at the end of a run.
- May need more float needle jet as well.
- Make sure ignition advance is 35deg at 4000+ but no more than 37-38 ever.
- Get a digital timing light and verify crank TDC timing marks.

My 1800 with dual 44 IDFs runs very strong. 7sec or so 0-60 based on 1/4 mile time slips. Easily hits 115mph+ gps verified speed.

As to headers:
I have neither the Vick nor the Allison, but a similar (to vick), Abarth style 4-2-1 header. I previously had a 4-1 header with short primaries. It would not run well at low rpm with big cams, overlap, due to intake reversal at low rpm due to the common collector.

A good header allows you to get gains from more cam w/o screwing up the low end totally. At a minimum I think one needs dual down pipes that separate the successive cylinder exhaust pulses into separate down pipes. Did some models have this from the factory? I think so. I single downpipe does not tolerate much bigger cam w/o driveability issues.

I think that a 4-2-1 header is good. Longer secondaries are good. This way, the exhaust from the previously firing cylinder does not push back on the next firing intake cycle (overlap). This helps w bigger cams with a lot of overlap.