Slant Six Forum

Slant 6 new owner.
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Author:  ChrisPee [ Tue Feb 07, 2023 12:54 pm ]
Post subject:  Slant 6 new owner.

Hello everyone, I bet you've seen dozens of these posts, but I have recently bought a 73 Scamp and would like some info on improving the performance.

I bough the car last summer here in England (the car was imported here in 2018) it runs, drives and is great fun. It's not exactly lively, but I've read many stories of making them better without rebuilding them. Basically I'm looking for simple mods regarding carbs, inlets, manifold, emission equipment. The car was a California car and I believe the emission equipment is still working. I'm used to rebuilding/working on British 60s 70s cars and this is my first American car. I've read some great threads on here today about Weber carbs and emission equipment etc, all very informative stuff.

Thanks - Chris.

Author:  hyper_pak [ Tue Feb 07, 2023 2:07 pm ]
Post subject:  Re: Slant 6 new owner.


Author:  ChrisPee [ Thu Feb 09, 2023 5:14 am ]
Post subject:  Re: Slant 6 new owner.

Thank you.

Author:  Dart270 [ Thu Feb 09, 2023 5:44 am ]
Post subject:  Re: Slant 6 new owner.

Welcome, Chris! There are many many things you can do to improve your car's performance and your enjoyment. Can you give us an idea of your budget (maybe in GBP/yr?)? Also, what restrictions to modifications do you have where you live?

Best wishes,

Author:  ChrisPee [ Wed Feb 15, 2023 6:31 am ]
Post subject:  Re: Slant 6 new owner.

Sorry for the late reply. It's my only Mopar, I specifically wanted a 70 to 73 A body with a slant, power steering and a/c. Unfortunately mine has the emission set up, which I believe is quite detrimental to performance. I have just found a 2 barrel manifold and have heard that a Weber 38 38 is a good conversion. Weber's are probably more easily available here in the UK. I'm not looking for high performance. Thinking maybe j8st a 2 barrel, headers and emission removal. I have found that there is a vacuum blocked off on the Holley, I really need someone to explain what parts to remove. I see that people recommend leaving the carbon canister - it still has that as well as what appears to be all the other stuff. Theres a breather pipe going back into the block (I think?) And the air pump is still running. Thanks everyone, and apologies for coming across dumb. By the way, the car is ex-Californian and extremely solid other than some small areas in the boot and passenger front foot well. I love it!

Author:  Dart270 [ Wed Feb 15, 2023 8:18 am ]
Post subject:  Re: Slant 6 new owner.

OK, cool. To rephrase my question: Do you need to keep all emissions devices work in the UK, or can you remove/modify/replace them at will? This will have a big effect on what you can legally do.


Author:  volaredon [ Wed Feb 15, 2023 10:23 am ]
Post subject:  Re: Slant 6 new owner.

I don't know about different emissions rules outside my area of the US, but in 73 emissions equip was pretty minimal. Mostly an EGR valve and 8 miles of vacuum lines to control that.

Author:  SlantSixDan [ Wed Feb 15, 2023 4:23 pm ]
Post subject:  Re: Slant 6 new owner.

ChrisPee wrote:
I bough the car last summer here in England (the car was imported here in 2018) it runs, drives and is great fun. It's not exactly lively, but I've read many stories of making them better without rebuilding them.
Have a look at this thread to help with your overall planning, though some of this stuff (better lights, etc) might've already been done for the car's SVA (single-vehicle approval) when it was imported to the UK.

Easy zero-cost items to make a substantial improvement in how the car runs, which won't run you afoul of UK emissions regulations (which trailed North American regs by many years):

1. Bypass the OSAC valve. This is the widget near the right edge of the firewall. One hose running to the carburettor, one to the distributor. Simply run a new hose directly from the carb to the distributor. OSAC = Orifice Spark Advance Control, a hang-on-and-pray widget thrown onto the cars to squeak them past the 1973 US Federal emissions type-approval tests so they'd be legal for first sale. This horrid device delays the vacuum signal to the distributor by 7 to 17 seconds, which means no vacuum spark advance except at sustained cruise, which means lower peak combustion temperatures for reduced formation of nitrogen oxides (NOx), and also demolished driveability and sluggish acceleration.

2. Disable the EGR. This widget is on the inlet manifold, sticking out toward the left side of the car from the plenum (conjunction of all six inlet runners). It has a vacuum hose going to it. Remove and plug that vacuum hose. EGR = exhaust gas recirculation, also aimed at reducing NOx formation by diluting the inlet charge with inert (noncombustable) exhaust gas to make the bang in the cylinder weaker (-->lower combustion temperature --> less NOx --> car legal for first sale and poor driveability).

Now go drive the car. If it runs without pinking (pinging, we say on this continent) on the petrol you buy, try advancing the basic ignition timing to between 3° and 6° BTDC with the engine ticking over at 700rpm and the vacuum hose to the distributor temporarily removed and plugged at the distributor end (only during timing check and adjustment).

Beyond that: follow the tune-up parts and technique suggestions in this post; pay careful attention to the tappet clearance adjustment, pay careful attention to the condition of the carburettor (carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download) and consider the HEI upgrade.

Pretty good odds at that point the car will run enough better to make you smile adequately.

(the air pump could be removed, but it's not really hurting anything; it takes minimal power to turn. The crankcase breather and ventillation system should be left alone. The charcoal can should be left alone, too.)

Author:  ChrisPee [ Thu Feb 16, 2023 6:23 am ]
Post subject:  Re: Slant 6 new owner.

Wow, Dan you are a hero. Emission control and catalytic converters didn't become mandatory in the UK until 1992. All cars manufactured over a rolling 40 year ld period are exempt from all regulations, such as MOT (a road safety annual legal requirement) and road tax. You can legally drive an army tank, tractor, combine harvester or a motorized sofa in this country if you want to.
As far as budget goes it's not a problem, but I really only want to do "bolt-on" improvements as I want to keep it road worthy. Would a twin weber or Holley 2 barrel make the best improvement?

Thanks again everyone, what a great site.

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