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Heat Riser On R3?


mfg
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On the few R3 Avantis that Studebaker produced, does anyone out there know if a heat riser plate was factory installed under the right header? Or was this part completely eliminated on these cars? Thanks.

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The parts manual only shows one for the R1/R2 and doesn't mention one for the R3. It's not conclusive as manuals are printed up ahead of production but it may not have come with one...maybe.

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The parts manual only shows one for the R1/R2 and doesn't mention one for the R3. It's not conclusive as manuals are printed up ahead of production but it may not have come with one...maybe.

Interesting, I think Stude R3 engines were equipped with functioning automatic chokes, so one would think a heat riser valve would have been a necessary part of the system, at least in colder climates.

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As I said...the manual isn't conclusive. Only nine production R3 Avantis were factory assembled so the final specs on whether a heat riser was provided might not have been finalized when the parts manual was printed. Production ended in December of '63...the same month the parts manual was released. There is an earlier parts manual (red, white & blue, July '62), but that was printed before the R3 was even announced and they're not seen very often. The black cover December '63 manual is by far the most common.

About the only way to find our for sure is to look at an original, unmolested and genuine R3 equipped car and see what the factory did. Even then, a running change could have been made and not all might be the same. Example...while you could buy a genuine R3 crate engine from Paxton, as they assembled them all...some, towards the end of production...came with R2 cylinder heads and not the special R3 heads. Since Studebaker stopped making engines, and R3/R4 blocks were special castings, the supply was being cut off so Paxton simply used up what parts they had on hand for the last of the R3/R4 blocks on hand.

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R3/R4 blocks were NOT special castings!!!! They WERE sonic tested for core shift so they could be bored out .093 safely. The heads were going to be the stock offerings on the 320, and 340 planned 1967 model year. They were not special race only offerings designed for the 289/304.5 cu in engines.

All the R3's I have seen or rebuilt had the short studs on the passenger side manifold and no heat riser. Including the first factory R3 Avanti

Edited by brad
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I always understood the R3/R4's used specially cast blocks. So a more accurate way of describing it would be specially selected blocks. It's always good to get the correct information. As always...thanks.

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I have no idea if this info is factual, but I've read that the earlier 'non full flow' blocks have thicker cylinder walls, and are more suitable for bore enlargement, than the later 'full flow' Stude V8 blocks.

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  • 3 months later...

I am confused about the heat riser on the right exhaust manifold. I get a constant gas smell in my garage after parking the car. Is this a problem with the heat riser and can it be prevented by disabling the riser? When the butterfly is closed does this allow gasses to heat the fuel or does the open butterfly cause the gas to heat the fuel?

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I am confused about the heat riser on the right exhaust manifold. I get a constant gas smell in my garage after parking the car. Is this a problem with the heat riser and can it be prevented by disabling the riser? When the butterfly is closed does this allow gasses to heat the fuel or does the open butterfly cause the gas to heat the fuel?

The heat riser forces the exhaust up and through the center leg of the intake manifold heating the manifold for better cold weather fuel vaporization. It functions when the valve is closed. There is no reason for it with todays fuel formulations. The fuel today is much lighter aromatic and evaporation rates and will only get worse with additional alcohol. Fuel is formulated to be under pressure in a closed environment.There has not been a carburetor factory used on cars since the mid 80's.....THAT'S 30 YEARS!!!!! Think of it like a pressurized radiator system...under pressure the fuel will not boil. Open to the atmosphere (like a carburetor IS) it will easily boil and evaporate, and make fumes. The trick is to keep the fuel as cool as possible eliminate the heat riser or disable it in the open position. Make sure there is a functioning return line. Increase the fuel pressure and regulate it as close to the carb as possible. Fumes can also originate anywhere there is a break in the sealed system. Look for bad hoses and connections, especially the large filler neck hose. Also look for rusted lines along the frame rails. There are areas where the factory slipped rubber protective hoses over the steel lines to prevent chaffing and often they rust under these rubber sleeves.

Edited by brad
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  • 2 weeks later...

As said, todays fuels "boil" more easily, including when parked in a garage. The fuel systems on the original car were "open" and vented thru a rubber tube of the top of the tank and into the inner quarter, and down to the bottom of the car. The hose rots, especially with alcohol in the fuel, and the odor increases as the area for the vapor to release to the air increases. Fix? I've seen the addition of an evaporative emissions canister and purge valve added on some older cars, that and new fuel lines metal and rubber (fuel Injection grade rubber) will minimize the smell.

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