Reply To: Re: Hemmings did an article on the Jetfire

Home Page Forums Discussion Topics – Ask the Experts Hemmings did an article on the Jetfire Reply To: Re: Hemmings did an article on the Jetfire


First, it is good to see another article on our little gems! I have yet to see one that has all the facts correct and this one is no exception. Kurt starts out the article by stating the Jetfire was “The Oldsmobile Jetfire was based on the brand’s F-85 compact two-door hardtop”. The ONLY 2 door hardtop in the F-85 line up WAS the Jetfire. The statement implies that you could get a two door hard top in some other F-85 body style, Cutlass or ?…….nope!

He is correct that the turbo system was “over” safety controlled! Three different methods to shut down the boost would have to be all working correct to allow the driver to “feel” the boost. By-pass controller, boost limit baffle in the throttle body (controlled by the fluid metering valve) and pop off pressure cap on the Turbo Rocket Fluid tank.

The dealer mechanics were NOT informed/taught how to service the units when problems arose. Primary fix was replace the turbo unit with another or 4 bbl system conversion. Oldsmobile records, that I checked on back in the 1980’s, stated about 80% of the Jetfire systems were converted to 4 bbl’s by the late 1960’s! Removed turbo systems did not have to be returned to Oldsmobile so the dealers could dispose any way the wanted, scrap them out or the mechanic could take them home. I talked to one mechanic at a dealership in the Chicago area back in the 1990’s and he said he had 13 of them in his basement that were replaced in the late 1960’s.

As for the Turbo Rocket Fluid, it only cooled the combustion chamber, primarily the piston tops. Had NO interaction with the internal turbine side of the intake system. It is injected into the throttle body and goes directly into the intake manifold, only contacting the fined compressor wheel.

Cooling and lubrication to the main turbine shaft and bearings was accomplished with engine oil. The flow of engine oil continuously flooded the shaft and free floating bearings any time the engine was running. Supplied directly from the oil pump to the top of the turbo housing and returning to the right side valve cover…all the time. I have NOT found a single bearing “froze up” on the rotation shaft, ever! The only obstruction that I have found to stop the turbine shaft from rotating is “coking” of oil that has to be supplied with the exhaust gasses to the housing and turbine wheel.This side of the turbo will reach 1500+ degrees and will “coke” oil fast! Primary failure seems to be the rotating shaft seal on the compressor side of the turbo housing allowing the lubrication oil to be forced into the intake, partly burned in the engine and then going to the turbine housing and wheel for final degradation to coke/carbon within this housing.

The turbine shaft is turning whenever the engine is running. At idle and low RPM’s, not fast enough to produce boost greater than the vacuum created and present in the intake manifold.

This has been the Jetfire turbo operation and failure short version………………

Recent Articles

Turbo System Safety Checks

Turbo System Safety Checks

The safety components of the factory designed turbo system have some interactive groups of safety "c...(read article)

Engine Front Drive Pulleys

Engine Front Drive Pulleys

The standard drive pulley has one groove. It drives the water pump/fan and alternator or generator. ...(read article)

1961-1963 F85 Car and Option Prices

1961-1963 F85 Car and Option Prices

Attached to this article is PDF file containing an extensive list of car and option pricing for 1961...(read article)

OldsJetfire Forum