DIY projects, work arounds, modifications, factory bulletins for 4-Cam

Discussion of 4-Cam Type 547 engines (and all the Fuhrmann racing variants) and cars that powered them.
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Jacques Lefriant
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DIY projects, work arounds, modifications, factory bulletins for 4-Cam

#1 Post by Jacques Lefriant » Wed Apr 07, 2021 12:44 pm

Hi Guys
lets make this forum work for us to KTF
j
Last edited by Jacques Lefriant on Wed Apr 07, 2021 12:55 pm, edited 1 time in total.
 

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Jacques Lefriant
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Re: DIY projects, work arounds, modifications, factory bulletins

#2 Post by Jacques Lefriant » Wed Apr 07, 2021 12:49 pm

One easy project is to replace the suction hose from the tank with one incorporating a check valve this is better than installing the check valve at the tank and losing the screen. The benefit is less oil ends up in the exhaust so at start up the smoking time decreases.
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Joris Koning
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Re: DIY projects, work arounds, modifications, factory bulletins for 4-Cam

#3 Post by Joris Koning » Wed Apr 07, 2021 3:09 pm

Good point Jacques. Also prevents the oil from draining into the crankcase and hydro locking the engine. Seems to happen with some frequency and cars which are not driven often. Worn oil pump??
'56 Coupe
'57 Coupe
'59 Cab 
'60 Coupe

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Jacques Lefriant
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Re: DIY projects, work arounds, modifications, factory bulletins for 4-Cam

#4 Post by Jacques Lefriant » Wed Apr 07, 2021 6:01 pm

Hi Joris
this also brings up valve stem seals on the exhaust valves.
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Jeff Adams
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Re: DIY projects, work arounds, modifications, factory bulletins for 4-Cam

#5 Post by Jeff Adams » Wed Apr 07, 2021 10:58 pm

The oil drainback issue into the crankcase seems to be hit or miss. I have built engines with oil pumps I know are in good shape, and still had the problem. I have informally surveyed several 4 cam builders on this issue and nobody knew for sure. Carrera 2 engines seem to be a little worse, maybe because the oil pumps are larger and have more surface area for the oil to gravity feed past the edges of the longer gears. I agree the in-hose valve is a better solution, I don't like the idea of eliminating the tank screen which helps protect the engine from larger debris.

Engines with factory exhaust valves can't use stem seals due to the 11mm to 9mm neck down area between the main stem length and keeper groove.

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Jacques Lefriant
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Re: DIY projects, work arounds, modifications, factory bulletins for 4-Cam

#6 Post by Jacques Lefriant » Thu Apr 08, 2021 11:35 am

Hi Jeff
Some builders install exhaust seals on the 11mm valves since they are partially effective depending on where the engine stops. I usually use 9mm exhaust valves and do not have the problem.
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Harlan Halsey
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Re: DIY projects, work arounds, modifications, factory bulletins for 4-Cam

#7 Post by Harlan Halsey » Sat Aug 14, 2021 4:15 am

I am confused about this check valve. The oil flows from the bottom of the oil tank to the pressure end of the oil pump. When the engine sits, the head in the tank continues this flow if clearance in the pump allows it. This oil makes it's way to the sump and if it is enough, into a cylinder. It seems that a check valve between the oil tank and the engine, if it prevented the leak would also prevent the normal flow with disastrous results. A check valve in the tank input line could prevent backflow siphoning up through the filter, through the scavenge end of the pump, if the input to the tank were below the oil level. i'm not sure the tank oil input is this high and the oil head would be pretty small.
I don't have much of a problem as I record the oil level in the tank and it doesn't go down much. Even so, if it has been some time, i roll the car in gear backward a few engine revolutions before starting.

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Harlan Halsey
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Re: DIY projects, work arounds, modifications, factory bulletins for 4-Cam

#8 Post by Harlan Halsey » Sat Aug 14, 2021 5:07 am

The Carrera was known for fouling plugs back in their day. This is because the piston-to-head clearance is very small, required because of the hemispherical combustion chamber. Porsche used side electrode, retracted gap plugs which didn't intrude into the chamber at all, but fouled easily.
My solution, 30 years ago, was/is to modify a projected nose plug ( NGK 3/4' reach) by shortening the ground electrode, and bending it to a side gap configuration. This put the spark into the chamber, at the end of the plug and reduced the plug projection height by about .060". Indexing washers put the threaded end of the plug flush with the cylinder head. I clearance the piston with a 1/2" ball end mill just enough to get .050" clearance. End of plug fouling. A side benefit for us DIYers is that I replaced a $200 set of plugs with a $25 set. And the engine seems to start much more easily.

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