Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

Discussion of 4-Cam Type 547 engines (and all the Fuhrmann racing variants) and cars that powered them.
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Mike Smith
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Re: Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

#46 Post by Mike Smith » Tue Mar 02, 2021 6:02 pm

Ibrahim,

GREAT to see people thinking outside the box -
Mike Smith (Essex - UK)

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Ibrahim Kuzu
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Re: Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

#47 Post by Ibrahim Kuzu » Fri Mar 05, 2021 2:22 pm

Appreciate it Mike...Love Engineering designs ,Challenges and Success in the end. Makes you happy.
IK

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Re: Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

#48 Post by Harlan Halsey » Sat Mar 06, 2021 6:49 am

Ibrahim,
One of the issues with Carrera heads, for me, was that because of the chamber casting, and the big valves, it was difficult to get more than 11:1 CR. I bet that with fully machined spherical chambers, and smaller valves, it would be possible to get a more decent 12-13:1. Higher compression combined with proper sized (smaller) passages should produce a useful gain in power. Also, it might help to move the cylinder sealing to the top of the cylinder.
Such heads atop LN aluminum cylinders, with high compression pistons, Carrillo rods, and a 692 or SCAT PB crank with a Hirth coupled lightened flywheel as suggested by Jacques, should make an interesting engine.

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Re: Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

#49 Post by Mike Smith » Sat Mar 06, 2021 7:30 am

It is interesting that all the experts appear to me Anti - the `Cone` Flywheel fitting method

Accepted that the Hirth method is more positive and the Cone method may seem a bit strange (especially thumping it with a heavy hammer a few times, to settle the cones) but in my limited experience it has never proved to be a problem
Mike Smith (Essex - UK)

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Ibrahim Kuzu
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Re: Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

#50 Post by Ibrahim Kuzu » Sat Mar 06, 2021 10:12 am

Hi Harlan,
We hear you.
Thank you for the input...We are at it ,and any one please chime in.
We do need advice from all the experts in intake /exhaust cylinder head design which performs the best on street and race....
Next casting we will be doing the intake and exhaust 36 mm just like old 911 cylinder heads. Valve sizes not 100% decided.
Custom porting for best flow numbers can be achieved by experts.
IK
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Re: Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

#51 Post by Mike Smith » Sat Mar 06, 2021 10:49 am

Ibrahim - What head is this ?
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Ibrahim Kuzu
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Re: Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

#52 Post by Ibrahim Kuzu » Sat Mar 06, 2021 11:31 am

Mike ,
Pictured cut view one casting date is 1966 911 cylinder head .
Bob Garretson brought it to my shop few years ago to copy the port size in Carrera cylinder head to make torque power in street use.
IK

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Re: Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

#53 Post by Jacques Lefriant » Sat Mar 06, 2021 12:24 pm

Hi Harland
Another reason to go to the seperate head configuration was mine and Bob's thinking that a 911 combustion chamber with it's different valve angles/ports/low volume that Porsche spent years developing would be optimun. you can glimpses of the development that was done with the 771 engine back then. the twin cam engines like the 916/908/917 used buckets to actuate the valves but just lately they have gone to finger followers like the Furman in the latest iteration of the 911 based 4-Cam.
Hi Mike
yes the cones work and was the only solution to be able to install the crank gear. It is a no brainer to make a PB crank with the zero angle bevel/curvic coupling but there were patent/legal issues and the machinery to generate was not available in the old days.
j
 

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Re: Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

#54 Post by Mike Smith » Sat Mar 06, 2021 12:29 pm

Jacques
Hi Mike
Yes the cones work and was the only solution to be able to install the crank gear. It is a no brainer to make a PB crank with the zero angle bevel/curvic coupling but there were patent/legal issues and the machinery to generate was not available in the old days.
Of Course - I just needed someone to sensible to point it out to me - thanks Jacques
Mike Smith (Essex - UK)

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Re: Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

#55 Post by Jacques Lefriant » Sat Mar 06, 2021 1:38 pm

Hi Mike
i forgot to point out that it also allows putting a TDC and advance marks on the flywheel for mid engine timing. I can't take credit for this it was Al Caddrobi's insite just like it was Bob's for my Differential conversion. I know you have contributed greatly to the cause so keep it up since the new generation are at a great disadvantage if we don't help .
j
 

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Re: Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

#56 Post by Olivier AUVRAY » Sat Mar 06, 2021 4:13 pm

Ibrahim Kuzu wrote:
Mon Feb 22, 2021 3:18 pm
No Jacques. Original head studs stays on the Engine case.
There will be two options to bold the Cam box to the cylinder heads.
Great question.
Thank you,
IK
Please let me know If the cambox can move a little bit. The idea is to align bearings (in engine case & in cam tower) of the long horizontal shaft.
I don't have your knowledge but on each engine that I've checked (only a few) the wear of the long shaft and associated parts was a problem.

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Re: Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

#57 Post by Joris Koning » Sat Mar 06, 2021 4:57 pm

Olivier AUVRAY wrote:
Sat Mar 06, 2021 4:13 pm
Ibrahim Kuzu wrote:
Mon Feb 22, 2021 3:18 pm
No Jacques. Original head studs stays on the Engine case.
There will be two options to bold the Cam box to the cylinder heads.
Great question.
Thank you,
IK
Please let me know If the cambox can move a little bit. The idea is to align bearings (in engine case & in cam tower) of the long horizontal shaft.
I don't have your knowledge but on each engine that I've checked (only a few) the wear of the long shaft and associated parts was a problem.
Yes Olivier, something Jim Wellington warned me of years ago. I know of people line honing/reaming these bearings to ensure there is no small "bind" placed on the bearings
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Re: Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

#58 Post by Ibrahim Kuzu » Sat Mar 06, 2021 5:45 pm

Hi Olivier,
I am a student of Jacques,Bill,Bob ,Jeff,Steve and other 4 cam mechanics. Learning as I go...And there is soo much to learn....
Your question is better answer it by them.
We machine the crank center to cam center to 105 mm and as you may know this dimension changes in each factory case very very little like 0.005 mm or so
Cam box definitely can be moved for long shaft 100% lining say .005~.010 mm or so
We do 2 dowel pin each Cylinder head to cam box Like 911 cylinder heads .
Thank you.
IK

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Re: Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

#59 Post by Jacques Lefriant » Sat Mar 06, 2021 9:39 pm

Hi Ibraham
it looks like you can not access the cylinder head nuts with the third piece attached. On a 911 you can offer the 3 heads and the cam tower as a unit to ensure the proper placement of the heads you then snug the head nuts then the cam tower is removed the heads torqued and then the tower is sealed to the heads and the cam rotation is checked is the way most do it. i think this is part of Olivier's concern. you could have a dummy plate that locates on the dowels and allows access to the cylinder head nuts to torque the head nuts then exchange the dummy plate for the third piece. the dummy plate may also have provision for the long shaft to check the fit.
j
 

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Re: Bob Garretson's idea 3 piece Carrera Cylinder Head work completed.

#60 Post by Harlan Halsey » Sun Mar 07, 2021 5:44 am

Ibrahim,
You probably know this, but developing the ports is an experimental process: You measure the flow over a range of valve openings with a flow bench. You then, considering the flow results, "port" the head and re-measure. When satisfied you assemble an engine and dyno test. Compare the result with the stock porting. Repeat until you cannot improve. Obviously this requires someone who knows how to interpret flow bench results, and someone who knows how to interpret dyno run results. Obviously the 2 Liter 911 port is a good place to start.
Many amature racers have done this, the cycle extending over several seasons. I suspect that manufactures do this as a part of development engineering nowadays. But it took the Porsche factory more than a decade before on outsider, Michael May developed the porting of the C heads.
I'm not suggesting that you take a lot of time to optimize the ports, rather that you have a few tests done, just to see if there's low hanging fruit here.

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