Can you mistakenly have an SC Head redone with S90 valves?

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Doug Thomson
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Can you mistakenly have an SC Head redone with S90 valves?

#1 Post by Doug Thomson »

I am in the process of restoring a 64 356sc. The 912 heads which came with the car are a mess and I am pretty sure they are trash. I have two 356 S90 heads, at least I thought they were 18 years ago when I had them redone. They are anodized black but they have the cast re-enforce triangles, opposite the intake valves. Doesn't this make them SC heads? Did S90 heads have these re-enforced triangles? There is a casting mark on the side of the head with an 83 and a 2 lying on top with a B next to it. In the valve area there is marking of 440 with two symbles under and an 8.

When I set the heads out to be redone, I sent them with S90 valves I had, exhaust 40 and intake 31. Is it possible for SC head , which normally has exhaust 38 and intake 34, to be seated with S90 valves?
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Re: Can you mistakenly have an SC Head redone with S90 valve

#2 Post by David Jones »

You need Vic to weigh in on this one as it is easy to get confused on heads. According to Pellow as well as S90 heads the SC heads and also some "C" heads were anodized black and I believe all heads from about 62 had the reinforcement wedges. I say no more or I could sew confusion.
If I had known I would live this long I would have pushed the envelope a little harder.
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Re: Can you mistakenly have an SC Head redone with S90 valve

#3 Post by Jacques Lefriant »

Salut Doug

i am sure it is possible to use S-90 valves in late heads. if you check the angle on th combustion side you might be able to ascertain what the heads were originally. if you had not supplied the retainers and keepers they were probably 22 degree heads to begin with. Talk to Olivier at AMS in Paris to clear things up.
bonne chance
j
 

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Re: Can you mistakenly have an SC Head redone with S90 valve

#4 Post by Doug Thomson »

Thank you Jacques and David for your help. I will measure the angle tomorrow and I supplied the retainers and the keepers with the valves. Thanks again.
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Re: Can you mistakenly have an SC Head redone with S90 valve

#5 Post by Greg Bryan »

Is there a part number on the outside bottom of the head below the valve cover sealing surface? Can't recall the entire P/N but C or early 912 heads end in '02'
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Re: Can you mistakenly have an SC Head redone with S90 valve

#6 Post by Doug Thomson »

No part number, Greg just the casting marks mentioned above. I think I found something in a post of Vic Skirmants dated Feb 13,2017 The "Exhaust port is noticeably larger on 30 degree heads". My exhaust ports for this head are 44.5 x 16 mm and the trashed 912 heads off of the engine I am rebuilding are 48 x 18 mm. So it looks like the redone heads are S90. Too bad for me. Would it be too bad to use them on my rebuild which also has big bore pistons?
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Re: Can you mistakenly have an SC Head redone with S90 valve

#7 Post by Mike Horton »

Doug, my '62 S90 heads do have that cast wedge you describe. I am in the middle of a street build with this old spare engine, with a SC/912 crank. My heads are the original 22* combustion chamber angle heads, with the black anodize coating, and in pristine condition. For this spare engine build, I bought a set of the AA cast iron cylinder, 86mm big bore P/C, with the piston domes made for the 22* heads. Per Jacques, and others, to use your heads, you'll either need to re-machine the head angle to the 30* piston tops as used in the C/SC/912 heads, or re-machine the piston tops to the 22* head angle, or... buy the new AA big bore set made for these 22* early, through '63B heads. Good luck,

(the AA P/C set is far less costly, than a set of heads)
Mike

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Re: Can you mistakenly have an SC Head redone with S90 valve

#8 Post by Doug Thomson »

Thank you Mike
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Re: Can you mistakenly have an SC Head redone with S90 valve

#9 Post by Al Zim »

It was not uncommon for S-90 valves to be installed in Sc heads. I suspect as with most 356 modifications this was to produce more HP than the old way! But it probably did not. For a While S-90 valve were nearly impossible to purchase because the demand was small. They are now available and Zim's sells them. Putting S-90 heads on a Sc engine was done at the factory starting with engine number P0800500 this was a run of less than 500 engines manufactured late in the model year of 1963. If you would like us to examine your SC heads for serviceability, contact Aaron 800.356.2964 and make arrangements with him. Be sure you check the valve stem for taper (i.e. the probability of oil burning) and the clearance in the guide (use he factory go-nogo gauge). If you are planning on keeping the engine and car for a long while I would suggest the 356C (or super P&C with the S-90 heads) I would using a set of German Pistons and cast Iron Cylinders. These provide an oil ring below the piston pin which reduces wear on the piston. You will have to shorten the skirt of the piston about 25mm to clear the counter weighted crank. The tolerance for piston to cylinder clearance is much closer than with the Pacific rim big bore sets. Be sure you blueprint the rods. al zim Zim's autotechnik 2018/08/09
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Re: Can you mistakenly have an SC Head redone with S90 valve

#10 Post by Doug Thomson »

Wow, thank you Al for your offer. I am living in France and I was trying to find a place within the Lyon or Grenoble are. Why cast iron cylinders?
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Re: Can you mistakenly have an SC Head redone with S90 valve

#11 Post by Jacques Lefriant »

Hi Doug
Cast iron has been the go to material for cylinders for many years. You must take into account that there are many grades of cast iron. Also in the execution there can be issues. It has been the experience of many that the AA sets provide exemplary service for regular engines. If you look at the decisions that Porsche has made over the years with aircooled engines you may infer that there may be a better fit for different executions. Besides modifying the pistons for the counterweighted crank you are stuck with an old ring design if you get the "C" P+Cs for about he same cost you could get Durabar(contnuously cast iron comes in different grades) and modern pistons that are closer to an SC.
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Re: Can you mistakenly have an SC Head redone with S90 valve

#12 Post by Jacques Lefriant »

Hi Doug
if you want some insane machine work done check out JPSAircooled in CH
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Re: Can you mistakenly have an SC Head redone with S90 valve

#13 Post by Doug Thomson »

Very cool. Thank Jacques. Are you from France?
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Re: Can you mistakenly have an SC Head redone with S90 valve

#14 Post by Doug Thomson »

I found a pair of 68 912 heads I have had for 15 years. They haven’t been fly cut and still have the anti-smog tubes attached. Can’t these be used in my SC rebuild. Couldn’t I use a machine bolts with copper washers to plug the holes from these tubes with the end result being similar to 69 heads?
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Re: Can you mistakenly have an SC Head redone with S90 valve

#15 Post by Jacques Lefriant »

Hi Doug
I am from New Orleans La.. yes you can use the 68 smog heads. the take on them is that they me be slightly more prone to having cracks develop but if they are good now they should be good for a long time.
j
 

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