cam and heads
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cam and heads
Are 42 intake valve and 39 exhaust too big for stock cam.I like this heads because of long spark plug thread.Engine is 1679
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Re: cam and heads
Yes, those heads are too big for your engine and stock cam. Pick some heads with stock size (35x32mm) valves.
- Piledriver
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Re: cam and heads
Will those even clear the stock bore?
Heads with valves that size are usually cut for larger jugs.
Heads with valves that size are usually cut for larger jugs.
Addendum to Newtons first law:
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
- Marc
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- Joined: Thu May 23, 2002 12:01 am
Re: cam and heads
1679 => 88mm bore. They'll be shrouded pretty badly, but they'll fit...even in 87s. Never tried it with 85.5 bore (the exact position of the intake guides would be getting critical at that point).Piledriver wrote:Will those even clear the stock bore?...
As you say, odds are that these heads are already flycut for a larger-O.D. cylinder...that can be remedied with spacer rings, but if the heads were intended for a larger bore the chamber walls are likely to have been laid back to where the cylinder seating surface would be compromised.
danyyo, there are four different outside diameters for 88mm cylinders (93.8mm, ~95.5mm, 97mm, and 98mm)...which do you have?
Because of the shrouding problem, it would be a waste of these heads to use them on the relatively small bore - and if the ports have been enlarged much beyond stock they won't work well with the stock cam, either...even with ratio rockers.
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Re: cam and heads
Hi! These heads are not machined for larger cilynders,they fit 88's perfectly
I dont now o.d. of cilynders because I didnt know there are diferent sizes ,so I didnt measure it.
Anyway I was put my engine togather in these few weeks,and it runs good.
There were some problems at higher rpms, but larger venturis in my 40 webers fixed it.
I dont now o.d. of cilynders because I didnt know there are diferent sizes ,so I didnt measure it.
Anyway I was put my engine togather in these few weeks,and it runs good.
There were some problems at higher rpms, but larger venturis in my 40 webers fixed it.
- Piledriver
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- Joined: Sat Feb 16, 2002 12:01 am
Re: cam and heads
Sounds like slip in 88s?
Addendum to Newtons first law:
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
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- Posts: 43
- Joined: Sat Jan 23, 2010 1:19 am
Re: cam and heads
I think so,they fit in the crankcase which is original As21 case..
.I get those parts as compensation for some my work in fiberglass,so I didnt have much choice.
.I get those parts as compensation for some my work in fiberglass,so I didnt have much choice.
- Marc
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- Joined: Thu May 23, 2002 12:01 am
Re: cam and heads
Classic slip-in 88s and the thickwall ones offered by AA both plug into an unmachined case (90mm nominal diameter). The former also fit into unmodified cylinder heads, which leaves them with a seating surface that's a scant 2.9mm wide (vs 4.15mm for a stock 1600 cylinder) while the latter have the same upper O.D. as a 92mm bore cylinder (98mm) resulting in a 5mm width => you can tell them apart from across the room.
The thin cylinderwalls of the "classic" slip-ins aren't very good at staying round under thermal cycling, so the rings never get a chance at final breakin - like classic 92s, they're known for short ring life and excessive blowby...especially if the engine's ever overheated a little. The seating surface is so narrow that it's not unusual to find the cylinders burrowing into the aluminum of the heads, with resultant compression leakage. That's more of a problem with 10mm head studs than with 8mm, since the latter maintain a more constant clamping pressure - you mentioned your case is AS21, so I'm assuming it has 8mm head studs.
If you received the thickwalled cylinders, there's nothing to worry about.
The thin cylinderwalls of the "classic" slip-ins aren't very good at staying round under thermal cycling, so the rings never get a chance at final breakin - like classic 92s, they're known for short ring life and excessive blowby...especially if the engine's ever overheated a little. The seating surface is so narrow that it's not unusual to find the cylinders burrowing into the aluminum of the heads, with resultant compression leakage. That's more of a problem with 10mm head studs than with 8mm, since the latter maintain a more constant clamping pressure - you mentioned your case is AS21, so I'm assuming it has 8mm head studs.
If you received the thickwalled cylinders, there's nothing to worry about.