Are Swivel Feet Worth the Trouble?

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Re: Are Swivel Feet Worth the Trouble?

Post by Marc » Sat Sep 17, 2016 9:09 pm

Big Ratfink wrote:I will order a solid rocker kit with extra shims. I think this is cheap insurance..
Yes. They usually come with enough ~.015/.030/.060"shims to do the job (the stock ones are .040"). The fancier ones have a fixed spacer tube between the intake rockers, but most use one that floats. You want .004-.006" side clearance on the exhausts, and on the intakes with the fixed spacer. With the floating spacer, the intakes can "share" it so less is acceptable, say .006-.010". There's enough slop in the mounting holes to upset the settings any time the shaft is removed/installed...after running the nuts down lightly you can tap on the end(s) of the shaft to shift it until the exhaust sideplays are equal again.
Watch out that the shims over the rocker stand/shims don't make contact at the bottom. Grind a small flat on any that do.
So, when installing the rocker assemblies for the final time you've got to keep an eye on the balls so they don't turn over as you're engaging the pushrods into the cups, and on the shims so the flats stay "down" - not that hard if you hold everything pinched together by pushing inward on the exhaust rockers until the shafts are in place.

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Re: Are Swivel Feet Worth the Trouble?

Post by Piledriver » Sat Sep 17, 2016 9:21 pm

Looks like miller is selling the info he used to have posted free... Try the wayback machine.
(but it sounds like you probably have read it )
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Re: Are Swivel Feet Worth the Trouble?

Post by Big Ratfink » Sat Sep 17, 2016 9:57 pm

[quote]Also on the shopping list is some .120 shims from CB. This is about the shimstack that worked right for parallel adjuster at mid lift with stock pushrods.
[quote]
That is with about .050" ground from the underside of the rocker for clearance for the ball retainer of the adjuster.
f

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Re: Are Swivel Feet Worth the Trouble?

Post by Big Ratfink » Sat Sep 17, 2016 10:05 pm

I did have the step machined out of my heads.

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Re: Are Swivel Feet Worth the Trouble?

Post by Piledriver » Sun Sep 18, 2016 4:46 am

Big Ratfink wrote:I did have the step machined out of my heads.

If the step was bore sized, and you are building a stroker it doesn't usually hurt, you can work around a step cut, but on a stocker its a curse for getting a tight deck.
I'd consider longer rods instead if i had the option, but then i'd probably also do a CW crank even on a near stock t1 build, just as an investment in case life extension.

All I'm saying is don't skimp on effort (or a set of cut to length pushrods if needed) here, as doing it properly makes a real difference, just like that annoying thermostat and having to put on all that engine tin and sealing bits, including the underneath ski jumps. A working thermostat alone can double ring/bore life, and a real air cleaner (the originals count if serviced properly, paper is a better filter for fines that eat rings and bores) can do even more.

(There''s a fellow that makes proper bellows thermostats, better bellows material than factory too)
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Re: Are Swivel Feet Worth the Trouble?

Post by Marc » Sun Sep 18, 2016 10:13 pm

It matters not one whit whether the piston-to-head clearance is achieved by piston deck height alone, or through the use of a head gasket, or a stepped head - any way you do it, the effective combustion chamber shape and "quench" is going to be the same.
If you're a "true-believer" in the benefits of running minimal piston-to-head clearance, you'll keep that tight (but I recommend no less than ~.050" on a typical Type I street motor) and if it's necessary to add unswept volume to keep the C.R. under control, achieve that by laying back the combustion chamber walls and/or milling a dish in the piston top rather than by using cylinder base shims. It's a much bigger deal on a Type IV because of their outsized intake ports, on a stock Type I head there's enough port velocity to create sufficient mixture turbulence that the benefits of "squish" are significantly less.

I'm running .220" piston deck in the 1849cc motor in my trike (old racecar heads I used are only 29cc), and it's running cooler and getting better mileage than the stock `74 1585 it replaced...the stepped `74 heads yield around .110" piston-to-head clearance, which is double the "ideal" (apparently VW engineers weren't too worried about it either). I imagine the throttle response might be a little crisper at low RPM if it had tighter piston-to-head clearance, but I can live with it since its main use is sustained ~3000-3500RPM highway running.

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Re: Are Swivel Feet Worth the Trouble?

Post by Piledriver » Sun Sep 18, 2016 10:32 pm

At .<=.030 there is ~zero carbon buildup in the squish area... If the bottom end is stiff enough and the RPM is reasonable it works fine. Does good things for idle and bottom end>low midrange efficiency and CHT, needs much less timing.

The "gotcha" issue with big deck is there is sort of a "bad" range that allegedly promotes knock between about .080" and ~.200"

If you have enough intake port swirl motion like a T1 (most 2v heads do inherently create ~good in chamber swirl) you can get away with a huge deck, it's the in-between sizes folks might end up at while chasing a magic CR# that can run into issues.

The Chrysler 2.2/2.4L turbo motors for example run almost .250" deck, with sort of a fin across the piston to reduce overlap flow between the intake and ex sides at TDC, probably also creates turbulence in chamber.

Those are 4 valve heads, so they are using "tumble" rather than swirl rotation around the chamber to create charge uniformity.
Last edited by Piledriver on Sun Sep 18, 2016 10:39 pm, edited 1 time in total.
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Re: Are Swivel Feet Worth the Trouble?

Post by Marc » Sun Sep 18, 2016 10:38 pm

Piledriver wrote:At .<=.030 there is ~zero carbon buildup in the squish area... If the bottom end is stiff enough and the RPM is reasonable it works fine...
Again, that's Type IV thinking. Type Is are NOT that "stiff" and all it takes to exceed "reasonable" RPM is missed shift at WOT.
The bare minimum for an 85.5mm bore Type I is .040" in my experience...and that gives you zero time to shut down between the time you hear the first knock and total destruction.

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Re: Are Swivel Feet Worth the Trouble?

Post by Piledriver » Sun Sep 18, 2016 10:49 pm

I confess, I think like that, I put ~150K miles on a T4 1700 @.023 deck.
(90mm x 66 with 5" fat, stiff little rods and 55 x 23mm rod journals and 24mm pins)

Oh, Mike, the Rootbeer Busses motor still lives on in my sons 78 bay as an 1800.
Still runs fine after the emergency rebuild in the snow in '92. (~all random used parts)

"Big RatFink"' is the fellow who got me started with T4s.
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Re: Are Swivel Feet Worth the Trouble?

Post by Big Ratfink » Mon Sep 19, 2016 10:42 am

This engine has.052 quench.
If I didn't have so much else going on I would un- bury my flow bench and do some playng around. I have a pile of junk heads. I have never done a vw head.
When it comes to bench racing there's a ton of food for thought and millions of opinions and alot of good sounding bad information.
One thing I thought about on the flow bench was if i could add a polycabonate cylinder under the head to try and get a visual idea of the port swirl.
I personally would like a tighter deck than what I can run with this case and crank, but I read that the Bergs can have good running low compression engines with their hemi cut heads. That hemi cut must negate most of the tradtional quench.

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Re: Are Swivel Feet Worth the Trouble?

Post by Marc » Mon Sep 19, 2016 12:46 pm

Big Ratfink wrote:...That hemi cut must negate most of the traditional quench.
Yes - although it still leaves more quench pad than a 36HP VW or 356 Porsche head has. Most pistons have sufficient crown thickness to allow milling in a dish (or better yet, a "reverse dome" that mirrors the chamber shape) deep enough to add 2 or 3 CCs with no negative effect on quench - IMO that's a better way to add unswept volume than the semi-hemi cut, but it's more trouble to do (esp. the reverse dome).
What's your bore/stroke, chamber volume and target C.R.? If this is a 1600 It sounds like it'll come in at ~8¼:1. I think that 2228 has about the same effective duration as a stock cam, for which I generally recommend not exceeding 7¾:1 - even if you plan to feed it better than Regular.

http://images.thesamba.com/vw/classifie ... 493589.jpg
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Re: Are Swivel Feet Worth the Trouble?

Post by Piledriver » Mon Sep 19, 2016 12:51 pm

Don't believe everything you read in Genes little blue book.
For some "'interesting discussions" Google for semi-hemi cut heads Gene Berg
The world has moved on since then.

My personal experience with semi-hemi cut motors (not on anything I built) were in all cases fuel sucking, hot running pigs that couldn't get out of their own way and were untunable for street use.
They idled smooth, but motors with no compression do.

They were ~ok at high rpm but still way down on power due to super low dynamic compression.

A round dish in the middle of the piston is relatively easy... works too.
Leaving the outer ~1/2" for quench area (at least) makes a huge difference.
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Re: Are Swivel Feet Worth the Trouble?

Post by Big Ratfink » Mon Sep 19, 2016 9:08 pm

It sounds to me like the ports must have pretty good swirl / turbulence and if that's the case the quench isn't as important.

That 2228 cam, I wish everyone that sells cams printed the whole cam card specs so people could make more informed choices, even though the lobe shape also factors in. This cam is built on 112 degree lobe centers, intake opens 0 degr, closes 44 deg atdc, exhaust opens 44 deg btdc, closes at zero. Valve lift advertised is .397 with 1.1 rockers, with 224 duration @ .050.

I'm running cheap Chinese replacement heads I got from Mofoco. (They are the only VW shop in my area and have given me good service.) The ports "LOOK" like they will flow pretty good, better than stock. I think your cr estimate is pretty much on the money, best I can remember. I cc'd the heads a couple years ago, but don't remember exactly what they came up with. I did plan running 91 octane. The cr might be a smidge high. I did run these heads before and I didn't notice much trouble. Hopefully the thermal barrier on the heads, piston tops, valves and exhaust ports will help keep head temps down and help with detonation. I coated the last engine also.

The exhaust will be the streetmaster CB is selling. The theory here I think is that with good intake and exhaust the cam should have good cylinder filling with little overlap loss to help with efficiency. Anyhow , that's the idea I'm running with.

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Re: Are Swivel Feet Worth the Trouble?

Post by Big Ratfink » Mon Sep 19, 2016 10:14 pm

69 x 85.5

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Re: Are Swivel Feet Worth the Trouble?

Post by Marc » Mon Sep 19, 2016 11:53 pm

Significantly more lift than stock (they're like .320"), in that respect it's like an "RV" cam - I've had a CB 2280 (they call it their "cheater" grind) on the shelf for years, destined for the next small/mild motor I build and I'll bet it's pretty similar except it's on the stock 108° LSA. I think the promise of improved mileage comes from the wide LSA/reduced overlap. That should both widen and move up the torque curve, although the peak torque would theoretically be a bit less (everything else being equal). And the later intake closure will drop the dynamic a bit, so you'll probably be fine as-is with good gas. What do you have planned for induction system, and what's it going into?

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