What to do with 1.7 Type 4 in 356 Speedster?

[Piledriver]

Lobe center.

Narrower LC increases overlap (probably increasing VE at mid-high RPMS) and also makes the dynamic compression ratio higher, as the intake valve closes a few degrees earlier.

Overlap is what causes the "big cam" lumpy idle, due to exhaust gas reversion diluting the Air/Fuel mix.
(which will be somewhat random)

[Mave]

Right, I just measured the deckheight:
#1: 1.575 mm (0.062")
#2: 1.524 mm (0.060")
#3: 1.557 mm (0.061")
#4: 1.524 mm (0.060")

Now what would be a sensible CR to go for? We have 95 and 98 octane fuel at the pumps here. So would I be ok at 9.0-9.5?

And with my set-up, is the Webcam 86 a good choice? (Keeping in mind I'm looking for a nice street motor: nothing too crazy)

Marcel

[Piledriver]

Do you have a step cut at the edge of your combustion chambers, or perhaps still have the gaskets in?
(They get stuck sometimes)

NEVER USE HEAD GASKETS. Even VW said so.
(Why they are still included in the gasket kits is a mystery, and unfortunate)

Rrrrrr.. Pet peeve. Everything should be measured//planned before cutting or ordering anything.

(rant)If the shop put a step cut in without being directed to do so, take it back to them and ask for another set of heads. They did you no favors, unless you desire high CHT and reduced power and poor fuel economy..(end rant)

T4s don't have much metal in the deck, and now you may have to have additional machining to set deck properly. (Choice: Cut heads again (bad), cut jugs, or deck block (seldom required on 1.7 blocks, but should be considered at this point)

OK, OK... its really not that cut and dried... Sometimes, the step cut is useful, in the case of a 1.7/1.8 with an block that has not been decked, is causes extra expense to do things right.

It should be DISCUSSED, not something the machine shop just does.
(*See end of post for common example where it helps)

A vanilla 17/1800 cylinder deck with NO head gaskets or base gaskets should be in the range of ~.020"/.5mm. Add the stock base gaskets, and you are at .030"... two sets, .040.

.060 is a horrible place to start unless you have base shims or head gaskets installed, removing them should drop you into a reasonable range. (.030"-.050"ish)

I ran deck at .028" for several hundred thousand miles, stock rev limit and mature driver etc.

.050 is the absolute maximum deck I would even consider "good", and then only under duress.

~1mm would be IMHO utterly safe to the safe rev limit if the rods, ~6200.

Use that .030>.050 deck range to optimize the CR based for the cam you choose.

I am in the "tighter is better" camp if you can buy decent fuel.


*)Example where the step cut is your friend: 2L, .010" block deck cut, factory jugs.
Piston/cylinder deck is ~ZERO +/-~.005".
1mm step cut, results in ~perfect deck, no gaskets or base shims.

[Mave]

The shop hasn't touched the heads yet. I figured I should measure deckheight myself first, before dropping everything off at them. They will be machining the heads to fit the 96 mm P&C's.
The heads did have the head gaskets in when I disassembled them, there were no base gaskets. I didn't put any base gaskets in either when measuring deck height, so this is "the naked truth".

What would be the best way to reduce deck height? Machining the cylinders, or the case? From what I read everywhere, I conclude that I cannot have this corrected in the heads.

The heads are currently at a glass bead blaster (and have been for two weeks already: they're slow....). Once they're back, I can drop everything of at the shop. They will do all the machining, and cc the heads. I just need to tell them what I want to have done.

Should I go for CR 9.5 and Webcam 86?

[Piledriver]

Do the heads have a raised ring the jugs seal on at edge of chamber, or flat ?
Some aftermarket jugs are extra long...it's another of those things that are a feature if planned for, and expensive to fix if not.

Most engine "assemblers" don't even notice...
Then we wonder why some motors suck gas, overheat, and leak oil like the Exxon Valdez...

[Mave]

The heads are still at the glass bead blaster....I'm expecting them to be finally ready next week. It's annoying having to wait for the heads before I can move forward!
I'm not sure if they have the raised ring: I think they were completely stock, as they also had the head/cylinder gaskets.

But regardless of the heads: I'm really struggling to determine which CR and (Web)cam to go for. Any suggestions would be greatly appreciated, as next week I intend to bring all parts to the machine shop, and need to tell them what I want them to do.

Marcel

[Piledriver]

You need all the dimensions to make the decisions.

The jugs may be aftermarket and a bit longer than stock, can only guess from here.

The Web73@108 is a nice all `rounder, and should equal or beat stock fuel economy and power, with the right heads and support it can pull to ~5800ish. CR limit on 87 R+M/100 regular is typically ~8.6:1, depending on heads.
It's frequently used as a stock replacement, even for factory EFI.

Web494, more cam needs more compression. @108 lobe centers ~9.0-9.5 is sane range, bit lower @104LC but will pull harder where you want it at the expense of some fuel economy... needs just a tad less CR @104.
Any larger cam needs dual springs, and the 494 could really benefit from them if you have large valves.

With 96s and 1mm deck, the 494 would be pretty decent in a lightweight kit car.

[Mave]

Hi
The jugs are new 96 mm AA's, and from I read might indeed be longer than 'normal'. I guess it would be wise then to take 1 mm of the jugs, so I can finetune to the desired CR with the basegaskets. Then they won't have to mess with the heads too much, besides opening them up for the larger cilinders.

What are your thoughts on the Webcam 86a for my application?

By the way, I've started a blog to document my project:
http://speedsteroutlaw.tumblr.com

Marcel

[Piledriver]

Hi
The jugs are new 96 mm AA's, and from I read might indeed be longer than 'normal'. I guess it would be wise then to take 1 mm of the jugs, so I can finetune to the desired CR with the basegaskets. Then they won't have to mess with the heads too much, besides opening them up for the larger cilinders.

What are your thoughts on the Webcam 86a for my application?

By the way, I've started a blog to document my project:
http://speedsteroutlaw.tumblr.com

Marcel

You should also check the block before cutting anything, it is not unusual if the deck needs a shave after 40 years.

I have not tried an 86a, seems a middle of the road option, some have run them with great results.

On a light car with enough CR (~9,3-9.5)I'd personally suggest a 163/86b@104LC.
Dual springs only, but pulls like a demon over ~2500.
Idles/putts around almost like a stocker under 2K.

[Mave]

Hi,

Well, in the end I opted for the Webcam 86a. I've had all parts balanced, blueprinted, CR corrected (to 9.0) and have yesterday put together the short block. See http://speedsteroutlaw.tumblr.com

Initially my plan was to use VFR800 throttle bodies, and a programmable ECU. But now I'm thinking it might be wiser just to start with Weber/Empi IDF's. With my 1911 cc I'm apparently right on the upper edge of 40's and the lower edge of 44's. I'm guessing that with my intended use, it would be wise to stick to 40's, right?

Marcel

[Mave]

It's been a while, life got in the way, but I'm restarting the project, and hope to be starting the engine in the coming months.

While I had the engine upside-down in the stand, the distributor gear popped out a bit, as I turned the crankshaft. I only noticed it when the engine was straight up again. So it is probably not engaged in the right position now.... Any suggestions how I can check this?

[wreck]

There are pics on the net on the correct angle for the drive in relation to TBC if you google "vw type4 distributor drive" . If you have an upright conversion then it's not that critical , it just means the distributor is not in the correct location for the vac can to clear the tin wear(factory cooling) , or the rotor to point to the mark on the distributor . It can still be tuned in any location as long as the vac can doesn't fowl on anything .

More important is the shim or shims under the drive , did they come out with the drive ?

[Mave]

Ah, thanks, true, I overlooked that. The drive didn't drop out completely, but moved enough to get disconnected from the teeth.
If I do want to put it back in the original position, how can I identify it is correct? (I mean: the pully indicates TDC twice; how do I know it it the right one to drop the drive in in the correct location?

[Piledriver]

You find TDC #1 via rocker arm motion, both valves will be closed and you will have lash.

[Mave]

Thanks!