Setting deck height for 9:1 compression Options

[Chad911sc]

Trust me! That was my first thought when purchasing a 914. Stick a turbo Subi engine into it, but when I seen this Olympic blue 914 on Craigslist, I loved it just as it was. I figured I would leave it original and possibly let my daughter, who just turned 17, have it as her second fun car to sport around on the weekends. I haven’t finished the bug yet, have all the fabrication work done but still have to finish the body work and paint. I can’t wait to drive it! The engine purrs like a kitten. I used the Cobb system to tune it and have it close, but I will go to the local Subaru dyno shop to get the perfect set up once it’s finished.
The 911sc engine is exactly like it came from Max Moritz, I had the local Porsche guru fit the new tensioners and Mahle pistons and cylinders when I purchased it over 20 years ago. I don’t think it had a bunch of extra hp, but when Sid Collins tore it apart to rebuild it, the case halves were polished internally and it’s fuel injectors were longer and different shape than the factory ones. Sid said it was done for better distribution of the fuel for efficiency in the burn. Never had it on the dyno, but it definitely scoots. I have only put about 10k miles on it in the past 23 years.
I bought the Corvette from a man down in Miami who had it stolen from his driveway and purchased a new one with the insurance money. They found it 3 months later in a shipping container bound for overseas. I picked it up for 7k and dropped 7k in the engine and suspension. It’s a Super fun car to drive….endless burnouts for days and Sooo much fun to power slide through long corners…lol.

[Chad911sc]

Talked to the machine shop today and they ended up taking .010 off of the deck to flatten it out on the crankshaft line, and .030 off of the heads to get me down to the 54cc target for my desired compression ratio. Pretty much what I was thinking.
Can’t wait to get back to Florida and start the assembly process once more!
Thanks again for all your help guys! So glad I listened to your advice and tore it back apart (IMG:style_emoticons/default/beerchug.gif)

[technicalninja]

Will .010 give you the deck height you needed?

I thought you needed .013 from your initial post...

I'd have gone a little bit deeper allowing for shimming.

If your using cast pistons it will probably work fine at .037 but that is getting close in my book.

[Jack Standz]

Merry Christmas everyone!

Well, you'll figure out the next step when you measure everthing and do the mock-up.

Fingers crossed that you're not too tight on the deck height. As technicalninja says, you don't want to be too close. Pistons hitting valves do tend to ruin one's day (IMG:style_emoticons/default/smile.gif) . But, sometimes we do tend to push the envelope. And sometimes the envelope pushes us. For a 2056, you don't need to cut it that close anyway and they are a fun motor in a 914.

[technicalninja]

I always check deck height of ALL of the pistons.

As tight as you are, make SURE you don't have one that is .002 different.

"Pop goes the Weasel" is what you want to avoid at all costs.

I sort of expect you know this already!

It's more for the other folks watching the thread...

I would not release a customer job that tight.

MIGHT use that shit myself...

You WANT to decrease piston to head clearance as much as possible in my book.

Close should be better!

Right up till the point the pistons KISS the head which always hurst the motor and sometimes DESTROYS EVERYTHING...

Have a Merry Christmas!

Rick

[Chad911sc]

Merry Christmas Everyone!!
After I had hand lapped the registers and rechecked my deck height on 2 of the cylinders I was at .050 total, so I should be right at .040 now that the deck has been decreased by .010
I figured I should be between .038 - .040
I always try to get my squish right at the perfect spot for combustion burn efficiency.
I will definitely clay check it on every cylinder to see exactly what my piston to head clearance is….
Thanks again guys!!

[technicalninja]

Will .010 give you the deck height you needed?

I thought you needed .013 from your initial post...

I'd have gone a little bit deeper allowing for shimming.

If your using cast pistons it will probably work fine at .037 but that is getting close in my book.

The above (and the next post from me) is TOTAL BS!

I even sucked Jack Standz in...

I got the math BACKWARDS AGAIN!!!!

(IMG:style_emoticons/default/headbang.gif) (IMG:style_emoticons/default/headbang.gif) (IMG:style_emoticons/default/headbang.gif) (IMG:style_emoticons/default/headbang.gif)

It looks like he didn't remove ENOUGH material.

This would have put the piston DOWN the bore, not up.

He's NOT tight, he's loose!!!!

I'm happy he rechecked his shit and choose the proper amount to remove.

In my book .040 is OPTIMAL and safe enough to release to non-technical folks.

He's as TECHNICAL as I am...

I still suggest checking all of them and (this might be important!) check to verify the jug fins are NOT hitting the head.

The check I did for him on register depth on my stock junk was eye opening!

It looked like either fly cutting head OR cutting top of jugs would require doing something to the fin section of the jug. Without the original compression ring it looked like they ALMOST touched the head in STOCK form!

And I truly believe, on pump gas, the deck height is the MOST important measurement to get right. Something without quench pads, something using fuel that is not prone to detonate, it's not nearly as critical.

But for the crap we can get out of a commercial pump (besides E/85) deck height is stupid important...

Merry Christmas all!
(IMG:style_emoticons/default/ninja.gif)

Edit: Everyone, even brand-new members, can add good info to the forum.
Chad has given me a small Christmas present (and he didn't even try!).
This guy has a functional turbocharged air-cooled VW (the Sun Bug) at 220 hp!
I want to know ALL about that set up!

I VASTLY prefer to force feed engines below 3.5L It's my NORMAL recipe.
I automatically discounted "turbo" due to the limitations of the T4.
Might have been short sighted...

I hope "Nickies" are not part of the equation; blows budget bigtime.

Chad, we will have PM conversations regarding this after the holidays.

And LOTS of folks on here would be interested in turbocharging the T4.

It would make a KILLER thread on its own!

[sixnotfour]

OMG...

[porschetub]

OMG...

(IMG:style_emoticons/default/agree.gif) ,hopefully for the same reason ?,that last reply made little sense to me .

[technicalninja]

I have a disease…..
Project mania…lol
Love to build stuff and can’t say no when I see something in my reach. I have some of them done, but most are still works in progress.
1) my daily driver, she is my true love. 15 years of daily driver flawless service! 2004 4Runner.
2) My first car from 1986 that I still have. Building it for my now 17 years old daughter. It’s a 74 Sun Super Bettle. Has 2110 turbo, 220 hp on water dyno
3) 1979 911sc Max Moritz German born import. Finished painting about a year ago, but this is how she still sits.
4) 1969 beetle with 2.5L turbo STI forged stuffed into it. Crazy amount of fab work. Done with everything but body and paint.
5) 1998 C5 naturally aspirated 470rwhp on the dyno….so much fun!
6) 1972 CJ5 lifted on 39.5’s with hydraulic assisted steering and 4 wheel disk brakes. First V8 that Jeep made AMC 304.
7) My daughters go kart
8) Dads go kart with forged internals of course..lol
9) 2006 Buell 1250 scg
10) 2006 Screamin’ Eagle V-rod
11-12) YSR 50 and the yellow one is a YSR with a IT 175 2 stroke 6 speed with custom frame and reinforced swing arm. Clocked at 87 mph in a 25 speed limit by local policemen in my neighborhood. He let me go (IMG:style_emoticons/default/first.gif)
13) 1991 FZR 400 with 632 big bore Wiseco motor stuffed into it. Also very fun little corner ripper that I take to the Dragon in Tennessee every couple of years.
I do all my own work on everything and nothing has stickers on them…all paint.
Oh yeah…and last but not least the 74 2.0 Olympic blue 914 that I’m currently building a 2056 for.

Actually, just the math was bad. The rest of the posts were fine.

I do not like to make simple mistakes. "In front of me" I'd have been fine.

Sometimes "over the keyboard" can create confusion.

In the "show us what you've got thread" Chad911sc posted this tidbit

"2) My first car from 1986 that I still have. Building it for my now 17 years old daughter. It’s a 74 Sun Super Bettle. Has 2110 turbo, 220 hp on water dyno"

He's got a bunch of nice stuff but that caught my eye as it is the most Type4 like.

I'd like to know how that was done, how long it's run, and what problems he's had along the way.

I'd stay Type4 on my 75 if I could make that type of power without spending 20K...

[emerygt350]

No kidding. I think it would be fun to try and build something like that. I wonder what boost and compression look like.

[Chad911sc]

That 2110cc type 1 engine was built by Sid Collins of Troysport of Orlando. He is retired now, but he was the MAN in this area for 40 years. He also kicked ass at Sebring in a little red 356 for decades. I had that engine built back in 1997 and it’s still sitting on my shelf in the garage filled to the brim with oil. I built the engine originally in 1989 but could never get the turbo to come on early enough to make it drivable. It would bog down horribly and then come on too hard to control around 2800 rpm’s. It went to a couple local shops in Indiana where it sat for over 2 years with no success. I then moved to Florida in 1992 and brought it with me because it was my first car and love. I was hit by a truck on my GSXR in 95 and it pretty much totaled me. I was bed ridden for over a year and then it took me 5 years to learn how to walk. In that time I used to go to my friend Scott’s cylinder head shop where he did custom porting work for Sid on his 356 race car. Over time Sid and I became friends and he offered to get the big engine sorted out for me. He told me it wouldn’t be done in a hurry but it would be right. 2 years later he called me and told me to come hear it run on the water dyno. It sounded so good and came on smoothly through the power range. He laughed and said, it might run for years, or it might grenade on the first pass down the track…lol. It has never made it back into the car. The superbettle body was perfect when I brought it to Fl but sitting in 100% humidity in a field for 10 years rotted it out badly. I have replace all floors and lower sheet metal in the past few years and it’s coming along slowly because as I said ….project disease!!!
As far as I remember…. Forged internals SCAT ( only thing that existed back then)
Rajay turbo feed by progressive 2 barrel
And then whatever Sid the guru did after he tore it all apart and
did his magic. I know he made custom pushrods because he said
my geometry was off. I didn’t understand any of that back in the
early days. I’ll try to find some picture in the next few days and
post them. I’ll uncover the engine as well and snap a few pics.

[technicalninja]

I did do a deep dive into turbo T4s after seeing your turbo T1 notes.

There is also another old thread that re-surface showing a baby system on a 1.7 that seems to "work" but at low levels (7-8 psi)

Lenn Hoffman set me straight!

He suggested a single 1.7 head casting (Q?) was the way to go and high boost would make the combustion chamber besides/below the exhaust port "droop", loosen up the valve seat, and "The Reaper" would arrive shortly thereafter...

There was also a long discussion on using some very special T4 heads that had side exit exhaust (like a T1!). Looks like these critters were 4-5K for a pair a decade ago.
These REQUIRED the DTM cooling system (like a T1 as well).

I saw enough to answer my "Hey, maybe boost is The Way" thoughts.

Nope.
No "blowing" a T4 in my future!
Water boxer Porsche 6 or GM LGX will be my path...
(IMG:style_emoticons/default/ninja.gif)

[Chad911sc]

I do remember that my boost exhaust gate was set at 6psi
Yeah like I said….may last a long time or grenade on the first track day…lol

[technicalninja]

Chad, I wouldn't spec a "draw through" turbo system on ANYTHING today.

Lots of pitfalls...

I wouldn't spec a "Blow Through" on carbs either.

One of my Mentors is Corky Bell.

I worked for him in the early 80s and he WAS doing blow throughs then.

He's dropped "draw throughs" years ago at that point.

Mikunis were Corky's go to carbs for forced induction, and they SPEW fuel everywhere past 14psi.
He did an intercooled blow through Mukuni on the first gen RX7 that took 100hp to 285!
Rotary is more like a 2 stroke than a 4 and they really like boost!
The Rotary engine is not robust enough IMO for long life under boost.

A mild system is below 15psi now. This was the upper limit back in 83 with all sorts of fuel systems mods, some of which didn't work very well.

A serious system goes 20+, some hit 30 today!

Digital FI. Injectors pointed at intake valves. Good intercooling, Flex fuel (E/85).
Modern turbo (the aerodynamics of the internals has changed BIGTIME over that Rayjay). COP ignition. Piston squirters.
The above is the "standard" recipe today.

The stand-alone digital FI MADE modern turbocharging possible!

[Chad911sc]

Ok….
Everything is back together after the deck was machined .010 and the heads were fly cut approx .030 to get my head cc total down to my desired 57cc with the valve relief figured into the equation. And yes they also cut .030 off of the ridge on the flat surface of the head so that it would seat fully down onto the cylinder. After assembling the cylinders and pistons without shims, my deck heights varied from—
.035 to .033 on cylinders #1 and #2
.041 to .035 on cylinders #3 and #4
I performed the measurements with a level and feeler gauges at the center of the piston, parallel to the pin. I then repeated the same test with my digital depth gauge magnetized to a steel mounted plate.
I then disassembled the pistons and cylinders and did the exact same tests, using the same piston and cylinder on all 4 different registers. The test shows the exact same results, so that should mean that the pistons and cylinders are equal in distance. This leaves me to think that the new forged rods I purchased must have some discrepancies in their length. Along with bearing differences as well added in there. The rods were supposedly checked and balanced by the seller. I did weight match all my rods and they were within .02 grams of each other.
From my research over the past few days I have found this is not uncommon. Just want to get the best path forward to achieve an engine that will perform and hopefully last.
I know there has to be an acceptable tolerance from head to head so that it will seal properly. And I’m sure there is an acceptable tolerance from one side of the case to the other.
In my head I am reasoning that if I shim one cylinder and not the other to correct the total deck height, it will then make the cylinder head rock on the uneven cylinders since they are all the same height.
So what is my best path forward?
Thanks again for your patience and time….Chad

[technicalninja]

On a single bank the jugs have to be level with each other!

The .002" range difference between 1-2-4 I'd live with.

#3 at .041" I'd "fix" on a serious motor.

Now, it's only a .005-7" difference between the rest.

In real life it shouldn't matter all that much.

You are not building a "tip of the spear" motor.

Yours is far more conservative than many.

I'd probably run it as is.

[Chad911sc]

10-4
That’s what I was hoping to hear…
In my perfectionist nature, is hard to leave things alone… Lol
I do have one wrist pin that’s a little heavy. I could take a few thousand off the top of the piston and then weight match it with the rest since I do have that heavier pin. If it’s worth the trouble to get them all within a tighter range. It’s true that it is just a street engine that will never see over 6k.

[technicalninja]

I wouldn't worry about flawless balance on anything!

When running there is a bunch of oil that is "roping" around the parts.
It's stuck to the surface and moves around bigtime depending on rpm.

Makes balancing tighter 5 grams pretty useless.

Now when it is on the bench I'm trying to hit +/- 1 gram.

This is fairly easy to hit.

Balancing to a fraction of a gram is "practice bleeding" in my book!

[Chad911sc]

Ok…sounds good!
I’ll leave it alone and move onto rocker geometry with my new pushrods and swivel feet (IMG:style_emoticons/default/beer.gif)