Off-set grinding a 1700, 1800 type IV crank

volksmann · Post by **volksmann** » Fri Jan 30, 2004 4:47 pm

I am going to have a 1700-1800 crank off-set ground to a 71mm stroke. As long as it is going to be ground,

Can I incease the stroke even further?

What would be the max stroke and still be somewhat reliable?

I do have a set of 2.0 type IV rods.

Ken

HAM Inc · Post by **HAM Inc** » Wed Feb 04, 2004 2:36 pm

Ken the 1.7 & 1.8 cranks can be ground no further than a 71mm stroke if you wish to use stock 2.0l rods and std. bearings. The crank can be offset ground an additional .75mm but you will have to use undersize bearings.
You're better off shooting for a std. crank.
Because the crank is made from a super high quality chilled German forging, the journals can be welded and further offset ground to push the stroke up more. Afterwards Nitriding would be a good idea.
Len

speedy57tub · Post by **speedy57tub** » Wed Feb 04, 2004 6:00 pm

HAM,
What other rods can be used and for what pistons? Can 96-mm pistons be used with bored-out 94-mm cylinders?

HAM Inc · Post by **HAM Inc** » Thu Feb 05, 2004 7:07 am

Speedy if your objective is to stay on a budget and use readily available O.E. components then you're limited to the stock 2.0 rod. 96mm pistons in bored cylinders is popular. Jake does a lot of this.
If you're willing to spend more money, the aftermarket is waiting for you with a plethora of rod, stroke, pin ht. choices. Higher rod/stroke ratios are great for higher revving engines. For race apps. I look for around 2:1. For street use lower #'s are fine. On a stock 2.0l the ratio is 1.84:1, which is not bad for the intended use.
Len

speedy57tub · Post by **speedy57tub** » Thu Feb 05, 2004 7:19 am

Ham,
Thanks!

I currently have a 1700-cc 914 core and a pair of 2.0 3-stud Porsched heads which I want to send to Adrian. I do want to stay in a budget

and I was considering the 1911-cc or 2056-cc. I do not have the rods or crankshaft and I was wondering what to do. Some places will not grind your 66-mm stroke to the 71-mm. Since 2.0 rods are weak or hard to get, I was wondering what my other options are. Also, I hear the 96-mm new cylinders are not as good as the "bored out to 96-mm" 94-mm's. Being that Type 1 rod options are plentiful, I was wondering which would be okay without breaking the bank. I plan to build this engine for future use and want to get it turn key ready. I want to go Type 4 since I hear from everyone who has that it is the way to go. Right now I have a nice 2110-cc but I guess I go the "Type 4 bug". Gee Jake and Joe, thanks alot!!!! LOL

HAM Inc · Post by **HAM Inc** » Thu Feb 05, 2004 12:01 pm

Speedy if you need someone to turn your 66mm stroke into a 71mm stroke I have a grinder near me that does mine. I've never had a minutes trouble doing this, even without Nitriding. As for the stock 2.0l rod I'm not sure what you plan to put this engine through, but I've done plenty of heads for road racers using stock rods with nary a problem, even with elevated compression ratios and oversize valves. (I know of at least two gamblers who didn't even install heavy-duty bolts!) They're heavy as a house but seem to be pretty tough. I believe I've got a matched set.
I know Jake prefers to bore cylinders rather than use the aftermarket 96mm's.
Len

speedy57tub · Post by **speedy57tub** » Thu Feb 05, 2004 3:26 pm

So far, I am really leaning toward the following:

- 71-mm stroke counterweighted crank (does C/W really make a difference?)
- 96-mm JE Pistons
- bored out stock 94-mm cylinders (who does this properly and where can I get a set?)
- Webcam camshaft (have any suggestions?)
- dual 40 IDF Webers on port matched manifolds
- 2.0 914 heads with P&P and stock valves with maybe dual springs depending on cam (should I go with larger valves?)
- Stock 1.7 rockers with 911 swivel feet adjusters
- Scat chromoly pushrods
- What lifters?
- What flywheel, clutch disk, and pressure plate combo will work?
- Balanced stock 2.0 rods (what HD bolts can I use with these?)
- Schadek 26-mm or 30-mm oil pump (which one?)
- DTM cooling
- Compression ratio around 8.5 - 9.25
- Mallory point or Unilite centrifugal advance dizzy with grey springs
- All balanced together

What do you think? What could I change?

HAM Inc · Post by **HAM Inc** » Thu Feb 05, 2004 4:34 pm

Speedy the answers to your questions depend on what you want out of your engine.
As far as counterweights go I'm against them for racing and ambivalent for the street. They don't make horsepower and we've proved that you don't need them for reliability in racing TypeI's (If the Magnesium case can hold-up to 14:1 compression at 7500RPM's for over forty races on dirt and the center main still look new...) Counterweights are nice for engines with cams that don't idle well (smoother starts and shifts). But if your goal is to accelerate quickly out of corners, stay away from them like the devil himself.
As for the heads I like the 44x36 or 44x38 set-up. When bumping up to 44's it allows me to profile the bowl area directly beneath the valve. I have cutters that I ground to my specs., specifically for TypeIV heads. The results are beautiful, consistent, and fuel mixture quality is greatly enhanced. And since the port diameter is approx. 35.5mm the valve to port ratio (80%) is textbook perfect. All the port needs is the casting marks smoothed out. The exhaust gets the same treatment. Stock valve sizes benefit from this treatment as well, but the resulting shape is slightly less defined because we don't remove as much material.
If you plan to turn more than 6500RPM's you'll need dual springs. If not stay with singles. Only use duals if the revs require it.

I have a machinist near me who bores cylinders to my specs.

Raceware offers H.D. bolts.

As for your other questions; since my specialty is heads, and Jake has conducted gobs of R&D in every area you specifically mentioned, I believe you would be better served if he addressed your other issues. Hope that helps.
Len

Guest · Post by **Guest** » Thu Feb 05, 2004 5:35 pm

Thanks Len, I kind of figured 71mm was the max. without welding.

Does anybody know where I can get a set of rings for 95mm pistons?
I have a set of mahle (I think) 95mm p/c for a type IV and haven't had any luck finding the rings.

Ken

Alpine · Post by **Alpine** » Thu Feb 05, 2004 5:55 pm

Tom Perso has a 2270 motor with the Webcam 163/86b camshaft and 48mm x 38mm valves and when I asked him what he would change on his motor he said he would change the valves to 44 x 36. I think that 44 x 38mm valves in a 2056 might be too much, at least for a street engine.

Len, the average port diameter for the 914 2.0L heads is 35.5mm? I was using 1.5" or ~ 38.1mm in my simulations - do you know what the port length and volume are?

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Thu Feb 05, 2004 9:42 pm

Alpine, Guess who convinced Tom that his valves were too big....

The biggest I run are 44x40..., we NEVER go over 44mm, on anything (except my 3.0

The 71mm crank is just an offset ground 66mm from the factory. The 66mm crank was/is a much better/stronger crank, especially the journals.

Alpine, you *REALLY* should just hook up with an engine kit and save yourself alot of work- really. Its all fun but when a mistake of one part costs you tremendously, you'll see... Ask Tom Perso what he would do if he had to do his entire project again- He'll answer that he'd buy a kit from me... Try it, and see.

HAM Inc · Post by **HAM Inc** » Fri Feb 06, 2004 6:54 am

Ken try Total Seal for your 95mm rings. 1-800-874-2753. They list them.
Len

HAM Inc · Post by **HAM Inc** » Fri Feb 06, 2004 7:22 am

Alpine I don't have port volume #'s on hand. I've cc'd ports to balance but damn if I can recall the #'s. (They say memory is the second thing to go!) But I will record and post some here very soon. (Along with some flow #'s)

Port length on a 2.0 is 45mm to the bowl area, its another 25mm to the seat.
Port diameter needs to be in the ballpark of 80% of the valve size for effecient flow and mixture quality. 80% of 48mm is 38.4mm. If the TypeIV port is opened op this much you hit the spring perch in about 12mm's. And it gets worse when you get to the bowl area. Any valve, regardless of size or port shape, requires a direct approach of at least 12.7mm's with more being desirable. to achieve this with a 48mm valve would require more material than the casting contains. Yeah I can shove a 48mm valve into a TypeIV chamber, but what's the point? It's just in the way. And even if the casting could support it it would only make sense on large bore engines (shrouding factor) and high RPM's. I LIKEN SHOPS THAT SELL THERE CUSTOMERS ON 48MM VALVES TO FISHING LURE MAKERS WHO ARE ONLY CONCERNED ABOUT CATHING FISHERMAN, NOT FISH.
Now look at the #'s for a 44mm valve. 80% of 44mm is 35.2mm. this is right in line with the casting specs. And while the port itself could support a slightly larger valve (provided the spring seat is not cut deeper) the bowl area directly beneath the valve is about maxxed out for a 44mm valve. On an unlimited race engine 45mm would be about it.
It does my heart good to hear Jake say that bigger valves don't make a better engine. It was one of the first indicators to me that Jake knows what he's talking about, and isn't just blowing smoke.
When I get caught-up I will post some photos of cross sections of a 2.0l head I sliced. With a precision steel rule laid across the ports one can see the limitations first hand.
All that said, yeah I can stuff a 48mm valve in there if that's what the people want, but I won't stamp HAM on the finished job.
Len

speedy57tub · Post by **speedy57tub** » Fri Feb 06, 2004 7:33 am

A kit from Jake is surely starting to sound good!! I wonder if I can use some of my parts at least for cores, what do you think Jake? I got the Type 4 bug!

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Fri Feb 06, 2004 8:00 am

Speedy, that will work fine.. I have the TI cooling system data ready for you to analyze when you want it.

The ONLY time I see a 48mm valve do anything, any good is in a super high torque application, where big balls are needed at extremely low RPM... Like my 3.0