Hi, I wanted to know if anyone has used the Molnar rods on their slant and how they liked them compared to the stock 198 rods.

I'm trying to decide if it's better to spend the extra $$ and buy a set of Molnar rods instead of having a stock set of 198 rods reconditioned. I have fourteen 198 rods sitting here. I've heard they have limits on horsepower and RPM but I've never tried them myself.

Also, has anyone built a long rod motor with the 198 rods and stock 2.2L turbo dished pistons? I'm debating whether to go with stock rods and stock 2.2L turbo pistons to make a turbo motor. My biggest fear is the compression ratio would be too high. The dish on the 2.2 turbo pistons is supposed to be 18cc. The stock pistons were cast hypereutectic so they're able to handle alot of boost plus the stock rings had a ductile iron top so they can handle alot too. The alternative to the stock 2.2 pistons would be custom forged pieces. I know they can handle alot. My 2nd biggest fear would be blowing it up on the first run and taking the engine home in 5 gal. buckets.

So, being on a budget, should I save up and buy the real race parts or take my chances with the stock cheapies? I guess I'll have to CC my head to see where it falls to find out the actual compression ratio.

Thanks,

Joel

I have a set of 198 stock rods and pistons, and have a set of Molnar Rods for the cast crank... the one item I notice on the molnar rods is they are not drilled with the mid bearing oiling hole like the stock rods....

This may not matter for drag racing, but might be an issue for street use or long term road racing....

Hi Joel,

It might help to know what are your goals for this engine? How much boost, HP, RPM limit, static compression, fuel, intercooler, etc...

I am running up to 12-14 psi on stock 225 pistons and rods and have not had problems, making up to about 360 crank HP. Others have gone higher with stock parts.

Best,
Lou

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Home of Slant6-powered fun machines since 1988

With an uncut block and head my 198 rod 2.2 turbo piston motor came out around 9.5-1. I ran a lot of street miles and many passes with it. It went as fast as 12.0@110 on spray. I used to turn it 6500 regularly, and went over 7000 just to see what it would do.

That being said, by the time you find a set of 198 rods, have ARP bolts installed, and have them resized you are getting into Molnar rod price range anyway. Also, IIRC, the 2.2 piston supply is drying up and even though the pistons are still fairly cheap the ring sets are quite pricey.

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Official Cookie and Mater Tormentor.

The 198 rods should be fine, assuming well built, and you already have them. Neon pistons have a shorter comp distance and similar diameters to 2.2L pistons, so that's another option for lower comp. You can find piston catalogs online and go through to find pistons with desirable comp distance, reliefs, pin size, bore, etc...

360 HP on the street in a 3100 lb car is pretty fun. Interested to hear your build goals/ideas.

Lou

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Home of Slant6-powered fun machines since 1988

I have 14 stock 198 rods so I'm good on those. My ultimate goal would be to make a turbo motor. 6000rpm would be the limits for me. That's a lot of stroke to be spinning that fast. If I can only get the compression ratio down to 9.5:1 with the stock 2.2 pistons then I'll be pushing the limits. I would like to keep it street drivable and not have to run on 118 octane race fuel at the track.

I am running 8.6:1 static comp and pump premium except I mix in some (1/3 or so) of 110 when drag racing all weekend. Probably fine without, but I drive my car everywhere... Should be in the 12s on my next drag outing, but my O2 sensor failed last time so I turned the boost down after a few passes Friday eve (13.10s).

You do not have to run high RPM with a turbo. I shift at 5500. I run water/meth injection and fill it with 1 gal -20F windshield washer fluid about every other fill up with fuel. No intercooler. Drives like a granny car until you hit the boost. I may decide to rebuild the old motor (175+k miles) this next winter, but it's still working well.

Lou

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Home of Slant6-powered fun machines since 1988

From memory there are two dish sizes in the turbo pistons,the earlier being the smaller? Anyways,I used the smaller dish pistons and machined the dish larger to suit my build. They were only good quality stock replacement hyper pistons and had heaps of material to allow me to do this. It was a year or two ago now but ring availability was ok,but may be worth checking by the sounds of it. We don't have this model engine over here so I ordered pistons and rings from the US....Any power increase you get will be out of the piston and ring package,not the long rod theory,many old books like Smokeys power secrets have never been updated to reflect the modern way of thinking on this subject. If your revving it the stock rods aren't the prettiest,but the lighter piston and longer rod will no doubt reduce recip weight,but slightly increase piston velocity ,overall still a better combo to reduce loads on the rods....on the other hand,if you've got 14 rods,sell them for like $200 a set maybe and just buy a set of molnars,not much out of pocket by the time you reco the standard set. I'm guessing the $200 price tag,but you get my idea I'm sure.

You can use a Toyota V6 ring set and save a bunch of money. I did the research on this nearly 10 years ago.

http://slantsix.org/forum/viewtopic.php ... ngs#156337

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Joshua

Josh, , that's what I was looking for. I missed that one. The only issue is the top ring is chrome steel but it is a steel top ring. The chrome isn't quite as durable as a plasma moly top ring but it's a whole lot better than a cast iron top ring. A Sealed Power E418K or a E453K has a ductile iron plasma moly top ring but they're only 4 cylinder sets. I think the only difference in those two sets is the radial thickness of the oil ring. Sealed Power's catalog shows the top two rings are the exact same.

The chrome plated rings are fine for N/A and mild nitrous/turbo builds. If you're going all out you'll have to get the plasma moly ductile iron rings though. If you don't you'll run a good chance of breaking the chrome off the top ring.

I looked at the specs on Neon rings and pistons. They have the same 87.5mm bore as the 2.2, but they have a lot shorter compression distance on the piston. You would have to have a rod that was about 1/4" longer or stroke the crank about 1/2" to make up the distance. The small rings would make a better set for a custom piston though.

On a normally aspirated engine, those 1.2, 1.2, 3.0mm rings would add quite a few HP compared to the stock 5/64" ring set.

Steve, you're probably right. If I sold all my 198 rods I could almost buy a set of Molnar rods. I doubt i would need any spares with those.

On the oil hole, the original purpose was to squirt oil on the cylinder wall way back when we had crappy oil quality(non-multi-viscosity which didn't come out until the mid 70's) and crappy aluminum castings so the piston wouldn't gall when the engine was cold and you revved it up before the oil was warm and flowing good. It wasn't really to lube the cam lobes. They did require some oil spash/spray from the rods and main bearings but it didn't take much after it broke in. That's the reason why you're supposed to rev a flat tappet engine up when breaking in the cam. It sprays way more oil than it does at idle plus it make the lifters spin better at higher speed.

I appreciate the replies because you've helped me make up my mind. Molnar rods it is but I'll use the stock 2.2L turbo pistons. I can mill out the dish on them to get the C/R down to a safe level for a turbo motor. BTW, when I get this put together, my target is as much boost as it can handle. 25PSI, 30PSI, who knows. It's cheaper to make the bottom end right the first time than to go back and upgrade later.

Thanks,

Joel

I might be interested in some of those 198 rods.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

Even if you sell one set of 198 rods it would fund the costs to reco the remaining set for your build maybe? If you go Molnar and want to move the second set I'm interested for a mild street build. Shipping would be to US to keep it easy. It would be very expensive but I believe Argo marine over here have done billet custom length slant rods in the past,nice custom piston/thin ring combo would be something special... Option options!