Lets Talk about 2L ConRods

9142 Views 46 Replies 22 Participants Last post by OzMidnight, Oct 8, 2007

smestas

Discussion Starter · Sep 25, 2007

I’m starting to plan out all the components for my 2L rebuild and thought Id start this thread to discuss the available rod options for a hoped up 2L motor.

For starters has anyone made a chart or graph with the different rods (stock, Carrillo, others...) and their weights and lengths?

What’s over kill and what’s beneficial?

What rod bolts are good (stock, ARP, etc...)?

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smestas

Discussion Starter · #2 · Sep 25, 2007

Here is some rod info that I took from the Carrillo Rods web site.

All four seem to have the same specs but different rod bolts and total weights. Which is the right flavor??

.

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Zunige

· #3 · Sep 25, 2007

I had a conversation with a well known Alfa engine builder from Ohio, and he expressed that the Carillo rods were overkill for a street engine. On the track, light rods such as the Carillos of course make a huge difference in performance. Racing components, such as Carillo rods, and aluminum forged pistons do allow you to rev your engine safely way above what you would do on the street. This builder also suggested that a good compromise was to have the stock rods balanced and shot-peened for strength.

The current 2L engine in my '84 is very nice. It's been done with a conventional approach: higher comp pistons, Sperry Stage V head, and 12 mm cams. It was built with conventional rods, for the occasional track use. (More than safe up to 6500 rpm, and can also handle 7000 rpm, but I like to keep it at 6500 rpm.) I'm in the process of having a second engine built, and this one will have aluminum forged pistons (already have the set) and shot-peened rods, since I just can't justify the expense of the Carillos. It comes down to expenses, because if the Carillos were a bit cheaper I would buy them.

Best regards,

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andyb6

· #4 · Sep 25, 2007

Tell us more about your motor and it's use. You should really only need Carillo's if you will be regularly reving 6500-8000rpm, at which point you really need 5 main oiling as well.

smestas

Discussion Starter · #5 · Sep 25, 2007

Why cant a stock conrod rev up to 8 grand? Is it because of its weight? I mean if you use the same quality of rod bolt why couldn't a stock conrod spin that high? I've always been confused by this. From all the engine failures I’ve ever seen they have always been from a broken rod bolt and never a rod failure.

Also does anyone know what a stock 2L rod weigh with or without bushings?

I'm going to try and make a chart. With as many specs as I can collect.

genericwood

· #6 · Sep 26, 2007

I haven't ever compared the weights of the stock rods vs. Carillos, but Paul Spruell's website describes the Carillo's as "10% lighter than stock and 100% stronger." Even though they are very expensive, when you think of the carnage a broken rod can cause, it might be considered relatively cheap insurance. On a race car of course. As a side note, one way to protect the rods is to run as light a piston as you can. Some of the commonly marketed "race" pistons are quite heavy, but can be lightened quite a bit if you pay attention to detail.

Erik

ALFASRGONE

· #7 · Sep 26, 2007

Best Rods

I think most of you already know there are some rods Max Banks of
Alfaholics uses in his track cars that are lighter and stronger than Carrilos.
I think they are the ultimate in quality but i think the cost is about $300 Ea.
I think it all depends what you want and how much you have to spend.
Bill

mojave

· #8 · Sep 26, 2007

The lightweight conrods at Alfaholics are 20g lighter than the Carillo conrods. They are made by Arrow Precision, and if you go to their website you can also have conrods made in titanium. It would be a custom order item, but since they already make an Alfa 2.0L conrod I'm sure they could do it. However, the engine would be extremely expensive.

papajam

· #9 · Sep 26, 2007

So I bring a 2l conrod into work today to weight it on the gram scale only to find that the scale goes to only 150 grams.

The cap weighs more than that! The bolts however, without nuts, weigh about 41.183 grams each.

Zunige

· #10 · Sep 26, 2007

ALFASRGONE said:
...Alfaholics ... are lighter and stronger than Carrilos.
I think they are the ultimate in quality but i think the cost is about $300 Ea. ...

At $300 they would be an incredible bargain, but they are $550 each (275 pounds). Also, that price doesn't include shipping. The rods used for racing are just very expensive, and that's why it's hard to justify the expense for anything but racing. By comparison other performance parts, like the aluminum forged pistons, are reasonable.

Best regards,

bryan

· #11 · Sep 26, 2007 (Edited)

How hot do you want this engine, Simon? For a hot street engine (150+hp) there is no need to go away from the stock rod. The idea of balancing and peening is good though.

For weight purposes, spending money on light pistons would have much more effect on minimizing rotational inertia. But, as previously mentioned, even many of the after market "race" pistons aren't hardly lighter than stock, some weigh even more.

IMHO, stock 9:1 pistons (lighter than motronics and borgo 10.4s and better burn characteristics), stock rods, with a head shave of 50 thousandths (to net approx 10:1 CR), some good cams, a little induction work (whether spica or webers), and some port matching (cheap cuz you can do it yourself) will net you a great hot street motor that will run great on gas you can get at the pump.

Just wait a couple months, we'll see

smestas

Discussion Starter · #12 · Sep 26, 2007

papajam said:
The bolts however, without nuts, weigh about 41.183 grams each.

Thanks for giving it a shot. At least we know how much the the hardware weighs. Hopefully someone chimes in with a weight of a stock rod.

Sprintn

· #13 · Sep 26, 2007

Somon... my take on it is... if the motor is completely apart and you are doing a lot of the labor... why not take the leap and put the good stuff in it? After all... when are you going to have it completely apart again? It probabply can't hurt... except in the pocket book. But if you are already asking this question, then you may have already budgeted for the trick stuff anyway.?.?
Just a thought.

smestas

Discussion Starter · #14 · Sep 26, 2007

genericwood said:
I haven't ever compared the weights of the stock rods vs. Carillos, but Paul Spruell's website describes the Carillo's as "10% lighter than stock and 100% stronger."

Actually his site now says that they are 17% lighter and 100% stronger.

smestas

Discussion Starter · #15 · Sep 26, 2007

Sprintn said:
Simon... my take on it is... if the motor is completely apart and you are doing a lot of the labor... why not take the leap and put the good stuff in it?

I agree on not doing it over again but I don't want to spend money on the “best” when it’s not necessary.

My main objective of this thread is to get enough data to make comparisons to make a decision on what is sufficient to do the job and to share that info with others. I'm thinking of some sort of rod spec chart. Up to now I haven’t seen any of this info here on the site or elsewhere on the web.

lowmileage

· #16 · Sep 26, 2007

smestas said:
I agree on not doing it over again but I don't want to spend money on the “best” when it’s not necessary.

While it's nice to have "the best," I think most of us are limited to some degree by a budget. I remember reading in one of Mr. Braden's books of him saying that the stock Alfa rod is very good. A strict racing application is an entirely different situation.

Sprintn

· #17 · Sep 26, 2007

I see your point. I believe the Arrow conrods are another step above the Carillo.?.? SO... you could probably go with good enough stuff so that the engine is more durable at higher RPM with out going Over-the-top.?.?

BEAR WABBIT

· #18 · Sep 26, 2007

I just went through what you are planning and spent a lot of time talking to Jon norman and Dan Marvin at Norman racing before making my choices.
Jon said he had never seen a 2L rod falier. and one orher engine builder said the same. That is not to say bolt falier but the rod it's self. So here is what I did after looking at all the options and listening to all the advice. I had Dan Marvin build a big valve head with port work, added Pittatori 11mm cams, Ground and polished the rods, Had the ends resized with new bolts and nuts.put in Motronic 10:1 pistons with new liners and Total seal rings. New bearingsand seals on a reground crank. Lightened the flywheel by 4lbs. and had the whole thing balanced. I then added a Wes Ingram HP Spica pump built to the breathing and compression specs of the new engine along with rebuilt injectors balanced with the pump. I expect 160 hp but will let you know After I start it this weekend.
good luck
jim

RossoGTV4Me

· #19 · Sep 28, 2007

Jim, I am assuming you are thinking 160 HP at the crank and not the wheels?
Please, definitly keep us updated!

BEAR WABBIT said:
I just went through what you are planning and spent a lot of time talking to Jon norman and Dan Marvin at Norman racing before making my choices.
Jon said he had never seen a 2L rod falier. and one orher engine builder said the same. That is not to say bolt falier but the rod it's self. So here is what I did after looking at all the options and listening to all the advice. I had Dan Marvin build a big valve head with port work, added Pittatori 11mm cams, Ground and polished the rods, Had the ends resized with new bolts and nuts.put in Motronic 10:1 pistons with new liners and Total seal rings. New bearingsand seals on a reground crank. Lightened the flywheel by 4lbs. and had the whole thing balanced. I then added a Wes Ingram HP Spica pump built to the breathing and compression specs of the new engine along with rebuilt injectors balanced with the pump. I expect 160 hp but will let you know After I start it this weekend.
good luck
jim

smestas

Discussion Starter · #20 · Sep 28, 2007

160 at the crank with pump gas is awesome.

Ill be watching to see the results also.

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