talk to me about rod length

[TimberwolfZ28]

I'm building a 2276. Right now I am at the crank and rod ordering phase.
I Can get the crank with regular or chevy journals. I see people say go with the chevy journal size, but it there a solid reason? Aren't the chevy rods heavier? Also , the journals are smaller...wouldn't this lead to a potentially weaker throw?
Also, if I go witht he 82mm stroke and the chevy rods, I use the 5.5 or 5.7 length?
Is there enough room to move the wrist pin up that far in the piston without getting into the rings or will I need barrel spacers?

[nsracing]

YOu want to play with the big dogs?

1st....you will need barrel spacers ..Period!

2nd...since the stroke is small..78mm - 82mm ...go with the VW rod journal. Why? because it is better to start out big and go down as you use the crank...regrinds after regrinds. You follow?

3rd...Go with the longest rod you can get for the rod journal size you have. I suggest the H-beams.. Don't worry..there will be plenty of room. It is NOT like you are building an 88mm or bigger stroke. It will be fine.

4th...you would want the stroker pistons...for obvious reasons. The engine will be not be too long and the dwell time of the pistons are improved. In other words..more HP.

Other than that...build away.

If you need help with machining..let me know if I can assist for whatever.

Good luck.

[TimberwolfZ28]

yeah I figured I would need the spacers. so in staying witht he VW rods, I can get what... 5.6? If I use the stroker pistons, then I only need the spacers to compensate for the extra .100 of rod length, and then any more or less would be to adjust compression, correct?
While I'm on that subject... what size combustion chamber would a set of 044s cut to 94mm have? my guess is around 56-57cc. With flat tops, and a .020 deck height, That's gonna get me around 10.5:1. I have no problem using the high octane fuel I'm gonna need, it's going to be FAR from a daily driver. And with the fuel injection, it should still get me down the road pretty good on it's small 5 gallon tank.

Is there less clearancing witht he H beams needed? Seems like I read that somewhere. Does ARE make good rod bolts for VW rods?

[ekimthemad]

I would use the vw journal on an 82 crank. Any bigger and I would go to chevy journal. The vw journaled cranks are stronger. The clearancing gets a bit tight but its not to bad. Just run a set of 5.5 inch h beams. There is no need to go longer than that unless you plan on turning a ton of rpm. Plus the motor will just get wider for no real benefit.

You need to keep the deck height higher than .020. That short and you can end up putting a piston into the head. I have seen it happen and it's not pretty. Try to stick to a minimum of .040. If you have to you can always flycut the chambers a bit smaller to get the desired compression.

If you don't want to run spacers you can buy century cylinders that are longer and have them cut to size.

Mike
59 single, 66 bug, 69 bus, 73 super
Member of the Ddk
_________________
Remember never argue with a moron. They'll drag you down to their level and beat you with a lifetime's worth of experince.

[nsracing]

I do not know if anyone turning some serious HP using short rods.

LOng rods will give you longer dwell time. The pistons will stay down longer and stay up longer. This dwell will be important on the top end when the motor is turning some serious RPMs. Also..the angularity of the pistons are less as they move up and down the cylinders. So...less wear and piston slap.

High piston pin placement also gives less rock and slap....so less wear on parts.

I hope these are serious benefits enough to consider going long rods and stroker pistons.

Keep the deckheight decent....0.040 -0.045 inch.....and just play with the chambers to get the right CR. Just be careful. It might just take a simple flycut to get the right volume in the chambers without hacking away.

Also...by keeping a decent deckheight makes it safer to run the motor. If anything should go wrong with the rod bearings, you have some time to burn. Otherwise, with tighter decks ...no time. Loose the bearings and instant pile of trashed parts. I mean that.

Good luck man.

[Alan_U]

with chevy journals you'll get alot more clearance and will have less clearancing issues compared to vw journal. Downside is less cross-sectional area between the main journals and conrod journals.

Since the chevy journals are smaller there appears to be less bearing area for the same load so this is why many guys like using clevite 77 bearings since they'll take more abuse due to the tri-metal bearing compared to bi-metal vw journal bearings commonly sold. clevites 77's are available in vw also.

Seems alot of guys have preference to 5.4 length for 82mm strokes. If your contemplating on stepping up higher to an 84mm in the future a 5.5 will work great.

.040 DH is tight. .020 with a high lift cam will start getting into valve to piston clearance issues. If you go with a .040 DH you'll have aproximately 10:1 c/r. Your gonna need to get those heads flycut to bump up the c/r.
_________________
11.92sec pump gas true daily driver. Who says it cant be done.

No more time for VW's.......

[nsracing]

I have never notched a piston for a stock configuration heads with 78mm - 84mm stroke cranks.

CB O44s or any other stock config heads really do not need to have the pistons notched. Unless you flycut the crap out of it....0.100 inch or more.

there would be more than > 0.150 inch clearance piston to valve with stock heads....even with FK 98 cam.

Now with an 88mm Full flange crank..it is a different story. But a 78mm - 84mm? Never had the occasion to notch.

[turbo_bob]

I would use a Porsche or VW journal on a 82 crank with a 411 center main. The rod length for a 82 crank in a street bug I would stay on the short side. Any of these will work good.

82 ^ 5.352 = 1.65 Porsche rod stock
82 ^ 5.4 = 1.67 VW rod stock
82 ^ 5.5 = 1.70 after market rod

84 ^ 5.5 = 1.66

[TimberwolfZ28]

[turbo_bob]

[TimberwolfZ28]

[Terry Cloyd]

5.5 rod with Porsche rod journals Terry

[jamestwo]

Chevy journal. 5.5 rods.

[nsracing]

Did I NOT tell you long rods?

You know CB even makes a 5.6 VW journal! If you want a LOT of HP...long rods.

If you want the stroke to 84mm, you can even go Porsche journal...not much bigger than a VW journal..but bigger.

Of course saving the crank for re-grinds by going with the larger rod pin journal will not be practical after you split the crank in half.

The motor will be a LOT of fun. The car will be a ticket-magnet! Burnouts in 2nd and 3rd are not so unusual.

Good luck man.

[TimberwolfZ28]

ok, so if I go with vw journals and 5.6 h-beams, how much case clearancing is going to have to happen?

[nsracing]

With H-beams...it is not a lot of clearancing. You have to notch here and there...behind the webs and some notch work on the cam.

Let me know if you need the case shuffled. 6 pins man!

[TimberwolfZ28]