Crank flex / rod angle, 86 or 88 stroke?

[-Alex-]

I cant decide which crank i will buy, 86 or 88 flanged.  Always bigger isnt best. With 4" piston and cylinders cc's will be either 2789cc or 2854cc.

I will buy all T4 mains flanged scat crank, and rods 5.7" long. (DRD crank order was no success..) Rpm limited to 7000-7300rpm

Long stroke otherwise will no be problem, since i am using TF-1 case with 0.100 dropped cam line

Bad choice 88 stroke crank? Will the be significantly more flex and more rod angle? Rod ratio drops to 1.64 from 1.68.

[max2919]

Is it a drag or street motor?

[-Alex-]

mostly street motor, little drag and track days.

[BeetleBug]

I thought 84 / 86 / 88 and up was to be considered old school? Short stroke - big barrels is the way to go. Just ask the F1 guys.

-BB-

[-Alex-]

I am thinking if there is noticiable performance difference if going 88 instead 86..Probably not much difference in hp, but torque maybe.

Short tracks and tight turns, ass kicking power is "needed"

[BeetleBug]

74-78 x 106 would be my choice.

[ALB]

A friend in Vancouver here has an 88x94 (86C, IDA's, enough head to make it work) and it's a monster! Bigger is better, if the combo is right. Don't the F1 guys use the short stroke/big piston combo because of the rpms they run? And if you only use a 78mm crank you'll miss out on 300cc's...

[-Alex-]

Yeah, how the hell 106mm bore fits to type 1 case 

[K-Roc]

88 Stroke at 8000 RPM is has a piston speed of 23.46 M/Sec .... getting up there....

[-Alex-]

I wonder, if with 86mm stroke engine size is 2789cc and estimated power 250hp,

Adding 2mm stroke engine size goes to 2854cc,  how much more power will more stroke give? 2-4hp?

[richie]

I wonder, if with 86mm stroke engine size is 2789cc and estimated power 250hp,

Adding 2mm stroke engine size goes to 2854cc,  how much more power will more stroke give? 2-4hp?

if you think you will only gain 2-4 hp then why not run a 69mm stroke crank?its only maybe 34 hp less and think how strong it would be? and how much cheaper

I think you decide what engine size YOU want to build, then buy the correct components to ge the most/best from it,buying a set of heads that flow 290cfm at 700lift is pointless if you run an intake that only flows enough for 250cfm,this is only an example.Only YOU know what you actually want it to do

A 2276 with the correct components will outperform a 2854 that doesnt have the correct components.

But this is the internet and its only my opinion what do I know?

cheers richie 

[-Alex-]

Only thing what i wonder, will 88 stroke flex significantly more than 86 stroke and will 5.7 rod be too short for 7500rpm engine?

[Greg G]

If you go with either the 86 or 88, I would get it with a 2.100 rod journal with theT4 main.

[Fiatdude]

Only thing what i wonder, will 88 stroke flex significantly more than 86 stroke and will 5.7 rod be too short for 7500rpm engine?

No -- I run a 90 with no flex with 5.7 on a 101.6

[nicolas]

the F1 guys don't seem to be so keen on 4 pistons as well... so i do understand what you are saying, but it is alas still another league.

a few years ago chevy journals were frowned upon because of the 'flex' with bigger strokes like 82, 84,... but now they seem to have been accepted as the advantages are bigger as the disadvantages.

[Erlend / bug66]

Yes. A longer stroke will flex more than a shorter one..

Same way that a longer mast on a sailing boat (given the same diameter on the mast and same sail) will flex and bend more than a shorter mast

[magic]

hmm ... I think BeetleBug is right ... long stroke is old school today .... And I love old school!
 But just follow the old maxim, Bore = rpm = hp .... stroke (= cc) = torque.  take BeetleBug's 74-78 * 106mm. (Type 4! ) 2610approx. To 2750ap. Of course it will have many cc. So it will naturally have some torque, but it will be EASIEST to find rev. In this engine. Ie horsepower!!!
  Now take your motor Alex... 86-88 * 101.6 mm. 2785ap. to 2850ap. There are a lot of bores, so it would obviously have some hp.... But here it will clearly be EASIER to go for the torque!

  Richie is absolutely right when he writes:  "A 2276 with the correct components will outperform a 2854 that doesnt have the correct components."

 But here I must add a few things. For the 2276 to be able to outperform the 2850, it will have to be a "screamer"!!!  And you really have to work hard to build your 2850cc. engine, so it won't outperform the 2276 in terms of torque !  And here we are at the core of this case...
In my opinion! (We're talking opinion here!!) There's too much focus on Drag Race engines, even from people who want a strong street engine or "weekend warrior" ... (I've been there myself! )The only mantra you hear is: hp hp hp hp hp hp hp .... What about torque? !! and frankly, it may actually be a bit "irritating" (or "violent" ) that you constantly have to keep the engine over a million rpm. to have "the ponies" available ... This is of course, completely irrelevant in a race car! You ain't often queued, and will rarely need to overtake someone in your own lane in a 402m race ....  And please, don't rpm. sound me! A 2.7 L sounds pretty good around 7000....(although the curve probably has leveled out after 6100.... He he ) What I'm trying to say is: race and street engines are living in totally different worlds!!!
 So, Alex, when you hopefully build your 2.8 L engine, presumably with high comp. IDA's and a aggssive cam (engine size taken into account). Then you'll automatically get an engine with a ridiculous number of hp .... So do yourself a favor and concentrate more on the torque! It will be easier, and cheaper, AND it will be an AWESOME street engine!!!

cheers. Magic

[max2919]

mostly street motor, little drag and track days.

If I was you, I'l look at Anders Roman 86x101,6 motor. It's one hell of a 4" N/A motor.
If you want a "low" reving 4" motor, look at UD Vegas racer.

[Simpsonshoe]

Good lawd! Here you guys are going nuts over astreet engine that you can probably use only half the power, if that, much of the time. talk about old school.. a 2180 was a big dog.. and a 2276 when the 94's were new and hot was the cat's meow.. then a few stepped it up with the 84/86/ cranks with a few mad warrior types with a gazillion bucks in the motor built BIG.. Now a 225 HP off the shelf parts 2276/ 2332 is a daily driver.. and THEY are a handful on the street.. Yes what was the trick racing stuff filters down.. new parts /techniques etc push the envelope.. Build that kinda torque into a combo is a little nutso.. But also kinda cool..I don't think if you build ANYTHING with 2500 plus cc's is gonna be a slug.. The heads are where the power is.. the right heads/cam/ carbs on a  daily driver 2.5  is good for over 250 HP..The thing is if you build that kinda torque you gonna need a line of credit at the MENDEOLA store..

[-Alex-]

Heads and cam truly make or kill the power   Somewhere i found that gene berg sold on all basic 2213 kits (86x90,5) only 5.5 rods, and even 86 stroke with 5.35 porsche rods would run well over 8000rpm with rigth combination.

[-Alex-]

Ok, Johannes recommended 86 stroke. I'v got eye on new -cheaper than shop prices- scat billet flange 86 crank.
Beast will be fuelled by 48mm throttlebodies and direct fire ignition, sorry no oldstuff here   Cam of course JPM, i am looking the 282@10.7mm version.
No mendeola or early baulk ring synrcho porsche trans to my car, berg 5-speed bus instead.

Over 250hp is a lot for beetle, even if it has driveability (germanlook)  Can you say allday wheelspin with street tires
Finnish vw fellow recommended torgue motor to get moving that heavy allsteel beetle. Well mine has only fiberglass fenders, no rearseat and full rollcage, quite close still to stock weight beetle.


Anders Romans 86x101,6 motor is indeed a beast, over 280hp..

hmm ... I think BeetleBug is right ... long stroke is old school today .... And I love old school!
 But just follow the old maxim, Bore = rpm = hp .... stroke (= cc) = torque.  take BeetleBug's 74-78 * 106mm. (Type 4! ) 2610approx. To 2750ap. Of course it will have many cc. So it will naturally have some torque, but it will be EASIEST to find rev. In this engine. Ie horsepower!!!
  Now take your motor Alex... 86-88 * 101.6 mm. 2785ap. to 2850ap. There are a lot of bores, so it would obviously have some hp.... But here it will clearly be EASIER to go for the torque!

  Richie is absolutely right when he writes:  "A 2276 with the correct components will outperform a 2854 that doesnt have the correct components."

 But here I must add a few things. For the 2276 to be able to outperform the 2850, it will have to be a "screamer"!!!  And you really have to work hard to build your 2850cc. engine, so it won't outperform the 2276 in terms of torque !  And here we are at the core of this case...
In my opinion! (We're talking opinion here!!) There's too much focus on Drag Race engines, even from people who want a strong street engine or "weekend warrior" ... (I've been there myself! )The only mantra you hear is: hp hp hp hp hp hp hp .... What about torque? !! and frankly, it may actually be a bit "irritating" (or "violent" ) that you constantly have to keep the engine over a million rpm. to have "the ponies" available ... This is of course, completely irrelevant in a race car! You ain't often queued, and will rarely need to overtake someone in your own lane in a 402m race ....  And please, don't rpm. sound me! A 2.7 L sounds pretty good around 7000....(although the curve probably has leveled out after 6100.... He he ) What I'm trying to say is: race and street engines are living in totally different worlds!!!
 So, Alex, when you hopefully build your 2.8 L engine, presumably with high comp. IDA's and a aggssive cam (engine size taken into account). Then you'll automatically get an engine with a ridiculous number of hp .... So do yourself a favor and concentrate more on the torque! It will be easier, and cheaper, AND it will be an AWESOME street engine!!!

cheers. Magic

[Roman]

Don't worry about high piston speeds. IHRA Pro Stock engines has up to 5.75" stroke and revs up to 8500 rpm.
Since we don't have a cc limit, go as high as you can or what is economical for you.

A big stroke engine makes everything you considered extreme.
With Terminators and a FK98 cam the 2789 still idled like a stocker and had tons of torque from low rpm. 

It can be rather costly though as you might need a type 4 main journal crank, bus trans etc to be on the safe side. Really light pistons as the JPM also helps.
The bus trans steals about 10 more hp than a type 1 trans and is heaver besides the added cost.

PS: The engine should have made over 300, but the cam went flat...
It now has a new home at a friend of mine -maybe it will run next year again.