can someone explain...

[Project_X]

how the effects of a cam have on a motor with the durations an lifts?
Example i found a cam i like since it is said its basically what i want out of performance.
Cb Performance selld a Eagle Racing cam for Offroad racing (Perf. Series 5)
But it has a short duration, higher lifts, an full range power.Power to come out of turns, precise throttle response in mud an sand (not really needed) an the performance to move down the straights.

Adv Duration      Duration @ .050"     lift @ cam       lift w/ 1.1:1 rockers

272 degree        234 degree            .371"                   .408"
276 degree        234 degree            .380"                   .417"
286 degree        243 degree            .386"                   .424"
298 degree        248 degree            .389"                   .428"
306 degree        250 degree            .424"                   .466"

So if I was to build a short stroke big bore motor what would I use?
I want to stay in the 1600cc range was thinking of a smaller bore like 64x92 just for fun, but as a daily.
thanks

[John Rayburn]

Cam aside, if you're using a 40hp crank, it's going to break.

[Project_X]

but what did the guys use that destroked there motors back in the day?

[John Rayburn]

I can't think of anyone or any trend back in the day that advocated de stroking.

[rick m]

Destroking a crank was a big deal in MINI STOCKS that used to run at oval tracks in the 70's.  They had a 1600cc stated motor size limit so the guys racing would build 60mm stroke motors with 92 bores...back in the early 70's.  This created a 1595cc (or 97cubic inch) motor.  These guys were running 48 IDAs on these motors with big valve heads.  Don't let anyone tell you it cannot be done or does not work. They are extremely cool motors if you are looking for an RPM machine. Remember, cam, carburetion, compression, bore size and valve size will make any motor size work.

Bob McClure, originator of BAE Turbo Charging in the 70's, ran an all steel oval window that had a destroked motor that was injected and turbocharged that ran high 9's at the early BUG-INs at OCIR. It was an incredibly impressive car.

Destroking is definitely a move that creates a high-reving motor. I know that GENE BERG helped some of these mini stock racers in the early days.  Gary Berg might even remember some of the cam selections used on these destroked motors. Don't be afraid to try it. As long as you have a reputable crank builder make the crank for you, don't be afraid of trying it.  You can have a crank destroked just as easily as you have it stroked.  It is just a welding and machining process no matter what size crank you build for an engine.

Rick M

[Project_X]

who builds cranks like these, and what do they cost?
So IM guessing I cant grab a 40hp crank off the samba and have it c/w then?

[Zach Gomulka]

DPR Machine. This little 1595 motor is going to end up costing you the same as a big stroker motor. Unless you just have to be different, there is absolutely no point.

[Project_X]

What kind of power did those little 1595cc motors push out with IDA's and big valve heads?
Id probably use IDF's with a mild cam, out of the selections above and use a rev limiter so I dont blow it up.
Anyone know if these destroked mini monsters were streetable at all?I mean, would they take off from a stop or di you gotta rev them up to a certain rpm just to get it going?

Also are the 64mm crank forged or cast and I read that DPR can counterweight them which is good.

[Project_X]

Well i sent DPR and email to see what a counterweighted 64mm would cost and also the 60mm crank.
 

[Jon]

I know there will be a project coming up here soon...  62x94... giving 1721cc... tastes a bit like Formula1 don't it?

[Project_X]

62x94? Sweet, but where do you get the 62mm crank? Are those lil destroked motors by chance good for the street as a daily driver/street toy

[Jim Ratto]

What kind of power did those little 1595cc motors push out with IDA's and big valve heads?
Id probably use IDF's with a mild cam, out of the selections above and use a rev limiter so I dont blow it up.
Anyone know if these destroked mini monsters were streetable at all?I mean, would they take off from a stop or di you gotta rev them up to a certain rpm just to get it going?

Also are the 64mm crank forged or cast and I read that DPR can counterweight them which is good.

Hi, I think you need to think long and hard about your plan here. Number one thing you need to realize about this plan is you're gonna have to gear the car to accept a motor like this and that means close ratios and a short final drive. You may not believe me, but I think the close 4th/short final drive is going to take a big bite out of enjoying the car if you plan on driving it.
A friend of mine that I worked under ran a mini stock with a destroked crank. I think it was a 59mm. He said the motor was an on-off switch and the "on" didn't happen until 5500rpm. He also said it had the longevity of a flashbulb, wiping cases and rods out. This was a race car he ran at Baylands in Fremont.
Scat used to advertise a 59mm Volkstroker crank in the catalogs we used to give away in the 1990's. For fun one day I called to ask the going price. It was more than a good 82mm Porsche journal crank cost  .
You mentioned above going with a mild cam and so on. This is going to make the motor just a little slow weakling in my opinion. If you want the good things about a short stroke rpm motor, why take away from what is going to make that work? If you lessen the state of tune, you'll make 90hp at best and slow piston speed way down compared with even a stock 1600, unless you have access to shorter (much) rods. A good running stock motor with Kadrons will show you taillights until your motor came up on cam. By then the race might be over.
For the outlay of cash it might cost you, you could stick with 69mm crank, and switch the money from destroked crank/possibly rods/welding combustion chambers up (to get some CR from the small stroke/mega deck height) to having a trick set of heads done by Jeff Denham and a set of 94's and have 160-170hp instead of maybe 110-120 and a lot more fuss.
Yes small strokes have dominated race classes since 1950's. But bore stroke ratios like 94 x 62 give were typically in engines utilizing more than 4 cylinders, so you have more "power" strokes per crank revolution (more torque). 

[Project_X]

Ok so the destroking idea is out.
I was checking out the DPR site and seen a 73mm crank with 2" Chevy rod journals, ballanced and a 8 dowel for 150.00.
What are they good for, anyone on here ever used one?

[Zach Gomulka]

They are good for almost 1700cc's with a stock piston, and it doesnt look like a bad price compared to the regular 69mm. You will have to buy some chevy journal rods though... I would use the short 5.325" to keep the engine narrow. Still gonna cost more than a 1679cc (88x69).... which is the same price as a 1915...

[deano]

I believe that Brian Hyerstay uses a 5.00-inch rod on some of his small/high rpm engines. He also shortens the cylinders...

[Jim Ratto]

Ok so the destroking idea is out.
I was checking out the DPR site and seen a 73mm crank with 2" Chevy rod journals, ballanced and a 8 dowel for 150.00.
What are they good for, anyone on here ever used one?

....and how much is a 74mm with VW journals?

[Project_X]

Ok so the destroking idea is out.
I was checking out the DPR site and seen a 73mm crank with 2" Chevy rod journals, ballanced and a 8 dowel for 150.00.
What are they good for, anyone on here ever used one?

....and how much is a 74mm with VW journals?

74mm Stroker - Balanced, 8 Doweled, Heat Treated     
280.00

[Taylor]

be carefull destroking a crank for a motor, especially if you are on a budget which it seems you are. you wouldnt think so but if you  destroke it a substantial amount the cylinder studs will cost you more than the crank.