Hey all...

ok my car is all ripped apart and bare now, its going in for media blasting and i'll be junking the old slant... I have a forged crank block that is complete (1970 model). I've been reading through the articles and have decided on building a monster stroker slant (260cid) but theres a few things i'd like to know first.

Would this setup beable to repeatedly hold 6000rpm on the strip and some nitrous? I've been plugging away and the rod ratio on that setup isnt really the greatest (1.44). My plans for the end are custom forged pistons, 11.5:1 compression, hyperpak intake, hookerheaders, fully ported head with large valves (professionally done) custom ground comp camp and much more...

I want to hit high 13's min. before nitrous and mid to low 12's with nitrous (my goal would be a properly setup fogger and a 200hp shot) this is all in a 3200lbs car.

what is it going to take to build this setup? i'm going to get the crank lightend, shotpeend and stroked to 4.5" like i the article but i'm not sure if there are any other special mods other than grinding away at the block for clearance.

thanks for any/all help!
:cheers

I'm not sure an extreme stroker is a good idea for a high revving racing motor. The crankshaft is not going to be as strong as stock; it's effectively a weird mixture of forged and cast, with a lot of possibilities for defects that could crack it. Also, you'll be using it with a cylinder head originally designed around a motor with 90 fewer cubes, so I'd expect it to have very restrictive breathing at high RPM, and may even be choked off and make less power but more torque. Some Desktop Dyno simulations I've run imply that certain buildups can make roughly the same amount of power whether the engine is a 170 or a 225, with the difference being that the 170 will need to be run to a much higher RPM.

This is just theory, though - anyone with practical experience who has one of these strokers or has conducted dyno tests between identically prepped 170's and 225's is likely to have better info here.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

I'd say that the stock head would really have to be milled out in order to flow anything good.. (ANYONE have any flow #'s for a stock head, then a mild or fully ported one?, i'm trying to gather as much info as possible)

According to desktop dyno with a compcams 264s you can make as much as 302hp and 330ft.lbs torque (11.5:1 compression, small tube headers with open exhaust, 1.78/1.56 furd valves on a lowperformance largvalve/ported head, and i have a single plane 600cfm 4bbl plugged into that.)

i'd say real world numbers would be off by as much as 20hp +/-. 6000rpm would be the absolute max that i'd ever want to take anyslantsix race or not. this will be a "race" engine and will be drivin on the street as a "sunday night cruser" only.

my fall/winter project has begun!

P.S. Doc are you still running this engine? i'd really like your expertise on this!

What rod are you referring to for 1.44 ratio?

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Math: deck 10.68"
1/2 stroke 2.25"
198 rod 7.006"
piston CD @ .00 deck: 1.424"
rod ratio: 1.557-1

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Panic,

I used a calc. on the net (think it was ringpinion.com) and came up with 1.49. This combo does not use the 198 rod. its a 4.5" stroked crank with the stock 225 rod.

If you go over Doc's list of things the Hpak likes you'll have to carefully pick your cam. The Comp Cam 264 would be wasted on an 11.5:1 motor...you're looking for something like the Engle cam (276). Some other considerations is the problem of long narrow runners on the intake, piston dwell time (at TDC and BDC) and how these will kill fuel distribution from a carb and how the carb can deal with what it 'perceives' from manifold vaccuum and load. I'm already done with 90% of my 'paperwork' phase of my long rod Hyperpak project and was able to dump a lot of 'headaches' by going MPFI....if I had another $1400 I'd add MPFI+NOS injection system...but I don't so I won't....

You'll have to get some real world measurements to see what your setup is going to do (i.e. get the calipers out). On my long rod, I see that by going 11:1 and doing a little piston modification I can take full advantage of the quench area in the chamber if everything is milled right, but it makes things a little tight for comfort on the valve to piston clearance. At that point it may really limit my cam lobe choices greatly.

With the Hpak intake you'll limit yourself to about 5500 rpm, and you'll need to make a 'choice' when selecting your components like cam choices (short duration, low lift, with Hpak = great torque and street manners...or high duration, high lift, great at 5500 rpm, may not idle too good on street, may get the same gas mileage as the guy with the stroked 360....).


Another item to ponder is gas availability as you approach 12:1 you may need to run some major octane to keep a set of flat tops from pinging in the open chamber (pending clearance, 'squish'/quench, and how open the chamber is. I chose 11:1 as a good 'middle ground', it's not 9.5:1 (which can still run 87 octane with some 'detuning'), but it's not 12:1 (how much for the barrel of 108?)....

If going Hpak, set the Desktop Dyno to "Tuned Port Injection", it's meant for fuel injected long runner intakes with smaller ports, 'open plenum' would be for the 'clifford shorty' (short runners, open plenum, wider ports).

Heck if going to get a bank loan for the lightened stroker crank, EFI kit, NOS kit, you might as well get a billet roller cam.... and go really 'BIG'....



-D.Idiot

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i think the longer throw on the crank might limit higher RPM, so think about building it to spin to 5000 or 5500 max. That is ok, since there will be super torque down low.

I think it would be possible to do what you want, but make definitely spend extra time ultra balancing the motor, use some really nice shape rods (pick of the bunch, polish the beams, double check for cracks) with ARP bolts and forged pistons.

The other guys 'round here can help with what rod ratio to use and compression. I think a 10.5:1 or 11:1 motor might be a little safer with the nitrous?

the comp264 cam would be too small for what you want to do, i'd say lift in the 480-520's and durations up over 230 @ .050, and use a split pattern cam based on the rest of the car, get a custom grind from Reed Cams or Comp Cams

keep us informed, as i was thinking about those 260 cubes being fun to build up!

I am still running my 260 stroker engine, it is alive and well in my 3500 lb 66 Dart station wagon.

I have a mild cam and low compression build-up (8.0 to 1) and the car runs a Holley 1920 1 bbl so performance is not earthshaking. I never Rev this combo past 4500 RPM, fact is that anything over 4000 is kinda a waste, it does not have enogh cfm to do anything at that RPM.

This engine is a torque monster and it would be even better with a longram manifold. Cam / compression choice will be important, that ram manifold has a "sweet spot" in the 3000-4500 rpm range and if you match that with the right cam, the engine will pull really hard in the mid range.
DD

"the car runs a Holley 1920 1 bbl so performance is not earthshaking."

Talk about an anticlimax. Somebody PLEASE sneak into Doug's garage some night and put a decent carb on that monster!!!!

At least then I can have a little dignity about being slower than a 1bbl wagon.

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1980 Aspen 225 super six

I do know that the 264S is a very small cam for an engine like this, just using that as an example.

my main concern is if this engine will hold up to repeated 5500rpm redlines? the last thing i'd want is to dump an insane amount of $$$ into an engine then have it come apart on me

Do you guys think this would be the right combo for what i'm looking for, or should i stick to the regular "longrod" slantsix or just a 225? I'm willing to work with people and experiment alittle, and if there are no hard facts saying "no do not use this combo, etc" then i'm more than happy to roll with it.

I dont really care about idle quality, gas milage or type of fuel to run (if i need it we have race fuel on hand at all times at work)... I just want people to look at me with that blank stare or when i make a pass or pull up to a car show.

i'm also not really up for a roller cam, or efi. I want this to be a combo that prettymuch anyone can use. I have a friend that is an owner of a machine shop that builds 9800rpm small blocks day in day out so if i buy the beer he'll help me out

it depends on your $ available, i think. it would be some good expirementing to do the 260 and see what it will hold up to.

if you just want to go high 12's with a slant, i think a solid 225 with forged pistons (2.2 w/198 rods?) a lightened car, a good fogger nox system = what you need... my opinion...

you may want to just do a simple cast piston motor, on the cheap, with nitrous, as a testing bed to get into slant building...

I'm starting to re-think this going big thing

i want to be no faster than 12 flats (if i end up faster its a bonus but not wanted/needed) My car will look totally stock (ok so it will look like a full bodied car from the exterior) but the interior will be gutted, subframes, mini-tubbed, and a fuel cell installed on the inside...

I dont want to go faster than 12flats because to me its just too much hassle building cages,etc...

I just scored this slant six with hyperpack guy said it did 10.8s!!

blast from the past.

10.8 on gas in the 1/8 mile

or 10.8 on nitrous in the 1/4 mile?

Greg

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http://www.youtube.com/hyperpack