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Author Topic:   2bl motor combonation?
mikee
Dirt Roller

Total posts: 12
posted November 13, 2004 06:26 PM  
Would like your opinion on what would be better. A short stroke big bore or a long stroke small bore? Both would use ported dart 180 heads 13.5-1 compression flat tappet cam and a holley 500. Also what do you thing about a 3.5 stroke with short rod length? also all would use 46-48 lb crank

streetstock82
Dirt Forum Racer

Total posts: 81
posted November 13, 2004 08:59 PM  
You will have to decide what you want that motor to do. If you want more low/midrange torque, the long stroke motor is going to work if your not going to rev it real hard. the shorter stroke will allow more rpm, but will lose some of the torque due to lost stroke. as far as rod length, everyone says something different, but I'll say I think shorter rod motors are not as good as longer rod due to the fact that the longer the rod, the longer that cylinder is at tdc. It also helps prevent piston/cylinder/ring wear. Alot of people say that a long rod creates stress risers in the rotating assembly.I always use either 5.7 or 6.0 rods on all our engines and have never had a real problem. Hope this was of some help.

sdhnc29
Dirt Forum Champ
Total posts: 934
posted November 13, 2004 09:55 PM  
Our most common 2bbl combo that we build uses the following.

3.280" stroke Bryant crank 283 mains, Honda journal, 30-31lbs

6.00"-6.125" Carrillo Honda rod (414g-420g total weight)

JE FSR forging, flat top .043"-.043"-3mm ring pack, lateral gas ported, contact reduction grooves, double pin oilers, coated skirt(flat top is used per most rules)

Bow tie or Dart Little M Block (4.180"-4.200" bore)

Dart Iron Eagle 215cc heads (angle milled .385" for flat top piston application)

Titanium or hollow stem Ferrea valve's

Edelbrock 2926 Super Victor raised runner intake (must be used if the heads are angle milled .385")

We found many years ago that the short stroke big bore combo does not really give up any torque over the RPM range. While a longer stroke engine in a 2bbl application might produce a little more peak torque, this torque is in a very narrow RPM band. In other word's a longer stroke engine in a 2bbl application will produce it's peak torque somewhere around 4,000-4,500rpm, and then fall off a cliff. The big bore short stroke will produce peak torque about 1,000 rpm higher, where most engine's need to be at to get off the corner, and carry this torque way out into the higher RPM range.

Also if you choose to use any stroke above 3.335", you should hang at least a 6.125" rod in it, preferably a 6.200"-6.250". 2bbl engine's really respond well to longer rod's in the mid crank stroke range. I know, I know......I've seen the post on rod length that is posted on here, and what Isky wrote. But one area that has not been touched on is cylinder fill in engines with restricted air intake, such as a 2bbl engine. The idea of the longer rod is to increase dwell time at TDC, and slow the piston speed down as the piston leaves TDC. This help's to draw more air/fuel into the cylinder, which gives you a better cylinder fill, and produces more power and torque. This HP and torque is spread over a longer/broader RPM range. Long stroke engines with short rod's will generally have a torque and HP curve that goes straight up, and comes straight down. Of course the better the head and induction system, the less that this is noticed. So the short rod theory can be proven wrong every time, especially in 2bbl applications.

Steve


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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

mikee
Dirt Roller

Total posts: 12
posted November 14, 2004 05:50 AM  
Steve, The combo you suggest is pretty pricey isnt it? Any chance you have any used parts like a crank rods and block? I cant use titanium valves so the heads wont be able to be milled sd far. Hvh makes a ported dart 180 head for our head rule and its milled like .340 or .350 and 46cc I would even be intrested in a used shortblock . We use a wet sump. I also have to use a brodix sp-1 intake and no spacers allowed between the heads and intake.

Istock66
unregistered Total posts: 12
posted November 14, 2004 08:24 AM           send a private message to mikee   Edit/Delete Message   Reply w/QuoteBBBBBB
steve,

what about when you get limited to a 350cfm carb??

I was thinking the 3.25 stroke in a 4.155 block would be the way to go, but several cam people etc said It wouldnt flow enough air to get to the needed rpm for that motor combo to work.

Im talking a piston like KB, not no je ultralight, etc.


sdhnc29
Dirt Forum Champ
Total posts: 934
posted November 14, 2004 11:51 AM  
mikee,

Yes this combo that I listed can be quite pricey, depending of course on the budget. In most cases we use Cup cranks and rod's that I get direct from Hendrick. Of course this saves a few dollar's. I do not have any short block's at this time. I will be going to Hendrick's in the next month or so, I should have plenty of used part's then.

Using titanium valves is not a necessity to mill the heads .385". I'm aware of HVH's heads that they make. My dad gave this combo to Terry at Performance Connection, and he had HVH angle mill their first set of Iron Eagles that far. Until that point, they did not angle mill that far. Before then, the only people I knew of who went past .300" was Clements and us. We originally designed these heads for our limited late models that run here in the South East. Anyway, without a titanium valve you can still get down to 40cc's with a stainless valve if you go .385". But this whole process is expensive. After a head is milled this far, each bolt hole must be milled and spot faced, the intake face must be corrected, and the exhaust face must be corrected. This also changes your valve angle in relationship to the deck, to 19 degree's. Of course this requires a custom piston.

If your not looking to start from scratch, my friend Bert Cheatham in Missouri has a 2bbl engine for sale that I built for him a few years ago. He has gone back to UMP late models, so he wants to sell this engine. This combo is a 3.450", big bore, 6.200' rod, 215 ported Iron Eagles, Wet sump, flat tappet cam, etc. I'm not sure it would work if you have a cubic inch rule. But if your interested in talking to him, just send me an email and I'll give you his phone number. sdhnc29@yahoo.com If you can't use the 215 head's, they can be sold easily enough, along with the ported Super Victor that is on the engine.

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

sdhnc29
Dirt Forum Champ
Total posts: 934
posted November 14, 2004 12:02 PM  
Istock66,

If your limited to running cast pistons, then you would probably be better off using a little longer stroke. The very short stroke engines really need the ultra light weight part's to perform at their best.

As for cams, talk to Dave Crower. He has our input and the input of many other engine builder's who work with him on R&D. So he can point you in the right direction.

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

Istock66
unregistered Total posts: 934
posted November 14, 2004 02:55 PM           send a private message to sdhnc29   Edit/Delete Message   Reply w/QuoteBBBBBB
thanks steve, thats what I thought a cheap combo would be too heavy of rotating assembly..

thanks for the confirmation!!

strstckracer
Dirt Roller

Total posts: 23
posted November 28, 2004 08:28 AM  
Steve

I have a few questions for you? Given the following parts, which would be the better option: 383 or 355 or 363?

12.5 to 1 Speedpro or Keith Black Piston
6" Eagle SIR Rod
350 CFM Holley Carb
3100 lb car
Mildly porteded double hump heads (2.02 & 1.6)

The crank for the 383 would be a Scat 9000 Series. The crank for the 350 would be a stock crank lightened up by 3-5 lbs or a Scat 9000 Series. The crank for the 363 would be a .10/.10 grind by Eagle (4340 steel).

The cam would be determined by RPM range and stroke and bought from Comp, Crane, Isky etc.

I value your comments and look forward to reading them. Thanks in advance.

sdhnc29
Dirt Forum Champ
Total posts: 934
posted November 28, 2004 11:17 AM  
What bore and stroke combo's are you using to get these cubic inch's? And are these part's you already own, or are thinking of buying? Is this a claim class?

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

strstckracer
Dirt Roller

Total posts: 23
posted November 28, 2004 11:56 AM  
355 - .30 over 350 with a 3.48 crank
363 - .30 over 350 with a 3.625 crank
383 - .30 over 350 with a 3.75 crank

We have the stock crank, but would need to lighten it. Everything else needs to be purchased.

I can buy the rods for $140. The pistons would be around $250. The 3.625 crank can be boought for $330. The Scat 3.48 crank for $140. The Scat 3.75 crank for $175 or a 48 lb, cast steel Eagle 3.75 crank for $190.

It is the IMCA Stock Car class with a $400 claim. The heads are already on the shelf.

Also, which intake would work best: Single plan Wieand 7547 or a cast four barrel with the center milled out (no port work done)?

strstckracer
Dirt Roller

Total posts: 23
posted December 01, 2004 10:05 PM  
ttt

sdhnc29
Dirt Forum Champ
Total posts: 934
posted December 02, 2004 04:21 PM  
I'd probably use the 3-5/8" combo. I would definitely use the single plain intake also. The claim deal definitely throws a wrench in buying good part's. If your running a track where there is really no claiming, even though there is a claim rule, you might want to invest in lighter part's, such as piston's, crank, rod's.

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

strstckracer
Dirt Roller

Total posts: 23
posted December 02, 2004 06:59 PM  
Steve

Thanks for the advice. We just purchased a used 355 with a steel crank, 6" eagle rods, and JE pistons.

The Weiand X-Celerator has to be stock. Do you still suggest using it?

Also, do you sell flat tappet camshafts?

Thanks

sdhnc29
Dirt Forum Champ
Total posts: 934
posted December 02, 2004 10:24 PM  
If that is the only single plain you can use, then yes use it. Yes we sell flat tappet cams as well, mostly custom grind's. But if you want to save a few dollars, I can probably suggest a book grind that would be close for you. Just give me a call. You can talk with me or my dad Bill.

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

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