Three ways to build a 485 BBC puller engine

[e-tach]

I am looking into building a BBC 4x4 truck pulling engine. In my class, max cubic inches is 485, cast iron block and heads (OEM, DART,MERLIN,etc.). We can use an aluminum intake manifold. Natural aspiration, will be running about a 1050 carb. Race gas, about 13:1 to 14:1.

Most of the guys are running stock 454 blocks bored .125" and a 4" stroke. It seems to be the standard.
A few are running standard bore 454 blocks with a 4.250" stroke.

What I am wanting to do is run a Big M block, 4.500" bore with a 3.76" stroke. Cubes would lbe about 477. What do you guys think of this big bore/short stroke combo? Heads would be fully ported Dart Iron Eagles 345cc, or possibly thinking of going to RHS 360cc. Solid roller cam, about 770 ish exhaust lift, 830 ish intake lift.

This class seems to be running anywhere from 8000-8500 rpm's.

Has anybody tried a combo like this? I am kind of scared to just build it and find out, but sometimes thats just what ya gotta do.

[Baprace]

e-tach , my personal preference would be a 4.125 crank, I believe you need all the torque you can produce and stroke is the only way that I know to make torque, in the northeast , DIRT big block modifieds run these cranks quite a bit so they are not really odd sizes. JMHO

[Ed-vancedEngines]

I like it. Why not go on up to almost the cube limit though? You can buy custom pistons in any diameter you want them as long as you can get rings.

I think that the combination you are talking of with correct gearing and turning it to the moon if built for it should work very well and be a lot more reliable and make more power at the same cubes.

When you bore the 454 to those sizes the ring seal is not the best in the world. You would have really thick cylinder walls and eliminate that problem. I would not be surprised that with same exact components iofit were possible, you would see 30 to 60 additional real horses just becuase of the thicker cylinder walls. If you build for it, BB Chevys love rpm.

Try a 4.525 bore and a 3.76 stroke with it. = 483.7 cu in.

I love it.

Ed

[e-tach]

I like it. Why not go on up to almost the cube limit though?


I want to leave a bit of room in the bores for future cleanup....ya never know when ya might need it. These blocks are expensive.

[Keith Morganstein]

I am looking into building a BBC 4x4 truck pulling engine. In my class, max cubic inches is 485, cast iron block and heads (OEM, DART,MERLIN,etc.). We can use an aluminum intake manifold. Natural aspiration, will be running about a 1050 carb. Race gas, about 13:1 to 14:1.

Most of the guys are running stock 454 blocks bored .125" and a 4" stroke. It seems to be the standard.
A few are running standard bore 454 blocks with a 4.250" stroke.

What I am wanting to do is run a Big M block, 4.500" bore with a 3.76" stroke. Cubes would lbe about 477. What do you guys think of this big bore/short stroke combo? Heads would be fully ported Dart Iron Eagles 345cc, or possibly thinking of going to RHS 360cc. Solid roller cam, about 770 ish exhaust lift, 830 ish intake lift.

This class seems to be running anywhere from 8000-8500 rpm's.

Has anybody tried a combo like this? I am kind of scared to just build it and find out, but sometimes thats just what ya gotta do.

Exact dimensions of Bore and stroke by itself is pretty much a wash, though generally you want a bigger bore for airflow.

It's all about the heads.

I would get together with the head porter first. Decide what head you will use (my guess is the good porters will want to use the dart head). Most will want valve size at least 50% of the bore. So if the head can run a 2.25 intake valve, the 4.5 bore will likely be good. 2.19 valve and the 4.375" will work.

[CamKing]

As long as you can run a gear that will allow you to turn more RPM, your idea will out-run the bigger stroked engines.
You're gonna want a head that takes advantage of the bigger bore, and out-flows the heads the other guys are running.
The shorter stroke will allow you to make power at a higher RPM without having to run a larger cam then the larger stroke engines are running.

When you're ready for a cam, let me know. Pulling trucks run in a very short RPM band, and there's a few tricks you can do with the cam to help the power in that area.

[PFC1]

You and Ed hit the bore and stroke combo right where it needs to be except go ahead to the 4.525-4.530 bore. Don't do the long stroke you can make good torque without the long stroke. The shorter stroke will like to make the RPM better. Shoot for an rpm window of 78-9000.

Like CamKing said pullers have a short rpm window. Many cam grinders do not understand this. I tell cam grinders I don't care about anything under 7500 for such a deal, because if she ever pulls below that...your done anyway.

Use Ti valves from the get go so you won't be rpm limited. I personally am not a big fan of the Dart 345 iron peice, they seem to be big for there flow potential. I'd look into the RHS 360. Super Victor works good.

Use a short deck block, long a rod that will fit, shoot for at least 15 to 1, cam numbers @.050 should be around 285ish and 296ish with a 112-113 or so lobe seperation. At least .850 intake and .800 or so on the ex. Depends on if the head continues to support the flow.

Two more things...with iron heads and lots of compression, do not scrimp on the octane/fuel, if you do you'll knock the bearings out of it in a heart beat. Have it dynoed for optimum timing and tune and then fatten it up.

The right combination should be capable of near 900 horse @ 8000.

My experiences, Bret

[Ed-vancedEngines]

In case you don't know the nick of PFC1 is a shortented version of Pulling for Christ. He, himself is also a Puller, so I would think he knows more about this than I would know.

Ed

[Dan Barton]

I personally think that I would recommend a 4.600 bore X 3.625 stroke... Stroke doesnt guarantee tq, but it may very well dictate at what rpm peak tq is made! I believe pfc1 is correct on most other things too! Angle mill the heads as far as you can and move it over with offset dowels or by other means, I would use 5/16 titanium valves and keep everything on that side of the valvetrain as light as possible and use no less than a .135 wall 3/8 pushrod on it, bigger if you can get it in there. Like Ed said... you can get pistons custom oversized to whatever dimention you desire, as long as rings are available, so a 4.602, 4.604 or a 4.605 piston is no problem to get and rings typically for a 4.600 bore come in a +.005 and that could give you 2 to 3 overbores right there and still be able to get you the desired ring gap required, and would still leave you under the cubic inch limit. I believe if it is done right the engine should make about 680 torque around 6200 rpm or so and 940 horsepower at around 8000 rpm. The big bore and short stroke has many benefits... airflow is one and being able to better control windage is another. Just my opinions! Good luck, Dan

[Ed-vancedEngines]

Dan,
You want to take all the guy's torque away from him. lol.

That was actually my first thought but becuase he was talking that stroke I kinda figgured he may already have some Chevy 427 or 396 cranks.

The idea of a long stroke to get torqque is a falacy that I believed for years, that is just not so. The total Swept Volume has a lot to do with the amount of torque an engine has. The long stroke small bore engines will seem to have more torque becuase the torque is peaked at a lower rpm.

At a 4.600 bore the Dart Big-M block has quite a number of re-builds or freshen ups left in it. With smaller bores it has even more.

When it is designed and is built for the rpm and has the camming and the air flow, he higher rpm winding engine will act like it is bigger and it is, becuase it is moving more air and is dumping more exhaust and is producing more power.

You can NOW get valve springs that have incredible life at high rpm too.

Ed

Was a BAD TYPO from me.

[Dan Barton]

Let me also add that if 485 cubic inch is the limit, build as close to that as possible! dont give up 8 inches for no reason!!! Look at it as horsepower and torque per inch and ask yourself if you would be willing to just "give" that up for no good reason! Heck... have a 3.640 custom crank built and even at 4.605x 3.640 you are still just barely under the max. Dan

[Ron C.]

I personally think that I would recommend a 4.600 bore X 3.625 stroke... Stroke doesnt guarantee tq, but it may very well dictate at what rpm peak tq is made! I believe pfc1 is correct on most other things too! Angle mill the heads as far as you can and move it over with offset dowels or by other means, I would use 5/16 titanium valves and keep everything on that side of the valvetrain as light as possible and use no less than a .135 wall 3/8 pushrod on it, bigger if you can get it in there. Like Ed said... you can get pistons custom oversized to whatever dimention you desire, as long as rings are available, so a 4.602, 4.604 or a 4.605 piston is no problem to get and rings typically for a 4.600 bore come in a +.005 and that could give you 2 to 3 overbores right there and still be able to get you the desired ring gap required, and would still leave you under the cubic inch limit. I believe if it is done right the engine should make about 680 torque around 6200 rpm or so and 940 horsepower at around 8000 rpm. The big bore and short stroke has many benefits... airflow is one and being able to better control windage is another. Just my opinions! Good luck, Dan

I like it, ......I would find a way to get the bigger pushrod in it and in that stroke neighborhood (3.61-3.62)you can find some excellent used Pro Stock cranks to save some bucks.
Work with Curtis Boggs on the heads and intake...and don't forget to put a "SpeedTalk" sticker on this Championship truck puller .

Blessings..........Ron Clevenger.

[Ed-vancedEngines]

Agreed with Dan and with Ron.

Man if you can do it in your budget, go out there and knock them dead within the rules for the class. Technology is now to be able to do it.

Trust me in this. I know for a fact that the 454 bored .125 can not have great ring seal, even with a filled block. There is horsepower to be made just there.

My previous post I made a typo about valve springs. YOU CAN NOW GET KILLER VALVE SPRINGS THAT WILL LIVE AT EXTREME RPM>

Contact me and I will tell you about them. They were invented/innovated are made by Chris Osbourne of PAC and are the Cat's Meow in valve spring techniology. These new springs will help you at the higher rpm levels to produce more power and to maintain valve control. IT was one of the best kept secrets in racing until Indy when they were officially introduced by him there. He calls it the Next Generation Spring in the 1300 series. The largest one that is designed for NHRA Pro Stock is 1.550 and the Top Fuel/Top Alchiol spring that runs at 10,500 rpm is only 1.500 in diameter. Both are light weight at the palce where weight matters the most in a racing engine.

Imagine that thing buzzing with a high torque curve in it that is strong and almost flat for 1,200 to 1,500 rpm. That is entirely possible.

Ed

[Dan Barton]

Ron, it would have to be an older pro stock crank because a 4.900 bore space crank I believe has the #2 and #4 mains spaced differently than a 4.840 bore space block... but I may be mistaken. Dan

[OBSESSED]

I also would do the 3.75 stroke and the 4.530 bore size. Spin it up. Don't wanna go to short of a stroke and that thing would choke off as soon as the pan drops. I would go NO less than the 3.75". And I presume you guys can run only 33" rubber also. So there is a need for some bottom end in it coming out of the hole and not so rpm picky or a extremly narrow band. Granted my limit is 530. I can drive mine out at 4500. Let the tires get ahold of something. Thats where to short of a stroke it won't be able to that.