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Xl1200r
| | Posted on Monday, October 29, 2007 - 09:54 am: | 
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While I'll agree that Ford and GM made street engines with similar or more power, neither of their designs are used as a basis for 8000 HP top fuel or funny car motors....
Okay, maybe some explanation - when I said 'crap', I meant it only in the sense that it really isn't some kind of 'magic answer', or a be-all head design. Sort of what Rocket was saying, it's good, but lots of other options are good, too.
I was talking about street engines, so being the basis for an 8000 rpm race engine wasn't even on my mind - anyways, this is the last place I would have expected anyone to be into old-style engines turning really fast, lol.
What I was talking about was numbers. The street 426 Hemi was rated for 425hp. The Ford 427 was rated for the same 425hp in peak street form. The Chevy 427 made 435hp in L88 and L71 variants.
Now, I'm the first to admit that all of these ratings are crap and these engines were all probably producing more like 550-600hp, but my point still stands. In a street engine, the Hemi is a good option, but not a godsend. There are a lot of good options out there. |
Djkaplan
| | Posted on Monday, October 29, 2007 - 10:27 am: |
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"In a street engine, the Hemi is a good option, but not a godsend."
I know the point you are making, and a lot of Mopar guys agree... for street use, the wedge head 440 was much easier to live with and could post competitive numbers at the strip, even against the the 426.
The simple fact of the matter is, the 426 Hemi was a purpose built engine for racing applications, much like a few other engines (the SOCH 427 Ford and SD455 Pontiac come to mind). These engines never worked well on the street compared to the 'cooking' engines they had to compete against.
I truly believe the best thing the 426 Hemi had going for it was that it was built for the stresses of real racing and saw lots of aftermarket developement, not because of any magic in the Hemi heads. The SOCH Ford was outlawed for racing by NASCAR and the SD455 Pontiac was just introduced way too late (1973) to make any impact on the streets or in racing circles. |
Strato9r
| | Posted on Tuesday, October 30, 2007 - 02:51 am: |
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"In a street engine....." is exactly the point. Buick, Olds, and Pontiac 455's, Dodge 440's, Ford 428's and 460's, and nearly any big block Chevrolet, in a decent state of tune, will produce a huge amount of torque WITHOUT a lot of RPM. Every one of those engines (oh, and dont forget 472 and 500 Caddies!) was more than capable of hauling 4500 pound barges around with little effort. Put that kind of grunt into a lighter Cutlass, Dart, or Maverick, and it cant help but be more fun, and still be reliable. True, at the drag strip, the more exotic setups are going to be faster, but those cars invariably do not make very good street transportation, and to maintain the tuning on a max output race engine to operate on the street is something I wouldnt wish on anyone.
The hemi is an old design, and H-D was using it not long after the turn of the last century. Those early Chryslers, and the later 404/426 series Hemis were and still are capable of amazing output; when in good tune. I once worked with a guy who was with Chrysler back in the sixties and seventies, and I remember him telling me that at one time, that there was a push to equip the 426 with either a single 830 CFM Holley, or the 6-Pack on street engines, because one of the big problems dealers had was keeping the dual carbs running properly. Many shops didnt have performance minded mechanics on staff, and a lot of cars suffered at the hands of owners who should have kept their hands off, but just had to start mucking around after reading some magazine article or hearing of some new trick of the week. Point is, that Al's non-descript, white-walled '66 Coronet kicked butt on a regular basis with a well tuned service replacement 440. "A helluva race engine, but a gas guzzling pain in the a$$ on the street", he said of the Hemi. For the street, it just didn't need over a thousand CFM of potential intake airflow.(And ironicly, it used a single carb for NASCAR use.)
Anyway, these "Hemi" heads for Harley engines, as nice looking as they are, do not have hemispherical combustion chambers. As stated, the 4 valve setup offers a few advantages in terms of lighter valvetrain mass, and potential airflow. But, on an engine with relatively high reciprocating weight, and an RPM ceiling that really does not need a huge amount of airflow to do what it does (make lots of torque over the widest possible range), I wonder if it is nessesary, beyond having something unique to show your buddies.
Speaking of innovative cylinder heads for Harley V-twins, does anybody remember Thunder Heads from around 1980? They were a slick, aluminum, bathtub chambered head that had XR-style ports, (hmmmm,where have I seen THAT?), came with flat top pistons and were designed as a complete kit for Ironhead Sportsters. |
Natexlh1000
| | Posted on Tuesday, October 30, 2007 - 07:16 am: |
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Are the thunder heads the ones with little lightning bolts on them?
how did they do? |
Diablobrian
| | Posted on Tuesday, October 30, 2007 - 09:49 am: |
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Most H-Ds are cammed to make their peak HP at around 3-4k rpms (right where they ride) and
do not need a head that works it's best above 7k rpms. It's that simple.
If there was a substantial improvement in flow available that would be useful for an air cooled
Buell don't you think they would have used 4 valve heads on the XBRR?
Service interval is not as big of an issue on race bikes as it is on street bikes so if
they were going to do it that would have been the logical place to try it. |
Djkaplan
| | Posted on Tuesday, October 30, 2007 - 10:29 am: |
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Those 'Thunderheads' were from Alan Sputhe. Sputhe Engineering is still in business...
http://www.sputhe.com/index.html
...but they no longer make those cylinder heads. They show up every now and then on E-bay, though.
A Sputhe head, XR framed Sportster was featured on the cover of Cycle World back in 1980 (or so). In the feature story, the homebuilt Harley road racer was claimed to be more than competitive against inline-4 competitors on west coast race tracks. Can't recall the displacement for the engine, but I recall it being bigger than 61 cubic inches (1000cc). The black painted bike looked like an XLCR with XR style heads and no bikini fairing... pure race bike.
I still have that magazine somewhere... |
Strato9r
| | Posted on Tuesday, October 30, 2007 - 11:52 pm: |
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I remember that article, too. That bike was insanely light, as well as insanely fast. Cycle World mentioned the article in the "25 years ago" section a while back. I had (and may still have, somewhere) a brochure for those Thunder Heads. It seems to me that there was a kit that included the heads, pistons, intake manifold and a Mikuni carb, and that camshafts were available. It was a very nice looking setup; top notch foundry work and machining, typical of Sputhe products. And yeah, they did have little lightning bolts on the rocker boxes. I was ready to send off a cheque for the kit to upgrade my Sporty, but got sidetracked by a REALLY nice Les Paul. Oh well....
.....they would have been wicked on an XLCR with good rubber! |
Djkaplan
| | Posted on Wednesday, October 31, 2007 - 09:25 am: |
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The Sputhe heads I saw on E-bay a few years ago came with Lectron flat-slides and a statement from the seller warning, "Don't expect me to hold your hand after you buy these...". |
Jandj_davis
| | Posted on Wednesday, October 31, 2007 - 11:51 pm: |
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I got my answer from the manufacturer. They said that the heads are actually shorter than the stock heads, the intake ports are in the same place, the exhaust ports are in a different location, and they only fit big-bore motors. |
Jaimec
| | Posted on Thursday, November 01, 2007 - 04:53 pm: |
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Air cooled, pushrod V-Twins with four valve heads:
http://www.starmotorcycles.com/star/products/model specs/480/0/specs.aspx
http://www.motorcycle.com/manufacturer/2008-moto-g uzzi-griso-8v-68608.html |
Mikef5000
| | Posted on Thursday, November 01, 2007 - 05:27 pm: |
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Anybody else catch the awesome 1125r ad at the top of that second link posted by Jaimec? |
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