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Re: Special 300 HP engine - first report
Duke,
This is of special interest to me, having a BSME and owning a 66 327/300hp base engine 66 roadster. I am particularly interested to see the final performance with todays low emission gasoline and in very hot ambient temperatures.
Regards,
Dave K. -
Re: Special 300 HP engine - first report
Current road testing has been done in 90+ degree temperatures with no reported detonation on premium unleaded fuel, even after the initial timing was advanced to 14 degrees, but I'm not sure of the posted octane number for premium unleaded in the owner's area - maybe he can specify. The late closing inlet valve allows a relatively high SCR (DCR is only 6.9:1 at 10.25 SCR according to EA), which leaves nothing on the table in terms of torque/power and fuel economy. Low end torque will be enhanced by bringing in the centrifugal advance earlier, and I believe it can be made much more aggressive without getting into detonation.
What most guys don't understand is that today's best 93 PON premiums are about 97-98 RON, which is only a couple of RON points below sixties vintage leaded premiums. So you don't need to lower most CRs below the OE level unless you want to run a lower octane gasoline, and if the installed cam has a later than OE closing inlet valve you can actually run higher compression than as OE built.
The other thing that guys forget is that actual OE ratios are less than specified and you cannot rely on piston "catalog specs" to determine compression ratios because they are all based on some deck clearance, head chamber volume, and head gasket thickness, which may not be representative of their individual engine. That's why everything has to be MEASURED, beginning with deck clearance prior to disassembly if you want to get the most out of your new engine and not leave anything on the table, but this kind of precision work is tedious and time consuming and likely not all owner's are capable of doing it.
The current plan is to find the ultimate rev limit and then quicken the centrifugal curve to the limit of detonation, and I believe the engine will tolerate a centrifugal advance curve close to the 365/375 HP engines, which is all in at 2350.
I prefer that dyno testing be done in cool weather. The reason is to keep the fan clutch from tightening, which will cost about 10-15 HP at the top end. Even in hot weather the fan clutch usually doesn't tighten at road speed, just at idle and low speed, so the "true" horsepower achieved in most driving conditions does not include any significant fan loss.
Detonation testing is easily done on the road. The objective is to have the engine in the best and most aggressive tune possible when it hits the dyno.
MEs who do their own disassembly/assembly, pay scrupulous attention to small details, can take the various required measurements and run the CR calculators, and closely supervise their machinists to do only the specified operations are good candidates to build this configuration and achieve a correct buildup and performance expectations.
DukeComment
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Special 300 HP Engine...
My 1962 300 HP and I were one of the two who decided to take a "leap of faith" with Duke's experimental engine build. My pet name for the project ended up being the "twin cam" Chevrolet, mainly based on Duke's use of two different OEM cam profiles married to each other in a single grind.
The engine is still quite new in regard to total miles. In addition, RPM limits have only been road tested to 5,500 & 6,000 with ease. The idle, road manners and driveability are absolute OEM. Throttle response is instant.
Now, the bottom line for this report is a SOTP (Seat Of The Pants) impression.
This reporter's initial reaction is that this engine pulls harder than any 327 I have ever driven - and it does it from "start to finish" - no waiting to come on the cam or waiting for hi rev horsepower.
Again, this is SOTP, my reaction may be faulty to some degree. Mr Dyno can be a brutal truth teller... In any case, I am one happy camper so far. Thanks Duke, Best, DennisComment
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Re: Special 300 HP Engine...
Sounds like a great engine guys! Is this by chance what powers your Nomad?
tcComment
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Re: Special 300 HP Engine...
No, as Dennis said, the Special 300 HP engine is in his '62 (Corvette). I think his '57 Nomad has a 383 SB.
I believe it goes without saying, but since I did not specifically mention it, I will state that the Special 300 HP configuration is 327-based (3.25" stroke), other than whatever overbore is required to clean up the cylinders as required. That's why it's so rev-happy. It is NOT a stroker!
DukeComment
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Re: Special 300 HP Engine...
Duke,
I have in past asked you several questions regarding the rebuild of my 1964 Corvette's 327/300. I am thinking about actually doing this rebuild with in the next year. I am very interested using your build up for my car. I want this engine to visibly look no different than it does now in its correct NCRS configuration.
What do I need to do to get started on procuring the correct pieces?
Regards,
James West
Omaha, NE.Comment
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Re: Special 300 HP Engine...
I'm happy to help others rebuild their 300 HP engines to this configuration, but I'm going to be selective. The reason is that I have been caught between unknowlegeable owners and "engine builders" who have their own ideas that are very different from mine. I don't want to repeat those experiences.
In a previous post in this thread I outlined the "ideal owner" as one with a solid technical background who has experience rebuilding engines - a meticulous and patient person who can do his own disassembly/assembly, make the requisite measurements, perform the required calculations, AND manage his machinist!
As I stated previously, the only non-OE/OE equivalent parts are the pistons, rods, and camshaft. In fact, virtually everything you need can be purchased at NAPA or a parts store that carries the Sealed Power product line from Federal Mogul. The Crower Sportsman rods are the toughest part to obtain because they are special order, and they are also expensive, but I may have found a less expensive and easier to obtain alternative that will provide the requisite durability. For sure your early 327 rods would be risky to reuse at the rev potential of this configuration. Everything else is basically off the shelf and the cam can be delivered in about three weeks.
It's important to understand that this is a very tightly system engineered configuration, and any significant deviation from the required specifications and parts may result in poor performance.
I think the best way to sequence the work is to do all the head work first and have them flow tested. Depending on the head flow data, I can "tweak" the camshaft as required to achieve the best performance for the actual head flow characteristics. Once this is done the camshaft can be ordered and work on the block can begin. The rods can be ordered prior to beginning work and the correct oversize pistons can also be ordered prior to beginning work on the block as long as bore measurements have been done to determine the required overbore.
It's never too early to start the planning process, so shot me an email and give me your "resume" and maybe be can work something out.
DukeComment
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Re: Special 300 HP Engine...
Duke, I seem to remember a while back you were looking at a similar redesign for the 350ci engine (using the L46 as the starting point?) How is that project coming along?
Best regards.
MarkComment
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Re: Special 300 HP Engine...
No, not specifically the L-46, but the Special 300 HP cam can be used in any small block. It will work well in a base 350 (with the head work and compression) with full dual exhaust, but is best with a few degrees retard relative to a 327. Same with a 383, but a few more degrees retard.
It will work well in a L-79 or L-46 - more bottom end torque and top end power in those engines with the head work and compression than the OE cams, but it will idle smooth, which some may not like.
Another option for the L-79 or L-46 is to go with a mechanical lifter cam.
After trying a number of combinations, I've finally come up with a Special Mechanical Lifter cam that outperforms the LT-1 cam, but it has much less overlap, so it won't idle like any OE mechanical lifter cam.
The bottom line is that even with the modest exhaust backpressure engines don't really like much overlap.
DukeComment
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