Here is a Blown 496
| RPM |
TQ |
HP |
| 3500 |
639.9 |
426.4 |
| 3600 |
626.2 |
429.2 |
| 3700 |
623.8 |
439.5 |
| 3800 |
624.0 |
451.5 |
| 3900 |
635.9 |
472.2 |
| 4000 |
652.1 |
496.6 |
| 4100 |
694.3 |
542.0 |
| 4200 |
702.3 |
561.5 |
| 4300 |
746.3 |
611.0 |
| 4400 |
785.5 |
658.1 |
| 4500 |
797.2 |
698.2 |
| 4600 |
806.4 |
721.6 |
| 4700 |
815.1 |
745.0 |
| 4800 |
836.7 |
780.6 |
| 4900 |
832.5 |
806.2 |
| 5000 |
826.3 |
818.5 |
| 5100 |
814.0 |
833.1 |
| 5200 |
801.8 |
844.6 |
| 5300 |
787.2 |
855.2 |
| 5400 |
772.8 |
853.4 |
| 5500 |
759.4 |
848.0 |
12.5 PSI |
| RPM |
TQ |
HP |
| 3500 |
578.0 |
385.2 |
| 3600 |
584.0 |
400.3 |
| 3700 |
587.9 |
414.2 |
| 3800 |
592.8 |
428.9 |
| 3900 |
595.0 |
441.8 |
| 4000 |
605.8 |
461.4 |
| 4100 |
623.4 |
486.7 |
| 4200 |
632.0 |
505.4 |
| 4300 |
626.8 |
513.2 |
| 4400 |
631.8 |
529.3 |
| 4500 |
640.9 |
549.1 |
| 4600 |
671.1 |
587.8 |
| 4700 |
674.0 |
603.2 |
| 4800 |
680.6 |
622.0 |
| 4900 |
688.6 |
642.4 |
| 5000 |
682.4 |
649.7 |
| 5100 |
675.2 |
655.7 |
| 5200 |
666.9 |
660.3 |
| 5300 |
662.9 |
669.0 |
| 5400 |
652.7 |
691.7 |
| 5500 |
647.1 |
698.6 |
| 5600 |
639.5 |
690.4 |
| 5800 |
618.0 |
678.2 |
5.5 PSI
|
The patient is a '72 Chevelle with a 0.030-over, 10.5:1 compression, 454 big-block with a hydraulic-cam and "049" cast-iron heads. I am running both heat and A/C. Please explain the difference between using a water pump bypass hose or deleting it. The intake is an Edelbrock Air-Gap; the water pump is a Weiand long pump. The fittings for the bypass hose make it very difficult to install the bypass hose without a kink. Do I need to change pumps, or can I eliminate it?
Theoretically, a water pump bypass hose serves two functions: it promotes quicker warm-up on cold-start, and helps prevent water pump impellor cavitation. Although most small-block Chevys have internal water pump bypass passages, the big-blocks do not, so in theory an external bypass hose is required. However, there are two workarounds that should let you slide by without connecting the bypass hose. First, if coolant always circulates through the heater core whether the heater is on or off (this is the case if there is no shutoff or vacuum-actuated valve mounted in-line on the heater transfer hoses or screwed into the intake manifold), the constant circulation pathway should be sufficient to accomplish the bypass function as well. Alternatively, you can experiment by drilling several small 1/8-inch holes in the thermostat's mounting flange underneath the water outlet housing.
|
  John I got the Chevelle running. It is very strong, 600 horsepower makes it feel like a race car. It takes some skill to drive. I have scared everyone that I've taken for a ride in it.
Thanks. Benny S. Texas.
|
LINKS TO MORE PAGES
Comparing Big Block Heads
Holley SysteMax
740BHP AFR BBC Magazine Feature
565CID 1000BHP
705 Magazine Build 
LINK TO GM BBC CRATE ENGINES
12370850 - ZL1 Aluminum Big Block $5600
The Chevrolet aluminum big-block is back and better than ever. This block was first introduced in the 1969 Corvette and Camaro. It was one of the rarest production engines ever built. Now the improved version is available. This block is based on the original tooling. The new casting is made from 356-T6M aluminum alloy and has a 4.250" cast iron liner that can be bored to 4.300". The bottom end has also been improved with new 4-bolt splayed steel main caps with dowel pins to locate and hold the caps in place. This block includes screw-in freeze plugs with o-ring seals and a two-piece rear main oil seal. the new block has a provision for both dry sump or regular oil pump systems and mechanical fuel pump. All GM Performance Parts cylinder heads will fit this block and it weighs only 110 lbs. The maximum stroke is 4.375".
| Engine Size |
Stock Bore |
+.060"-over |
Stock Stroke |
| 366 |
3.935" |
3.995" |
3.760" |
| 396 |
4.094" |
4.154" |
3.760" |
| 402 |
4.125" |
4.185" |
3.760" |
| 427 |
4.250" |
4.310" |
3.760" |
| 454 |
4.250" |
4.310" |
4.000" |
| Mark 5 — 502 — Mark 6 |
4.468" |
4.530" |
4.000" |
| 454 Engines |
3.760" |
4.000" |
4.250" |
4.500" |
4.750" |
4.875" |
| Stock bore = 4.250" |
427" |
454" |
482" |
511" |
539" |
553" |
| Bored .030" = 4.280" |
433" |
460" |
489" |
518" |
547" |
561" |
| Bored .060" = 4.310" |
439" |
467" |
496" |
525" |
554" |
569" |
| Bored .090" = 4.340" |
445" |
473" |
503" |
533" |
562" |
577" |
| Bored .100" = 4.350" |
447" |
476" |
505" |
535" |
565" |
580" |
| Bored .125" = 4.375" |
452" |
481" |
511" |
541" |
571" |
586" |
| 502 Engines |
3.760" |
4.000" |
4.250" |
4.500" |
4.750" |
4.875" |
| Stock bore = 4.468" |
472" |
502" |
533" |
564" |
596" |
611" |
| Bored .032" = 4.500" |
478" |
509" |
541" |
573" |
604" |
620" |
| Bored .062" = 4.530" |
485" |
516" |
548" |
580" |
612" |
629" |
| Bored .092" = 4.560" |
491" |
523" |
555" |
588" |
621" |
637" |
| Aftermarket Blocks |
4.000" |
4.125" |
4.250" |
4.375" |
4.500" |
4.625" |
4.750" |
4.875" |
5.000" |
| 4.500" bore |
509" |
525" |
541" |
557" |
572" |
588" |
604" |
620" |
636" |
| 4.530" bore |
515" |
532" |
548" |
564" |
580" |
596" |
612" |
628" |
645" |
| 4.560" bore |
523" |
539" |
555" |
572" |
588" |
604" |
621" |
637" |
653" |
| 4.590" bore |
530" |
546" |
563" |
579" |
596" |
612" |
629" |
645" |
662" |
| 4.600" bore |
532" |
548" |
565" |
582" |
598" |
615" |
632" |
648" |
665" |
| 4.625" bore |
537" |
554" |
571" |
588" |
605" |
622" |
638" |
655" |
672" |
6410-1029
|
Hey John,
Got the engine fired Up and running pretty strong, Wow I like the low end power!!!!
It definately sounds good and runs strong in the lower RPM range, more than I thought it would.
I also have sent you a couple of customers to inquire on building engines.
James T. Kalamazoo Michigan
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BIG BLOCK CASTING NUMBERS
EXAMPLE
NOTES:
Notice the camshaft is advertised to make peek power at about 6400rpm, but in fact made peek BHP at 6100 this is a result of the longer .250" stroke.
A solid lifter cam was chosen to create more torque and horsepower than a similar hydraulic cam would produce.
A flat tappet hydraulic cam would require special race lifters to maintain power beyond 6000rpm.
A Hydraulic Roller cam will make significantly more power and torque than the solid cam, but require a Rev Kit to maintain power beyond 6000rpm.
A Hydraulic Roller cam will cost $450 more and the Rev kit $175
The 274 is recommend to use with a 2500rpm stall speed torque converter, however you can get by with a 2000.
Longer duration cams will increase the peek BHP and lower the torque values below 3500rpm. They will also reduce vacuum and require higher stall speed converters.
A single plane manifold will also increase BHP and lower TQ at low RPM
Using a Mighty Demon Carb will lower the price $330
To further increase power and torque I recommend AFR 305 CNC chamber heads with 11.0:1 compression, add $750. These are excellent heads. Larger port heads will increase peek horsepower but lower torque
______________________________________________________________________
The head bolt holes line up. The steam holes line up just like stock. (Four holes in gasket, three line up and are functional on each side.) I see NO place where the holes in the block or heads could overlap the gasket and leak into the lifter valley. The holes in the Gen 6 head are oddly shaped, and there is an "extra" one, but this is all properly covered by either a Gen 6 gasket or a Mk IV gasket. "Should" be no leakage.
The benefit of this conversion is to use the tiny-chamber L-29 Vortec heads on all those old 8 to 1 compression pickup truck 454s. The same deal as converting all the old small blocks to Vortec heads! These L-29 big block heads have the BIG oval ports, a modern heart-shaped 100 cc or so combustion chamber that would work great with flattops. Drawback is the special (but readily available) rocker studs to convert to adjustable rocker arms. Heads come with exhaust seat inserts, and the intake especially has nice-looking ports, that should provide swirl. The exhaust may need some clean-up around the valve guide, it's mighty blunt. There is no exhaust heat crossover passage.
I compared a core "049" casting head to a new L-29 head. Bought one of each gasket, the old Mk IV and a Gen 5/6. (Victor catalog lists same gasket for '91 through 2000.) I checked these with a core 454 block that I think is from '73.
What I can figure out is this:
MK IV block, no modifications
Gen 6 "vortec" head, no modifications
Use a standard, ordinary MK IV head gasket.
I can see NO problems with this installation. All the goofy-shaped coolant holes are covered where they need to be, open where they need to be, water should flow through the head in standard MK IV cooling pattern- It will be SERIES COOLED. That means the water enters the front of the block, goes to the rear of the block, transfers up to the rear of the head, and comes forward to transfer into the intake manifold and thermostat area. Millions of MK IV engines used this coolant flow, and they seem to get by just fine. Recognize that the coolest water comes in the front of the block, gets warmer all the way to the back of the block, transfers into the head, gets warmer still all the way to the front of the head. Coolest part of the block is right below the warmest part of the head. Even so, seems to work just fine.
OR!!!
MK IV block, minor modifications
Gen 6 head, no modifications
Gen 6 head gasket, no modifications
Drill four 3/8 holes in the block deck, using the Gen 6 gasket as a template. Elongate two existing holes, won't take much. (Three holes each side, between the cylinders at the lower part of the deck.)
Again, goofy shaped holes are covered where they need to be, and open where they need to be. This parts arrangement provides for PARALLEL COOLING. There are two large openings at the back of the block for coolant transfer into the head. The larger one is BLOCKED by the Gen 6 gasket. The smaller one is open. Coolant flows just as the example above, except in much smaller quantity. This smaller quantity is supplimented by the three additional holes on each side that you drill or elongate in the block. So coolant comes in the front of the block, some "geysers" up though the first hole, between the first two cylinders,some geysers up thru the second hole, between the second and third cylinders, some gyesers up through the third hole, and the last goes all the way to the back of the block and transfers up there. This is how the Gen 5/6 engines are cooled, again millions made and it seems to work. I consider this a "better" way, as it may "even out" the temperature extremes of a series cooled engine- from one end of the block to the other, and one end of the head to the other. This way, the back of the block should be a bit warmer, and the front of the head should be a bit cooler, I think Parallel cooling is the way to go!
What won't work, is:
Mk IV block, un modified, no extra holes drilled. (But see note 3)
Gen 5/6 gasket, Un modified
Gen 6 head, un modified
The cooling system will be series, with a touch of bleed though from one "geyser" hole on each side. Not enough coolant circulation, I think it's gonna run hot.
I'm gonna build a Mk IV block, Gen 6 head Frankenstein engine over the winter. I'll use a MK IV gasket, and NOT drill the extra holes. If it overheats, I'll rip off the heads, drill the holes, and slip Gen 6 gaskets in.
Note 1: This is going in a boat, and it uses (cold) lakewater for cooling. The existing Mk IV takes forever to warm up. It's not the best situation to test for overheating. If this was in a car with existing heating problems, I would drill the holes and be done with it.
Note 2: You could, if you cared, parallel cool a pure Mk IV engine. Just get a gasket that has the additional four holes, or use a Gen 6 gasket. The Mk IV heads already have the holes needed to line up with the extra holes you would drill into the block. No need to modify the heads at all.
Note 3: I only have one block to look at: I am suspicious that GM may have built MK IV engines that ALREADY HAVE THE EXTRA HOLES, and are Parallel cooled. I have seen a picture of a Mk IV head gasket that has the extra holes, makes sense that some blocks do, too. Unlike the Gen 6 gasket, both coolant passages at the back were still open, though. I'm thinking "who cares, the thermostat can regulate this".
Note 4: Swapping heads between Mk IV and Gen 5/6 got a bad reputation right away. It seems that it's only a problem when using older heads on a newer block. Using the Gen 6 heads on a Mk IV block is "almost" a direct swap.
Spec's on the L-29 Vortec BB head vs a peanut port BB head (PPH) per the article..
L-29 intake ports = 233.2(S) and 239.5cc(L).
PPH intake ports = 192.4(S) and 198.0cc(L).
L-29 exhaust port = 81.2cc.
PPH exhaust port = 101.3cc.
Chamber volumes. L-29 = 100 and PPH = 118.4cc.
Approx. CR's on a regular stock, small domed 502, PPH = 8.74CR. and L-29 = 9.74CR.
For a flat-top piston 502, the L-29 would make 9.3CR.
For a stock 454 flat-top P/U truck motor PPH = 7.9CR. and L-29 = 9.0CR!!
Valves = the same for both heads at 2.065"/1.72".
NOTE: Use Fel-Pro headgasket 1017-1 to use L-29 heads on the early IV BB blocks AND check coolant holes CAREFULLY!!!
______________________________________________________________________
Mark IV head gaskets have two openings at the front; a GEN V-VI gasket has only one opening to force coolant to flow rearward through the block and cylinder heads.
every
unique
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