SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: N2GLOCK on September 19, 2011, 09:25:09 PM
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Do the numbers that are stamped on my block and cylinder heads mean anything at all? The shop that is doing my carb needs info on my setup and I know nothing about my motor. If the numbers mean anything, is there some sort of book or web site that would help me decode? Mainly I'd like to find out if my heads are oval or square port and if I can figure out what kind of vehicle the motor was built for then may be I can figure out other things like intake/exhaust valve sizes and compression ratio.
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yes they do !!! the numbers that you need are the cast ones. the stamped numbers give the dates.and i beleave the horsepower. if you get the cast numbers and type them into your search engine it will come back with what you have. if not let me know i have a couple of books.good lucks!
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Maybe...casting numbers are just that....they identify the casting. Very few 30+ year Old engines have the same stuff that chevy put in 'em at the factory.
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you can call a chevy parts dealer the can tell you what you have
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I have this chevy motor sitting around....
its a 4 bolt main
Stamped on the block i found
GM 7 4 L G
and by the oil filter its stamped :
K 2 3
4 4 5
Hi perf
p a s s
any ideas?
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giv me the cast # on the back of the block.
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14015446 is whats stamped on the back....
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1975-87 4 bolt main 454 ...
now im sure this is a easy question too.. but how do i find out if its a gen 3, 4 or 5 ? :screwy:
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I don't think the gen 5 started til 1991. So I would bet its a mk IV.
Someone correct me if I'm way off.
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1975-87 4 bolt main 454 ...
now im sure this is a easy question too.. but how do i find out if its a gen 3, 4 or 5 ? :screwy:
It's certainly a MK IV block, but unless I am wrong,, and the "445" block come either 2 or 4 bolt, but you must have it apart to have stated that it is a 4 bolt.
Also, the "7.4" on the side of the block designates 454 cubic inches.
The "K 2 3" should indicate that it's a 1983 block,, I forget if "K" is October,, seems like they don't use the letter "i", don't want to look it up right now, and the "2" means 2nd day of the month.
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gen v started in 91 but some trucks in 91 still had gen iv. at least the early ones did.
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thanks for all the info!!!
i also have a pair of supposed " 572s " ... Ill grab the casting numbers off those and see what they really are :)
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GM Casting # 14044807...454T............Bowtie, MkIV, Tall deck, 4.25" bore or 4.500" bores
had no idea there were so many diff models of big blocks... I have a pair of these motors that came off out of a cigarette boat. I thought they were 572's for some reason. What are your thoughts on this block? and what does tall deck mean? and another stupid question... these blocks have a bow tie stamped into the side of them.. Does this mean anything?
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tall deck refers to the height of the bore area. most tall deck blocks were used for trucks. gm used them and then would use 4 rings per piston. so basically they ran a taller piston and made the block handle them. nothing else is different. for big stroker motors there ok but .... idk
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This is all coming from the "chebbie" camp that claims "we stuck with a proven winner for how many years....." and blast the Ford camp for interchangeability issues because designs or even whole patforms changed on a whim......... :screwy:
Just messing with you guys! Yes, interesting to know. I would like to see a thread EXACTLY outlining the differences, and ID, between the MK4, MK5 and MK6 blocks and what will/will not interchange. Even though Chebbie guys say Chebbie is Chebbie................. :sly:
Ray
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GM Casting # 14044807...454T............Bowtie, MkIV, Tall deck, 4.25" bore or 4.500" bores
had no idea there were so many diff models of big blocks... I have a pair of these motors that came off out of a cigarette boat. I thought they were 572's for some reason. What are your thoughts on this block? and what does tall deck mean? and another stupid question... these blocks have a bow tie stamped into the side of them.. Does this mean anything?
The "bowtie" is the best of the GM blocks. Just knowing the casting number will not automatically tell you the size of the engine. With a 4.500" bore and 4.500" stroke you can have a 572 cubic inch engine.
The "tall deck" means that the "deck" or surface that the cylinder heads bolt to is .400" further from the center of the crankshaft than a standard deck block. They were originally used for truck engines, so some people call them truck deck blocks. The truck engines had pistons with 4 piston rings instead of 3.
The advantage of a tall deck block is the ability to use longer connecting rods and straighten out rod geometry, which can actually promote better engine life (less cylinder wear), and better ring sealing, which translates to more power. Instead of a stock 6.135" long rod, it's common to use rods as long as 6.700" and 6.800" long with certain off the shelf pistons.
Bowtie blocks also came with either forged or billet main caps, and when the block came new from GM,, there was a sheet delivered with it showing the cylinder wall thickness on four sides of each cylinder.
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I would like to see a thread EXACTLY outlining the differences, and ID, between the MK4, MK5 and MK6 blocks and what will/will not interchange.
I believe that I know most of the differences,, they are not that complex and mysterious. The later blocks are termed Gen 5 and Gen 6, and the earlier ones MK IV.
Besides casting numbers,, the Gen 5 used a 10 bolt timing cover, similar to the MK IV timing cover, but they are not interchangeable, due to differences in the oil pan. Gen 5 and 6 pans are the same, the MK IV different. The Gen 6 timing cover is a 6 bolt cover. I believe there may have been some crossover blocks between Gen 5 and 6 that didn't have the "proper" number of timing cover bolt holes.
The Gen 5 block has different water passages in the deck surface, and causes a sealing issue if you don't use Gen 5/6 style heads (including GM bowtie). My understanding is that is one of the key reasons the Gen 6 block was developed, to allow aftermarket and MK IV cylinder heads to seal the water passages properly. The cylinder head bolt pattern has remained the same for all three series of blocks.
Gent 5 and Gen 6 blocks use a camshaft with a stepped nose, and therefore a different timing set. The step allowed the use of a camshaft retaining plate to control thrust. A MK IV style camshaft will fit into the block no problem, but requires the MK IV style timing set.
Gen 5 and Gen 6 were the first of the factory roller cams, as far as I know, although there were some flat tappet cams in some of the Gen 5 I think. The Gen 5/6 rollers use a new style roller lifter that requires the "dogbone" type stablilizers to hold the roller in line with the cam, and then a sheet metal "spider" that bolts into the valley to retain the 8 dogbones.
The factory Gen5/6 cylinder heads are not set up for valve adjustment, they have rocker bolts instead of studs that retain the rocker arms, so for a performance application, the bolts should be changed to studs to allow for deviations in valve train geometry from factory pushrods and cams, or if you want to run a mechanical cam instead of hydraulic.
Gen 5/6 harmonic balancers and flywheels/flexplates have a different counter weight, and of course the crankshafts are of the one piece rear main seal variety. You can purchase a two piece rear main seal adapter and run a MK IV crankshaft in a Gen 5/6 block.
One of the less obvious, but more important changes in the Gen 5/6 block is the oiling system. It's considered a "priority main" oiling system, and is the same basic oiling system in the aftermarket blocks like Dart. For long time users of the MK IV blocks, it's especially important to understand the two pressure bypass system in the newer blocks, one of which diverts oil to the oil cooler outlet and inlet cast into the block in front of the oil filter location.
Another thing with the newer blocks is that GM recommended a maximum over bore of .060". I have done some visual inspection of some of the blocks, but have not paid to have any sonic tested for wall thickness, so would have to say they have a reason for suggesting that limit.
Most of the Gen 5/6 blocks lack provision for a mechanical fuel pump, but I think the tall deck (or truck block) still have it, as well as the Bowtie and also the HO 454 crate engines.
Might have left out something,, but time for something for dinner!
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yes they do !!! the numbers that you need are the cast ones. the stamped numbers give the dates.and i beleave the horsepower. if you get the cast numbers and type them into your search engine it will come back with what you have. if not let me know i have a couple of books.good lucks!
Ok, I decided to look for some numbers on the block and heads. The rear of the block has 361959 stamped on it. I did a quick search and came up with a mid seventies 250 h.p. 454 motor. On the front of one cylinder head is HLC94079 This # yielded me zero results on google. The rear engine mount has a tag that states that the engine was built by Harman Marine and that timing should be 10 degrees and 94 octane fuel should be used. If I recall correctly, I remember seeing some stuff stamped on the block near the oil filter. Getting to that area is a bitch, but if those #'s are of importance I'll do whatever needs to be done to access those numbers.
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The casting number for the heads is going to be under the valve cover.
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Ok, I decided to look for some numbers on the block and heads. The rear of the block has 361959 stamped on it. I did a quick search and came up with a mid seventies 250 h.p. 454 motor. On the front of one cylinder head is HLC94079 This # yielded me zero results on google. The rear engine mount has a tag that states that the engine was built by Harman Marine and that timing should be 10 degrees and 94 octane fuel should be used. If I recall correctly, I remember seeing some stuff stamped on the block near the oil filter. Getting to that area is a bitch, but if those #'s are of importance I'll do whatever needs to be done to access those numbers.
As mentioned, if you remove one of the valve covers you can find the cylinder head casting number. The casting numbers alone don't tell you too much about what may have been done to the engine when (and if) it was rebuilt, certainly nothing about the cam or compression ratio unless you know the engine has never been apart. What the cylinder head casting number would tell you is if the ports are oval or rectangular shaped, and if they were a performance type head,, or just something that should be on a truck.
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As I remember...most all of the 4-bolt blocks (early ) had a 3/4"Pipe plug ( for oilcooler ) above the O/F boss. Many round-port heads had "hi-perf pass" cast into them. Stock engines also had 3/8" dia pushrods.....medium perf had 1/2" ones....and the hot-rods had 7/16" "telephone pole" pushrods. I'm guessin Harman had 1/2".
Greg
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So can i run markIV heads on my GEN VI 454? Which would be a good set of gm heads with a single 750 holley on an edelbrock air gap with HEI dist thru logs and snails. In a 78 18ft eleminator bubbldeck w berkeley 12 jc-a-h jet w place diverter and ride plate. Any cam recommendations?
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So can i run markIV heads on my GEN VI 454? Which would be a good set of gm heads with a single 750 holley on an edelbrock air gap with HEI dist thru logs and snails. In a 78 18ft eleminator bubbldeck w berkeley 12 jc-a-h jet w place diverter and ride plate. Any cam recommendations?
Yes you can. What have you got on the engine now? Is it an oval port Air Gap? Drop me a PM if you like and we can talk camshafts.
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So how can I tell if I have a Mark IV or Gen V? Do I have to pull the pan and see if the rear main seal is 1 or 2 piece or is there an easier way?
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I am sure I will be corrected if I am wrong.....but I believe the gen v has no fuel pump boss.
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So how can I tell if I have a Mark IV or Gen V? Do I have to pull the pan and see if the rear main seal is 1 or 2 piece or is there an easier way?
You previously stated it was a "959" " mid seventies" block, which means it would have been a MK IV block.
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You previously stated it was a "959" " mid seventies" block, which means it would have been a MK IV block.
Thanx for the 411 Check your PM