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Old 11-16-2010, 03:38 PM
Chevyfreke
 
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votec heads

I have a set of heads with the casting # 10128374 350 GenII, LT1, 53cc, angle plug, Corvette, Alm., reverse flow cooling, 168-175 cc intake port
what is the most cam lift i can go with out working them I have a 350 0.40 over

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Old 11-16-2010, 04:43 PM
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Quote:
Originally Posted by chevyfreke
I have a set of heads with the casting # 10128374 350 GenII, LT1, 53cc, angle plug, Corvette, Alm., reverse flow cooling, 168-175 cc intake port
what is the most cam lift i can go with out working them I have a 350 0.40 over
First things first, these heads only bolt to Gen II blocks which are configured for reverse cooling. They do not fit a Gen I block without a lot of cooling passage rework. So what are you proposing to bolt them to.

In stock form, the head will take about .49 to .50 inch lift before you have to mess with the top of the guide. For performance applications you need to look at beehive springs as there just isn't much material to accept a larger spring pad.

The small chamber volume prevents you from optimizing the compression ratio when using the stock circular dish piston. To keep the compression where premium unleaded will be tolerated and power optimized requires a lot more squish/quench than these engines have from the factory. Between the top of the piston being .025 inch down the bore at TDC combined with GM's .053 inch thick head gasket can end up being that clearance of .078 inch plus another .050 to the dish floor which makes a squish/quench distance of .128 inch over much of the piston area. This results is a weak squish/quench which in turns forces the engine to be operated at less than it's optimal timing, mixture, and operating temps for best power and efficiency. To really make use of these heads the pistons need to be replaced with a D dish configured piston crown.

They can be modified to operate on Gen I blocks but unless you have the shop and skill to do it, the cost of modifications gets to a point where you could just by a set of GM Fastburns, which is essentially the same head with standard coolant flow.

Bogie
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Old 11-16-2010, 04:50 PM
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how can I find out if it is a gen1 or gen2 block
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Old 11-16-2010, 05:17 PM
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Casting number on the back of the block, by the bellhousing, driver's side.
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Old 11-16-2010, 05:21 PM
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it is a jasper # 576114
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Old 11-16-2010, 05:45 PM
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Quote:
Originally Posted by chevyfreke
it is a jasper # 576114
Look on the drivers side rear, on the bell housing flange will be the GM casting number, if it is anything but 10125327 it isn't a Gen II LT1 or LT4 block. Only that block will mate with the reverse coolant LT1 or LT4 heads without having to do a lot of work to make them into a configuration that will mate to a Gen I block.

Bogie

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Old 11-16-2010, 06:08 PM
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it dont look good casting # 10066036 with a small tab has 576114
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Old 11-16-2010, 06:22 PM
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those would be LT1 heads, not the "Vortec" heads everyone talks about, only good for a LT1 Gen II.
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Old 11-16-2010, 06:55 PM
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Quote:
Originally Posted by chevyfreke
it dont look good casting # 10066036 with a small tab has 576114
This is a Mexico casting used a lot for the Targetmaster and Mr. Goodwrench replacement engines. It will not accept Gen I, LT1 or LT4 heads.

But they can be modified to work on older blocks, the large coolant holes on the rear portion of the heads can be welded up and a new hole drilled following a Gen I head gasket pattern. Then the heads have to be milled as the welding will pooch them a bit. An external coolant return has to be made into the front of the heads where the vapor return hole is located. You have to use the LT1 conversion to carb intake which is pricey this also reverts the distributor to the conventional rear mounted position. Then you have to fabricate a coolant return manifold. There are several ways to do this, a thermostat adapter for each head with a hose to a Y fitting to get to the radiator, One thermostat housing and a hose from the right head that then flows to the radiator is another config, this is not unlike the coolant return of the 1950's era Chrysler Hemi. The last would be similar to the preceding except the thermostat is mounted in a housing fastened to the front of the intake and connected to each head with a hose. The rear vent holes would be plugged off except perhaps for a small vent line because in conventional cooling it is necessary that the bulk of the coolant enter the block cold. As it flows from front to rear is warms. Most of the coolant then flows into the back of the head and gains more heat as it flows forward to the return. This balances the engine's heat budget by placing the coolest cylinders 1 & 2 at the front having the hottest combustion chambers. At the rear, 7 & 8 have the hottest cylinder walls but the coolest combustion chambers. I know, it's crude, but for all but heavy competition motors it works pretty well.

The cost of modifying the LT1 heads is considerable, especially if they need a valve job, by the time you're done saving money you will spend about as much as a new set of Vortecs. Guess how I know? but actually this conversion is done more frequently than you might expect.

I say expect to pay about $150 for welding and milling. This goes better if you buy a piece of 3/8ths to 1/4 thick aluminum and make plugs the welder can install rather than trying to fill that hole with bead. The coolant returns can be done simply with some stainless fittings from Precision Stainless and some heater hose to a common return with the thermostat, Morso makes some if you can't carve your own, http://www.moroso.com/catalog/catego...?catcode=26342 hers' some other solutions http://www.moroso.com/catalog/catego...?catcode=29400

So just bring money and ability, as this can be done.

Oh! The intake, that's around $350, but a set of Vortecs take a pricey intake as well.

Bogie
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Old 11-16-2010, 07:02 PM
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i would just get Vortec's and pick up a Used intake off CL or something, No messing around and way cheaper.
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Old 11-16-2010, 07:02 PM
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To add to what Bogie said, the intake bolt pattern is unique to the LT1 and LT4. Carbureted intakes from GM are available but aren't cheap.
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