400 HP bulletproof short block
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From: Central Cal.
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Last edited by ETriggs; Dec 7, 2021 at 12:39 AM.
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Keep in mind the Gen III 5.3L engines these heads came on had 8cc dished pistons and had a 9.6:1 CR. If you were to use flat tops it would go up to 10.47:1.
Last edited by G Atsma; Dec 7, 2021 at 10:35 AM.
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You then want a totally stock Gen III 5.3. It will have the 191/190 cam, 862/706 heads, and dished pistons.
The Gen IV 5.3's have 243/799 heads, flat tops, and 9.9:1 compression.
Those with DOD/AFM have a copy of the LQ9/late LQ4 cam. Those without (LH8, LH9) have the same grind as Gen III.
The Gen IV 5.3's have 243/799 heads, flat tops, and 9.9:1 compression.
Those with DOD/AFM have a copy of the LQ9/late LQ4 cam. Those without (LH8, LH9) have the same grind as Gen III.
OP, your Gen4 block can be bored to 3.905 making it a 5.7 only better than an LS1 and that’ll meet your modest HP goals much easier without laying out money for a 6.0 block. You could then use lower priced Wiseco forged Pro Tru pistons if you’re looking for something more than a flat top.lots of options out there.
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If its going to be Naturally Aspirated then I would sell the 5.3 and get a 6.0L (LQ4, LQ9, LY6, L96). The 6.0L would get you that power level easily and will give you room to grow if you decide you want more power down the road. My L96 that I have in my 1965 Cutlass came stock with 360hp/380tq. Install a decent set of heads (243, 799, 823), truck intake manifold, cam, springs, pushrods, headers and you are GTG! If you want to increase the compression install some flat tops and a thinner head gasket (just check PTV clearance with your choice of cam).
Here is what I have in my 1965 Cutlass
Engine: L96 Gen IV 6.0L (replaced the dish pistons with some Mahle Flat Top Pistons)
Cam: Cam Motion 224/236 .595/.595 112 +3
Heads: 823's with BTR dual valve spring kit and BTR .040 head gaskets
Intake: Truck manifold
Headers: Hooker Long Tubes
ECU: Holley Terminator X Max
Trans: 4L80 with FTI 3200 stall
Here is what I have in my 1965 Cutlass
Engine: L96 Gen IV 6.0L (replaced the dish pistons with some Mahle Flat Top Pistons)
Cam: Cam Motion 224/236 .595/.595 112 +3
Heads: 823's with BTR dual valve spring kit and BTR .040 head gaskets
Intake: Truck manifold
Headers: Hooker Long Tubes
ECU: Holley Terminator X Max
Trans: 4L80 with FTI 3200 stall
Last edited by grinder11; Dec 7, 2021 at 11:58 AM.
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Verdad Gallardo TECH Senior Member
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From: Central Cal.
OP, your Gen4 block can be bored to 3.905 making it a 5.7 only better than an LS1 and that’ll meet your modest HP goals much easier without laying out money for a 6.0 block. You could then use lower priced Wiseco forged Pro Tru pistons if you’re looking for something more than a flat top.lots of options out there.
That IS good news for those needing something to replace the now-getting-rare LS1/LS6 aluminum blocks. Only difference is minor, moving the knock sensors to the side of the block.
The aluminum Gen IV 5.3 can be bored that much? Wasn't aware of that (never asked either... lol).
That IS good news for those needing something to replace the now-getting-rare LS1/LS6 aluminum blocks. Only difference is minor, moving the knock sensors to the side of the block.
That IS good news for those needing something to replace the now-getting-rare LS1/LS6 aluminum blocks. Only difference is minor, moving the knock sensors to the side of the block.
Last edited by 64post; Dec 21, 2021 at 01:58 PM.
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Good news for C5 Vette owners who don't feel like going to a 6.0 or 6.2, and don't need an iron block adding 100# extra to their front end. Messes up the handling... donchaknow... lol
A stock short block is more than enough. But the advantage of a stock short block is it was not assembled by you. Now that you took it apart you might as well do whatever you want. If you want the best odds of success for a cruiser then buy factory GM short block.
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Teching In
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I didn’t pull apart, only bought the bare block already cleaned, honed, and new plugs/cam bearings installed. I’m not interested in using engines others build, only the engines I build. If it works great, I’m proud. If it conks out, I have no one to blame but myself.
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Finally getting to the point of building the engine. Had a bunch of other projects pop up that took priority. My local machine shop that does my work has a balanced crank, rods, flattop pistons, and rings and bearings. Should be ready just after Christmas. The path this motor is gonna take is in my 57 Chevy. It’s a 4 door hardtop set up for the occasional cruise and daily driver reliability. It has a 66 327 set up like a 350hp out of a 66 Corvette right now but that will come out and go in a future project (68 Camaro).
Plan: AFM delete kit, 799 or 706 heads, and this cam: https://gwatneyperformance.com/produ...-3l-6-0l-6-2l/
I know the compression ratio will be up there, I already run 93 octane in the 327 (definitely overkill at 9:1 compression) but it’s good stuff.
Question, for the better low end torque and longevity, should I go 799 or 706 heads?
Plan: AFM delete kit, 799 or 706 heads, and this cam: https://gwatneyperformance.com/produ...-3l-6-0l-6-2l/
I know the compression ratio will be up there, I already run 93 octane in the 327 (definitely overkill at 9:1 compression) but it’s good stuff.
Question, for the better low end torque and longevity, should I go 799 or 706 heads?
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i don't know of any head rebuilders, but I would bet that the problem Castech heads would have been discovered by now, hopefully.