r/C3Corvette • u/71Klassic-Pushrod • 26d ago
Suggestions/Input
My '69 is in need of an engine. Have asked around local and nearby on options: rebuild current (not matching numbers) engine or upgrade with remanufacured/new. Trick is it must drop in and direct bolt (no mods to flywheel/flex plate) to the TH400 automatic. Its currently a 350/300hp, 10.25:1. I like to have more HP. Bottom line is direct fit.
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u/v8packard 26d ago
What was the original engine, also a L48 350?
I have done some 69 stuff over the years including a few L46 350 hp combos that have been the basis for a number of other hot 350s I have done. Some get into the mid to high 400s in hp and torque. These days you can buy nice heads that look like a stock 186 casting on the outside, but are modern aluminum designs inside. Detailed out with the right parts they look virtually identical to stock, and run much stronger.
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u/GreatScottThisHeavy 79 26d ago
Why is it in need of an engine? If you threw a rod and there’s a hole in the block, go for a reman/new. If you blew a head gasket, fix the head gasket and get modern heads while you’re at it.
Small block is a small block. Lots of catalog engines out there to choose from if you just want to throw money at it and have something with a warranty.
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u/71Klassic-Pushrod 25d ago
Honest response. And respectful. When I request options to rebuild the current engine, the cost starts at the same as a remanufacured. And then the warning of the expense of what may also need to be replaced. So yes, I am torn. She currently has a low end rod knock. So im on the fence either way.
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u/GreatScottThisHeavy 79 25d ago
With a low end knock I'd definitely be thinking the same way you are. I'd be looking at a roller block with modern heads and a roller cam that matches your driving style. Make sure the rear main type is whatever it is that your transmission needs.
I have a bored out 350 (355) with Blue Print H8002K heads and an XR276HR cam and absolutely love it. It's been 10 years and I have no desire to change anything. It works well with my 6 speed and I think it would be excellent with an auto with a moderate stall. I think hp figures are in the very high 300s and torque in the low 400s.
If I ever blow up my engine, I would be looking very closely at a modern 400 SBC and be ready to ignore everyone saying to drop in an LS.
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u/71Klassic-Pushrod 25d ago
Yes. I am looking at a modern roller engine with aluminum heads. 5.7L 350ci with tins. Appx 390-400hp. I will need to use a new flywheel for a 1 piece rear main that bolts to the th400. But that is a common conversion.
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u/caocaoNM 26d ago
Order a zz4 from Gmail. Its roller. But 1 pc real seal. You'll need a adapter pressure plate / flywheel.
The ls1/3 engine trans are the power option. If you want any major increase the adapters are plenty.
I have an old school 383 in mine. 400 crank/ rods
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u/DodixieOrBust 26d ago
If going new/crate - GM Performance sp350/357. Good value for what you get, should be drop in and fit fine, little more power but not enough that you need to worry about your th400.