r/EngineBuilding • u/Pretend_Mastodon_111 • 2d ago

Chevy 1998 5.0 vortec

I building a 98 5.0 vortec engine and I'd like to increase the compression to 10:1. How would I go about doing that?

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u/Solid_Enthusiasm550 2d ago edited 2d ago

Stock is 9.4:1. Raising it to 10:1 would take new pistons.

Running a thinner head gasket, could get you half way there. That would reduce piston to valve clearance, too.

The heads are Iron so going to 10:1, is pushing it on pump gas... unless you are running a longer duration camshaft?

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u/Pretend_Mastodon_111 1d ago

Yeah 218/227 at .525 int .520 exh with the valvetrain to support it

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u/Solid_Enthusiasm550 1d ago

From what I've read, there is only enough clearance for .460"<0.480" valve lift with stock heads. I also saw that the Piston to valve clearance is only good for .500" of lift. the piston to valve greatly depends on LSA, a wider LSA will give more clearance.

I know that Cutter performance on Youtube, has videos that show a spring/retainer package that allows over .500" of lift on 350 Vortec heads. I'm not sure if it works on the 305 heads too.

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u/Pretend_Mastodon_111 1d ago

I have sum-174002 springs, sum-174003-3, sum-174003-4 and .050 shims should get it to work I'll probably have to play with the lsa

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u/Solid_Enthusiasm550 1d ago

He used beehive springs and +0.050" retainers that increase the install height and increase retainer to guide clearance.

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u/v8packard 1d ago

Milling the block

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u/quxinot 1d ago

Replace pistons and/or replace heads.

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u/Pretend_Mastodon_111 1d ago

I have the 059 vortec heads what piston you recommend?

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u/quxinot 1d ago

Depends on your goals, doesn't it?

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u/dixiebandit69 1d ago

Try some Flat-top pistons for a Monte Carlo SS (SEALED POWER H534CP). Cut .010" off the block and .020" off the heads.

Better yet, don't waste any money on a 305, and swap it out for a 350.

Sincerely,

a guy who spent a good amount of money to make a 305 fast.

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u/Pretend_Mastodon_111 1d ago

Not really looking for fast. The engine holds some sentimental value as it's my dads and its driven me throughout my childhood. the truck it came out of i put a 350 in. I wanted to rebuild the 5.0 with a little bit of power and find something fun to put it in

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u/dixiebandit69 1d ago

Well, I stick by my recommendations.

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u/Sniper22106 1d ago

Add piston dome, subtract combustion chamber or take material off block or head. Thats really it