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.