4.8 to 5.3 conversion cam question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dwcsr · 09-29-2010, 10:59 PM

I have a 4.8 I'm making a 5.3. I have the floating pin flat top pistons, 862 heads and a cam with .467/.479 lift from an LS1. The stock lift is .457/.466.

The questions I have are do I need to use other than the stock 862 valve springs and do I need to be worried about the piston hitting the valve with the flat tops.

My thinking was its almost stock and should be no issue but I'm not up on LSx motors

68GMCCustom · 09-29-2010, 11:38 PM

...now I thought the bore of the 4.8L and 5.3L was the same...and that the stroke was different.....

dwcsr · 09-30-2010, 12:09 AM

Quote:

Originally Posted by 68GMCCustom

...now I thought the bore of the 4.8L and 5.3L was the same...and that the stroke was different.....

correct, I should have said I changed the crank, rods and piston to make it a 5.3

Super73 · 09-30-2010, 01:14 AM

If you have 5.3 rods and pistons you should be fine. If you have 4.8 rods with 5.3 pistons, I can't answer your question as I don't know the rod length...

dwcsr · 09-30-2010, 02:22 AM

Quote:

Originally Posted by Super73

If you have 5.3 rods and pistons you should be fine. If you have 4.8 rods with 5.3 pistons, I can't answer your question as I don't know the rod length...

I purchased a 5.3 crank, rods and flatop pistons. I thought it would be ok but didn't know for sure.

blazerboy72 · 10-07-2010, 09:14 PM

Do you have 4.8 rods and pistons too? The 5.3HO is really just a 4.8 with a 5.3/6.0 crank, if you want a little extra compression.

09-29-2010, 10:59 PM	#1
dwcsr Hollister Road Co. Join Date: Apr 2005 Location: Houston Posts: 6,131	4.8 to 5.3 conversion cam question I have a 4.8 I'm making a 5.3. I have the floating pin flat top pistons, 862 heads and a cam with .467/.479 lift from an LS1. The stock lift is .457/.466. The questions I have are do I need to use other than the stock 862 valve springs and do I need to be worried about the piston hitting the valve with the flat tops. My thinking was its almost stock and should be no issue but I'm not up on LSx motors

09-29-2010, 11:38 PM	#2
68GMCCustom Truck and auto performance nut Join Date: Feb 2007 Location: McKinney,Texas Posts: 3,848	Re: 4.8 to 5.3 conversion cam question ...now I thought the bore of the 4.8L and 5.3L was the same...and that the stroke was different..... __________________ Kurt - '68 GMC short step - NIB '09 LY6 6.0L crate motor w/mods, NIB '12 crate 4L85e w/billet 3k stall Circle D, 3.73 posi 12 bolt, DynaTech f-swap headers, 3/4 drop, handling mods, etc. - my toy '72 Chevy LWB C-10 Highlander - 350/350 ps/pb/tilt/ac - not original but close '06 Chevy TrailBlazerSS - LS2/4L70e - little black hot rod SUV - my DD '18 Kia Sorento - wife's econo-driver '95 Chevy S10 - reg cab shortbed, LS, 4.3, auto... my '68's powertrain and chassis build -links broken A surprise phase - carb to efi -links broken

09-30-2010, 01:14 AM	#4
Super73 Registered User Join Date: Nov 2007 Location: Bay Area, Ca Posts: 2,841	Re: 4.8 to 5.3 conversion cam question If you have 5.3 rods and pistons you should be fine. If you have 4.8 rods with 5.3 pistons, I can't answer your question as I don't know the rod length... __________________ ------Motor---------------Bottle 60'---1.53---------------1.41 1/8---6.58 @ 105.92----5.87 @ 118.41 1/4---10.38 @ 126.97----9.24 @ 142.49

10-07-2010, 09:14 PM	#6
blazerboy72 Senior Member Join Date: Mar 2002 Location: Temple, Ga Posts: 854	Re: 4.8 to 5.3 conversion cam question Do you have 4.8 rods and pistons too? The 5.3HO is really just a 4.8 with a 5.3/6.0 crank, if you want a little extra compression.

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