many sbc questions:)
daveshapellSVT
09-12-2007, 07:59 PM
hey guys i'm in need of some assistance. I have a sbc 350 thats rebuild and .030 over. right now it has a real mild cam and some stock chevy heads. I'm having trouble figuring out how to pick a head,cam,rocker arm combo. Money is a real problem being married and all so i have decided to deffinately go with the cast iron 64cc vortec heads, but now i'm stumped with a few questions....
1) what profile cam should i get to maximize performance out of this head? the springs on the head are good for .475 lift.. does that mean i go with a cam with lift specs around .460-.475?
2) theres a hydralic flat tappet in the engine now. does that mean i'm limmitted to a hydralic flat tappet cam?
3) do i need to replace the lifters and pushrods or will the ones i have already work? if i need to get them new do i just get them the same size as the ones i have or do i need different sizes for the different cam and heads? on the same note will i need a different timing chain or distributor or is all that stuff usable?
4) whats the deal with rocker arm ratio's? i know that if you go from a 1.5 to a 1.6 it raises lift, is 1.5 like the stock ratio or something. my real question is if i go with a cam thats rated at like .475 lift would a 1.5 rocker raise it further?
Theres a lot i need to learn about small blocks and hopefully you guys can help me out. i hope to have the new combo in by spring.
1) what profile cam should i get to maximize performance out of this head? the springs on the head are good for .475 lift.. does that mean i go with a cam with lift specs around .460-.475?
2) theres a hydralic flat tappet in the engine now. does that mean i'm limmitted to a hydralic flat tappet cam?
3) do i need to replace the lifters and pushrods or will the ones i have already work? if i need to get them new do i just get them the same size as the ones i have or do i need different sizes for the different cam and heads? on the same note will i need a different timing chain or distributor or is all that stuff usable?
4) whats the deal with rocker arm ratio's? i know that if you go from a 1.5 to a 1.6 it raises lift, is 1.5 like the stock ratio or something. my real question is if i go with a cam thats rated at like .475 lift would a 1.5 rocker raise it further?
Theres a lot i need to learn about small blocks and hopefully you guys can help me out. i hope to have the new combo in by spring.
poormillionaire2
09-14-2007, 08:52 AM
hey guys i'm in need of some assistance. I have a sbc 350 thats rebuild and .030 over. right now it has a real mild cam and some stock chevy heads. I'm having trouble figuring out how to pick a head,cam,rocker arm combo. Money is a real problem being married and all so i have decided to deffinately go with the cast iron 64cc vortec heads, but now i'm stumped with a few questions....
1) what profile cam should i get to maximize performance out of this head? the springs on the head are good for .475 lift.. does that mean i go with a cam with lift specs around .460-.475?
2) theres a hydralic flat tappet in the engine now. does that mean i'm limmitted to a hydralic flat tappet cam?
3) do i need to replace the lifters and pushrods or will the ones i have already work? if i need to get them new do i just get them the same size as the ones i have or do i need different sizes for the different cam and heads? on the same note will i need a different timing chain or distributor or is all that stuff usable?
4) whats the deal with rocker arm ratio's? i know that if you go from a 1.5 to a 1.6 it raises lift, is 1.5 like the stock ratio or something. my real question is if i go with a cam thats rated at like .475 lift would a 1.5 rocker raise it further?
Theres a lot i need to learn about small blocks and hopefully you guys can help me out. i hope to have the new combo in by spring.
Ok, I think I can answer some of these, just not as well as some of the other guys.
1) To maximize performance out of the heads and the cam, you should try to get the heads port-matched to the flow characteristics of the cam. With that said, there are companies out there that sell heads/cam packages that work well together.
And you can always change the springs on the heads if you want more lift.
2) Don't know.
3) Depending on how old the parts are, you may want to go ahead and replace the lifters. Not everyone does that with the lifters though. Pushrods are almost always a yes when changing the cam. You'll most likely want to get hardened pushrods so they don't snap with the increase lift and stress of a new cam. Depending on the cam also, you may need to get different length pushrods than the ones you already have. The base circle as well as the heads (I think) affect what length pushrods you need.
As far as the timing chain, while you have all that stuff off, you might as well replace it with a new one. Cheap insurance I think.
4) Yes, higher ratio rockers change the gross lift of the cam. I believe on the SBC's, 1.5 is the stock ratio. Just be careful when increasing the lift that you still have proper clearance between the valves and the pistons.
As far as overall lift and what rocker to use, you'll need to know what type of rocker the manufacturer used to determine the advertised lift on the cam. Seeing as your stock rockers are 1.5, I would assume that the manufacturer did the same also. So, that cam with the rated .475" of lift I would assume is with a 1.5rr. If you want to know the lift with a different ratio, say, 1.6, you'll have to divide the lift by the 1.5 ratio, then multiply that anser by the new 1.6.
1) what profile cam should i get to maximize performance out of this head? the springs on the head are good for .475 lift.. does that mean i go with a cam with lift specs around .460-.475?
2) theres a hydralic flat tappet in the engine now. does that mean i'm limmitted to a hydralic flat tappet cam?
3) do i need to replace the lifters and pushrods or will the ones i have already work? if i need to get them new do i just get them the same size as the ones i have or do i need different sizes for the different cam and heads? on the same note will i need a different timing chain or distributor or is all that stuff usable?
4) whats the deal with rocker arm ratio's? i know that if you go from a 1.5 to a 1.6 it raises lift, is 1.5 like the stock ratio or something. my real question is if i go with a cam thats rated at like .475 lift would a 1.5 rocker raise it further?
Theres a lot i need to learn about small blocks and hopefully you guys can help me out. i hope to have the new combo in by spring.
Ok, I think I can answer some of these, just not as well as some of the other guys.
1) To maximize performance out of the heads and the cam, you should try to get the heads port-matched to the flow characteristics of the cam. With that said, there are companies out there that sell heads/cam packages that work well together.
And you can always change the springs on the heads if you want more lift.
2) Don't know.
3) Depending on how old the parts are, you may want to go ahead and replace the lifters. Not everyone does that with the lifters though. Pushrods are almost always a yes when changing the cam. You'll most likely want to get hardened pushrods so they don't snap with the increase lift and stress of a new cam. Depending on the cam also, you may need to get different length pushrods than the ones you already have. The base circle as well as the heads (I think) affect what length pushrods you need.
As far as the timing chain, while you have all that stuff off, you might as well replace it with a new one. Cheap insurance I think.
4) Yes, higher ratio rockers change the gross lift of the cam. I believe on the SBC's, 1.5 is the stock ratio. Just be careful when increasing the lift that you still have proper clearance between the valves and the pistons.
As far as overall lift and what rocker to use, you'll need to know what type of rocker the manufacturer used to determine the advertised lift on the cam. Seeing as your stock rockers are 1.5, I would assume that the manufacturer did the same also. So, that cam with the rated .475" of lift I would assume is with a 1.5rr. If you want to know the lift with a different ratio, say, 1.6, you'll have to divide the lift by the 1.5 ratio, then multiply that anser by the new 1.6.
Morley
09-14-2007, 12:13 PM
1) If you go to Vortec heads you will have to get a different intake manifold. The bolt pattern is different for the intake on the Vortec heads compared to non-vortec heads.
If you are intent on getting different heads, try Summit's own brand of aluminum heads.
If you just get your stock heads ported and port matched to your intake manifold, you'll be fine. Also get the pressed in rocker studs either pinned or changed to screw in type.
Then check Summit for one of Lunati's cam kits and talk to their tech line to see what cam they recommend for your setup.
2) If you have a flat tappet cam now and are budget limited, then yes, you are limited to a flat tappet cam.
3) You MUST replace the lifters if you replace the cam or you WILL have catastrophic failure of the cam/lifters.
To get the right pushrod you need to get one solid lifter (any auto parts store will have them for about $5) and a pushrod length checker. This is a pushrod that screws apart in the center.
Then go to Crane cam's web site and they have a nice tutorial on how to check the pushrod length. Get the pushrods indicated (get hardened rods for use with guideplates)
4) get a set of "better" rocker arms, Crane and others sell a food roller tip rocker for about the same price as stock ones andthey are mfg'ed to closer tolerances and come in a 1.52 lift. Stick with 1.52 lift if your heads are not able to support very high lift cams.(over .500")
If you are intent on getting different heads, try Summit's own brand of aluminum heads.
If you just get your stock heads ported and port matched to your intake manifold, you'll be fine. Also get the pressed in rocker studs either pinned or changed to screw in type.
Then check Summit for one of Lunati's cam kits and talk to their tech line to see what cam they recommend for your setup.
2) If you have a flat tappet cam now and are budget limited, then yes, you are limited to a flat tappet cam.
3) You MUST replace the lifters if you replace the cam or you WILL have catastrophic failure of the cam/lifters.
To get the right pushrod you need to get one solid lifter (any auto parts store will have them for about $5) and a pushrod length checker. This is a pushrod that screws apart in the center.
Then go to Crane cam's web site and they have a nice tutorial on how to check the pushrod length. Get the pushrods indicated (get hardened rods for use with guideplates)
4) get a set of "better" rocker arms, Crane and others sell a food roller tip rocker for about the same price as stock ones andthey are mfg'ed to closer tolerances and come in a 1.52 lift. Stick with 1.52 lift if your heads are not able to support very high lift cams.(over .500")
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