Ok so back story is I bought my car about 3 years ago with a 305 with a performer intake and rv cam. It's reasonably quick with 3.73s but I wanted a little more so I bought a 350 to swap in. I don't have the time or space to build it though so it's been sitting in a shed. I honestly don't need 400hp to cruise around on a nice Saturday and have been thinking about sticking with what I have. I've been getting the tinkering bug lately though.
I have some vortec heads I bought for the 350 and am thinking about putting them on the 305 since that's something I can do with what I already have. I'll be taking care of the exhaust at the same time.
The cr with 58cc heads is 9.5:1 & the new ones are listed at 64cc but I've read they're usually closer to 62. I don't want to mill the heads in case I do end up using them on the 350. How much cr will I lose with a .015 gasket? I've heard different specs for the factory gasket but the most common is .028.
I have a q jet on the car right now and a 600 edelbrock 1405 laying around. I don't have any problems with the current carb but it really limits what intake I can use. I'd like something more performance oriented than a performer style. Maybe the summit stage 2. How will the 2 carbs compare in this application?
Any guesses how much power to expect out of this combo?
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So I ran the numbers and swapping over to 350 vortec heads of the 906/062 design is pretty much a wash on compression when using a steel shim gasket .015" and assuming 62 cc's, now if they are 64 cc then looking at .1-.2 drop in compression. Your still power ahead because of the better heads.
I did this swap on a 350 for dirt cheap, I bought two sets of vortec heads for 80 bucks, I researched both casting that what I had and found out they are the same, so I picked the cleanest set of the two.
I took the vortec heads apart and filed down the valve guides with a flat bastard for more lift clearance, I got a spring kit.
Vortec Head Spring/Retainer Kit - Straub Technologies
I hand lapped the valves in to clean up the pitted seats til they looked good. I was done with heads.
i f I was to do it again I would just file down the guides and just buy new springs for about 35 bucks and be really cheaper than the kit, being first time down the vortec road I did not know how the kit was getting it's clearance, so you could save a few bucks just doing some manual labor.
So no real money in the heads, in fact I sold the other pair on craigslist for 100 bucks.
With a little longer search you can probably find cheaper, but I saw these, less than 30 bucks for your steel shim gasket.
Felpro 7733SH1 Steel Shim Head Gasket Small Block Chevy 4 100 034 Bore 016 034 Thick | eBay
depending if you have rocker arms, if you need to buy some I got something like these for dirt cheap. 60 bucks
Chevy SBC 350 1.5 Ratio 7/16" Self Aligning Steel Roller Tip Rocker Arm Set
So now you should be able to slap the heads on and lash the valves, so this leaves for the intake which I bought a cheap 100 dollar rpm knock off at the time I found on ebay it was a display model, I did a quick search on ebay theres a 160 dollar cross wind intake that's just like I bought.
Professional Products 52028 Crosswind SB Chevy Vortec Aluminum Intake Manifold | eBay
So then I would invest in a very good carb you can later carry over to your 350, so I would get a very nice 750 holley vacuum secondary, even for your 305, your not going to kill a thing, about everyone on the planet would say go with a 600 cfm carb and 750 will kill the engine, HOGWASH, I have done several track outing thru my life and my sons 305 ran great with a 750 holley ( we went from a nice 600 holley I built for him to my old friend 750 cfm I have had for decades and his car didn't slow down one bit).
Valve covers, go find some stockers and clean them up, I got some for free from a friend who was going to toss them, so you might be able to do the same.
What the cost, not much around 350 bucks and a learning life lesson, you might be able to sell your current carbs and invest in a nicer 750 holley, you should be able to pick one up from ebay or craigslist for under 200 used- cheaper if you can rebuild them, I see fine good examples often or you can dish out about 300-350 for a new one.
Hope this helps and every part transfers over to a 350, so your just pre fitting your top end on a 305 is all.....lol
Hope this helps