Performance street SBC build

jakob stevanus

New Member
Oct 11, 2021
26
Makes sense I guess I need to be realistic with my self mostly going to be a fun street car not much strip . I think I will try that set up you said first And I'll go with your camm and lifter / spring set up .230 @ .050 is ok with those heads and springs ? .also So I can port the bowls and use The same valves ? Whats is best way to clean up valves before re install also make sure the go back in the same opening correct ?
 

G72Zed

Veteran Member
Sep 8, 2015
3,745
Canada
Looking at your pic's of the pistons and bores, to me they look like 4 eyebrow with a centred dish. If you use these, cc them to make sure what you have.

A 355 cubic inch needs 85.5cc at TDC to hit 9.5 CR, if you want 9.8 CR, the TDC CC's shrink to 82.5cc. This assumes a Zero Deck.

The typical 355 cubic inch with 64cc chambers, composition HG of 9.1cc, a 2 valve relief FT piston with 5cc, and a 1cc crevice volume you have 79.1 cc A TDC, that's 10.17 CR.

Just make sure you can get everything done for the 3,500-4,000 budget, and spend the money where it counts.
 

jakob stevanus

New Member
Oct 11, 2021
26
From what I read about my heads 193 swirl they are 64 cc SO . I think the pistons are 12cc from what I can see online so that would bring me to 76cc plus HG ? Average 9 cc ? So 85 cc total ? So I would be at 9.5 now ?
 

jeff swisher

Veteran Member
Apr 26, 2018
1,933
Yukon Oklahoma
You need to check retainer to valve guide clearance and make sure they will not hit.
Some gm heads will go .650" lift without contact and others barely make it to .450" lift.

You will be money ahead and way smarter if you buy that How to port heads book.
It covers all that stuff.
Before I ever built my first SBC I researched it for 2 years.
No internet then.
I started with the 268H cam and still use that grind today.
It just flat works well.

I Clean the valves on a bench grinder that has a wire wheel on it.
Then paint thinner.
I do not keep all the valves in the same hole ..you can if you wish.
I will many times rob valves from other heads and use them.

I do like to use Viton valve stem seals and remove the umbrella oil shedders to lighten the spring retainer area.

Many times the retainers will hit the valve seal at max lift and on stock GM retainers I have ground them down to get more clearance.
I do that on a bench grinder on the side of a new stone.
I then polish the scratches out.

That is when you have a lot of time and not much money or are just feeling like a tight wad.
35-60 bucks will get you new retainers.

230 @ .050 will work with any head if it has the clearance for it.
Always check never assume.
Buy the book it will be money well spent and it has tons of pictures to let you know exactly what he is talking about.
That literature in it will work with all heads not just the SBC.
 

jakob stevanus

New Member
Oct 11, 2021
26
Ok I will buy the book before I get started thank you . When using the old valves in different ports they need to be lapped again for thee hole correct ?
 

biker

Veteran Member
Gold Member
Dec 7, 2014
4,687
Canada
Ok I will buy the book before I get started thank you . When using the old valves in different ports they need to be lapped again for thee hole correct ?
Always a great idea to lap the valves in when you reinstall used stuff. Light compound, suction cup stick for lapping. It's fun and you learn lots. It will reveal any valve seating issues, and correct any very minor ones.
 

G72Zed

Veteran Member
Sep 8, 2015
3,745
Canada
From what I read about my heads 193 swirl they are 64 cc SO . I think the pistons are 12cc from what I can see online so that would bring me to 76cc plus HG ? Average 9 cc ? So 85 cc total ? So I would be at 9.5 now ?

Well,yes, your math looks good, but I have seen heads 1-3 cc bigger, sometimes the outboard or inboard ones vary, and if the pistons are in the hole, you could be in the low 9’s for compression. If the cam you use needs more Static CR than that, and your low on CR, it will be lacking power, tq, throttle response and leaving mpg on the table.

If you go aluminium heads, you Need more CR than Iron.
 

jakob stevanus

New Member
Oct 11, 2021
26
Makes sense. I would like higher. I will most likely do new flat tops pistons with like - 7cc to keep cr up . Thank you .
 

hd_cat

Veteran Member
Sep 6, 2013
126
United States
Hi I have a 70s 350sbc I am swapping in my 78 Camaro for the current 305. It is a z28 with 4 speed t10 and 3.73 posi rear end . Looking for advice on pistons , heads and cam looking to make high 300s in hp and good driver aswell . Maybee occasionally a track day . O will be sending block to machine shop to be bored .030 and just. Need to decide on parts I also have airgap performer for it and street Demon 650

Thank you .
A good example would be to model the shortblock after a '71 LT-1 10:1 Compression Forged Pistons, Steel Crank, Steel Rods (Original - beams polished, shotpeened, magnafluxed, resized) or I-Beam or H-Beam Rods 6.0" length, Head studs, Main Studs, a modern Hydraulic Roller Cam with 280 - 300 duration and 0.500 - 0.560" lift. Higher compression with Aluminum Heads 11: 1 - 11.5: 1, same recommendations for a 383 stroker, you'll be amazed at the difference over the 305. I have a 377 with similar specs, and had a 350 with the Comp XE274 Cam, both were very good combinations
 

Steve74

Steve 74
Dec 20, 2019
9
Hi I have a 70s 350sbc I am swapping in my 78 Camaro for the current 305. It is a z28 with 4 speed t10 and 3.73 posi rear end . Looking for advice on pistons , heads and cam looking to make high 300s in hp and good driver aswell . Maybee occasionally a track day . O will be sending block to machine shop to be bored .030 and just. Need to decide on parts I also have airgap performer for it and street Demon 650

Thank you .
Just finished a build on my 1974 sbc 350. Bored .020 NPR cast aluminum pistons. Decided to lose weight and gain power using Brodix IK180 64cc Aluminum heads. Used the 262XE comp cam 218 / 224 @.50 right about 460 [email protected] .50. (L82 cam) Easy 350HP. Runs beautiful. I believe I ended up with about 9.8 compression. Runs on 91 octane pump gas.
 




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