Need sbc engine help internals
Thread Starter
Instructor
Joined: Jun 2008
Posts: 142
Likes: 7
From: Syracuse NY
Need sbc engine help internals
I want to rebuild a 400sbc and will most likely need new crank/pistons/rods. And probably re-work vortec heads or spring for aluminum but I have questions I can't find answers to so I'll reach out to anyone who can help me...
1- which is better and why?
- small chamber head, dish piston or...
- big chamber head flat top
I've read the combustion should happen in the block then some places say the heads idk what to believe. I want 10.5-11 compression n/a 93 octane
2- what's the limits of compression ratio on 93 octane I've read using vortec heads allow a higher ration due to the heart shaped chambers. Is this true? I have vortec heads currently on a stock 400 and run 93 with a very advanced timing with no detonation. So what's the highest. Umber I can safely go? Are aluminum better? What are my
Options? I would like more info and can't find strait answers online
1- which is better and why?
- small chamber head, dish piston or...
- big chamber head flat top
I've read the combustion should happen in the block then some places say the heads idk what to believe. I want 10.5-11 compression n/a 93 octane
2- what's the limits of compression ratio on 93 octane I've read using vortec heads allow a higher ration due to the heart shaped chambers. Is this true? I have vortec heads currently on a stock 400 and run 93 with a very advanced timing with no detonation. So what's the highest. Umber I can safely go? Are aluminum better? What are my
Options? I would like more info and can't find strait answers online
Melting Slicks
Joined: May 2012
Posts: 2,192
Likes: 343
From: Allenton Wisconsin
For my 434 sbc build the engine got a set of Dart Pro 1s 64cc with Mahle flat top pistons. Current timing is 14 degrees BTC at idle and 34 all in. The engine runs on premium 93 octane and sometimes on the midgrade. No detonation problems. Yes aluminum heads are better [Dart, AFR, Profiler] check out their websites, just match the cam to the heads and if you are replacing the rods go with the 6 inch. T
Thread Starter
Instructor
Joined: Jun 2008
Posts: 142
Likes: 7
From: Syracuse NY
For my 434 sbc build the engine got a set of Dart Pro 1s 64cc with Mahle flat top pistons. Current timing is 14 degrees BTC at idle and 34 all in. The engine runs on premium 93 octane and sometimes on the midgrade. No detonation problems. Yes aluminum heads are better [Dart, AFR, Profiler] check out their websites, just match the cam to the heads and if you are replacing the rods go with the 6 inch. T
Do you know your final compression ratio?
What made you choose flat tops and 64cc?
Are all alumnium heads generally better or just name brand?
Melting Slicks
Joined: May 2012
Posts: 2,192
Likes: 343
From: Allenton Wisconsin
My short block was professionally built by C&S Performance, the Dart heads came off my 350 because I needed to lower the compression on that engine for a super charger and installed AFR 74cc heads. The 434 in the 69 coupe is a street car only and it needed to run on pump gas. I would have to find the build sheet for exact compression ratio, but it's around 10.5 to 1. C&S decided which pistons to use to come up with final ratio and they are flush with the block deck when up. Brand name heads have done the research and development. Both Dart and AFR heads preform flawlessly for me and I've heard nothing but good reports on the Profilers. C&S set up both sets of heads up with the proper springs for the cams that are being used and also went through the valves on brand new heads. The 350 in the 6t8 with the Dart heads with a solid roller cam with around 5.70 lift hit 411 RWHP on the dyno [before S/C] with very nice street manners. T
Thread Starter
Instructor
Joined: Jun 2008
Posts: 142
Likes: 7
From: Syracuse NY
That's why I keep trying to find better info on the actual technical side of things because I've heard certain head/piston combs with high compression totally fine on pump gas and then different set ups with lower ratios needing to run on race gas so I'm really trying to get some strait answers on the science side of everything so I can decide what combos to save up and budget for.
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
I want to rebuild a 400sbc and will most likely need new crank/pistons/rods. And probably re-work vortec heads or spring for aluminum but I have questions I can't find answers to so I'll reach out to anyone who can help me...
1- which is better and why?
- small chamber head, dish piston or...
- big chamber head flat top
I've read the combustion should happen in the block then some places say the heads idk what to believe. I want 10.5-11 compression n/a 93 octane
2- what's the limits of compression ratio on 93 octane I've read using vortec heads allow a higher ration due to the heart shaped chambers. Is this true? I have vortec heads currently on a stock 400 and run 93 with a very advanced timing with no detonation. So what's the highest. Umber I can safely go? Are aluminum better? What are my
Options? I would like more info and can't find strait answers online
1- which is better and why?
- small chamber head, dish piston or...
- big chamber head flat top
I've read the combustion should happen in the block then some places say the heads idk what to believe. I want 10.5-11 compression n/a 93 octane
2- what's the limits of compression ratio on 93 octane I've read using vortec heads allow a higher ration due to the heart shaped chambers. Is this true? I have vortec heads currently on a stock 400 and run 93 with a very advanced timing with no detonation. So what's the highest. Umber I can safely go? Are aluminum better? What are my
Options? I would like more info and can't find strait answers online
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
I have 72cc Dart heads and flattop KB pistons in my 406......
The Valve relief I believe was -4cc and it works out to 10.5 to 1 with zero deck.....
With a 244@.050 cam.....it runs great on 93.
Timing is 20 degrees initial, 34 total.
Current Dart heads have a fast burn chamber and the Aluminum helps as well.......
10.5 to 1 is easy.
Jebby
The Valve relief I believe was -4cc and it works out to 10.5 to 1 with zero deck.....
With a 244@.050 cam.....it runs great on 93.
Timing is 20 degrees initial, 34 total.
Current Dart heads have a fast burn chamber and the Aluminum helps as well.......
10.5 to 1 is easy.
Jebby
Last edited by Jebbysan; Sep 3, 2017 at 06:33 PM.
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Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Thank you Bob....I agree with what Mako says a lot as well.....
Just as an FYI....I run an Eagle cast steel crank and 5.7 SIR Rods in my combo....I had the pistons so my choice was made....
A 6" rod will hold the piston near TDC longer and the rod angle is not as severe....but I knew my RPM threshold and my oval track friends have proven these parts to be strong.....they run 4000 to 5500 and mid range is the order of the day....
In fact my whole engine is a Canadian Modified dirt track engine....torque as flat as Kansas....not stressed at all....
A ported Team G and flowed 785 Holley round this off....the heads are 200cc.....instant, brutal torque....over 450 ft. lbs available from 3500 to 5500 RPM.....
The stock 72' drivetrain loves it....M20 and 3:36 gears.....ton-o-fun
Jebby
Just as an FYI....I run an Eagle cast steel crank and 5.7 SIR Rods in my combo....I had the pistons so my choice was made....
A 6" rod will hold the piston near TDC longer and the rod angle is not as severe....but I knew my RPM threshold and my oval track friends have proven these parts to be strong.....they run 4000 to 5500 and mid range is the order of the day....
In fact my whole engine is a Canadian Modified dirt track engine....torque as flat as Kansas....not stressed at all....
A ported Team G and flowed 785 Holley round this off....the heads are 200cc.....instant, brutal torque....over 450 ft. lbs available from 3500 to 5500 RPM.....
The stock 72' drivetrain loves it....M20 and 3:36 gears.....ton-o-fun
Jebby