[Sayiwont38]

I'm building a sbc 406 and I have a few questions. My goal is a streetable strip car. I have gm 2.02 fast burn heads 4cc domed pistions. Currently I have a comp .540 lift cam. I bought the motor off a buddy and needs assembled. My question is 1... How much compression will this make and 2.... Cam choice....the head has comp 410-16 spring as of now. The motor has been machined line bored ECT. I'm thinkinh of running somewhere around a 3000 stall on a built th350 trans with 390 gears. Any help would be appreciated.

 

[RifRaf]

Your going to need to provide a little more information before calculating accurate compression ration (cylinder head combustion chamber volume... 62cc?, deck clearance, and compressed head gasket thickness).
But my guess is your going to be about 13:1 compression ratio with your setup.

You may want to consider a "dished" piston with your selected heads. You might have too much compression to run on 93 octane pump gas. I run a 18cc "D" dished piston on my 400 with 64cc heads for a 10:1 compression ratio. No problems running pump gas.

A 72cc head is going to get you down to about 11.6:1 compression ratio with your 4cc domed pistons. That might be doable with high octane pump gas and aluminum heads (you could always retard your timing a little... if needed)

See the link below. It is a compression calculator on the Summit Racing web site. It is pretty easy to use. Just click on the link and scroll down until you see the calculator. Fill in the requested info and click on "Calculate".
https://www.summitracing.com/newsandevents/calcsandtools/compression-calculator

If you are purchasing an "off the shelf" torque convertor, the advertised stall speed is based on the torque of a mild small block chevy. If you were to put an "off the shelf" 3000 stall torque convertor behind your 406, your true stall speed is going to probably be higher.

I previously had an "off the shelf" 3000 stall 10" torque convertor behind my 400 small block and I hated it. It felt mushy from a start during normal driving and never felt that tight.

I recommend contacting Edge Racing Converters and talk to them about your goals (see link below - for a turbo 350 trans). I now have a custom built Street Edge with a 2800 stall behind my 400 and could not be any happier! Feels like a stock converter under normal driving... but you get the stall when you mash the gas.
http://www.edgeracingconverters.com/th350-c-12_15/

 

[Deeznuts]

How much will the car be raced?

That will determine alot. For a car that is primarily a race car that will verry occasionally drive to a local car show, or out to dinner etc... you can run alot more stall speed and tolerate it. Same with compression if you are willing to run race gas.

I am a big fan of getting a converter built to your specific combination. Off the shelf converters give up alot of et reduction at the drag strip, they are typically very inefficient and are just not great on the street either since they are 99% of the time built to a different combination than yours.

 

[Sayiwont38]

The heads are 62cc chamber and were probably going to use a .050 or .070 head gasket to try and lower the compression a bit. Im Trying to avoid having to buy a different set of pistions and selling the ones I have.

 

[Sayiwont38]

Its going to primarily a race car but will goto a car show or dinner like you said. It will not be a daily driver.

 

[Sayiwont38]

Sorry but I forgot to mention we plan on running this motor on E85

 

[Deeznuts]

Do the compression calculations, make sure your cam will work properly for that compression ratio. Dyno the engine, talk with a good converter builder, I like Dice Converters in southern California. Match the components and it will be a good combination. Are you planning to add any nitrogen?? If you stay naturally aspirated I think you will need at least a 5000-5500 stall converter for a dedicated drag car.

What rear suspension is under your car?

 

[RifRaf]

Sorry but I forgot to mention we plan on running this motor on E85

I have to admit... I didn't know that much about E85, so I read a couple articles about it. WOW! Very impressive characteristics of using E85 in a high compression engine.

With the .050 head gasket, you would be sitting at around 13:1 with your current setup.
With the .070 head gasket, you would be sitting at around 12.3:1 with your current setup.

From what I read, both setups look very doable with E85 and your vehicle's usage goals (mostly strip with some street). Just be sure to check the piston to valve and cam to connecting rod clearances with your selected cam.

 

[Sayiwont38]

E85 works very well with high-compression motor I'm just not too sure the highest compression and still be streetable. The problem I'm running into is I don't know anybody that builds these motors and I can give me good answers.

 

[RifRaf]

E85 works very well with high-compression motor I'm just not too sure the highest compression and still be streetable. The problem I'm running into is I don't know anybody that builds these motors and I can give me good answers.

Below are a couple links that might give you some guidance. I am sure there is a lot more E85 info out there. From what I was able to read, 13:1 in a SBC using E85 was ideal.

https://www.hotrod.com/articles/ccrp-0611-e85-ethanol-fuel-test/
https://www.onallcylinders.com/2015...-is-safe-effective-compression-ratio-for-e85/

Good luck with your project.

 

[Sayiwont38]

Thanks for all your input...gotta lot of research to do

 

[xten57]

The heads are 62cc chamber and were probably going to use a .050 or .070 head gasket to try and lower the compression a bit. Im Trying to avoid having to buy a different set of pistions and selling the ones I have.

Lots of good information and advice has already been posted by guys who are smarter than I am. But, it might also be important to consider how a thick head gasket (.050 - .070) may negatively affect your quench area. This could lead to pre-ignition problems.

Gerry

 

[wht73]

Do you know or have the exact part number of the pistons?
Do you know IF your zero deck'd OR in the hole?
Head gaskets volume?
CC's of the chamber?
ALL of this info needs to be present or we are just guessing.:yes:
Does the compression "need" to be that hi?
Are you up in the mountains where it would be beneficial?
My lil 406 in my sig is 10.5:1 and ran on 91 octane in the video and times in my sig.
Dizzy locked out at 36*,262/269 @.50" .630"lift SR cam
Oh yeah, studded 2 bolt no fill block.

 

[xMLMx]

The heads are 62cc chamber and were probably going to use a .050 or .070 head gasket to try and lower the compression a bit. Im Trying to avoid having to buy a different set of pistions and selling the ones I have.

As others have said, you need a lot more information on the motor to calculate compression and get final numbers... but those dome pistons are hurting your end goal.

Running a thick head gasket (read: over .043) is not really a good solution to your problem; it will ruin your quench (which you want to be closer to .040-.050") and lead to detonation problems, which is already hard to control on a high compression engine. Also, gasket bore size and availability need to be considered; head gasket selection for 400 small blocks isn't great thanks to the steam holes... ask how I know.

Some things to consider for E85: Ethanol is hydroscopic, so it will wick in moisture constantly. Read: if the car sits a lot or isn't driven often, it will ruin the fuel. Also, it's corrosive; you need to take into account your higher fuel requirements to run ethanol, how it will affect your carburetor and seals, as well as your fuel tank.

I went through a very similar gauntlet of what you're doing now with the 355 in my Nova; way too much compression and not streetable. My solution was to go from a 62cc chamber head to a more-modern 72cc combustion chamber head, use a cam with lots of valve overlap to bring the dynamic compression down, and lots and lots of math to sort out how it would all work harmoniously.

 

[sbc1320]

I'm doing the same thing, but with flat tops. Have to pick up some pistons and some AFR heads for it. Need to get the T350 built and will put that Hughes 3500 converter in it. I mic'd block and it only has .005" wear so I"m only going .020" on it. Have a new Scat forged crank and their 6" stroker rods will clear up to a 3.800" stroke so no small base circle cam needed plus the rods have the 7/16" ARP cap screws. Then I'm gonna have to find an older C10 truck for it.

 

[bracketchev70]

All I will say is I don't know anything about running on E85. If you know how to tune for it, then by all means build whatever the fuel can handle. Along with that, don't bandaid the engine to force the parts to work with a fuel. If your parts won't work for E85 either change the parts or change the fuel.

 

[wht73]

John, check for clearance on the pan rails with the 7/16" bolts.
Ask me how I know?
This was Scat 6" H beams.:yes:

 

[Sayiwont38]

Just a little update... Found out the gm fast burns won't work with domed pistions due to clearance issues. So right now trying to decide weathed to keep heads and sell pistions for some flat tops or sell heads to use domed. I'm not gonna use the cast crank so I bought a forged scat. I'm still up in the air with converter.

 

[wht73]

FWIW, I used scat's cast steel crank.

 

[xMLMx]

My advice would be to get new pistons and use the heads.

Flat tops allow for better flame front travel, and opens up your options for later use of better heads, too.