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Wage92 12-29-2012 05:29 PM

406 small block review
 
Okay guys, im new to this board but have often come here when i am in search of engine help, so i finally decided to join.

Heres the deal, im building a 406 small block that will go in a truck (yea its not a hotrod, and yes i would trade it for a 30s chevy coupe in a heartbeat)

This is my plan so far and i just wanna run it buy you guys to see if im on the right track:

400 small block that ive ran before getting bored .030"
Probe dished pistons 14cc
Scat 6" stroker rods
scat cast crank
cam: 12-246-3 - XTREME Energy

Aluminum heads with 2.02/1.6 valves and 64cc chambers
Edelbrock rpm intake
holley 800 double pumper

probably 7qt pan, high volume oil pump


Anyway so far with that setup my compression is 10.3:1 and a dynamic compression of 8.35. That will work with 93 octane if what i have been reading is correct.

My main question is how will my quench area be, stock deck height (which is about .025 if ive read correctly) and a .027" head gasket. Thats .052", and ive read that it should be around .040". How big of a deal is this? I have not purchased the rotating assembly yet so i can potentially switch it to get a bigger dished piston and therefore run a thinner gasket and still stay in the low 10's for compression, but i do like the setup i found, so basically im wondering is .052" killer, or will it not be bad? I want a solid running engine and i want it to be able to turn 8k although it will not get that high very often.

496CHEVY3100 12-29-2012 06:07 PM

After you wake up ,start all over on your parts list ? A stock 400 block A cast crank , *8000 IMPOSSIBLE,why 6 in rods cam would not let it turn 8000 in neutral Not critasizing choice <just fact .Instant Road side Bomb

Wage92 12-29-2012 07:27 PM

Quote:

Originally Posted by 496CHEVY3100 (Post 1628477)
After you wake up ,start all over on your parts list ? A stock 400 block A cast crank , *8000 IMPOSSIBLE,why 6 in rods cam would not let it turn 8000 in neutral Not critasizing choice <just fact .Instant Road side Bomb

what parts in my parts list need to be changed? and stay in the same price range. i will use the same block and heads i already have. the rotating assembly im getting is balanced and 900 bucks. and i thought 6" rods were better than stock?

LATECH 12-29-2012 07:51 PM

Read through lhmurphys post about 406 build...whatdayathink.
Lots of good conversation about the tech aspect.
Your build recipie/goals are not plausible.
Cam wont support 8K rpm
Heads might...with tons of porting...if you dont ruin them
Rods will be hanging out of block at around 6500 rpm due to excess length(6.0 in) and weight Vs. velocity
Block will need decked, which means you need all parts going into to it, physically in your possesion, so you can measure the "stack" to give you a height that you need to deck the block to.
Lots more trouble here...too much to list.
Do some more reading, when you think you have read enough...read some more, then start asking some questions.
Not trying to be flip, you just need to read up and learn some more before you start dumping money into a build.

Wage92 12-29-2012 08:13 PM

Quote:

Originally Posted by LATECH (Post 1628505)
Read through lhmurphys post about 406 build...whatdayathink.
Lots of good conversation about the tech aspect.
Your build recipie/goals are not plausible.
Cam wont support 8K rpm
Heads might...with tons of porting...if you dont ruin them
Rods will be hanging out of block at around 6500 rpm due to excess length(6.0 in) and weight Vs. velocity
Block will need decked, which means you need all parts going into to it, physically in your possesion, so you can measure the "stack" to give you a height that you need to deck the block to.
Lots more trouble here...too much to list.
Do some more reading, when you think you have read enough...read some more, then start asking some questions.
Not trying to be flip, you just need to read up and learn some more before you start dumping money into a build.

Okay forget the whole 8k thing. Moving on from that, i have read the thread and not gotten the answers i need. Block will not be getting decked as this is just a fun build, not looking to go race with it, just want about 400hp and something reliable, its a good block and until i took it apart it ran great. And its a budget build so im not gonna shell out a couple thousand or more. So what exactly is wrong that i need to fix (parts wise) to get about 400 horse and have something reliable?

LATECH 12-29-2012 08:35 PM

2 Attachment(s)
Your static compression with that cam and stroke etc will be 11.4 ish to one and the dynamic will be around 9.1 to one. Way to high for any pump gas, and... that is figured with the block decked and a .045 quench height.
Without a good quench , the chamber shape on the heads you have wont do diddly for you. You wont run on pump gas without it detonating itself to death.
If you deck the block, get a good quench,run a slightly larger duration cam, keep the cooling system working very well, keeping the engine at 170 degrees F (or a bit less) you will be on the edge with 92 octane.
Here is a little chart for dynamic comp Vs. octane Vs. temperature
I stare at it for hours sometimes :D
Also last photo bump

LATECH 12-29-2012 08:39 PM

Seriously...you need to read more here. Search out posts that have titles like yours about builds. Learn the terms and study the physics behind it so you understand it better.
:cool:

Wage92 12-29-2012 08:40 PM

Quote:

Originally Posted by LATECH (Post 1628523)
Your static compression with that cam and stroke etc will be 11.4 ish to one and the dynamic will be around 9.1 to one. Way to high for any pump gas, and... that is figured with the block decked and a .045 quench height.
Without a good quench , the chamber shape on the heads you have wont do diddly for you. You wont run on pump gas without it detonating itself to death.
If you deck the block, get a good quench,run a slightly larger duration cam, keep the cooling system working very well, keeping the engine at 170 degrees F (or a bit less) you will be on the edge with 92 octane.
Here is a little chart for dynamic comp Vs. octane Vs. temperature
I stare at it for hours sometimes :D
Also last photo bump

I just said im not decking the block, i dont think its needed. i already calculated my compression and its 10.3 static and 8.35 dynamic. My only question is if .052" quench is too high, i know its not the .040" that people claim is needed but ive seen professionals build engines with higher quench...

LATECH 12-29-2012 08:41 PM

OK then...you should be good to go.......:rolleyes::rolleyes:

Wage92 12-29-2012 08:47 PM

Quote:

Originally Posted by LATECH (Post 1628527)
OK then...you should be good to go.......:rolleyes::rolleyes:

how does a 6" rod act on the street? i know there is tons of debate over 5.7 or 6 and 6" are suppose to consume oil and all that, but how do 6" rods last in the long term?

496CHEVY3100 12-29-2012 09:37 PM

Just a couple tips ,try to find a 400 block from 78 or older blazer WITHOUT center freezeplug much stronger,when i build 434 small blocks from a 400 for dirt racing late model midified i vat the block in radiator vat not a hot tank then fill the block thru water jackets with epoxy 2" deep to strenthen block and better ring seal i saw you lowered expacyions of rpm & horsepower to 400 hp which is very abtainable and still be streetable.as far as cost the 2000 you mentioned,our engines have rev limiter set at 8200 rpm but they do not run at that rpm ,usually 7600 on good trackno dry slick ,as far as cost to freshen up mid year usually 20 low 30s high -fresh build from scrach 55 or better we are running bow tie block since aftermarket dart and others are not allowed hope this dont discurage your build but this is all out racibg engine never ran below 5000 Would Not stay together on street Build a good streetable 406 and enjoy it, David .

cdminter59 12-29-2012 10:59 PM

406 small block review
 
All right let's do a review on your block and parts. Let's start with the block. Suppose you were to install the crank and a piston at all four corners to calculate piston to deck height. The factory block height of a SBC is 9.025. Most likely you will end up with different measurement on each corner anywhere from .020-.025. To find the deck height you measure from the centerline of the crank to the top of the deck. To find out if the rotating assembly will fit into the block you measure (half the crank stroke - rod length - compression height) = parts stack height. Using yours for an example 1.875 + 6.0 + 1.425 = 9.300. This means the pistons will be .005 above the deck. This would take a .051 thick head gasket for a quench of .046. Your static compression would be 10.492 and the DCR 8.437. Be sure to use modeling clay to check valve to piston clearance. Using 5.7 rods, 1.875 + 5.7 + 1.425 = 9.000. This means the pistons will be below the deck .025. Say you want to use a .027 thick head gasket which cost around $100 each. For me it's easier to mill the deck to .005 and use a stock .039 thick head gasket with a bore of 4.166. You would have a static compression ratio of 10.492 and a DCR of 8.472 which will run on 93 octane gas with the correct timing. With the quench close like this there is less chance of detonation. BTW the 400 engine is not designed for high rpms. Your camshaft has an operating rpm range of 1800-6000. The crank probably has a safe rpm range of 6000-6500 rpms. Rpms is what kills engines not horsepower.

Wage92 12-30-2012 07:56 AM

Quote:

Originally Posted by cdminter59 (Post 1628547)
All right let's do a review on your block and parts. Let's start with the block. Suppose you were to install the crank and a piston at all four corners to calculate piston to deck height. The factory block height of a SBC is 9.025. Most likely you will end up with different measurement on each corner anywhere from .020-.025. To find the deck height you measure from the centerline of the crank to the top of the deck. To find out if the rotating assembly will fit into the block you measure (half the crank stroke - rod length - compression height) = parts stack height. Using yours for an example 1.875 + 6.0 + 1.425 = 9.300. This means the pistons will be .005 above the deck. This would take a .051 thick head gasket for a quench of .046. Your static compression would be 10.492 and the DCR 8.437. Be sure to use modeling clay to check valve to piston clearance. Using 5.7 rods, 1.875 + 5.7 + 1.425 = 9.000. This means the pistons will be below the deck .025. Say you want to use a .027 thick head gasket which cost around $100 each. For me it's easier to mill the deck to .005 and use a stock .039 thick head gasket with a bore of 4.166. You would have a static compression ratio of 10.492 and a DCR of 8.472 which will run on 93 octane gas with the correct timing. With the quench close like this there is less chance of detonation. BTW the 400 engine is not designed for high rpms. Your camshaft has an operating rpm range of 1800-6000. The crank probably has a safe rpm range of 6000-6500 rpms. Rpms is what kills engines not horsepower.

Okay im confused now, firstly if the deck height is 9.025" and with 6" rods the stack height is 9.300" then the piston would be .275" out of the block....and secondly i thought that no matter what rod you use, that doesnt change compression....

LATECH 12-30-2012 08:56 AM

Quote:

Originally Posted by Wage92 (Post 1628602)
firstly if the deck height is 9.025" and with 6" rods the stack height is 9.300" then the piston would be .275" out of the block.....

Exactly the point.

cdminter59 12-30-2012 09:46 AM

406 small block review
 
Your stactic compression did not change but your DCR did. Sorry about the math mistake. Anyway .275 above the block is something to consider real hard. Personally I wouldn't build an engine with the piston that much above the block for the street. That is some close tolerances measure carefully. I might have considered it at .005 but not at .275. What happens if your block has been milled in the past? I think the best solution would be to use the 22.5 dished pistons with 5.7 rods. This assembly would give you 9.497 static compression and a DCR of 7.689. But you will still have to deal with the quench of .053". I can suggest something but you will have to contact Cometic Gasket INC. They will make you a custom head gasket with the compressed thickness and bore size you need. I would rather check on this and try to get closer to .040 for quench. But who knows you could use the .027 compressed thickness gasket and not have any problems. I remember back in the day just using the head gaskets from the gasket kit with a .039 compressed thickness with flat top pistons and 76cc heads with a DCR of .064" and never heard any pinging.


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