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about to pick up 400 short block this weekend been looking at post to see what path for build up learned some interesting stuff why do people suggest dished pistons on 400's instead of flat tops like on 350's looking to do a mild street build on an extremely tight budget but I have all winter 400 is a 4 bolt main 1st time building an i need some insight 350-400 hp all im looking for going in a 78 chevy malibu also can buy 400 heads from neighbor for 50 bucks
i think people suggest dished pistons in a 400 because the bigger bore naturally makes higher compression so people use a dished piston to offset this.
??? bore dont change compression .Quote:
Originally Posted by Hopper111
1hp per cubic in is pretty simple . be real carefull on camshaft choice .
How much do you want to spend? That seems to be the qualifier as to what advice to give you. It will be hard to make 400 hp using stock 400 heads.
400's make lots of torque, great on the street. Don't overcam it, they don't need to rev. Any SBC heads work if you drill the steam holes, the stock 400 heads aren't the best. I had 2.02 camel humps on one, and a cam made for RV's and tow trucks(!) and it worked good in my '72 Camino.
Im guessing by the post you mean this will be you 1st motor build from start to finish or is this your 1st motor build ever???? If it is your 1st motor ever the main thing to consider is buying a set of feeler gauges, check the clearance on all moving parts and you should be just fine....
well my cousin is going to help he's built a coulple of 350's my uncle is thier but he has alot of projects he working on so were trying to do this on are on I have about 1000 to 1500 to spend now but if heads are that important to get 400 hp out of it i'd wait till spring to finish top have already have intake an car edelbrock eps an performer 750 so no expense their whats a good cam an so I should go with dished pistons instead of flat top thanks for quick replys keep em coming
If you want some good heads at a reasonable price try the factory vortec heads they have a 64 cc fast burn chamber on a 400 10:1 comp.
Camshaft should be up around the .480-.500 lift 230-240 @.050 these heads work the best best with 1/2 inch lift cams. You will make 380/400hp easy.
I'd keep the compression down so I didn't have to use a long cam which would lead to the expense of a looser converter, insufficient manifold vacuum, yada, yada, yada. Even though they are a thin casting, prone to cracking and require a dedicated intake manifold, I still think the Chevy Vortecs are the best bang for the buck. Just don't get 'em hot!!!!
I'd bore it 0.030" and use KB hypereutectics hung on 5.7" Chevy rods. Static compression ratio would be 9.0:1. I'd zero deck the block and use a 0.039" gasket for good squish with regular pump gas. I'd keep the cam short for good torque, ability to use a stock converter and keep costs down, build good manifold vacuum to operate accessories. Another reason for a short cam with Vortec heads is that unless they are modified for higher lift at further expense, they are limited to lift at the valve of about 0.450".
http://webpages.charter.net/beckracing/page34.htm
http://www.cranecams.com/?show=brows...tType=camshaft
http://www.sdpc2000.com/catalog/2173...mer-Intake.htm
cylinder volume is a factor in compression ratio...
http://e30m3performance.com/myths/mo...comp_ratio.htm
In that article the writer gives a formula for compression ratio.
He also says "Now if we look carefully at the equation for compression ratio above we note some interesting trends. Even if the volume of the combustion chamber (V2) is kept constant, we can increase the compression ratio simply by increasing the stroke and/or the bore size.
So let's say you rebuild your engine, but all you do is bore it out slightly and install identically shaped, but bigger pistons. You don't shave the head or change the stroke, or decrease the volume of the combustion chamber. You will still increase your compression ratio." Therefore, bigger bore = more compression compared to a smaller bore of the same engine. For example, a 400 at factory bore, 4.125, will have less compression than a 400 with a .030 bore, 4.155. I'm saying this because I just went through it with my own engine.
Before you get started, take the block in to a reputable machine shop and have it checked for cracks, particularly in the webbing. 400's are more prone to cracking that 350 blocks. It would be a huge waste of time and expense to put money into a cracked block.
Because of the size of the engine a cam's power band will start earlier in a 400 vs. a 350.Quote:
Originally Posted by maineevent
The largest cam you can really run in a 400 with out going to a looser stall is around 225 at .050.
To get the 350- 400 hp you will need a about the 225 at .050 size on the intake side.I would try and run a 6 degree spred or more favoring the exhaust side.,a 9 to 1 comp. ratio,good rpm performer style intake,a 670 cfm Holley should do the trick.
After 225 at .050 I would start to look at a looser stall.
The hyper. pistons will work fine for what you are trying to do.
The 400 heads will work but I would do a good valve job,bowl blend,gasket match.
At the very least I would try and install a 1.6 exhaust valve.
The 400 does not like as much timing as the 350.I would start around 34 total and try it.
Also loose the stock 5.565 rods and try and put a set of 5.7 rods in it.