New 400 SBC Build

[LilSpann601]

Just got my hands on another sbc 400 bored over 30 and notched for a 421.I can see where there is section below the piston area where is cleared/notched. the guy I bought it from told me to put a 434 crank into or I might as well keep the 305. I knew you could put a sbc 400 crank in a 350 but what other small block cranks are there to put in a sbc 400?? or is a 434 like a stroker crank.

On this build I want to run pump gas. I just have the bare block so Im going to need rods and pistons/ Should I go with 6 rods or 5.7?

 

[ssn696]

The main bearings on a 400 crank need to be turned down to 350 size, then you have a stroker 383. If your crank is good, why not just build the 400 up with 5.7 350 rods and the appropriate pistons? I had a stock 400 with the stock short rods, and the seatback dyno tells me that it made plenty of torque to lob my wagon down the quarter mile. I spent the money on a race balance job, and had that monster crank out to 6000 RPM several times and the motor still lasted 70000 miles.

 

[565bbchevy]

Just got my hands on another sbc 400 bored over 30 and notched for a 421.I can see where there is section below the piston area where is cleared/notched. the guy I bought it from told me to put a 434 crank into or I might as well keep the 305. I knew you could put a sbc 400 crank in a 350 but what other small block cranks are there to put in a sbc 400?? or is a 434 like a stroker crank.

On this build I want to run pump gas. I just have the bare block so Im going to need rods and pistons/ Should I go with 6 rods or 5.7?

Before spending a dime on parts I would want the block checked out by a reputable shop including being magnafluxed for cracks and then sonic tested to see how thick the cylinders walls are, since 400's do not tolerate a lot of overbore and I am guessing it was already ran at 30 over.
Now a days with the affordability of aftermarket performance blocks like Dart SHP etc. many people skip the drama of pushing the limits of a 400 block when stroking it and typically buy the time you buy a block and get it machined and strengthened with slayed caps etc. you are already approaching the cost of an aftermarket block that would be far stronger and can go even bigger in the future.
Anything larger than a 400 crank will be an aftermarket stroker crank and will require a minimum 6" rod just to get in the 1.5 rod ratio area.
If the block checks out your best bet would be buying a balanced aftermarket rotating assembling so you don't have to try and piece parts together and possibly mismatch components.
Unless you have a lot of money to spend on this I would probably just keep it as a 406.
If you decide to go the 434 route you will need some good aftermarket heads and induction system to support the cubic inches along with your expensive rotating assembly.
I think you should come up with a budget and base your plan on that.

 

[LilSpann601]

I dont think im going the 434 route. I was trying to build a daily driver to replace the 305 in the car now. The guy I bought the block from claims its ready to built. The entire block is clean looks like new cam bearings,freeze plugs were put in. The only bad thing I could see if a sleeve has been put into the cylinder closes to the oil filter. I was thinking going back with 5.7 rods and 400 crank. Im on a budget right now and the cheapest rotating ive seen was around 700 for a sbc 400. So i was thinking about getting brand new parts off ebay and having them balanced.

 

[crotchss]

If you are building a daily driver I would check ebay for a balanced SIR rotating kit from Eagle . There are many sellers on ebay that have these kits around $750-$770 all balanced and ready to drop in. I have used alot of these kits for 383s and 406s, never any issues. They are rated for 500-550 hp and come with all you need. By the time you search for all the components needed and get it balanced, you can't beat the price. I have used a seller named "abad71camaro" and always had great luck with him. Your cylinder head chamber size will determine your piston (either flattop or dish). If it has a 76cc chamber I would go flattop and 64cc chamber I would go dished as a general guideline.

 

[LilSpann601]

Lol thats who I have been getting my eagle crank and most of my parts from him off ebay

 

[565bbchevy]

That is also ASA Performance and I bought quite a few low buck items from them, most recently some nice AN fittings made by PPD.
I was actually looking at Skip White ( Whiteperformance1) on Ebay when I was looking for a SBC rotating assembly before I bought my project car and I think member "83MONTESS" bought his BBC 496 rotating assembly from him.

 

[Joe87MonteSS]

To answer your question as to what other cranks will go in the 400 block, a 350 crank (3.480 stroke) will go in with the use of spacer bearings, making a 377 ci. Or a 327 crank (3.250 stroke) making a 353 ci also using spacer bearings.

A 377 can be budget built, but most people build them for the high RPM, so quality parts are needed.

 

[rwd_pete]

I have a 400 in my Malibu. It has a Crane 272 cam, Performer RPM intake, 750 Holly, ported 58 cc GM heads. It should be about 300 hp according to Computer predictions. Currently it has a 2.41 gear and a 3 speed std. It has lots of torque and you can pull it down under 1000rpm in high gear and drive away. The bottleneck are the heads feeding the displacement. Stock with a 2 bbl it wouldn't rev over 4000 rpm, with a 4 bbl 4400 rpm. Even with the highway gears, 400's are tough on fuel mileage if you care. Lots of power for a daily driver. This year plans are to replace it with a LT1350/4L60E for power and economy. I drive it daily in the summer.