High Compression 400 sbc

[FullTimeRacing]

what is the highst comp ratio that should be used in a 400 sbc 817 block?

I have a std bore block low mile I want to build to a 420cid with 3.875 stroke.All opt are open

this will be for drag racing only.

[zipper06]

We're running 14.5 with cosmetic gaskets in a 434" motor no issues as of yet, with close to 200 passes.

Zip.

[FullTimeRacing]

I was told the cyl would bollon in time.

[zipper06]

We fill the block up to the bottom of the water pump inlet with hard block and use total seal rings. Leakdown is still within 2 to 3%. I'm sure that an after market block will seal better, but it's what works for us.

Zip.

[thedude]

Hello, with a factory block, especially a GM 400, the real question is, what is the target horsepower figure you are trying to accomplish with this build? If you intend to go with a higher compression ratio and the cubic inch that you specified, I would estimate with a properly matched induction combo (roller cam/intake/heads), you will be pushing somewhere around 600+ horsepower depending on how well the combination is put together. I personnaly don't reccommend using the 4 bolt main 400's, simply because the main webbing where the outer main bolt is drilled and tapped through during factory procedure makes a great breeding ground for stress or cracking. If you must use a factory GM 400 block search for a 2 bolt main and have a reputable machinist install splayed 4 bolt caps. Please keep in mind after all this trouble and machine work/exspense, you could have probably bought a reasonably priced aftermarket cylinder block such as Dart's new entry level SHP (there are many posts about this block on the forum). Aftermarket cylinder blocks seem out of reach on a tight engine budget but machine processes to get that old iron suitable for higher horses will put you into the $1000+ range, unless you have a good engine machinist that owes you a favor. Long story short factory iron is good for between 500-550HP MAX, not to say you can't put more into these blocks, many will tell you they have with great success, as have I but with great preparation put into the block. Years and years ago I built a 670HP alcohol 377cid out of a factory GM 400 with splayed caps, I wouldn't go to that trouble again though, deck plugs, splayed caps, grout block fill, pan rail clearancing for alum. rods, etc., etc. I hope this sends you in the right direction and you are doing what any good racer does,....homework. Thanks.

[FullTimeRacing]

I have brodix track 1's no port work on a 360 cid hv intake 1050 dom and was looking to put more cube's under it.260/270@50 630 lift cam,c 12 gas

the block i have is a two bolt std bore. cyl look beutiful dont need to be bored.Was just going to have it honed for piston clearance and deck

I know i'm going to need a small base circle cam

[us7race]

You don't have to run a small base circle cam if you use Eagle Stroker Rods...That is what I have in my motor...

[FullTimeRacing]

love the info,13.5 to 14.0 would be the most i'd want to go.not looking to set a record just go a lil faster.

[johnracer]

You'll need to consider that, IMO, even a 406 will be DONE by 6500rpm with those Track 1's. A 420"er will be even lower. It'll make great mid range power but won't like rpm. You'll need to regear to keep it in the power band.....

[FullTimeRacing]

I was thinking a power glide would make good use of that power

right know I shitf at 6500 and go through the lights at 68 to 7300 depending on the weather.

[FullTimeRacing]

another ? In your opinon what is better for drag racing 377 406 421 ?

[bjuice]

what kind of drag racing you speaking of ? Racing to some ( heads up run what ya brung) and dumping 1,000 hp shot of nos,high boost superchargers/turbo's and hanging on for dear life...while for others its a sunday drive of round robin at a 7.90/8.00 1/8 th mile local brackets.
Both are fine don't get me wrong....just gotta know what you wanna do.

just for the record all the above will work on the consistant bracket stuff....if ya gonna want to sqeeze one pretty good to really get her to run..then scratch the 406ci...,THEDUDE pretty much explained why.

i personally like the 18 degree 434's turning 8500 rpm..

but if i had to use the CI you listed..i would go with the 377ci and build it to handle a minimum of 300 shot


just to let you know
My wifes 69 camaro with the old 377ci engine.. stock suspension (slapper bars only) on 26x10's at 3400lbs with a 300 shot plate with (progressive) ran a best of 5.84et at 126mph in the 1/8th...(still spinning alot)

[FullTimeRacing]

It's 1/4 mile bracket racing where i'm at,just looking for what is best for the block I have before I spend a dime.We all ways want to go faster.It will be all motor no power adders. this is on c-12 gas

I have a nice lanait 3.48 crank and 6in rods in my 350 and have the 400 block.Just looking at all options