what do to with a 400sbc
so some of you may know i have a complete 1973 400 sbc and it is completely apart now i want to rebuild it myself with the help of my dad and his vast experience and i need suggestions as to what i might want and what to look out for etc....
the crank needs to be turned and i need new pistons.
and im basically working off of a low budget
since i dont need to bore the block i will be getting a set of standard bore 400 pistons (8.5:1)
now my dad was suggesting a simple rv cam, 425 lift (how will this work out with 273's gear ratio)
i will be buying a set of hooker headers 1 5/8 etc.. (any of company i may want to look into)
for the intake i want a dual plane ( performer, air gap) *about the air gap is it compatible with a a/c p/s (my el camino has all the options)
and finally for the carb i have the stock q-jet that came off the car and it was rebuilt professionally and it works great but i could probably get my dads 600 holley vaccum secondary)
and the heads are 194, 150's so they flow plenty for my liking and we will be porting them and such
with all these mods i ran it through desktop dyno and i am getting a 330hp@5000 and 392ft lb's@4000 (with a motor like that in an 5th gen el camino somewhere between 3600-4000lbs, what kind of 1/4 am i looking at)
thanks for all the help
You have the makins for a fine everyday good running motor, go with the performer and the Q-jet (even tho I hate'm), keep it simple, you will have lots of torque to haul that rear gear ratio.
Check your heads (Magnaflux) for cracks between the steam holes and center head bolt holes, check the block between the bores and bolt holes. If you can afford it use the 5.7- 350 rod and proper piston, you will like the better torque and the motor will like the less cylinder wall loading, keep the cam duration short and the lift tall.
Get higher compression pistons. You want 9:1 to 10:1. Get a flat top piston. 8.5:1 is a waste.
bump it for the weekend
Sounds like a good streetable setup. :thumbup:
If I were going to make one suggestion it would be to go with a bit larger cam even with the high gearing.
You have more cubic inches to deal with than a 350, so a .425 lift is 'very' mild. Consider looking at something in the .450 range. (mild for a 400sbc) This will give you some added power with your setup without comprimising it's streetability.
Have fun! :mwink:
400 sbc q's
i just recently built up my 400 smallblock, and ill tell you what i found... the car is a '71 caprice classic, so i have AlOT more weight to push around.since your block is a 2 bolt, the webbing is stronger than my '71, so a higher comp. ratio can be used without the fear of failure. since the machine shop is gonna have to tank the block anyways, spending the extra 90-100 dollars to bore the block is worth the investment. itll keep down the engine noise of piston slap and make the motor tighter, while helping to unshroud the valve for a few more cfm. since your going to buy new pistons most likely, the oversize pistons wont cost much more than std. bore size pistons.Since a budget must be followed, you can stick with the stock rods. But if you have an extra 200 dollars, upgrade to 5.7's and get the arp bottom bolts in there for the rods.also note that the 350 rods may not clear and have to be notched in some cases, but this is generally with newer style ('87-0n) 350 rods,but since the crank needs cleaned up, the rods will most likely also be out of round, needing cleaned up. Rods are cheap and plentiful, so finding a decent se tshould be no problem.I went witha 10.0:1 comp piston with a .020 overbore and .020 off the deck, making it 10.8:1.
The cam you have chosen sounds good on paper, but what i've found after three cams, the more lift the better. My first cam was like what u describe here. The cubes eat it up in a heartbeat, and with the higher compression, itll run outta air WAY before the intake and carb do. Instead of porting the heads and using a small cam, which will make it a dog. spend the money on good machine work and stiffening the bottom end for performance.Remember that most of your money will be spent in the machine shop, not the summit catalog, so get as much done there to ensure a good motor as you can, before starting to pile on power. i went with the summit cam kit with 212/224 @ .050 and and .442/.460 with a small converter. thi cam is great with midrange power with 1.94 heads and the cubes make gobs of low end grunt. your intake and carb sound good,same as what im running, except the manifold, but make sure the electronics are up to the task, that 30 yr. old distributor and coil just arent gonna cut it. At the least get a fresh set of points and a re curve kit.all in all, doing my own valvejob and assembly of heads,getting my intake for free ( ****ty 305 z intake from '85) reusing the carb with headers and all, i spent right around 1900-2400 dollars, thats assembling it myself too. The bills add quick, so make sure you have the cash b4 u start. but this combo runs great in my caprice, fires em off thru first and parts of second( peg leg rear) and runs cool with a 190 t stat in it.also, for an extrea 90 bucks, some roller tip rockers will do wonders for noise and for tope end stability.
Highest compression you can run and still use pump gas. Air gap dual plane manifold...excellent choice!. Q-jet is less problematic than Holley (from my own experience). The 600 cfm Holley may be a bit small for a performance 400 anyway.
Headers are good, if you are on a budget try a set of Summit Racing brand for $80.
Might just as well order a set of higher compression pistons while your at it.
As for the bumpstick, I ran a Comp Cams 268H in a 350 , It still idled decent and provided all sorts of low end torque. You could go little bigger with the 400, without losing streetability. Check out Summit and Jegs as they have Edelbrock power packages (intake and cam kits) at a good price. Make sure you read the footnotes for the kits though, or ask their reps what they recommend. Another item that wouldnt cost you any more is an advance/retard timing chain/ sprocket set. This allows you to move the "power band" up or down in the RPM range.
Your ported stock heads should do just fine, especially since you are on a budget.
Again, just my opinion,
I have a .030 over 400 SBC in my '86 ElCamino. I used slightly dished forged TRW pistons to keep the compression to around 10:1, with 64cc Vortec heads. I also used the Comp Cams XE268 and found it idles a lot smoother than I expected. Engine's very good...trans is however another area.
Lots of good advice here I agree go with a cam in the .450" lift range its a big displacement small block so it can take more cam with out hurting the low end much. I think your idea of keeping the compression low is a good one, especially if you are looking to run cheap pump gas I'd go between 8.5-9.2 you won't gain that much power with any higher compression and with a shorter duration cam you can get into detonation territory easily. I also agree with keeping the q-jet its hard to beat for the street.
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