I just picked up a running '73 400 out of an Impala along with its TH350 trans for $250.I am contemplating how to build this combo for my Z?!Here is my set parts list..1973 400 (virgin bore..heads pulled to make sure)..will go .020"-.030" over to clean up,AFR 195's..64cc street heads (on current 350) and I plan to steal the Summit Pro Line 4340 5.7 full floating rods out of my current 350 when I pull it this winter.I don't want a stroker either..just a 400 with 5.7 rods.I also plan to rebuild the Th350 and match up the stall convertor to whatever cam I end up going with.Rear gear is a 3.73..car is mainly a street toy..occasional strip use.Weight is right around 3300lbs.Emissions are of no concern obviously.I would like to see close to 500hp/500ft lbs if I were to dyno the motor but won't..realistically looking for 400hp/400ft lbs or more at the wheels?,but a STREETABLE combo?Lets see what you guys come up with??Rather proven combos over theoretical!

 

compression. You will need some killer cam timing to get that to run on pump gas.

You can roll the chamber out a little at the head gasket area (usually get you a couple of ccs), maybe run the pistion in the hole a little or try a .044"+ gasket
.
Mine is about 11.3 and I mix 30percent 100 race.

Get the afrs flowed and on a least a port or 2. Make sure you have a real 230-240 at .4, 265+ at .5 and close to 280 or better at .6". Then get the numbers to a cam grinder. Shoot for something in the 235-245 intake duration with close to .6" lift at the valve.

Should be n/p making those numbers with some tuning. A 1 to 1 3rd gear will limit road time some with 3.73s. Shoot for a 26.5" tire and you will kill some of that gear. Id be prepared to go with a 3500 rpm converter to get it to leave real hard...
oh yeah, work on suspension.

 

Yeah that's alot of compression...I wanna keep it closer to 10.5-11 max..may have to sell these heads and get some 72-76cc heads.I'll have to way the options.Just building it on paper right now to see what i need $$$.Yeah the 3.73's and TH350 will spin some rpm's but I usually don't take many highway cruises..just a friday/saturday cruise toy.I was planning on at least a 3500 or higher stall to get to my "goals" and I know that will not help much either.Suspension is already set with a Moser 12 bolt, Random Technology lower control arms & adjustable Torque Arm,Spohn LCA reloc. brackets and a Spohn panhard bar.Subframe connectors are also included in case anyone is wondering.TIA..keep em coming..

 

I know I was hoping to get 400/400 to the tires and be "streetable"....

But you soon find out that what one person defines as "streetable" and what another person defines as "streetable" are two different things.

You'll run into detonation issues with compression that high, especially on a 400. Most builders recommended I stay in the 9-9.5:1 ratio to run on pump gas. (with iron heads)

I'd think you could get away with a slightly higher compression since you have aluminum heads. To get that much to the rear wheels, you'll need to flywheel dyno at around 450-460.

Just a thought since you mentioned "occasional strip" use. And get retro rollers! I didn't and wished I had. Much better cam grinds in the roller dept., and more "streetable". OOps!! There's that word again! lol

EDIT: Looks like you're more prepared to handle the power than I was!

 

Yeah.."streetable" is a hard word to nail down like you said.I define streetable as a motor that can hold at least a 1000 rpm idle (rough or not is no big deal..not a daily driver anymore)..vacuum is nice but power brake woes can always be fixed witha vacuum pump if needed so not too worried there.A solid roller is theoretically in the plan anyway so I was heading in that direction.Something like a Comp 280 XE solid roller...but a lil bigger.Will upgrade the radiator as needed for cooling..already have high water flow March serpentine kit to help out also.Fuel system is good to go with a Holey black pro series electric pump but will upgrade to 8AN feed lines.Did I mention this is also occasional gonna get hit with a bottle?The n20 system has its own dedicated fuel system. so any nitrous specific ideas will come into play also.

 

400's can take a lot more cam than a 350 and still retain decent street manners (perhaps a better term than "streetable").

That being the case, I would look into a custom grind. AFR heads have a good I/E ratio so you could probably get away with a single pattern grind. Depending on how you want to go with things, perhaps the 3316 lobe for both the intake and exhaust. Have it ground on a 110 LSA. That lobe is 288 advertised, 236 @ .050" with .555" lift with 1.6 rockers. There is also the 3196 lobe which has the same duration, but larger lift, .585" with 1.5 rockers. You could do those on both intake and the exhaust. That gives the lower durations to make for better manners, but higher lifts to take advantage of AFR's flow rates. The 3196 lobe would require more spring to control valve float better as they are more agressive ramps.

Or, if you want to get creative, you could run the 3196 lobe on the intake with 1.5 rockers and the 3317 lobe on the exhaust with 1.6 rockers. That would give a cam that looks like this:

adv. duration: 288/293
.050" duration: 236/242
lift: .585/.575
LSA: 110 (112 if you want to tone it down a tad)

So many choices.....

*edit* of COURSE, you HAVE to say SOLID roller now that I post....

This is where it gets fun.

 

Wow! You just described my engine's characteristics!

Did'nt need a vacuum tank though. I ended up getting a Griffin alum. radiator, and a Summit iron high volume water pump to keep it cool enough.

Since the one your getting is a roller, I'd guess the vacuum would actually be better. At least that's what I'm hoping for when I convert!

The cam I have in mine right now is a flat tappet 110 LSA cam ....IMO, it's on the ragged edge of "Streetable". lol

But geat power in the mid to high rpm range. Everyone's always told me that you don't need to wind up a 400 real high to get power from them. I love the torque they make!

 

https://www.thirdgen.org/techbb2/sho...5&pagenumber=1


mine idles at 800 rpm in gear, it's as drivable and streetable as my other T/A with 305 TBI, it ran 7.8's on street tires with no suspsension mods. IMO, it's a extremely streetable 11 second car. oh, it also has 3.23 gears, overdrive and lockup.

 

Thanks LilJayV10..I have read that whole post..lot of great info in there.Food for thought.

 

no problem, just hope you have better luck with your rings sealing than i did.

 

I have read about and talked to quite a few people with 400's that built or had it built with ring sealing problems.I'll have to see..and hope for the best.

 

And people with 305s, 350s, 235 6-cylinders, F*rd motors, and everything else in the world.

And I've also built quite a few myself, with no ring sealing problems whatsoever.

There's absolutely nothing unique or special or different about a 400 from any other engine in this regard. I certainly wouldn't not build a 400 just because "I heard" that somebody screwed up the rings in theirs.

Proper cylinder wall prep will get the job done right, every single time.

 

Agreed...I didn't intend to make it sound like it was a 400 specific problem.And I most certainly intend to build this 400 I just picked up regardless of the wives tales I have heard (never said I believed them) over the years about 400's.It's a motor like any other..build it and beat it.Proper machine work,properly matched parts & proper assembly..this big bastard is gonna make some power:lala:

Oh yeah..and a hit from the jug once in awhile just to keep the pistons cleaned off..maintenance of sorts

 

Bringing this post back from the dead!

I've had some time to review my plan here and some changes have been contemplated.I am looking for opinions on what y'all think?

New build will hopefully go like this:

1973 400 bored .020 over (leaves room to go .030 down the road if needed)
Eagle Cast Steel crank
Eagle SIR 5.7 5140 forged rods with cap screws and bushed for full floating pins
SRP forged pistons #139624 -21cc inverted dome/9.8:1 with 64cc heads.
AFR 195's with 64cc chambers (off my current 350)..box stock
Comp Cams solid roller XR280R with all the necessary components.
Fluidampr Street Dampr #790100 ..also looking at Pro-Race?

The motor is a 2 bolt "817" block.I plan to run ARP main studs at the least.I would like to convert it to splayed caps..but it kills the budget I am trying to stick to.Realistically I would love to see somewhere near 400/400 at the tires.I am looking to stay at or below $1500 for all the parts needed to screw this short block together..minus the cam and matching components and machine work.Tell me what ya think so far?

 

Be sure to have to block "0 decked" so the pistons come right up to the top of the deck to get your 9.8:1 ratio.

For 500hp use a port matched vicJR and a 850cfm HP holley. If you're willing to give up 10 hp at the peak to gain alot of low midrange average torque throughout the useable power band use a RPM airgap instead of the Vic Jr
This motor is going to want the 850 in either case..

I wouldn't rob parts from the 350 other than the heads.
Stick it in the corner for the future, a spare or sell it ..

Order the pistons with standard width ring lands. This motor is not a high rever and the thin race rings will get you nothing and not last as long in a street motor.

Many people have ring sealing problems because they build the motor with too much static compression ratio for the available fuel and the exessive heat and shock from even mild detonation causes the rings to butt under power. this kills the rings fast. Build for the octane you plan to run everday.
Forget "dynamic compression" theory and cam overlap etc etc. and fit each ring to each cylinder. Don''t try to minimize ring gaps in search for power. take a que from professionally built marine high performance motors and keep the cr at or just under 10:1 for street driving on 92 octane and concentrate on airflow to get power. You'll go a lot faster, for a lot longer.

 

I do plan to have it zero decked for that exact reason.

I plan to run my Weiand Stealth/Demon 750 DP for the initial build..kinda want to go with a RPM air gap later on..maybe.Is there any real gains over the Stealth though ya know?!?!.850DP does look like a reality though.I may give up a few ponies over the single plane for useable power/torque with the dual plane as the car is 90% street toy..10% raced at the track.So the 500/500 may be a lil far fetched...lol.Hopefully not though.No parts being taken from the 350 aside from the heads..plannin' to sell or store like you mentioned.Love that motor..hard to part with it.Pistons will have standard 1/16,1/16,3/16 width ring lands.

10:1 for street driving on 92 octane is exactly what I am aiming for!Ring gaps will actually be set a lil loose (around .024-.030..have to talk to SRP about their recommendations on that subject) for the occasional juice run.Gotta have the bottle.So the motor will also occasionally be sprayed if I didn't mention that

Thanks F-BIRD'88!Anything else or anyone else is more than welcome!

 

It will run very nicely with a stealth and a 750 but will make a little less peak power . You may want to experiment with a carb spacer on that intake. Either open type or a divided type and see how the engine likes it. The spacer on top of a stealth will add a little top end. You'll have to experiment and see what works for your engine. If the car performs like you want it too then stick with the Stealth+ what ever spacer it likes. ( its a nice intake manifold) . The only way to tell for sure if the EDE RPM manifold will be better overall is to bolt it on and try it too.
Both these dual plane manifolds will favour a larger cfm carb on your motor Because of the split plenum.
Don't get wrapped up in the HP numbers, go with what works according to the time slips at the track.
(I think your overall combination is a good one)

Again, the 750 carb will work very well but you may see a gain overall with a 850 on it. This motor is moving enough air to use an 850 or a tweeked 750 (820cfm)
The only way to tell is to try it.
the nice thing about the Stealth is you have the under hood room to add quite a bit of carb spacer. If it likes a 2" spacer , use it. Something like this one may work for ya. Don''t be afraid to experiment

 

I never do...I just want it to perform.This lil 350 leaves some big shoes to fill..lol.What would you change about the combo if you could to make it a lil better?

I run a Demon 750Dp with the choke horn milled off nicely.Plus they flow an actual 810 according to Demon's flow methods anyway.So hopefully it'll work for awhile.If not..I'll step up a few months after it's in.Budget build here!

 

Would you recommend having the deck plugs done on this motor when i get it machined.I wanna make it as stiff/sound as possible for when I do spray it.Or is that a no no on a street motor?

 

No don't bother. The secret to success with nitrous is
big(er) top ring gaps, high octane fuel and attention to fuel pressure on the nitrous system. Invest in a ignition retard box for the nitrous.

You can pound it with plenty of nitrous if you pay attention to the combustion process.
If you don't, you'll find the weakest part in a hurry.

If you plan on adding more than an honest 175/200 hp use strickly racing fuel 110 octane minimum.

Interesting project, where will you be doing your testing?
(what track?)

 

Sounds good!I have all the basics (and even border on overkill as far as the n2o setup goes)covered.Dedicated fuel system,pump,WOT switch,MSD timing control to turn the timing down when I do spray,etc,etc.It's been tried and trued on the 355 currently in and the few before it.They were the learning motors..lol.I plan to gap the rings accordingly for the jugged runs and talk to SRP about recommendations for their pistons.I plan to play with 100-150...but occasionally hit it with 200 just so I know what it can do.The juice is always fed with at least 108.No pump gas in that cell.I tend to err to the rich side on spray for safetys sake.

I regretfully admit the car was never ran at the track on spray.Mainly a sunny day street toy..and I was a self described youth blurred street racer hero.Kids,marriage,and responsibilities have scared that stupidity out of me and now I plan to play mostly at Island Dragway in Great meadows NJ.Been six years since the car last ventured down there for some legal runs.

Shooting for some mid 11's NA HOPEFULLY!

 

Does anyone have any experience with the Professional Products Powerforce series harmonic dampers?I am looking at the SFI approved ones.They are about $80 cheaper than the Streetdampr ($220) I am leaning towards at the local circle track speed shop..which helps the budget theme of this motor!Although Fluidampr is tried and trued.I have always run them.