I have a chance to buy a 400 sb completely rebuilt for $800 (maybe less), with reconditioned 882 heads & alum intake I might be able to sell to lower the investment in the shortblock. It was a .030 over standard rebuild on the 400, which I feel would be adequate for my daily driver application. I would go to 5.7" or 6" rods (maybe stroke it!!) in any subsequent rebuilds, but I think the standard rods will hold up for now. If he used cheap pistons I will swap these for this build. Buying the 406 sounds like a good idea since I need to overhaul my 71 GMC truck (the enabler for my third gen obsession), and I could use the 350 out of my GTA, rebuilt 2 yrs ago, in the truck and spend the money on the 406 instead. That's my justification and I'm stickin' to it!

This is what I have for the new motor, gathering dust & providing homes for various species of spiders in my garage:
* ported/polished Super Ram
* ported/polished Sportsman II's
* a new Accel base intake that will be matched to both
* Accel 58mm TB
* 30 lb SVO injectors
* 1.6 rr's
* streetdampr (purchased for the 350, will it work on a 400?)
* I will likely buy SLP 1 3/4 headers on the current GP
* The car has the stock 700R4 that may be replaced by a T-56, or rebuilt & used with a 2800 - 3200 stall (input?)
* 3.27:1 9-bolt rear end

I have the Edelbrock TES but don't think they will be enough for whatever I build. I feel like this new induction may be overkill for the 350 and have considered more cubes (383ci) for a while, then I saw this 406 that makes my mouth water!

How do you folks who have one like the 406? What is your impression of it compared to a moderate performing L98 (see my sig)? Do you have overheating problems? I'm aware of the need to drill steam holes. I researched all the archives on 400's (bigtime thirdgen lurker!) but thought it would be nice to converse with those who have more experience & knowledge about this. :hail:

Can you suggest a cam range for this application? I'm considering retro roller lifters & roller cam to get faster ramps & good lift numbers, but am not 100% sure of this yet. Any input regarding this? I have to retain emissions legal status, will this be an issue with a 406? I have the Comp HR269 (?), 218/224 cam in the GTA now and passed emissions easily once I replaced the gutted cat. I thought something in the 224/230 or 230/236 range might work well and get past emissions, but I'm not the most enlightened person when it comes to camshaft applications. Maybe I can go with a little more cam, but passing emissions imposes limitations. I understand the importance of matching my combo, which is why I'm bugging you guys!

Will the 64cc combustion chambers on the Sportsman's create too high a compression ratio for pump gas on a 406? If I go with the 406 I will unshroud the valves more, and the chambers will be smoothed and polished. The heads will be cc'd after the machining and I'll confirm the deck height so I'll know the true chamber volume prior to assembly, in order to accurately determine compression ratio.

I also understand the need to tune for the application, I've already started doing some preliminary stuff - TunerCat, scanning with laptop & C. Moates software - and have burned a couple of proms at work using modded ARAP bins. I'm gearing up to get into tuning more seriously & learn with my current config while I build the new motor. Please don't turn this into MAF vs SD tirade, I will likely convert to SD later but will start out using the MAF system to get it running and eliminate potential start-up problem variables.

Thanks in advance, sorry for the long post & numerous questions,

Shawn

 

You have a very similar situation to mine...

For the cam specs, go with a 224/230 combo. Keep in mind that your redline with a stock-type bottom end on a 400 should be 5600 or so...You will make massive torque, so just build accordingly. This engine, in stock form, doesn't like to rev and the stock rods will not handle it like a 350 due to a smaller rod/stroke ratio.

As for the compression ratio, it depends on what pistons you have. If you have flattops, then you are in trouble. I rebuilt my engine with the stock-type dished pistons...so when I swap on my ported L98 Vette heads with a 58cc chamber, I will be ok running 92 octane for sure. As for you, stick to 9.5 to 1...

HTH,

 

Oh yeah, ditch the Edelbrock headers...they are restrictive...You need to find a true 1 5/8" header set or 1 3/4" when budget allows.

Also, the SR is a great choice for maximizing the torque. Expect around 475-500 ft/lbs of torque at peak...more than enough...to justify modding the suspension

 

I still have a lot of tuning to do, You will love the 400 though, My car is my daily driver I put about 100 miles a day on mine, and love every minute of it. You will have alot more area under the curve than a 350 with the same peak numbers.

IM using a new stock replacement radiator, 180* stat with the stock dual fans, the first fan comes on around 190* second one 208* the car never goes over 212* degrees in heavy traffic. Runs cooler then the 350 did with the stock settings.

I agree with 88TPI406GTA on the exhuast, run as free flowing system as you can afford. Even with all the problems with SLPs I will be using there 1 3/4 headers in place of my Tes soon.

IM using the LPE 213 cam in my setup, 224/234* of duration with 1.6 comp rockers. It has a noticeable/choppy idle, I wouldnt use any more cam for this setup in a daily driven SuperRam 400 IMO. IM dont know if it will pass emissions though, we dont have testing here.

As already mentioned, I wouldnt push the compression either, stay conservative. You want to be able to run full timing without having to worry about a bad tank of gas/detonation killing power, or the motor. Even with the fast burn head chambers.

I would port the Accel intake also if you havent already. The SuperRam will be the restriction, in your setup. IM using a stock corvette converter it stalls around 2400, seems to work really well with my setup. The cam starts to really come on around 2400. The torque is awesome, the car will spin for blocks. But still makes decent horsepower, allowing you to feather the car off the line on street tires and still come out of the hole quick without alot of tire spin.

As you already know tuning will make all the difference in the world. You have the stuff to burn proms so it sounds like you will be all set to go.