SO I tend to get easily bored, so I started looking for a new project...

I found a 400 block in Grove City for $175 - Had it checked out by a qualified machine shop, and is a good core to build from. I expect to pick it up late next week or early the follow week. I've never had a 400 sbc, so I may be looking at a potential swap down the road, if I carry this one out. I am looking for guidance on part selection, but want to reuse parts where it makes sense - I have:

A good 383 long block, with AFR 195 heads. Currently it is running an edelbrock 7104 intake with QJet;
I also have an RPM Airgap with a 4150 DP (750 CFM) that I've used in the past;
Stall converter is a B&M 2200 RPM converter, and the cam is XR270HR (I tend to favor mild cams with low-mid torque) with 1.65 roller rockers.

The 400 is going .030 over, will be machined for splayed mains (it is currently the 2-bolt version with thicker webbing, but I don't recall the serial number).

I have a balanced 400 rotating assembly on order through the machinist - cast steel but rated up to 550HP; that is higher than I want to go with this build anyway. Shooting for 10:1 compression ratio.

One thought for this project is to re-use the AFR 195 and one of the two intakes - I prefer the QJet but like the Holley too – it’s simple and straightforward.

The cam is still a question for me -I have modeled the same cam in the new 406 block, I think it would make great low end torque - but am looking for better suggestions or opinions.

I'm very open to getting a new cam/torque Converter if it suits my driving style.

This will likley go into my 79, with a 700r4 and 3.55 rear gears - I do a lot of highway driving, but do like to have some fun in it when I have it out. I like low-end grunt, but almost never hit 5500 RPM - just wanting to build a really stout, fun 406.

Any guidance is appreciated - Thanks!

Jim

 

What will the compression ratio be?

 

Planning 10-1 static - have not put thought into the dynamic comp ratio yet, but I guess that will come with cam selection. Edited that into original post.

 

I went with the xe288hr with 9.1 to 1 it runs good, but I think it needs 10 to 1 on the compression, and really think the afr heads would benefit from a lot more lift. So I'm going custom, only because I think with out a cam shaft suited to both compression and head flow I'm leaving some on the table. The 288 will spin the tires, cones alive at 3000 rpm and pulls string up top.

 

I just finished my 406 for the second time. Now I knew what I wanted it to do. I used 5.7" connecting rods, Icon Forged pistons, Comp XE268, Scorpion 1.6 roller tip rockers, Dart Pro 1 215cc aluminum heads and air gap intake. Just make sure that when you put your heads on that they put the steam holes in. Dont let them talk you out of it. Your heads will make the motor. You will love the motor. I ended up about 10.2:1 and it really hits good.

 

Vett400 - why a cam with shorter duration than I typically here of - Good lower end torque?
Bluedawg - I take it you are running AFRs - what size? I want a good match for my AFR heads, but don't want all my power up too high in the RPM range - although I realize I can compensate for some of that with the right torque converter stall.

I'm struggling with going with something around 270 vs a cam that will extend the power range like Bluedawg's - Would like to know what factors went into those choices, those are the sort of things I'm trying to work through...

AS I typed this - Just got a message from the machine shop - the block and my rotating assembly will be ready by Friday afternoon---Stoked! Now I really need to sort out the cam and torque converter questions!

 

This cam was recommended to me using the 1.6 rockers by some of my dirt track guys. I do have great low end torque and still have enough vacuum to run my car. Found that I liked the launch more than the top end. In my build it ended up being a great combination. Could not be happier with it.

 

http://www.crower.com/camshafts/chev...-cam-4121.html With your 1.65 rockers and a 24-2600 stall convertor

 

Afr 195's street port. Like I said it runs good, I based the cam selection of a build on afrs site for a 383 cid. They did it with 9.5 to 1, made 500 horse, and I'm by no means disappointed with the cam selection, I just think that the heads would benefit from more lift and and my compression ratio would work better with less overlap, Not a bunch less. I won't be changing the cam until fall or at least that's the plan. Hope to make it to the midnight sun fun run for a base line the way it sets. Vacuum on this cam barely runs the lights and brakes and comp says 9 to 1 minimum, I'd think that 10 to 1 would be better minimum. If you got gears and match the stall converter to the cam shaft you wouldn't notice any low end loss.

 

I have the compcam equivalent (XR276HR) to this one in my 406 with vortec heads. It's a real stump puller, and I can cruise comfortably at 1800 RPM in 5th gear. It has a noticable idle with a slight shake, and 12 or 13" of vacuum (IIRC).
With those AFR's you'll get that and much more above 35-4000 RPM...

Whatever you do make sure you go roller cam....

 

Definitely going roller - only way to go IMO.
My heads are also the AFR 195 street version. No complaints at all.
63Mako - will check that cam out - thanks!

 

Before I posted this, I had thought about the XR276 cam, it seemed like a comparable performance curve but with the added benefit of more cubic inches.

I don't want my power band any higher in the rpm range, but don't want to leave good power unrealized either (wanting to have my cake and eat it too).

The crower is similar but better (higher) lift. After mulling it over, I bit the bullet - crower cam is on order. I'm going to see if I can get at the part number of my converter and verify the stall rating (i think it's close, but need to know).

Now thinking about the AFR heads, and researching drilling steam holes - have read people on either side if this topic. Any input on this subject?

 

I cant say for the 400 block, but for the shp block you dont need steam holes.

 

You will need springs for those heads.

 

Yes, realized that I will need the new springs after talking to Jegs - on order - thanks

 

I agree with cam choice and that you'll also need valve springs.
With a factory 400 block the steam holes are required and make sure
you use head gaskets with them.You should have a good running car
when all is said and done.

 

Selecting the right cam. Heads will determine much of the cam. One key item is I/E ratio, what % does the exhaust flow of the intake. At 75% a single pattern cam is best suited at .050" duration. Below 75% the duration will favor exhaust (larger), above 75% the duration will favor the intake (larger). For every % point you can add about 1.25 degrees of duration.

AFR's have high I/E ratio and like duration at .050" very narrow split or maybe the same. If you put to much duration on the exhaust you blow torque right out the pipe. If you don't put a enough you smother the engine as it can't rpm because exhaust is contaminating the fresh intake charge. If you see a dyno sheet and HP stays the same for more than 400 rpm, it is smothering. Add duration to the exhaust and it will climb.

Your max rpm of 5500 warrants something like:

550/520
220/223
108

This would give you a square power engine 500/500. Excellent driving manners and power no matter where the tach needle is.

 

Cstraub69 - excuse my ignorance, still learning here - I assume I read those numbers as:

550/520 I/E lift?
220/223 I/E duration @ .050?
108 LSA

Ive looked at a lot of cam specs online, i think this sounds like a custom grind?

 

Except for the new Clay Smith Legend Hyd. Roller series I don't have any cams on the shelf. All my stuff is one off. Yes the above is based on what info you have posted. It's your money. When I spend mine I want what I want.

 

Just built a 406 and the one thing I wish we did was use a bigger head... It has AFR 195's on it now and I think a 210 would have been a better choice. We were pretty conservative with the build since its going in a ~3500lb car with a .5 overdrive gear and 3.90 rear gears. The motor is VERY mild in terms of streetability. Doesnt buck at low RPM in overdrive, idles @900. Now that its done I wish it had a bit more power. The damn thing wont smoke the tires into 3rd!