CHP magazing has a buildup of a 406, with AFR 180cc heads, 230 deg Lunati cam, 1.6 rockers, RPM intake, and 750 holley. This sucker makes 525 lb-ft at 4100 RPM and 490 HP at 5600 RPM. Those are awesome numbers at real street-usuable RPMs. I love it. Especially because I have a '73 standard bore 400 SB sitting in my basement. I think it would make a real nice future motor for my 68.

However...

I'm not a hard-core race guy. I'm more of a cruiser and weekend warrior. I don't want a highly modified, racey looking machine. I'd want to do it as a semi-sleeper. That means I don't want to jump to a BB or L88 hood. I've read the threads about which intakes work with a drop-base aircleaner, and although the RPM has worked in a few cases, I might have to consider a lower intake. With this much power and torque on hand, I think I could live with the outcome, even if performance take it in the shorts a little. That's my question for you motor builders...

How much power would I expect to lose with a Performer EPS, Weiand Action Plus, or something similar? I doubt I'd see much change in low-end torque because the RPM is already a pretty decent piece out of the box. Another alternative is the Torker II, which is similar in height to the Performer EPS. In a way, the single plane might be a decent option. With all the torque and airflow of this 406 (over 500 lb-ft at 3300 RPM), a small drop off in the lower revs might be acceptable. I'd imagine the drop would be quite a bit less than with a 350 because the airflow at any given RPM is so much higher.

What's my best 'short engine' combination?

This is a classic Corvette design issue. Remember when the 427/435 engine was changed from 67 to a lower intake for 68?

Just curious for your opinions.

 

You and I think alike!

That is my motor almost exactly. I have a Performer Airgap manifold on there now and will probably switch to a single plain variety.

Really because I can afford to trade some TQ for HP.

I have a standard dropbase air cleaner. Its actually a knock-off of a Corvette LT1 cleaner, which is a drop base. It fits fine. My engine idles smooth as stock. Its really a fun setup for the street. Nothing like being buried into your seat at 3000rpm too!

 

I wouldn't worry about the intake, you can put just about any intake on a sbc in Corvette short of a tunnel ram with a drop base air cleaner.

Take some time and match the components correctly, to get that much power out of a 406 with that cam and heads those guys new what they were doing when they picked the parts.

Build a 406ci you won't regret it

 

The Performer is a low rise and should fit.Losses over the RPM would be minimal due to the range of rpms the 280 degree cam would pull. If I were doing it I'd steer clear of a single plane.They were designed to shine over 5000 rpms where most of us usually run.
I actually blew my 700r4 shifting at 6500 with the RPM intake I currently run,so just because it's not a single plane,doesn't mean they can't turn up the rpms.

 

i started out with a Weiand high rise dual plane intake, it worked great with the smaller cam, and cleared the stock hood. i am running an RPM Airgap now, and had to go with the L-82 high-rise hood. a nice dual plane will work better with the cam you looking at. a single plane will kill throttle responce and make the motor soft off idle. when you build the 406, make sure you start with a two bolt block and run 6.0" or at least 5.7" rods. the stock 400 rods suck the big one. a sonic check on the block will also let you know if there is sufficient metal at the bottom of the cylinders. what ever heads you run, make sure they have steam holes drilled for cooling. there are several very important issues that need addressed, when building 400's, to make them bullit-proof. they don't cost much extra if you have the info upfront. by all means build a 406, 426 or 434 small block and reep the rewards of big displacement and small block weight. Brian

 

I've emailed with a couple guys who have the RPM airgap. It's possible to fit it under a SB hood but far from easy. The Weaind Stealth is a tad shorter in the rear so it might help.

I'm hestitant about the performer low-rise. I've read several tests where it runs out of steam at 5000 on a 355. If it runs out of steam at 5000 with a 355 it will run out of steam at 4300 with a 406. Remember, the manifold doesn't know what engine it's on; it just knows airflow and a 406 flows a lot more air. The cam can't change that. Now with some agressive intake porting in the plenum....

In my reasearch, I ran across an old Car Craft dyno test where the compared a Performer, a Performer RPM, and a Torker II. The Torker II was the dud of the test, barely matching the top end performance of the Performer with far less low-end. The RPM was the king across the board.

This decision is a little ways off. I'll continue to play around and figure out what's the best tradeoff. Maybe I need to dust off the LT-1/BB hood I have in my basement. It'll kill off some of my sleeper-ness but maybe that's OK.

 

I just stumbled across this:

http://www.holley.com/HiOctn/ProdLin...AMSM/7525.html

That looks like a decent alternative....

 

The Wieand Stealth manifold is superior to any of the Edelbrock rpms.

I use this with a 1/2 wood thermal open spacer and a 3 X 14 K&n open element http://www.holley.com/HiOctn/ProdLin...AMSM/7530.html

To everybody looking at this post. The problem point is the front edge of the air cleaner to hood clearance. The hood sloopes up and the engine actually slopes down towards the rear. That's why manifolds are higher on the back to bring the carb to a more level position. So the front hieght of the manifold is the most important number.

 

Gkull:

Thanks for the comment on hood/aircleaner clearance. That was somthing I was wondering about as I looked at different manifold heights. Make sense!

Now I really question the Stealth. Its virtually the same height as the RPM Air Gap. The Weiand 7525 is looking promising! Of course, now I'm finding that it's no longer being produced...

 

I am fortunate to have www.summitracing.com about 10 minutes from my house. So when I was buying intake manifolds I went down and bought four different kinds and took them home and took them out and looked over each one.

Every time over the years that I've unboxed a Edelbrock no matter if it was an RPM or RPM air gap or one of the Victor Jr's. I was just pissed at the poor casting quality. The output ports are not aligned or even the same size. So it would take a few man hours to port match to their respective Felpro 1205 or the larger FelPro 1206 gasket size for the VJ series of intakes.

On the other side the World products, Motown , and Weiand were nice castings without port flaws and it only takes an hour or so to do an exact port match. That's bolting a bare head and the manifold together and using a bore scope to look inside to figure out where to grind to perfectly match the intake to the head.


As for the 7525 I had that and a Edelbrock 750 on my Vette for 10 years. I just gave it away this last spring. I would ask Summit if they have one in a warehouse

 

I tried Summit and was told they have no more 7525s and that they're discontinued.

I set up an alert on ebay if anyone puts one up for auction. It looks like that's my best bet.

 

Is there any difference in 500ft/lb of small block torque and 500fl/lb of big block torque?

 

Since Holley purchased Weiand, things are a little confusing on the manifold front. Back in the day there was only one Weiand "Stealth" manifold. Now just about intake that's released with the Weiand name has "Stealth" applied to it in the marketing materials. I'd be suprised to discover that they're not calling Weiand water pumps "Stealth" these days. LOL. If you can't find what you're looking for with the Weiand name on it, call Holley's tech and see if there's a Holley-branded intake that's comparable (if not the same thing.) They'll hook you up.

 

weight!!! and lots of it.