74vetteman

Do you guys think that the RPM heads will flow enough for a 406 ci small block? As cast they flow 233@500 lift and have a 170cc intake port. As far as the rest of the engine, I will be using a Scat cast steel crank (3.750 stroke), 4340 h-beam rods (6.00"), and forged flat top pistons on a zero deck motor. Intake is a single plane Team G street ram with a 750 cfm holley. Cam is a comp XE274 hydraulic with 1.6 rockers (230/236 dur.). I may also look at getting a 3.875 stroke crank to bring displacement up to 420ci.
Any thoughts or imput on my combination? I want decent streetability as well as being able to run in the high twelves.
The car has an m-20 with a 3:73 rear and weighs around 3400lbs with me in it.

Beach Bum

I would think you would want to jump wayyy up with your head selection. I haven't run your set-up on an engine simulator, but I would guess that some AFR 210's or equal version Brodix head and you should be able to feed your monster mouse. I think the Edelbrock heads you have mentioned are more intended for 327-350 cube motors, and I think you'd be bottlenecking your motor with them. As a note, I think you'd be selling yourself short with high 12 second expectations, I would think solid 11 second et's would be your potential.

good luck
Beach Bum

The Green Rocket

If you are thinking of 406, and possibly 420 cubes, then you need larger intake ports. As Todd said, the 170 cc's are for 350 or fewer cubes. You need at least 210 cc's intake ports, which would be minimum with 406, for the 420 cube engine you need minimum 220 cc's intake ports, 230 cc's probably wouldn't be too large.

You can of course run the 170 cc heads, just be prepared for an early end to the horsepower parade - like around upper 4,000 rpm and then the show is over!

Gordonm

I agree with the others. 170 is way to small for 406 or 420. You should be in the 220 range. Also the cam selection is a little small for a 406 or 420. When you go up in displacement you also need to go larger in the cam. What applies for a 350 is to small for a 406. A well built 406 should get you into the 11s.

89vette

Now way. There are tons of great heads out there for yor car. I had the CNC ported L98 heads and now the AFR 195 Competition ported. Both were great heads. Depending on your intake and your goal, the 210's might be better. AFR's are pricey with the full works but I have to say that they are a quality piece.

74vetteman

Thanks all for your replies. I can see the consensus is that the rpm heads are too small.
The machinist who is going to prepare my block recommends the Edelbrock Victor heads. They have a 215cc intake port with 265cfm@500 lift, and a 2.08/1.6 valve. At higher lifts they flow better but my cam selections highest lift is around 540 (or so). They are also in my price range. What do you guys think about these heads?
Streetability is still a concern. I don't want a dog on the lowend. If you read my signature you can see my current setup. The Comp xe274 idles a little too rough for me but may be just right with a 406. My best 1/4 is 13.8@103 (at 3500' elevation) although my car is not optimized for drag racing (stock mufflers, street radials, road race type suspension set-up, and not quite enough compression for the cam[9.12-1]). All out drag racing power is not what I want. I want a car that idles decently at 750 rpm, has decent lowend power, and makes maximum power at 5000-6000 rpm.
Keep the suggestions coming.

gkull

I can see what your trying to do. by using your cam heads and intake to save money. It would run fine up to a point. I don't know how many rpm you want to do but for a 5500-6000 it would be way above any 355 in terms of HP and TQ.

All big port heads do in raise the power level across the total rpm range and if you have enough cam give your motor a chance to breath at higher rpm.

I had a XE274 in a 355 last year. They are pretty roudy. If your want to look at it another way. cars of many years ago with iron heads ran great. Yours are better flowing that any of the old stock iron heads. I would try it, and a year or two down the road improve if you think that you need too.

JAKE

Well, here's my 2 cents worth.

I'm running those heads on a 415 and for what I was looking for they are perfect.

Sure, AFR 210's will make more power because they will breath better up top, but I turned down a set of those (free) to keep my Edelbrock RPM 6073s because of what I'd set my sights on.

My car is a daily driver and has never been down the quarter, although I use to drive a low 8 second roadster when I was young(er) and crazy (ier).

Just to give you an idea of what I mean about my "sights", I'm about to pull my Walker DynoMax SuperTurbos and install a pair of 'reproduction
Quiet Flow' mufflers - and give away about 11 Hp in the process - because I want smooth and quiet instead of having the exhaust talk to me.

So, it depends on what you're looking for.

Jake

korvetkeith

JAKE, I'll take those 210s if you don't want them. I used to think the Victor Jr.s were good, until i saw CHPs head comparo. The AFRs outflow the Edelbrocks at all lift levels, and especially in the lower lift numbers where the Victor doesn't catch up till .700" lift, which no street cam would have anyway.

gkull

Your money would be better spent on an internally balanced forged crank 3.875 or 4 inch, 6 1/4 Fluid type damper and a light weight 168 tooth. Then get a real cam and heads

74vetteman

Well, I went to the local speed shop and purchased a internally balanced Scat 3.75 stroke crank for 6" rods (can use my current flywheel and dampner), 4340 6" h-beam rods, and KB hypereutectic pistons that will give me approx. 10.5:1 compression which is getting close to borderline for the street. I will follow Gkull's advice and use my old heads, cam and intake and see if I like it.
I think I will put on a two piece timing chain cover so any future cam or head changes will be easier.
BTW, Chevy High Performance magazine built a similar engine utilizing the same cam, less compression (9.5), same carb, dual plane intake (vs. single plane), 1.5 rockers (vs. 1.6), Dart iron eagle heads (200cc intake, 72cc chamber, 2.02/160) vs. rpm heads (ok. got me there). It dynoed:
max. torque-509@4000 rpm, max. hp.-452@5300 rpm. At 2500 rpm it still made 441 ft/lbs of torque! This is pretty much what I am looking for. If I can make close to that I will have a great mannered street car with decent power.

Lt1er

I think that your going to be all smiles when you get it running. But your going to be like me wishing for some kind of over drive.

JAKE

Sorry, big guy, they've been sold. One of the guys on this forum jumped right on 'em.

Jake

El Mago

74vetteman:
Our setups are very alike, only difference is I have an Edelbrock Pro-Flow FI, which I'll be replacing with a Team G and an Edelbrock performer RPM Q-Jet.
My heads are fully ported, so they might have slightly larger intake ports, I'm running a CC solid roller 224º/224º @.050 w/.56" lift (1.6 roller rockers), comp 10.0:1
The engine is powerful (see sig.) but peak HP happens at 5300rpm.
Torque IS impressive though, just to give you an idea, the car cruises in 6th at 1000 rpm and it pulls nicely from down there (3.08:1 rears).
Nice street engine, fun and fast, but you CAN feel it runs out of breath "early".
What's more, @4600the engine is at 320rwhp, and by 5300 it's reached 360, larger ports will surely gain much more.
If you're interested I can mail you the dyno #'s.
I'll probably go with AFR 220 or something on that range by the end of the year.
Gary



[Modified by El Mago, 1:56 AM 8/18/2001]

74vetteman

El Mago,

I would be quite pleased with the hp and torque results that you have. Do you have any 1/4 times with your current setup? Why the change back to a carb after fuel injection?
My biggest concern would be losing driveability with larger port heads. Is that a valid concern or is the engine large enough to use that big of ports and not lose any low end response? I am willing to trade some hp for a civilized driver.

CORKVETTE1

here is my 2 cents i dont think you need 210-220 cfm heads i said it before and i will say it again i went 10:89 et in the 1/4 with a 82 camaro with 195 cfm afr heads on a 420 cid motor with 3:31 gears and 3400 stal converter very driveable at 3500 lbs with me in it here is a link to pic http://hometown.aol.com/corkvette1/m...age/index.html

El Mago

74vetteman:
as to port size, mi line of reason is: the big blocks heads have port sizes that range from 220-330cc on the average, valve size is also larger and on 396 BB I've never heard of any driveability problems. Remeber that until '70 the largest BB was the 427, so 21ci difference on a 406 can't change the engine character so much....
Stick to a 190 - 195 intake port and you'll still be just fine, remember the cam is very influential on idle quality... mine is a solid roller but at 224º I/E it idles beautiful at 800rpm's
As to the FI, I bought it in '94. Back then, no internet, no forum, it was a very rare piece. I've never been eable to get it right, I even suspect one of the reasons I'm short on power because of it, the other being the small (for a 406) intake ports. I'm going to try with a carb/manifold setup and maybe someday go back to FI, either Accel's, Speed-Pro or I've heard Holley's pretty good.
NO quarter times, but the car is wickedly fast!!
Gary

MCAF84

74vetteman: I am currently using the set up you are talking, but am using a duel plane intake. It makes GREAT torque all the way to 5000 RPM. I have not noticed any drop off in power in the upper ranges. I do have traction problems, thru first and second gear. I drive the car every day with A/C its HOT in the south.

Monty

I think you would be short changing yourself with those heads. I'm sure the motor would be very responsive and have tremendous low rpm torque. However, I think you could have equal throttle response and low-end torque, with more mid range power and more rpm range with larger heads. 233cfm is not very impressive in all honesty, maybe for a 305 or a mild 350, but even a 383 would like something closer to 280+cfm.

Port volume has gotten alot of attention in the past few years as people have realized that intake velocity is a significant consideration in making a responsive, torquey motor. However, just because a port is larger, does not mean it will lead to a loss of response and low-rpm torque. If the port size is increased but low valve lift flow is not reduced, that's an indication that it is an efficient port. Alot of people like AFR heads, and they are very good, especially for the money. If you compare their flow across the valve lifts with theose smaller Edelbrocks, I'd bet you'll see the AFR's outflow them at most all lifts.

The heads I run on my SBC427 have 255cc intake ports, yet they outflow most any smaller head, even at low lifts, and the motr is very repsonsive and makes good torque, over 500+ ft lbs from 3000-7000 rpm. I'm certainly not recommending such as large inbtake port, but I think you should check out AFR's 210, 220, and 227 cc heads. If you are willing to use a raised port design, AFR's 215RR heads are awesome. I wouldn't be surprised to see you run mid to low 11's with a AFR215RR equipped 406 with a nice roller cam in the 230's/240's duration.

Smitty's75

Also check out the Dart Pro 1, A whole lot of head for the money...and you'll find more Dart & Brodix heads at the dragstrip than all the others combined,,must be a good reason for it!!!!!