I have been in a descussion over on LT1 Tech about putting these on a stock bottom 350. Apparently the car is a daily. My question is, aren't these heads too larger for a 350? This kinda goes back to the HotCam too big decussion that Bret started a while ago. Some think it is too big, others say that the HotCam is a small cam. When does a head become too big? I know it has more to do with cross section, but is there some kind of a guideline?

I personally wouldn't mind running some TEA port 190 AFRs, they endup being a 207cc port and have great flow. The thing that I am affraid of is it will lack good enough port speed. I have seen a guy run 210s on a 360, how much does added cu ins help large heads?

Thanks
Jeremy

 

Interesting post. I personally think you would be fine with those heads on a stock ci LT1. Personally the heads (non LT1) that I am going to run on my stock ci LT1 are going to be about 215cc after being worked.

I'll be watching to see what the Bauers and others have to say about this more indepth though.

 

Well IMHO it is all in the eyes of the beholder.

What are they willing to live with and what do they want. Parts matching is a must. There is no way I would be happy driving my 400RWHP car with stock gears and stock Torque Converter. Yet with a Yank 3,800 and 3.73s I love having fun in my car and I still get over 20MPG on the Hiway.

For some a Hot cam and big heads will not deliver the Drivabilty they expect in rush hour traffic on a day to day basis. With Stock gears and a good tune it will still surge to much in 6th(4th A4) to really want to drive every day.

On the other hand there are the people who visit this area often For most of us it would only be scratching the surface of what we truely expected

When I freashen the Wifes Motor up next winter(115,000 miles so far) I will be going for the first view. I will be stuffing a mild yet torquey LPE 211/219 in it with a mild set of cleaned up heads. This combo should make 325-350 RWHP and still be very drivable to my wife. WHile doing this we expect to keep our 19MPG stop and go commute economy. We drive this car 60-80 mile every day.

For many of the people I know a small cam and mildly ported heads will fill the bill. for others it is only a start. Most won't know fro sure till they junp in and start.

The first motor I built for my 95 Z28 had a ZZ-409 cam cut on a 115 LS...it also had a 14# pully turning the ATI ProCharger

That combo felt JUST right!

 

Are we talking about big power here? Or stuff you give your wife like Ellis is talking about here.

I started the HotCam too big thread only because I wanted to inject a little small cam thinking in around here. It blows my mind to see 230 duration intake cams on motors that consistantly peak HP at 6,000rpm with cams with much less duration. It just doesn't make any sense. You can make big power without huge lumpy cams, not that I don't like big cams I will regularly spec out race cams in the 260+deg range but we are talking about a low wide useable RPM range here.

Cubes and port volume are directly related, the more cubes you have the larger the port you can use easily. To put it in simple terms.

On top of that the camshaft and the heads are a combo. They work together and compliment one another.

As i've said before i'd rather have a larger head that flowed alot more and back off on the camshaft.

You really have 2 options, you can either have a bigger port that flows more w/ a smaller cam or a smaller port with high velocity and less flow that has a larger cam. Either way they will drive similar it's just how do you want to make the power.

The min cross sectional area does have something to do with all of it, and so does the shape of the head port. Comparing LS1 stuff to SBC stuff on ports that flow about the same, the min cross sectional area of the LS1 stuff is huge compared to the min cross sectional area of the SBC stuff. Port volume is really a hard way to compare them against each other since you could be looking at 220cc for the SBC and 240cc for the LS1. The funny thing is that the SBC 220cc heads are said to be TOO BIG on a 383 motor by the average board rat, and the 240cc LS6 head is placed on a 346 cube LS1 and makes stupid power and everyone wants one. Same board rats, different motor.

Talking about LS1's the basic design of that motor was to have a larger better flowing port vs the LT1 or LT4 design which is a smaller port that does not flow as well. The stock camshafts are similar in specs too. I'm not saying the only reason the LS1 stock dynos so much more is because of the better head but it is one of the many reasons and shows where the evolution of engine design is going on production motors.

The port volume is a range for what you have, what it flows and what the intended useage is. For example if I was to build a 383 for our people hauler Impalla I would probably drop on a set of heads that was around 195cc-205cc so anyone could drive it. If it was going to be my personal driver then the head volume would be much larger and I would wind out the motor a little higher.

On a stock cube LT1 with a stock intake you could run a 205cc head no problem. Ported LT1 stuff can grow to be about that large, normally it's in the 185-205cc range so there are guys out there right now with heads like that on a 350 bottom end already.

BTW what kind of flow are you looking at with those heads?

Bret

 

I may be the poster boy for putting heads that are "too big" on my engine. I'm running some Brodix -10's on a stock bottom end LT1. It runs really well, but I think that with better parts matching, I could do a lot better. I'm only spinning to 6500, and I'm sure that I could easily make good power to 7000 with these heads. Power never peaks before fuel shutoff. I'm running a 226/231 cam. Running too big will require higher RPMs to make power to the capability of the heads and can kill the bottom end. I make good power, but I'm not maxing these heads out by any stretch. I did lose some bottom end. Below 2000 isn't where my engine likes to be. It's OK above 2000, but it really takes off above 3000. I have an M6, and 4.11 gears helped a bunch.

When it comes time to rebuild, I'll use the heads to their potential on a stoker.

 

i find this pretty interesting and have always been a bit curious of how true it really is

what would you say the extremes of this idea are?

i've had this bookmarked for a bit, would you say this is a perfect example or a freak pump-gas race engine?
http://hotrod.com/howto/113_0206_1000/index.html

from what i gather, the heads on that engine are really intended for 600 cubes, and 7k+ rpm
oval port big chief type things

it doesnt have the low end of the dyno, but it makes peak power at 6500 and torque at about 5400

can the same be done with a 400cube small block and raised port canted valve heads?


and now to my next question.... if you can have a streetable motor with either big cam OR big ports (drives nice under 2k rpm), which ones kills gas milage?

i'm guessing its one and not both
it seems all big n/a hp motors cross some line where they leave their stockish characteristics behind and drop the gas milage right down into the low teens, is it due to the cam or the intake port having sluggish velocity at low rpms?

 

Try this thread...similar questions were asked:

http://web.camaross.com/forums/showt...hreadid=101736

 

Ok, I was reading the big cam/small head thread and it got me thinking. I know how how big cams lose lowend and can lose some mid range compared to a smaller cam. Will the same be true with heads? Will a big head lose lowend and some mid compared to a smaller head with the same cam? Just for argument sake, put the AFR 195 vs AFR 210.

 

Supercharged and turboed cars are basically Big Head/Small Cam theory!
LOOK AT WHAT THEY DO AND HOW THE DRIVABILITY IS RETAINED TO SOME HUGE HP/TQ NUMBERS!

Just thinkin out loud.