cam shaft and head recommendations

Hey,

anyone have any recommendations for a cam and cylinder head to improve road performance for my 1968mgb its a twin carb setup and i recently replaced the manifold.

nicholas.

Piper or Kent 270 & a Stage 2 head from Burgess.

http://www.teglerizer.com/mgstuff/mgbcamspecs.htm
http://www.mgcars.org.uk/peterburgess/

Here's the thing Nick, unless you do some other things like putting some $$$$$ in the head and various other modifications including carburetion to improve CFM's. Just pluging a cam into a motor doesn't do a whole lot. I tell my customers by caming up a motor you might see some improvement on a dino, but as far as seat of the pants you not going to get a whole lot other than bragging rights. Now I'm sure there have been those that put a "FAST ROAD" cam in their car and felt that there was a huge improvement. I say, That's no more than the power of suggestion.

Tom Bedenbaugh Wrote:

Port the cylinder head. Sean Brown can do it. We can do it. Lots of people can.

For a street engine that isn't going to have it's lower end rebuilt/balanced get a VP-11 cam from Dave Anton at APT. Dave's a great guy, he knows what he's doing with camshafts and deserves the support. If you were rebuilding and doing some balancing I'd go for a VP-12, but since you won't be revving past 6k the 11 is perfect.

I remember reading a post from Carl Heideman saying that the best money spent is on polishing and porting the head.

My thoughts on cams and engine modifications. Unless your going to do it all. Cam, ajustable cam gear, high ratio rockers, wasted stem valves, P&P the head, lighten, polished,& balanced rods, upgrade to SU HS 6's or 45 DCOE Weber, free flow exhause, and blue print the engine $$$$$$$$$$$$$$$$. Then your better off just getting a new stock pre smog cam and leaving things alone. There's an old saying about hot roding a motor,"YOU PLAY YOU PAY." I advise my customers to go with the stock billet cam from Crane unless they really want to go full boar to build a truely 130-150 HP hot street motor. You got to know 5-10 HP doesn't make a whole lot of difference. High strung motors don't have any gray areas. They had better be right and require more maintanance.

The only modification to my 72 GT motor (other than a weber installed recently) was a rebuilt head with a P+P. There was a noticable zip added to the car. Not sure on specific numbers, as it was not dynoed before and after.. but it was sure better and very noticable.

I would say the P+P would be better money spent than a cam, of the 2. But do both for a significant improvement...also a larger exhaust might help too..as you need to get air OUT as well as IN.

There are tons of go-fast goodies you can add..

BUT JUST to save gas, I would leave it alone! the amount of $ you save on gas (say 1-3 mpg ...if that) would take a few hundred decades to pay off the work done to the motor!

If you want to do the work to make the car snappier..more fun to drive..and if you save gas at the same time..go for it. But I think it is a false economy to spend a grand or 2 on an upgrade to save 50 cents on a tank of fuel in fuel economy!

(edit to clarify - stock motor on my 72 GT)

Paul I assume you did that to your 80 RB. That's a whole different bag of beans. When you do a Weber or SU convertion to a water choke B then you just added about 50% HP to a 62 HP motor. It's hard to believe but the series A Midget motor has more HP that the seriously choked up 75-80 1800 B motor made for the USA. The cam, MANIFOLD and water choke Stromberg SUCK. Mostly it's in the desine of the manifold.

Tom Bedenbaugh Wrote:

While not inexpensive, I’d recommend porting the head before investing in a big cam. Reason why- Power is made by flowing air. Anything you do to improve flow will result in an improvement in power. The detail to look at is airflow that occurs during a single cylinder cycle of the engine.

Airflow can be improved by going to a big cam, big valves, or ported head.

Look at published flow vs lift numbers at http://flowspeed.com/process.htm First, looking at a stock cam, max lift is about .375” You can see that there is 10% more flow at most lifts (intake valve). If you were to plot the lift vs. time at that lift, you’d have a curve that could be used to estimate total airflow improvement. Compare that with the similiarly shaped but smaller stock airflow curve. That change would be result in increased power. The ratio of difference of the airflow curve areas would determine the amount of power increase.

Similiarly, changing camshaft will will also raise the starting point of the curve (longer duration) and the max flow number (greater lift) than stock. Looking at stock port flow values, you can see that the change from .400 to .500 lift results in an increased flow of only 5cfm, where a ported head at .400 flows 21 cfm more than stock (Inlet valves used as example). What this means is that you need significantly more duration and lift to achieve the same airflow as a good port job. This would be a non problem, except it comes at the cost of moving the torque peak to a higher rpm.

While this same torque peak value would result in higher HP than the same peak torque value with a ported head, the essential sweetness of the MGB engine is compromised. It moves from being a kind of the fun girl next door to a high maintenance b***h, demanding more shifting to keep power on the boil.

There is nothing wrong with re-camming an engine, as long as you have a handle on where you’ll end up. There’s nothing wrong with high maintenance cars or women, if you’re willing to sign up for that. The reason most people recommend relatively soft cams is because a lot of people talk about big hp numbers, but aren’t willing to live with the pain it can be to achieve those numbers. I’m more than willing on the little green race car to make all kinds of sacrifices, but I always like coming back to a softeer, sweeter engine.

So…

Ginger or Mary Anne?

My take on a lot of this is what are we compareing to? I did some DIY porting on my head, VP12 cam, 020 over 8.8 AE pistons and played with several carb setups before settling on the Mikuni. Did I notice a difference? Well yeah but the original motor was bone stock with 90,000 non OD miles.
When modifying any engine the same concepts hold true. Everything needs to work in harmony. The only truely bolt on stuff that makes a difference "in some cases" are a different fuel delivery and exhaust. Tom mentions a perfect example of converting a late ZS and cat converter car to earlier spec or alternative carburation. My TR8 was another good example. When I got it with the stock carbs and exhaust, the acelleration was OK but rather liesurely. Simply bolting on an Edelbrock, Holley carb and a set of headers transformed it into a hot rod. This is probably why SCCA has the Street Prepared class for stock engines with only induction & exhaust mods. Once you start changing things around inside, you need to consider how all the modifications will work together.

Limey Wrote: