Current setup: 434 Small Block

Current cam: 250 / 256 @.50 on 106, installed 102
Lobe Lift : .440 /.440
Rocker ratio : 1.55 / 1.55
Intake: Mini Ram (Cut, ported and welded ) flow max out at 336 cfm.
Compression Ratio: 11 :1

Heads
Brodix 15º Flow Numbers
LIFT INTAKE EXHAUST
.200 153 120
.300 228 170
.400 282 216
.500 322 233
.600 332 240
.700 340 252

2.150 Intake 1.600 Exhaust
· 60CC Chamber
· 262 CC Intake Port
· .550 Offset Rocker Arm
· 180 Offset Lifter

New setup: 434 Small Block

Requirements: Peak torque around 5500 to 5800 rpm, redline around 7000 rpm. Do I need a cam change? I would like to fatten up the area under the curve. This is top end car for The Maxton / Texas mile. All suggestion are appreciated.

Compression Ratio: 11 :1
Intake : Edlbrock 2955 spider converted for fuel injection
Rocker ratio : 1.55 / 1.55

Brodix 15º Flow Numbers (Ported By Rons Porting Service)
lIFT INTAKE EXHAUST
.200 155 125
.300 230 175
.400 290 210
.500 340 232
.600 375 241
.700 386 251

· 2.200 Intake 1.600 Exhaust
· 69CC Chamber
· 297CC Intake Port
· .550 Offset Rocker Arm
· 180 Offset Lifter

Thanks
Yedi

 

are you asking if switching to the higher flowing heads will help increase midrange power? I don't see where they could hurt anywhere but your bank account. Your powerband could move up and to the right, but that should allow you to accelerate quicker. If you don't or can't change your gearing, then simply advancing your valvetiming should move the power curve back a bit.

 

Man, those ported exhaust numbers look kind poor though. I'd want to see MUCH better balanced percentages. And for top end, who cares what's under the curve, gear it to get to maximum output and stay there at WOT.

 

It would help to know dyno numbers now, where it peaks especially.

Rich

 

That does not work for my application because the distance of 1 mile and breaking the tire loose under hard acceleration. In your opinion what balanced percentages would be better?

 

When I return home, I try to find then. it has been several years since I saw them. I do remember Max torque was at 5500 (622 ft. lbs.) Max horsepower was 6500 (719 hp)

 

I THINK THE EXG SHOULD BE ABOUT 80% OF THE INTAKE FLOW. CHEVYS HAVE ALWAYS BEEN A LITTLE WEAK ON THE EXG SIDE. YOU COULD RUN A LITTLE MORE EXG. DURATION TO HELP. OR SWITCH TO A SB2 TYPE HEAD. BUT EVEN WITH THE SB2 HEAD YOU WILL ONLY GET IN THE 280`S ON THE EXG SIDE. CK THIS LINK THEY HAVE A BUNCH OF HEAD FLOW #`S http://users.erols.com/srweiss/tablehdc.htm#Chevy

 

If ya have enough P/V clearance go up on the rocker ratio. Maybe 1.8+. I don't know what fuel you are allowed but your compression seems low.
If you have a 4.030 bore that big intake valve is shrouded a lot,unless the heads are canted valve and open to the center of the bore and I am not sure of that.
According to the rule of thumb a 4.030 bore should have no more than a 2.115 valve max. According to some of the more knowledgeable head designers/porters,if ya go bigger you are "DEAD in the water"
Ya see the BIG numbers on the bench but the engine never see's anywhere close to the bench numbers.

 

I have a set SB2.2 heads for another project, and the exhaust flow is not much better

 

Your BMEP @ power peak (~202 psi) is low for good 15° heads, IMO. I assume you have a 4 inch arm and a bore around 4.155.

Is there a reason you don't want to spin it above 7? With a 4 in stroke, 7500 is 5000 fpm mean piston speed. How about looking for power ~72-7300? With a 210 BMEP, which is doable, you'd be north of 825 @~72-7300 rpm.

You might want to look at more lift, as the (new) heads seem to like it. I'd get a pro to design the engine/valvetrain.

 

yes it is a 4.155 bore with 4 inch stroke, I have seen motors that let loose at high rpm's, It was not a pretty site. The piston can take 7500 rpm, which is the max rpm that are designed for, I am not against it, it is just a preference. The valve train is a Jesel because of the offset lifters and rockers.
"With a 210 BMEP, which is doable, you'd be north of 825 @~72-7300 rpm."
How do I accomplish this? New heads with bigger cam, if so what do have in mind? I have talked to several engine builders and 15:1 compression will give about 820 HP. That is not something that I want to have, a track only car. i enjoy driving way too much to tow it to the tracks then drive it home.

 

I have enough P/V clearance to use a 1.8 but why would you want to run .792 lift when max flow is at .700 lift? I have a 4.155 bore, currently I have a 2.15 Vallve, If I change the other heads have a 2.2 Valve. The 18º cylinder heads were released for Chevrolet 350, 9.1 compression NASCAR racing engines. Those heads were recommended for cylinder bore diameter of 4.000"-4.155" and has a common Intake valve diameter is 2.15" My current 15º heads fit well into into the bore size maybe on the small size.

 

It isn't just compression that will give you 820+, it's a lot of things. I take it you run standing start 1 mile races?

No offense, but from your posts, your best bet is to find an engine builder you trust who will tell you generally how he plans to achieve the BMEP and rpm necessary. Ask him about lifting the valve past it's max flow point, and why he would or wouldn't do that. Your published flow numbers don't indicate that max flow is at .700. Graph those numbers and you will see tha flow curve is still climbing.

The piston is only good to 7500?? Generally it's the rod that has the problem with rpm and holding the forces generated by the piston gs.

OK so if your shortblock isn't 4-bolt steel caps, decent forged crank and rods, and decent forged pistons, it's a whole other ball game. Generally folks overbuild short blocks, but yours may be the exception. We can't tell without knowing what parts are in it.

 

As far as higher ratio rockers, there is more to consider than max lift. What they do is increase the rate at which the valve reaches each point on the lift curve. In effect, they increase the duration at each point on the lift curve (other than closed). You can't achieve the same valve acceleration just by grinding the cam differently. There is a maximum rate of lifter acceleration which is primarily a function of the lifter diameter. Some max effort builds involve boring out the lifter bosses for that reason - so that larger diameter lifters may be installed. Also, if you get the acceleration at the cam, the whole mass of the lifter, pushrod, and that side of the rocker has to be accelerated more rapdily which puts added strain on these parts.

Rich

 

Did you get Ron's shelved 15 degree brodix package? I am not ashamed to say these are the nicest wedge brodie's around!! The 80% exhaust rule is much more an urban legend than a rule...The rule is a properly designed exhaust port reguardless of flow numbers...period! Ron's program is spot on for what the head was intended for...BUT!!! Your engine design is not optimum for the head.... Did you talk to Ron or just who answered the phone.

IMO....
1. Why is the compression so low?
2. The cam is of poor design...especially for ECTA racing with this head..
3. Why so low on the revs?

Basically...you bought a ferrari to mow your grass...

One thing I can say for sure...Ron does a helluva job with those brodie's...and I am not a brotherton fan!!

And another important point...if you are talking to Ron and he tells you something...the dumbest thing you could do is come on a forum like this and question him! I am one of his competitors... IMO...in this business there are 3 people that are really pushing the edge...and Ron is one of them!

Dennis