Desktop Dyno pros in here

DanM · #1 (**permalink**) 07-30-2004, 08:36 PM

Hey guys,

Trying to run through some preliminary 351W #s using DD2000. What I'm noticing is that going from stock heads to ported stock heads to GT40P heads is showing almost zero difference in DD2000. I've used a CR of 9.5:1, about where I figure I want to be, and a Comp XE274 cam which is what I was thinking of using. I just expected that with that cam, and well-breathing intakes, that I would see a greater improvement in going to better heads. I'm wondering if some of you pros could check over my files/setup and make sure everything looks correct...

Here's my saved workspace file (right click and do a saveas)

That has a 9.5 CR, and XE274 cam, but with stock heads.

Here are my flow files for the other heads I've tried. None seem to show much difference.... any ideas?

Thx for the help.

Edit: BTW, I got the head flow #s from here ... do they seem reasonable?

Hotfingrs · #2 (**permalink**) 07-30-2004, 10:39 PM

Just because you put on better flowing heads, doesn't mean you'll get more horsepower. Your cam also has to be able to flow the extra air. Just from reading your post, the cam you want to use, stock heads will pretty much handle all the air the cam is able to flow. You need more lift and longer duration for the bigger heads to come into play....

DanM · #3 (**permalink**) 07-31-2004, 06:52 AM

Thanks... yeah I realize that. The XE274 isn't a HUGE cam, I know, but it's much bigger than stock (274/286 duration, 523 lift), so I thought it would at least show a bit more response to better heads than it did...

griffinzein · #4 (**permalink**) 07-31-2004, 09:30 AM

is there a shareware version of desktop dyno? if not how could i get for cheap...... wal mart aint got it around here

HighPlainsDrifter · #5 (**permalink**) 07-31-2004, 09:41 AM

Hi,
In the real world a set of stock heads with a mild cam will make MORE power up to 3,800 rpm and ported stock heads are good to 4,200 rpm. Bigger heads will then flow better after that,but not by much will a mild cam. On the street I can't justify the cost of bigger heads when the stock heads are quicker to 60 mph. A small shot of NOS on a stock motor will wake it up better than big heads.
My 2 cents.
Perry.

DanM · #6 (**permalink**) 07-31-2004, 11:54 AM

Perry,
Well DD seems to agree with you. According to it, I'd get way more performance if I went with a roller cam + stock heads than I would with a flat tappet cam + GT40P or better heads. Those two options would come out costing roughly the same too.... so would you recommend sticking with stock heads, then? And using the money elsewhere? (ie a roller cam, for example)
Dan

HighPlainsDrifter · #7 (**permalink**) 07-31-2004, 12:18 PM

Dan,
The roller cam will free up some HP, keep it small, 1,500 to 5,200 rpm.I would keep the stock heads for the street . A good example was my 91 5 liter coupe. stock it went 14.4 ET, with 3.08 gears. I ported the heads,matched the intake gaskets, 180* termostat, 12* initial timing,K&N filter, it went 13.8's at shifting at 5,200 rpm with a shift light, the factory tach is 300 rpm slow! I went to 3.55 gears and BIG mistake for the street, now I have no traction and the car lights up at 1/2 throttle so I'm losing the stop light drags. At the track I'm 14.2 on and off the gas tires slipping. With drag radials I went 13.5 but still not good on the street. You need a simple combo that doesn't overpower your traction.
Good Luck,
Perry.

DanM · #8 (**permalink**) 07-31-2004, 12:24 PM

Perry,
I'm in the process of building the engine now. Still working on the block, so it'll be a while before I have to nail down my heads for sure. It's a 351W stock stroke, my target is 350hp (probably 5500ish rpm) and 350-400tq around 2000-4500ish. I found someone with a similar config to mine here ... you can see his dyno results there, and they're roughly what I'm after.

I had planned on GT40P heads (as that person did). But I could certainly save some money by using ported 351W stockers if you think they'll do the job.....

Dennis Kelley · #9 (**permalink**) 08-04-2004, 08:19 PM

Just my opinion I feel that gt40 heads are way to small for a 351W I think they are to small for a 302. Horsepower is made with heads that flow in the low lift on a street car with a mild cam. Look at average flow of the heads over the lift of your cam. there are a lot of heads that make good power for the money. I like AFR's but Ebrock, Brodix, Trickflow, protopline all make excellant products. I have a set of gt40 heads on a mustang and there flow is very poor however they are a lot cheaper than aluminum heads.