Hi again! I'm getting down to the nitty-gritty on my engine buildup, and i wanted everyone's advice. Right now i have a dual plane (Edel. RPM air-gap), but i think my new engine might benefit from a single plane. However, it's a daily driver too...and i know single planes aren't great for the street. Here's my engine: -302 +.040 -Forged crank/rods/ 11:1 Probe pistons (i wanted higher CR like some suggested, but it looks like i can't get them for the TFS heads). -Ported TFS track heat heads, should flow ~275 intake/ 210 ex. (guessing, might be higher, haven't gotten them back from the porter yet). -CompCams solid roller, 236/242 .602i/.608e 110ls My other concern is that with the air-gap manifold there's no way to port, so my heads may outflow my manifold.... Open to suggestions, thanks! ~Chris
Chris, The RPM performer won't flow enough to give you the estimated 7000+ rpm that your cam will allow at peak HP. You will need a manifold rated at 7000 RPM to get that last bit of RPM. You are going to be idling between 1000 and 1500 RPM with a real lope. You will be getting close to the 400 HP mark and will need a carb in the 750 to 800 CFM range. The software that I have predicts 11 second quarters and recommends 4.14:1 rear gears with a manual transmission. The software also predicts a life expectancy of 32600 miles with street driving. here are the details: 308 cu" 390 HP at 7000 359 Ft Lbs at 4250 Volumetric efficiency is 85% 3200 pound car ET 11.61 seconds speed 121 mph PaulS
The air gap would be a better choice for the street, UNLESS you have a manual transmission and aren't afraid to wind it or you've got a 4500+ converter to take advantage of the top-end charge of the Jr. Dad & I have run both of them on similar combinations, and we can tell you first hand that it takes a serious 302 to work with a Vic. Jr effectively. Dad routinely spins his up to 7000+ with his air-gap, though my little bro's Mustang is 1-2 mph faster at the stripe than dad's car. That could be any number of different things, but when I changed from single to dual plane, the 60' times improved dramatically, going from mid 1.6's to consistent mid 1.4's...and besting a 1.41 with the 302/c4 combo. MPH suffered a loss of 1 at the stripe. That was noo other changes, just the manifold. The Air-Gap would be my choice if there's any street-driving.
Youch! 32,000 miles with street driving? I guess i should have expected that. This is my daily driver for now, but i will soon be getting a different car for a daily driver so i can retire the mav to weekend duty. It is a 5 speed, although i only have 3.55's in the rear. I have a 780cfm proform carb for it, so that sounds just about perfect. I also live at a 5700ft. elevation, so i'm only hoping for about 300rwhp here, and i was figuring that ought to help out with longevity of parts (that, and i don't race a whole lot). It sounds like a dual plane is the way to go (i also use a spacer)--i don't really need to worry about an extra mph or two at the track, and some level of streetability would be nice. Thanks for the help! Paul, what software are you using? Also, why 3200lbs? I figured i was down around 2800? I think i need to go get weighed.
Daily driver? I hope you live close to where you drive. That sounds like a gas guzzler for a daily cruiser. I'd find me a beater to get around. JMO- Seth
You guys are making me realize this is definitely going to be a weekend driver...but that's alright, i kinda had that in mind to begin with. I'll drive it for a month till it drives me crazy Just out of curiousity, what causes the low engine life that your software is predicting? Is it the power output? The compression? The rpms? I'm going to lose some of that compression when the heads are ported, and the elevation will affect my output.... Of course, i won't be redlining it all the time either. I don't mind pushing the limits of streetability, but i'd like to get a few more miles out of it than that....
It's not my program, but I would imagine that it takes all of those things into consideration. RPM's probably influence it more than anything.
CACollo, you probably will get less than 300RWHP at your altitude. The dual plane manifold will build more vacuum and streetability but you will have to watch your mixture - at 5700 feet it could go rich real easy. The weight of the Maverick is 3200 pound at the curb, you said it was a daily driver so I assumed that it had carpets, matting, and all the stuff that makes it nice to drive. It is hard to get rid of 400 pounds. Weighing it will be a good idea. The software is a program that I wrote to help in my selection of cams with my 351W. I got a lot of help with the calculations from Erson cams and Colt industries and Edelbrock. The software is real old (DOS based) but it still does a good job of calculating quarter mile times and the rest. I didn't put in a variable for altitude - an oversight I now regret - but I live so close to sea level it doesn't matter. I even sold it to an engine builder in South Africa back in 1993. PaulS
73 Maverick 2 door, GVW = 3830 minus 3 passengers (540 lbs) = 3290 If you look at the drivers door jam it will carry label that gives this information - figure 180 lbs for each absent person. (4 max) 72's were about 100 lbs lighter due to the lighter bumper PaulS
The software that I use is a program that I wrote as Shareware before most of you were old enough to care about cars. I got some help from Colt Industries and Erson Cams for the math involved but it is sadly a DOS based program and won't run in windows after ME edition. It does ok on windows 95, 98, and ME but I am not going to update it without good reason to do so. The only commercial buyer was a company in South Africa that built racing motors. PaulS
thats pretty cool. i use a new program called desktop dyno 2000, or a newer one known as dyno sim... ya its easy to use, but sometimes i question how accurate it will be. i dont think it compensates for things like a poor ignition system, or drag imposed on the crank by accesorys.
