289 build up

[Jim Downard]

Looking for input on a 289 build up for my soon to be delivered MDA GT40. I've got a '66 289 and the crank measures out to standard. I'm going to keep the block and crank, all else goes. I'm looking at Eagle rods, forged pistons around 10:1, AFR 185 heads, solid roller cam (although I'm not decided on lift/dur yet), MSD ignition, and either webbers, or stack fuel injection. I want the torque curve to have it's peak a little high and have the ability to rev to 7500+ rpm, also, I'd like to have it be driveable at lower revs.

Any thoughts guys.

Jim Downard

[blykins]

Rev past 7500 rpm and be streetable at low revs? That may be a hard one to design.

You just want it to rev past 7500 or do you want power past 7500?

I wouldn't go with the Eagle rods....you want a bulletproof bottom end for turning that kind of rpms.....If your crank is cast, I wouldn't use it either. If you really wanna go through with the high revver, use some higher quality rods....and make sure they're H-beam. Venolia, Callies, Carillo, Oliver would be some good choices.

Your cam specs will be the toughest to come up with. Just call Crane or Comp cams and tell them what you want. They can give you the best choices.....and I'd say you'll have to sacrifice a little on either your low end power or your high end power.

What kind of horsepower you looking to find?

[Jim Downard]

Not really looking for a bunch of HP. Around 400 would be nice. I also don't figure I'll really rev it that high very often, however, with the wonderful sound coming from those crossover exhausts, I'd love for it to be able turn some R's on occasion. Realisticly, I'm thinking it would be more like 7000-7200 rpm, and then only on rare occasions. I'm leaning toward fuel injection, so I'm hoping that will help with the streetability some, also, I'm not really sure I need to go with a solid roller at this time. Can a hyd roller handle the occasional burst to 7000-7200. I just don't know. This is why I'm asking for some input.

I've got a pretty good engine builder who is going to do the machine work, and I'm sure we'll set down and make sure all the parts are going to work well together.

Jim

[blykins]

Hydraulic rollers aren't that good for high revs....and I really doubt you'll find a hydraulic roller cam suitable for spinning that high. The lifters just won't allow it. A solid roller would be my choice.

I don't see why you couldn't get 400 hp out of that little engine. You can probably go 10.5:1 with aluminum heads. I did with mine.

You can still use a carb setup....but a big cam that's suited for high rpms just won't have any low end power. Especially on a small displacement engine like a 289. No torque. No horsepower. That will make it rough on everyday driving. I guess you could supplement the high revs with a real low gear so you could get the engine up and keep it in the sweet spot as you drive.

Go to www.compcams.com and look at their 289-302 cam catalog. Scroll down to the solid roller page and you can see what the powerbands look like. They also put little notes at the left side of the cam specs so you'll know how to prepare for it. For instance you can look at some of the high lift, high duration cams and it will tell you that you need a 3.73-4.11 gear or maybe a 3500-4000 stall converter for an automatic tranny.

[Jim Downard]

I guess I don't really need a bunch of torque from my little 289. The GT40 only weighs 2250 lb., and it's not a drag racing car. As long as the engine does not have drivability problems at lower revs, then I can live with the low power available. My cobra with the 393W has a comp cams with a power range of 2000-6500. It doesn't much like being driven below 1900 rpm. It gets kind of jerky. I've heard that roller cams can have a more aggresive profile while still retaining a good idle and drivability trait. Also, the stack fuel injection is also supposed to provide superior air fuel mixture agian helping with smoother low rpm operation. I'm hoping that's the case.

I didn't see any solid roller cams listed on comp cams website.

Jim

[blykins]

I found 4 cams on Comp's website for your application. Look under "mechanical roller".

The ones with the power range you're looking for all had over .600" lift. That's getting kinda steep....and most of them had "radical idle" next to them...due to the fact that all of them had a 110 degree lobe separation....or less. So there's a good deal of overlapping when the exhaust and intake valves are open.... But a radical idle is awesome in my book.

Go to the very bottom of this page:

http://www.compcams.com/Technical/Cu...HTML/68-75.asp

If you're gonna be zipping up at high rpm's a lot....you might wanna look into having the block drilled and tapped for 4 bolt mains...or use a main girdle. Don't skimp on the bottom end.