HP/TQ numbers

It does sound like a good combination overall. Not sure why you pick on your exhaust, the headers are fine for what you are doing as long as you have 2-1/4" pipes and decent mufflers. Your heads should be adequate for what you are hoping for, at least at the bottom end of the range. I would think that if you were to make sure to have the carb and ignition tuned correctly and replace the cam with something a bit more robust, you could pull 375-ish horses. I don't think you need a whole lot of head work, they flow pretty good now. Perhaps a bit of port matching would be nice, but I think the cam and tuning will get you pretty much where you want to be.

Just my thoughts!

Chris

PS: I am about where you want to be using a 390 with stock 291C heads, same headers and a Group 19 cam. I do have 30 more cubes, but you can use a bigger cam and have flow advantages.

Red20 wrote: Sonic Silver wrote: WesternRed wrote: I would have guessed around 300, if chasing 400HP, you will probably need to increase compression, add a decent cam and do some headwork. That's about what I was thinking, but I was afraid that I would make him mad, so I didn't say anything.  Hold on now! I don’t have a history of getting mad over the interwebs, haha! I can name a few guys who do...

I have about the same combo on 2 cars, and they both run strong. I was going off the NHRA factoring a 70 model 360 at 280 hp, and another similar build to yours dynoed at 272 with freeflows, if I remember correctly. Most engines were overrated from the factory. 

Sounds like you have the exhaust under control, though I would say the 2" pipes from the mufflers back is a bit marginal and may not be good enough if you upgrade other things. Funky sounding set up!

Chris

Boris Badanov wrote: 270hp, 330 ft lbs. It should be a great ride no matter what! IMO More compression and cam are needed to get near 400 hp.

It’s been a great motor for just over 10,000 miles so far. And I’ve beat on it on the street... That said, I wouldn’t be a blue blooded American (Canadian, Aussie, you name it) if I didn’t go to sleep at night dreaming of just a little more power and speed!

I don’t have the money to bump compression anytime soon. I am thinking about a Summit 8601 cam. They’re just so darn affordable. The not terrible high and more modern split duration should keep some static compression while the around .500 lift should move some air. And it has a decent LSA for the 360 cu.in. I only know the basics I read about cams, but it seems like it’d work ok on a lower compression 360 with a 2200-2400 stall converter. When I did the math, figuring everything including head gasket compressed height and gasket bore size, etc., I got 8.7:1 for compression. Although I didn’t actually CC the heads. Just used factory figures. According to intake alignment, they may have been cleaned up a bit on the mill in the past, so that number may be a touch low.

That said, the performer grind cam I’m running has been a GREAT driver cam. But hey, I’m a young idiot in search of elusive cheap performance. And the smile on my kids’ faces and grimace on my wife’s when I pin them back in their seats is priceless.

Well, until you get home from a car show and your 9 year old says “Mom, the Javelin went over 100 on the way to car show. There was this ugly red Mustang beside us and he couldn’t keep up. Dad says any old fool can buy a stupid Mustang and we were gonna show them.”

Many people will use a bigger pipe up until the mufflers and then something smaller after. Even a rebel Machine did that if I recall correctly. When the gas cools down it loses volume so it may be ok.

Most people do that because there is not always enough room over the rear axle to accommodate bigger pipes. There should be room for 2-1/4" over the axle on your Javelin though. Do you have shorty headers now? If so, I think you will like the mid range gain from proper tuned headers.

Turn downs are ok, but your wife may not like the noise, any more than she likes you doing 100 mph with her offspring in the car! I have been ratted out by my kids too, it makes for great family folklore!

Whatever you do, make sure the pipes and mufflers are adequate for what you are doing. 2-1/4" is ok up to about 400 hp, generally speaking. I doubt that you will hit that with 2" pipes. I suspect that your 15-20 hp is very doable with bigger pipes and better headers. There was a dyno test posted here a while back that suggested that shortys/free flows were producing about 15 hp and 20 lbs of torque less than tuned headers. Butt dyno comparisons to friends cars with free flows support that, with most gains in the mid range, where you want it for the street.

Good luck!

Chris