408 build

[crossfire800]

Hey guys newbie here. I'm trying to get some insight here on an engine im building. I just purchased a 351 ford racing block,eagle competition rotating assem,srp pistons, afr 225 heads 58cc,alum stud girdle comp is 9.8 to 1. everything is already assembled and together my intentsions are to build an efi system for it so i can run twin turbos. this car is not going to be a daily driver weekend toy thats it and to and from work on nice days 35miles each way. Ive searched this up and down and cant really find exactly what im shooting for in a combo. I would like to be around 700ish at the crank. I guess my question is can i get 700 on pump gas without turbos? should i just run a carb and be done with it ? or is efi the way to go with turbo or charger. After reading i got a little lost with all the fuel injection stuff my last engine was a 557 stroker carbed in a notchback any suggetions or advice on combos would be great thank and this is going in a ffr cobra

[cwhoofgator]

Get with Wayne @ Very Cool Parts forum vender. He will have what ya need...

[Don Payne]

Well, with 9.8:1 cr, pump gas, and efi, I don't think 700fwhp is possible without power adders. That said, I would have lowered the cr more with larger combustion chambers if you are planning on running turbos. You should really talk to Wayne Presley.

[1cobra]

Hi,
A couple of things to consider.
- you are at 10 to 1 compression, way too much for turbos, 8 or 8.5 is ideal.
- your 408 will make 550 hp and be a nightmare in a light cobra, you will never get more than 1/3 throttle without killing yourself on street tires. Race tires at a track will work if you are pointed straight.
Good Luck and figure out what you are actually going to do with the cobra.
Perry.
Picture; this cobra had 425 HP.

[JoeE]

Just to be fair 425 hp does not mean hitting walls. Most of us on the dark side run 400 to 550+ no problems with the right tires and skill set. I feel over 600hp is a waste of effort and $$ unless it is purposely built. That pic was either a fool at the wheel or something bad happened on launch.

Originally Posted by 1cobra

Hi,
A couple of things to consider.
- you are at 10 to 1 compression, way too much for turbos, 8 or 8.5 is ideal.
- your 408 will make 550 hp and be a nightmare in a light cobra, you will never get more than 1/3 throttle without killing yourself on street tires. Race tires at a track will work if you are pointed straight.
Good Luck and figure out what you are actually going to do with the cobra.
Perry.
Picture; this cobra had 425 HP.

[1cobra]

Hi,
Yes he broke a wheelie bar and launched 15' in the air and barrel rolled 3 times on the cement gaurd rail just infront of the windshield.
You run slicks..... you stress your parts and will break things.
Perry.
PS- He ran low 10's.

[cobrarandy]

I agree with every thing said here. If he only has 450 horsepower there was way too much bite dialed in to break wheelie bars. If you talk to people running in the 400 horsepower range you will find most are quite satisfied. There is a limit to how much these cars can make use of on the street. If you plan on being on a drag strip on a regular basis that is another story. I show 349 rear wheel horse on the dyno with a mild 351 combination. The car is an older mark II with 3 link and runs in the 11's at will on street tires. On the street traction in 2nd gear is an issue. The engine is currently apart after 30,00o enjoyable miles to repair a few leaks. I thought now would be a good time to increase the displacement, compression, and cam but after much thought have decided to put it back just as it was. It is so enjoyable drivable the way it is and is much quicker than most can comprehend.

[crossfire800]

Thanks for the info guys I decided to go with a carb NA setup. I went with a victor jr intake and think im going to run a 750cfm carb and a comp cams custom grind cam. The car is not really going to be a drag car just a weekend car and a day or so during the week to work

[Bob Cowan]

Now that you've "decided", let me change your mind again. Don't worry, you'll change your mind a few more times before you're done

If you bought the Ford Racing Boss block, you can easily build a 427 or 454 with off the shelf parts. And it can easily spin to 7,200 rpm's with the right parts.

The boss block is really strong, and has 4 bolt mains. There's no need for a main cap girdle. It can handle a lot of power and a lot of boost if prepped properly.

My car makes 510hp on the chassis dyno. Using standard formulas, that's well over 600hp. There are no power adders, that's all motor.

To make that much power, you need a huge cam, big air flow, and lots of compression. Managing that with a carb and standard distributor is tough. That's where EFI comes in. Driving down the highway at 80, down the rural roads at 65, or the city streets, the car is a real pussy-cat. Idles smooth, accelerates easily, well controlled and well mannered. Even gets good gas mileage; it's cheaper to drive than my diesel pick up.

But if you mash the skinny pedal, it screams like a banshee and takes off like rocket. I'v never driven or ridden in a car that accelerates like this one does.

I live at high altitude - 6,400' ASL. My driving could be anywhere from 2,000' to 11,000'. With EFI I don't worry about it. It automatically adjust for air density - the mixture is just right all the time. When it gets hot, it adds a little fuel to cool it down. When it's cold, it adds a little timing for power and economy. It is the best of all worlds.

I don't have a lot of experience with turbos, but I do have a little. Turbos with a carb can be a tough combo. The don't always run as well as you'd like them too. I found mine to be hard starting at anything about 9,000', and tended to run poorly below about 3,000' - especially if it was hot. I didn't do well at all in Vegas in June. If I was ever going to use a turbo again, I would only use a good EFI system to control boost, fuel, and spark.

[Wade Chamberlain]

Originally Posted by Bob Cowan

If you bought the Ford Racing Boss block, you can easily build a 427 or 454 with off the shelf parts. And it can easily spin to 7,200 rpm's with the right parts.

Unless Ford has extended the casting around the bottom of the bore (I don't think they have), I'd buy a Dart SHP. Similar money and better piece.

[edhunter]

Originally Posted by Wade Chamberlain

Unless Ford has extended the casting around the bottom of the bore (I don't think they have), I'd buy a Dart SHP. Similar money and better piece.

As an owner of a BOSS block engine, I agree with Wade.... buy the SHP block if you're going more than 3.25" stroke. My engine is a 342 (4" bore, 3.4" stroke), lives in a road race mustang. Sees 6300-6500 regularly. I run a used oil analysis every oil change (approx 8-10 hours run time) and so far I'm not getting any evidence of wear on the pistons. But the short(er) cylinder wall is a major fubar by Ford in my opinion...
(EDIT: This applies to the 302 block, no idea about the 351 Boss block)

[Edward B]

If it is only a toy (read, race car) you can make the power (700+) just on motor. Here is a link to what Joe Sherman did with a 8.2 inch deck height motor: 750HP 347ci 205cc
I think a pair of turbos running 7-10 lbs of boost sitting on top of a 400 hp motor gives you the best of both worlds; lots off idle response in a little car then enough power to have you run in the 10's. :-)