I have a 400 in my 1979 F150. I bought a Wieand Stealth intake (the ad said cobra jet, but I didn't think they made cobra jet intakes for the 335 class engines.) I just rebuilt my Holley 600cfm vacuum secondary carb. I put 68 jets in it and then just finished the carb off with the various parts included in the trick kit. I pulled the choke out of it too cause I hate messin with it. Even when I have a manual choke on I get pissed off at it and end up pullin it off. I was gonna buy some headers for it as well. However, I was wondering what kind exhaust system I should run. I have some mufflers and some glass packs that are 2 1/4 ID, but with all those cubes I thought maybe it would need 2 1/2. What do you guys think. Also, what kind of gains should I expect?

Erik

 

I'm a bit befuddled but can go with some of what I have heard- not experienced so be liberal with the grains of salt. No cobra jet. I've heard wieand makes a decent intake. I'm really not sure about the carb..but the increase in flow should aid a bit- if you went from a 2bbl carb and intake you will notice some additional hp and, hopefully economy- but nothing that will surprise you I bet. Headers will add marginal hp as well. The exhaust flow, while not great, isn't a main issue and you will lose torque if you loosen it too much without adding the need for it. 2 1/4 in the pipes is fine unless you are building a real man's 400 which takes new pistons, timing gear, cam etc. I have a tired 400 in my truck that has the edelbrock manifold and carb and it is a crap motor. I'm building what I hope will be a decent replacement.

imo: imho: The 400 is a waste of metal unless it is built right- an absolute boat anchor. You gotta get the compression up with flattop pistons. Then if buy the good heads (aussie) you have to buy forged pistons at nearly $500 and get them ground down to the compression that you want which is then 9:1-9:4-1 or so to burn pump gas- go to TMI and he has a build that does this and makes great power on 87 pump. But then expect to have over 3K in your motor. If you were to do the minimum to your motor to make it decent you would have to pull it and get the kit from TMI for about $450.00 or a little more +machine work and odds & ends that will include flattop pistons and a roller timing chain etc. I think you would go from about 160hp to around 300 and torque a bit above 400. And you will get the best mileage possible from this motor- imo.

 

I just rebuilt my 400, bored .030, Crane 260H cam, Wieand Action+ intake, Holley Truck Avenger, Hedman Elite headers, 2 1/2" pipes to flow through mufflers, 3" pipes to the end. It runs great, pulls the travel trailer with no complaints. The 400s are good motors, run well and produce good torque.

 

Roger I think your problem is in the carburator. The lack of power suggests that you have a common problem that most people miss. If you remove the carb and hit it repeatedly with a big hammer, then go buy a used Holley and a Trick Kit you should notice a big improvement. Don't forget to get a spring kit and some larger jets and maybe a quick change spring kit if it's a vacuum secondary carb.

 

The problem is that some engine building wingnut built it to factory specs and a '77 400 produces 164 or so hp stock. Then add a bunch of miles (65k) and it's down to about 7:1 compression. Most folks who use the edelbrock on this motor are happy and when they compared professional builds the holley was barely slightly better. I have to be overcarbed now I'm sure- but I'm rebuilding and will, hopefully, grow to like the 400- maybe even as much or more than the fe...but I doubt i will ever go with a high maintenance Holley unless I am building a 460.

 

I have a buddy that had an Edelbrock 650 on his 400. He ran 15.6 at the strip in his Performer Package 400. With a little convincing he replaced the Edelbrock with a swap meet Holley that he rebuilt for about 50 bucks. He now runs 15.1 . The "high maintenance Holley" made a world of difference.

Opiate

 

Just put the Steath and Holley on and oh god!!! What a difference!!! The engine never seems to run out of power. The high end is unbelievable compaired to before the manifold. The bottom end is good but I need to get a kickdown hooked up before I go beating on it any more. The headers will also help with power. Together, the kickdown and headers will make the motor feel much... much... much... better.

Erik

 

Sure would like to see the difference on a dyno...

 

Flat tops, rebuild heads(one piece valves,smooth exhaust bumps,early castings better stay away from potbelly exhaust guides) a *mid* 260 duration cam (dual pattern cams help, and stock heads start slowing down after about .520 lift), headers (small and long), 4v manifold and a 600cfm carb (holleys make more power, cartes and there knock offs have to be retuned less), AND strait up timing( dual roller or gear). Good for a little more than 300 Horse and 400+ FTlbs of torque. All before it hits 5000rpm. The trick is matching the cam with the flattops and heads to get a decent DCR without going to far and inducing a motor that pings badly without reducing the base timing to nothing. These engines like advance and good fuel. (stroke and open chamber heads). Alot of people try to get quench to reduce pinging and increase performance. I don't think the added cost of rengineering the piston to head relationship is worth the performance increase. Just watch the DCR and and save the money.

Geeze, I think I just paraphrased all I know about building 400 fords in one paragraph.