I have the 400 motor 351c heads(open chamber 4v i think not 100%) 351c pistons around 10:1 compression ratio my question is the motor builder put a comp cam grind number in FC 280AH-8 specs are as follows:

Gross valve lift INTAKE .554 EXhaust .554
duration at .006 tappet lift INTAKE 280 EXhuast 288
duarion at .050 intake 232 exhuast 237
lobe lift .3200
lobe sepreation 108
my question is does this cam use the open chamber heads with the high rpm or should i swap out the cam for something else
this is in a mud bogger truck so day to day drivability isnt an issue i understand what the cam means but not sure what i need thanks for sheading light onto my project

 

What are you using for an intake?

We assume you are having the engine balanced etc.

Sounds like a good cam but you may be able to go bigger. Some of the stock 351C 4V cams were bigger duration but not quite as high lift. Some of the users here may be able to run dynamic compression given enuf information.

 

The intake im using is a weind 351c 4v intake
I have desktop dyno and i guess in a knuckle head because the information that i have on the cam card and the information that its askin me in the desktop dyno are conflicting im not sure what numbers to plug in.

yes the motor is balanced btw

Im going to be tearing it down this winter i have a diff cam in there and not happy with the results so i think im gonna tare out the cam tare out the timing chain and put in timing gear might as well im in there. thinkin about porting out the heads. Thanks for the information im just not sure what cam i want/need

 

If I use 75.4 cc for the combustion chamber and a 351C piston with 1.67 CH and 3cc valve relief, I get 9.87:1 Static CR. The Intake Valve Closing angle of the Comp Cams 32-312-4 cam is 68 degrees. The Dynamic Compression Ratio is 7.69:1.

I like the cam. It has lots of lift which 351C-4V heads need. It has enough duration for high RPM, but your DCR is low for a performance application.

I assumed that you have a Weiand X-CELerator single plane intake and a 750CFM carb.
I get torque 406 ft-lbs@2000 RPM, and peak 493@4500 RPM. The peak HP is 481@6000 RPM.

If you advance the cam 4 degrees, it will boost your DCR to 7.93:1. That is better, but it could be higher.
The Torque is now 416@2000 RPM, and peak 496@4000 RPM. The peak HP is 475@5500 RPM.

The real problem is that you don't have enough Static Compression to support that cam, and you need that kind of cam or more to make those heads work.

I think that a set of Tim Meyer's flattop Zero Deck pistons will help a lot.
With the cam installed 'straight up' the DCR will be 8.28:1.
The Torque will be 412@2000 RPM, and peak 501@4500 RPM.
The HP will be 491@6000 RPM.
Of course this will require good high Octane pump fuel.

If you port the exhaust side, you can improve this more.

 

well that help alot thanks because I thought that cam wasnt the right one i put it into desktop dyno and it had a crappy torque curve so i didnt understand why he would do that. I wish i knew more about the motor so i can clue you into whati have.
Would changing the heads over to the aussies be a better idea or to a 351c closed chamber head. I contacted CHI and my good heavins that is the head i want 2k is kinda high for me right now because im building a garage to build my beast in. (out grew the last one) and the aussie heads are goin on ebay for around 300ish. But if im changing the heads id like to do the cam swap while im in the motor and not do it 2x what sort of cam should i be looking for duel pattern? rollar cam? like i said this isnt a daily driver so day to day driavablity isnt a concernt just raw mud kickin POWAH is what i want thanks for your help more questions to come im sure

 

Most Mud Boggers like lots of torque at low RPM. If that is the case here, then a smaller duration cam will help. You may have enough CR for a shorter cam.
You also want a dual plane intake.
You should get a hydraulic roller with about 0.550 lift and timing similar to Comp Cams DEH265. The IVC is 58.5 degrees ABDC. The DCR is 8.25:1.

Now you will have 445 ft-lbs torque@2000 RPM, and 471ft-lbs@3500 RPM. The HP will be 400@5000 RPM.
A shorter duration cam will give you even more low RPM torque, but your DCR will be too high and you will have detonation problems. This combo will require 93 Octane or better.

 

most definitly, go hydraulic roller duel pattern, ford heads love duel patterns. a roller rocker conversion is also a good idea, and also a good way to free up a little HP. i ran a crane roller cam in my 400 part # 529551 it has a lift of .568in/.609ex 224/232 duro. and made 500+ft-lbs of tq

 

what sort of duel plan intakes do you reccomend?

 

Take a look at Weiand.

 

If you run 4V heads you have to use a spacer for optimum port match. A 351M/400 intake needs one about .300" thick. a 351C 4V intake needs a spacer 1.1" and a 351C 2V manifold will be closer to 1.4"

"what sort of duel plan intakes do you reccomend?'

Consider an Edelbrock Performer RPM 351C 2V air-gap or a Blue Thunder 351C 4V intake.

 

"part # 529551 it has a lift of .568in/.609ex 224/232 duro. and made 500+ft-lbs of tq"

This has an IVC of 74 degrees ABDC. It will make power at high RPM, but low RPM torque will suffer.

 

so basicly if i build it to turn im going to sacrafice low end torque but gain it at higher rpms?
as for intakes what about tunnel ram is that a bit to much?
heads do some port work or change out for aussies?
thanks for all the information guys youve been a great help im goin to take my engine to the builder in a month or so and have him swap out the cam timing gears etc

any other information is great thanks much

 

If you have Desktop Dyno, load your motor specs and then try different cams. You will see a flat torque curve from 2000 RPM to about 3500 RPM with a short duration cam. As the duration of the cam increases, the torque at 2000 RPM will drop off and the curve will peak at a higher RPM. Horsepower is only Torque x RPM, so to get high horsepower, you need high torque at high RPM. The cam timing only determines the RPM at which peak torque occurs. So pick your cam timing based on whether you want a broad flat torque curve from 2000 RPM to whatever, or a torque curve that peaks at high RPM, but sags at low RPM.

The best torque curve would be one that is flat from 2000 RPM to beyond 4000 RPM. That can only be obtained with head flow and valve lift. If you plot head flow vs valve lift, you will see that the head stops flowing more above a certain lift. You want the valve to open to at least 90% of the max flow, if possible. You also want the head to flow good at low lifts, since the cam spends a lot of cycle degrees at low lift.

This is the advantage of heads like CHI-3V, CHI-2V, AFD, and even ported Aussie, and 351C-2V heads. Some of these heads will flow good from 0.100" lift to 0.600" lift or more.
Check the flow numbers for the Powerheads Ported Aussie heads.

www.powerheads.com.

If you plug in the flow from any of the above heads, with a short duration (260 to 270 degrees) cam that has enough lift, you can get a nearly flat torque curve from 2000 RPM to beyond 4000 RPM.

Tunnel Ram intakes have poor low RPM response.

 

Danlee said "This has an IVC of 74 degrees ABDC. It will make power at high RPM, but low RPM torque will suffer."
I for a fact ran this cam in my 400 and performance was second to none i thought. But i guess you can say it did suffered from low rpm tq because on the rear wheel dyno my 79 f-250 w/37'' boggers only made 449 ft-lbs of tq from 3000-3500 rpm and 363 hp at 5000 rpm to the rear wheels. On a real dyno these are real world numbers on a real dyno. Multiply those numbers by 17% in accessory and drivetrain loss and it comes to 425 hp & 525 TQ, but who needs 400 hp & 500+ ft lbs of tq. Don't always believe what you read out of a book or desk top dyno. but danlee you are right i am suffering from not haveing enough power. But because i sank my truck in a 8ft mud hole. I'm rebuilding my 400 and adding a new air gap intake, more head work, more carb and a msd 6AL box. 400's RULE!

 

I would like to see the dyno sheet on that one, those are some impressive numbers.