I have a 351C with 4v open chamber heads, 280H camshaft with .530 lift, forged flat top pistons. It has the stock connecting rods with arp rod bolts, and i have not yet upgraded the intake and it has a smaller carb on it right now. I want to get more power out of the engine and i am not sure what way to go. I was not sure if i should stick with the open chamber 4v heads, or mabey get a set of the closed chamber 2v heads and go from there. If I got the 2v heads i was wondering if porting them was helpful, and also what size cam goes good with those cams. I am open to ideas about engine setups and I was wondering what way would be the best in getting good power.
I need help building my 351C
- Thread starter porkchop
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ok first the only closed chamber 2v heads are from australia, so shipping is going to be expensive. second, you really dont need to upgrade your intake as the stock 351c 4v intake is pretty good as is. for a carb i would recomend using a 750cfm edelbrock carb. find a decent set of headers for your car with a 1 5/8" primary tube and run dual 2 1/2" pipe out the back with a set of borla mufflers. keep the open chamber 4v heads and run a set of port plates in them to reduce the port size and improve flow velocity. as for porting, not with the 4v heads they flow plenty already. depending on how much power you are looking for, you have a good settup already, you just need to tune it. your combination should be making around 350-375hp easy.
I have hooker competition headers on the motor right now with 2.5 dual pipes with an h pipe crossover. as far as the port plates go how well do those and port stuffers work and also what do you do about the ports on the intake manifold to match up to the plates. also i was wondering what kind of cam specs would be best to run with on a set of 2v closed chamber heads
the port plates work just fine on a 4v motor, and you dont need to do anything with the intake. they actually improve low end and mid range torque output by reducing the size of the ports in the head. as for a cam , the one you have right now will work just fine if you should choose to try and find a set of 302c heads from australia.
Hack
15 Year Member
Your question is very vague. What does "good power" mean to you specifically? What are you going to use the engine for?
In my opinion, you can make "good power" with any of the heads available for the 351C. The 302C CC 2V heads from Australia are good, but the 4V OC are fine as well. The CC 4V heads are very good as well, probably the best of the factory heads - again depending on your goals. Do the heads you have now have the original 2 piece valves, etc? Has a bunch of money already been put into them (screw in studs, hardened seats, guides, better valves)? Yes, the heads can benefit from some porting work, but porting is also expensive. Also, my understanding is that the "quench" in the CC heads requires the piston to be a certain position in the block, which may require decking and/or new pistons for the most benefit.
In my opinion, your decision should be based on exactly what you want to use the engine for, what you have now, and whether money is a big issue to you. Once you consider all the work required to freshen or upgrade a set of cast iron heads, the aftermarket offerings don't look bad. CHI makes some good stuff, and they have a variety depending on what "good power" means to you.
http://www.network54.com/Forum/119419
There's a lot of good information on 351Cs on this forum. You will find a variety of build information as well.
In my opinion, you can make "good power" with any of the heads available for the 351C. The 302C CC 2V heads from Australia are good, but the 4V OC are fine as well. The CC 4V heads are very good as well, probably the best of the factory heads - again depending on your goals. Do the heads you have now have the original 2 piece valves, etc? Has a bunch of money already been put into them (screw in studs, hardened seats, guides, better valves)? Yes, the heads can benefit from some porting work, but porting is also expensive. Also, my understanding is that the "quench" in the CC heads requires the piston to be a certain position in the block, which may require decking and/or new pistons for the most benefit.
In my opinion, your decision should be based on exactly what you want to use the engine for, what you have now, and whether money is a big issue to you. Once you consider all the work required to freshen or upgrade a set of cast iron heads, the aftermarket offerings don't look bad. CHI makes some good stuff, and they have a variety depending on what "good power" means to you.
http://www.network54.com/Forum/119419
There's a lot of good information on 351Cs on this forum. You will find a variety of build information as well.
as far as the heads i have on there right now they have new exhaust valves but they have the original intake valves, if i opt to keep the 4v oc heads then i will replace the intake valves as well. The heads also have hardened seats, screw in studs and also pushrod guides. Right now i have roller tip rockers but i would also switch to a full roller rocker if i decide to keep these heads. Mainly what i am trying to get is more torque out of my motor. Thats why i was considering the 2v heads in place of my 4v heads. and the 2v heads with the cc design would also give me the boost in compression and I was not sure how much of an advantage that raised compression would help me out. What brand of port plates or port stuffers would you guys say are the best type out there. When I think of it as far as money I will probably stick with what I have now with the 4v heads. I would like to get somewhere close to the 400 hp mark . with some more torque as well. I was thinking that for more torque that the blue thunder dual plane would be a good intake but i am not quite sure what kind of cam to run I was looking into the comp cams xtreme engery series for a hydrolic lifter cam. Thanks for the help so far
Hack
15 Year Member
I can't give you specifics on a combo for 400 hp. It should be very easy to get there, though. I have heard some bad things about port plates (namely that they don't work well), but mostly universal agreement that the blue thunder tongues are good.
I think you should be able to use pop up pistons with the later OC heads to raise your compression. That's what the Boss 351 had.
I'd recommend you go to the network 54 Cleveland forum I linked above. They are the true experts.
You should also let them know what car this is in.
I think you should be able to use pop up pistons with the later OC heads to raise your compression. That's what the Boss 351 had.
I'd recommend you go to the network 54 Cleveland forum I linked above. They are the true experts.
You should also let them know what car this is in.
Stick with the heads that you have but get them ported and upgraded. Don't run with those stock valves they are 2 piece and tend to seperate at higher RPM's and destroy the engine. For a 400+HP motor that is very streetable I would recommend the following – 750 Holley, Blue Thunder intake manifold, 4v heads with 10.25:1 compression ratio, performance cam, 1 ¾” headers to a 2 ½” exhaust, 3.90 gears, electronic ignition. These are just the basics.
I would get a different cam than the one that you have. It's decent enough but you can get one that is just right for your application from a cam grinder that knows Clevelands.
In terms of ugrading the heads I would get Severe Duty Manley valves, springs that match the cam, titanium retainers and 10 degree locks, roller rockers, port the heads, get screw in studs. That should do it.
It is not difficult to get a Cleveland, even a mild one, into the 425 HP level. It is in the details and making sure that the parts are all well matched.
Ask questions.
I would get a different cam than the one that you have. It's decent enough but you can get one that is just right for your application from a cam grinder that knows Clevelands.
In terms of ugrading the heads I would get Severe Duty Manley valves, springs that match the cam, titanium retainers and 10 degree locks, roller rockers, port the heads, get screw in studs. That should do it.
It is not difficult to get a Cleveland, even a mild one, into the 425 HP level. It is in the details and making sure that the parts are all well matched.
Ask questions.
Well right now i have purchased a blue thunder intake, and i have also ordered new intake valves to replace the original valves, and i orderd a set of harland sharp roller rockers. I was looking at the comp cams xtreme energy hydrolic flat tappet cams and i think i have narrowed it down to the xe 284 , and the xe 276. so i am looking at lifts of .584/.588, and with the 276 >.562/.565. If i were to go with the 284 would i need to get the heads machinned to reccess the valve springs?
Hack
15 Year Member
I've seen the 284 recommended for street Clevelands before, but I believe you want to make sure your compression is up there when using that big of a cam with a heavier vehicle. I looked through the thread and didn't see what car you're putting the engine in. I think a big cam with a lower compression motor can really reduce the low rpm torque, which might stink on the street.
I can't help with the valve clearance question. There's been a thread on how to check very recently. You'll have adjustable valve train, you need to assemble it and check for clearance.
I can't help with the valve clearance question. There's been a thread on how to check very recently. You'll have adjustable valve train, you need to assemble it and check for clearance.
porkchop said:
Well, the XE284 is a very stout cam, particularly for a flat hydraulic cam. Your vehicle will have a rough idle and be quite grumpy. It isn't what I would call a street cam, unless you consider street driving a drag strip. That cam is o.k. if you have a 3000+ stall convertor (or manual tranny), and 4.10 gears. I'd recommend a single plane intake for that also because it will start making power after 4000 RPM's. It depends how you want to use the vehicle. You need to let us know. With the 4v heads I'd consider a good solid lifter cam over a hydraulic grind, but then you will need screw-in studs in the heads and be able to adjust the valves once in a while.
The question is will this be a daily driver or a weekend cruiser? Do you want all-out performance or do you just want the car to be very powerful but easy to drive?
With the Blue Thunder intake, 3.50 to 3.90 gears and a 750 Holley, I would get a solid lifter cam in the upper 230 duration range at .050 for a very streetable combo that would rip. If you want something a little more hairy then take a look at my combo, but it is more money for the solid roller set-up and the 950HP Holley carb, and ported heads.
A good person to speak to regarding cams is Scott Main at Cam Research, 303.762.8196. He can recommend a good grind based on what you want and he is very familiar with Clevelands, so he can give you advice on the rest of your combination.
Hack
15 Year Member
It doesn't necessarily take high RPM. Check this out.bswor said:
http://www.network54.com/Forum/thread?forumid=119419&messageid=1117582753
Here's a thread discussing OC vs CC Cleveland heads and engine design
http://www.network54.com/Forum/thread?forumid=119419&messageid=1118314895
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