351C Rebuild - Heads

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cheezsnake

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So, I think it's time to rebuild my 351C 2V for my '71. My reasoning ... 1) the nylon timing gear is shredded (learned that with help from another post), 2) I already knew there is lower compression in a couple cylinders, 3) the engine is already half out, given I had to raise it to remove the oil pan, 4) it looks like the motor has never been touched, and I would hate the tear the front end apart to replace the timing set, and decide next spring I should have just done a rebuild.

Here's where I could use some advice. While I'm getting it rebuilt, I would like to bump the performance. Would like to keep it a good street performer. ... not planning to take it to the drag strip every weekend. Although I don't put many miles on the car, I would prefer to be able to run on pump gas without octane boost.

I'm considering the following ... 600cfm 4-barrel carb, dual-plane aluminum intake (2V ports ... already have dual exhaust and intend to keep stock 2V manifolds), flat top pistons, Lunati 10321004 camshaft (hydraulic lifters) ... the cam is their factory performance series, so hopefully good performance without crazy duration and lift (270/286 and .481/.490 lift).

My big concern is about the heads. There's a lot of (sometimes conflicting) information out there about 351C heads. I respect the experience and opinions of this forum, and am interested in your thoughts ...

- Open chamber heads (which I have) are prone to detonation ... avoid them if you're doing any kind of performance build

- 4V head ports are too big for the street ... pull like crazy at high RPM, but not great torque at low RPM

- Aussie 2V are the best of both worlds ... quench chambers for higher compression, and 2V ports for better low-end torque

- Aussie 2V heads have smaller chambers (59cc) than the 4V quench, which means you need to be careful about compression ratio

- High compression is OK with the quench heads because the design helps prevent detonation

- To get the full quench effect, you should go with zero deck height and avoid dish pistons (but, that further raises compression)

- Aftermarket aluminum heads may be the best choice (but I can't get past the price tag)

As you can tell, a lot of info/opinions to filter through and try to make a good decision. I think I would lean towards the Aussie heads if I was pretty sure I would get a decent performance bump without a detonation problem. 4V quench heads would require a different intake and exhaust, and I may not use the benefit of the large ports. As I said, I respect the advice from this forum, and am interested in your experience and thoughts.

Thanks.

 
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Nothing wrong with just getting a good rebuild on your stock heads with better 1 piece valves, have the pedestals cut for guide plates and studs and if you want some porting and polishing, but nothing crazy. Unfortunately, with the cost of parts and labor this will likely run you 6-700 bucks.

Use a pop up piston to increase compression to somewhere in the 10:1 ratio and detonation should not be a problem. I believe the most important choice in a build is to match the cam to your other components and to the cars intended usage. I'd go with a hydraulic roller cam. Tie bar lifters make this conversion easy and greatly reduce the likelihood of losing a cam lobe due to poor lubrication. Look at the Lunati or comp cams sites and find one that has the rpm range and idle characteristic you are looking for with your car's weight, gear and transmission type and use that as a sort of general idea of what you want and then call about getting a truly custom grind to exactly match your needs. Expect the roller cam and components to be about a grand

 
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- 4V head ports are too big for the street ... pull like crazy at high RPM, but not great torque at low RPM

- High compression is OK with the quench heads because the design helps prevent detonation

4V quench heads would require a different intake and exhaust, and I may not use the benefit of the large ports. As I said, I respect the advice from this forum, and am interested in your experience and thoughts.

Thanks.
I can give you feedback from my experience on the items above. The prior owner of my 71M code had taken the 4V heads off and put 2V heads on, why, who knows probably because he felt it would increase the low end torque and he could use cheaper gas. He had also put a Performer Intake on so he could use a 4 Barrel Carb. I took it all off and put closed chambered 4V heads and the original cast iron 4V intake back on. I also put original cast iron 4V exhaust manifolds on. The set up is close as it came out of the factory as I could get, with the exception of using an Edlebrock carb.

The bottom line I "haven't" noticed a loss of low end torque but have noticed more power in the higher RPM range, for performance driving I've noticed a big positive difference and it's perfectly fine on the street. But, I can no longer use anything but high octane fuel or it'll ping and it's more cold natured than it was before, it takes longer to warm up to a point that I can drop it in gear and go. Soooo, if it was a daily driver, I would consider the 2V heads a better fit, but since it's not I'm happy with my switch to the 4V heads.

I now have to pay more for a higher octane fuel and wait longer for it to warm up than I did before, but after that it's just as street able and screams if I want it to. That's my experience with the switch.

 
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MeZapU

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I wouldn't worry about your 2v heads. As long as your cooling system is in good shape you will not have anything to worry about. A good rebuild with good valves and they will last a long time. How much you decide to upgrade them in regards to springs and rockers is up to your performance goals.

I would advise you to run headers. The results are quite dramatic even in stock engine trim vs the manifolds.

A 4v intake upgrade is expected, but I advise against the Performer 351 2v. It is really lazy and not much better than a stock intake manifold with a 4 barrel carb flange on it. High low end torque but the horsepower peaks around 4k and falls off fast after that. You should look into a Air-Gap or small single plane intake like a Weiand X-cellerator. They both work quite well and are very streetable while having good hood clearance.

Is your car an automatic? If so a new higher stall torque converter would pay dividends in helping performance and taming any bigger cam at idle.

 

Otto

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Quite the discussion. Back in the day Cleveland heads were limited. Thanfully now its getting the respect it deserves. With that, I my opinion the 351C Aussie heads would be the best iron heads. My 72 came with the 2v Cleveland. At the time, it is what was needed. Open chamber and low compression for emissions. The redeeming qualities were it was a larger displacement of the small blocks and the engine could spin higher that other SBF engines in stock form. Australia didn't have the same emmisions bs....regulations so they were able to build better heads. They were two versions that fit the Cleveland. The 302 Cleveland with chamber cc's in the upper 50's and smaller runner volume. There were also the 351 Cleveland heads with chamber cc's in the mid 50's and larger runner than the 302 Cleveland AND the American 2V. If you are going to redo your heads, the standard hi performance mods are machining for screw in rocker arm studs, bronze valve guides, hardened seats, stainless valves along with whatever cleaning and additional machining is needed.

I did these things to my set of Aussie heads about 13 years ago. The reason for this is there wansn't much for the Cleveland back then. The heads are great. They have smaller runners than the 4V heads which is good for lower end torque, the closed chambers which allows higher safe compression and better runners than American 2V heads (194 cc intake, 115 cc exhaust volumes in most cases). These are the reasons I changed out my 2v head for Aussie 2v's. I still like them and I am actually about to improve them even more with some swirl polish 2v valves with hardened tips (for hydraulic roller cam), viton seals and most likely a mild port. The remainder of the parts come with the cam kit (springs, retainers, locks)

The downside of going with either of the above is cost. For the price of parts and machining, you can come close to cost of modern aluminium heads. Bare heads cost around 1400-2000 bucks while fully assembled head cost around 2500-3500.

It comes down to what kind of personality do you want the engine to have? Where do you want to operate in the rpm range? Will it be a street car, occasional Do you prefer iron heads? Is the handling of the vehicle a concern (weight)? I would also suggest reading some books on engine airflow, head porting and "Ford 351 Cleveland Engines" by George Reid. I hope this helps

 

cheezsnake

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Thanks, Everyone. Some real-world experience and ideas I hadn't considered, like using pop-up pistons with an open chamber head. I was thinking it would be geat to know at what compression you're likely to start getting into trouble with either style head, closed chamber and open chamber. Is that informaton available somewhere? I have no problem running premium fuel in the car, if needed. Like I said, I don't plan on putting a lot of miles on it, and it's certainly not a daily driver. I do have an automatic, so when I pull the motor, I can decide what to do with the transmission. Some of this may come down to budget, and how much I want to invest in the top end. When you start talking roller valve train or major machine work, the price climbs quickly. Even the dome pistons look to cost a lot more than flat tops.

One common theme with the group seems to be going with screw in studs and, I assume, solid lifters. What do you find are the benefits for not running hydraulic lifters in a street engine?

 
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For the street Hydraulic lifters are fine. Solid only helps at really high rpms. But do consider going with roller lifters vs traditional flat tappet. There is less break in worry. Additionally you can squeeze out more performance with a roller cam. A roller cam allows for a more 'aggressive' ramp. This means less overlap at idle and low rpms and more open time at higher RPM's. Search the web on roller vs flat tappet and you see why there is an advantage.

The disadvantage is the roller cams can wear out sooner than a flat tappet but they still last a long time.

You will spend a lot more on a roller cam. In my humble opinion they are worth it. I regret not going that route on my current build and will, without a doubt, go roller cam on my next iteration.

 
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MeZapU

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I had a set of Australian heads on my old combo for the last 15-16 years. Honestly they have never lived up to my expectations. I gave them all the supporting hardware, Manley valves, ported, rocker stud conversion, hydraulic roller cam, good intake and exhaust. By the numbers they seem the best street option but you never see anyone really putting down respectable power numbers with a set. I too could never get them to perform the way I thought they should have. Now that there are better options in the aftermarket, they really do not make sense to sink the money into unless you already had a pair of the heads, and good supporting 2v intake and exhaust components. I just built up a set of bare 4V quench heads that I paid $250 for and have about $2k in now. They are now some sweet heads but good components cost big money, as well as all the machine work required. If it was not a progressive build I would have spent the money on some aluminum heads without all the hassle. Trick Flow heads are on sale at Summit Racing at the moment for $1800 for the pair. A really decent deal IMO. If money is the main concern, then do what you gotta do. I just don't want you to go down a road with certain expectations and then not have them met, like what happened to me.

 
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Studs allow adjustment. With a hydraulic flat tappet cam, you can avoid this step and save some money. But if your break in fails or you don't use a zinc rich oil, you might have to do it over again. You lose the ability to run the better grade roller rockers which eliminate a lot of friction. Roller lifters further decrease the internal friction and wear. If you go with the stock head set up, you have to use shims or different length pushrods sometimes to accommodate a shaved deck and heads which is a much bigger hassle that adjusting a nut and polylock.

Honestly, a worn out nylon timing gear is no big deal, I would pull the front and replace the timing set and keep running it. A timing gear change is a one afternoon job and the parts are under a hundred bucks.

5 grand in parts for a good strong street engine isn't at all unusual. 1500 in machine work on heads and block and balancing is not out of line, and then you need a few hundred in gaskets and other I forgot about thats ie., break in oil, oil filter, oil, oil filter, antifreeze, spray adhesive, gasket maker . . . .

and that is if you assemble and install yourself. $7500 to 10K is not an estimate you may want to hear, but if you take short cuts, you might as well build it back to stock with upgraded 1 piece valves and stock equivalent parts.

 

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The 4V head not being a good street head is a mith. If your good with a mild street engine around 350 hp stick with the 2V head. If you want closer to 400+ get your self a set 4V heads. I've been down this road. I did the typical performance build to my 71 351 2V. I thought it ran well. Then my brother smoked me with his bone stock 85 GT. Eventually when the 2V motor gave up I had a mild 70 4V motor built. The build was not any different other than what it took to make the 4V motor work in the car. All I can say I beat my brothers 5 litter by 3-4 cars with the 4V motor. My 71 Grande became allot more fun.

 

cheezsnake

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Thanks for all the great input. I've learned a lot. One interesting thing I've noticed both on this forum and around the web, in general ... I've heard guys that are OK with a rebuild on the U.S. 2V heads, and others that regretted not going to 4V. Some like the performance of switching to the Aussie heads, and others wouldn't recommend it. And, some think aluminum is worth it. But, I haven't found a story where someone regretted swapping the 2V heads for 4V ... haven't come across anyone that said it was a mistake going to the bigger iron heads.

 

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The single most important factor is matching the camshaft to the heads. You need to talk wit a specialist as off the shelf cams are designed with "who knows what" type of configuration. Was it for 2v heads or 4v? Open or closed chambers. Automatic/manual transmission, 2.75 to 3.91 gears, 2-barrel or 4-barrel carb, headers or manifolds. The differences of the various cleveland engine combinations are arguably the biggest differences in the small block world. This is not a small block chevy where there were there were only so many differences back in the day. So the law of averages works in their favor.

 

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4V closed chamber heads if you have the bucks...4V stock, or 4V performer, manifold build it old school by the book use the old CJ cam and you will not be disappointed. 3.25 rear gears.

750 or 780 cfm.

The cam of choice back in the day was the hydro grind version of the Boss 351

Ford hydraulic camshaft, part number D1ZZ-6250-BX. Still around today here's the spec's.

290°/290° duration @ 0.004"

0.505"/0.505" lift

Exhaust valve opens at 84° BBDC

Intake valve closes at 74° ABDC

62° overlap

219°/219° duration @ 0.050"

114° lobe separation angle

Intake lobe centerline = 109° ATDC

Don't mismatch aftermarket with the 4V stick with what Ford designed as it all matched. Deviate from this that is when you loose the bottom end torque.

2V open chamber heads I deck them .030" and add shims .030" under the rockers to compensate. Port and polish. This will get your compression up where it pulls better and works with a cam having more overlap. Use the 4V head rockers, one piece valves etc....as the 2V are junk for performance applications. I run the 4V performer manifold with the 2V heads a little grinding and they match great. The 2V performer manifold the ports are way to small.

 

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As MeZapU has already stated, headers are a must if you are trying to achieve any significant performance increase.

If you are merely looking for a refresh using the 2V heads with some basic performance parts/upgrades then the manifolds won't hurt as much.

 

c9zx

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Just my take on the statements below.

Open chamber heads (which I have) are prone to detonation ... avoid them if you're doing any kind of performance build Partially true Getting the quench right helps mitigate the problem somewhat. You'll have the same amount of money building 2V heads as you will 4V heads. About $1300 for quality components and machine work.

- 4V head ports are too big for the street ... pull like crazy at high RPM, but not great torque at low RPM False. This is dis-information spread by people who selected the wrong cam based on small in-line valve experience with SBC and SBF cam selection. Think relatively short, split durations, high lifts, and a wider lobe separation than an inline valve head.

- Aussie 2V are the best of both worlds ... quench chambers for higher compression, and 2V ports for better low-end torque False. The chambers are somewhat better but the flow no better than the 2V open chamber heads. The expense of the cores and the resulting performance are not warranted in my opinion.

- Aussie 2V heads have smaller chambers (59cc) than the 4V quench, which means you need to be careful about compression ratio Partially true. There are many ways to manage the static compression ratio to obtain the dynamic compression ratio desired.

- High compression is OK with the quench heads because the design helps prevent detonation Partially true. While the closed chamber heads is somewhat more resistant to detonation, you still need to have a compression ratio that is compatible with the fuel being used.

- To get the full quench effect, you should go with zero deck height and avoid dish pistons (but, that further raises compression) Partially true. 0 to .005 in the hole is a good idea to lessen the likelihood of detonation and obtain a more complete burn. I do think a flat top has better flame propagation than a dome or a dish but I've used all types with good results.

- Aftermarket aluminum heads may be the best choice (but I can't get past the price tag) Depends on goals and budget. Be aware of relocated ports on several of the heads, which in some cases requires different/unique manifolds.

Having said all that, you can build 2V hads that perform reasonably well. It takes effort, time, and money. And in the end they will still make significantly less power and torque than a 4V head. The only real difference in cost is the cost of the cores. In the end it always boils down to,"Horsepower costs money. How fas do you want to go." Good luck with the build no matter which way you decide to go. Chuck

 
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Aluminum saves weight and can give you some arguable increased resistance to detonation. The available designs are all over the place in terms of modified ports etc. I personally like the CHI 4V head's appearance and specs.

http://www.chiheads.com.au/shop/4v/4v-ford-cleveland/

They are not cheap, and I would buy them bare as I don't know what parts they use in their build ups. I would have the exhaust valve seat opened up to 1.71 as they do it no charge, but if you are having a builder assemble, ask them what they prefer.

Probably won't make any more power than iron 4V heads, but are more repairable, and shave a goodly amount of weight off the front of the engine. (I think the weight savings is somewhere between 60 and 80 pounds!)

 

cheezsnake

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Great feedback, everyone. As usual, not disappointed with the help from this forum. I think I've decided to go with the iron 4V heads, aluminum dual plane, and exhaust headers in the rebuild. Found a pretty good price on both the cores and the machine work. I will spend some time on the cam selection to make sure I get the most from the stock heads. Haven't fullly decided yet on rollers, but leaning towards hydraulic flat to keep the cost down. Would like good street performance, but doubt I will be stressing the valve train very often. The car may never see the track. Starting the process of removing the radiator, accessories this weekend. Hope to be able to pull it in a couple weeks, depending on my work schedule. Could be awhile to get it all back together, but I'll let you know how it turns out. Thanks!

 
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Great feedback, everyone. As usual, not disappointed with the help from this forum. I think I've decided to go with the iron 4V heads, aluminum dual plane, and exhaust headers in the rebuild. Found a pretty good price on both the cores and the machine work. I will spend some time on the cam selection to make sure I get the most from the stock heads. Haven't fullly decided yet on rollers, but leaning towards hydraulic flat to keep the cost down. Would like good street performance, but doubt I will be stressing the valve train very often. The car may never see the track. Starting the process of removing the radiator, accessories this weekend. Hope to be able to pull it in a couple weeks, depending on my work schedule. Could be awhile to get it all back together, but I'll let you know how it turns out. Thanks!
Try to find the money for the roller cam. It is one of my regrets that I did not go for the roller. I will next time for sure.

 

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