351 2v to 4v conversation

[73FastBk]

So fellas I’ve been doing plenty of research but wanted to talk to the guys here who know or have done similar swaps. I have a 351C 1973, I just got a set of 4v closed chamber heads. As of now I need a carb and also looking for a good dizzy.

My question is what is a great intake manifold that’s a true 4v size and also dizzy combo. I’d like to keep the dizzy smaller size not the huge cap.

Also what’s a good stall rpm? I’m still learning about that stuff which is over my head atm haha. Ty in advance!

 

[Sheriff41]

It really depends on your goals for your car. Dual plane intakes are more street friendly (better low-end response) while single plane intakes provide top end performance. Either will work with the right combination of engine parts and driveline mods.
Blue Thunder makes a dual plane intake that works well on the 351C 4V heads. If you have Ram Air, though, you may have clearance issues. The Edelbrock Air Gap intake is designed to work on both 2V and 4V heads and has decent dyno numbers, according to some online reviewers -- do a Google search and see for yourself. I run an Edelbrock 351 4V Performer RPM since it was what was available back then. No complaints. There's a few others out there from Offenhauser and Weiand, but I'll defer to other's opinions on these.
There are several good ignition systems to consider. If you're running a carburetor I like the Ford Duraspark 1 setup. There are different Pertronix setups members on here use -- some have opinions on these.
If you're planning to go fuel injection ask some of the members on here which ignition systems work with EFI.
Stall speed depends on you cam profile and gear ratio. You'll want to do your homework on these to get a combination that works well before spending your money on anything.
You need to think about a cam that will help you take advantage of the 4V heads. Many are converting to roller cams for the benefits provided. Again, you need to think about how you want to use your car and choose a cam that helps achieve your goals.
Also, consider what gear ratio will compliment your combination and objective.
Finally, ask plenty of questions on here. We are fortunate to have some knowledgeable straight shooters that will give you some honest feedback.

 

[kcmash]

So now that you have the "cool" heads, yep, ask yourself what your goals are. I am set up like Sheriff41. 351C with quench chamber 4V heads, adjustable valve train, roller cam ground to Boss 351 Specs by Cam Research, an Edelbrock Performer RPM intake that reduces the intake port size and a Pertronix 1 electronic conversion. This is backed by a 4 speed and a 3:25 limited slip rear end.

I don't race mine. I do like to have fun with it. It's very driveable on the street and to cruise nights and shows. On the highway I turn about 2100 RPM at 70 MPH, so its fun on the highway too.

I have a couple Duraspark Dizzy's in the garage. That will be my next performance upgrade, mainly for a smoother ignition.

Remember the 351 4V was developed for NASCAR performance. The intake and exhaust ports are great for higher RPM, but struggle on intake velocity at idle. That is why the Edelbrock is a good choice for daily driving.

 

[jpaz]

I have a 72 Q code mach1. I changed the heads to the 71 quench heads with a Blue Thunder intake and a 735 cfm vacuum secondary Quick Fuel carb. 350 gears and a True Trac Posi. C6 auto with a 2800 stall converter and it runs great! It has a Crower flat tappet cam and hydraulic lifters with Crane Gold roller rockers, it’s a really great set up. I need wider tires though, it will break the tires loose at a 45-50 roll. I can give you more specifics if your interested. The guys on this site really helped me out with figuring everything out, especially Chuck. He has an extremely nice 72 Mach1, one of the nicest restored cars on this site, along with quite a few others too.

 

[73FastBk]

I have a 72 Q code mach1. I changed the heads to the 71 quench heads with a Blue Thunder intake and a 735 cfm vacuum secondary Quick Fuel carb. 350 gears and a True Trac Posi. C6 auto with a 2800 stall converter and it runs great! It has a Crower flat tappet cam and hydraulic lifters with Crane Gold roller rockers, it’s a really great set up. I need wider tires though, it will break the tires loose at a 45-50 roll. I can give you more specifics if you’re interested. The guys on this site really helped me out with figuring everything out, especially Chuck. He has an extremely nice 72 Mach1, one of the nicest restored cars on this site, along with quite a few others too.

First Thank you for the response. This is more or less what I’m going for, I want something that isn’t crazy but I’d like to have enough power to make the tires break at 45-50 mph ). My dad bought this stang when it was new and he gave it to me with the promise of taking care of it and giving it a nice refresh. Right now ive got the heads and a 4v performer intake. But I wanted to see what was the best options since I still have time before sending it to the shop. Im basically sending it for a full rebuild from the front to the back. I just want to buy all the part now so that the shop has everything the need. Im super excited but still have a LOT to learn. I had no clue how many variations of Cleveland’s there were until last year. Haha

 

[73FastBk]

So now that you have the "cool" heads, yep, ask yourself what your goals are. I am set up like Sheriff41. 351C with quench chamber 4V heads, adjustable valve train, roller cam ground to Boss 351 Specs by Cam Research, an Edelbrock Performer RPM intake that reduces the intake port size and a Pertronix 1 electronic conversion. This is backed by a 4 speed and a 3:25 limited slip rear end.

I don't race mine. I do like to have fun with it. It's very driveable on the street and to cruise nights and shows. On the highway I turn about 2100 RPM at 70 MPH, so its fun on the highway too.

I have a couple Duraspark Dizzy's in the garage. That will be my next performance upgrade, mainly for a smoother ignition.

Remember the 351 4V was developed for NASCAR performance. The intake and exhaust ports are great for higher RPM, but struggle on intake velocity at idle. That is why the Edelbrock is a good choice for daily driving.

Sounds like my idea of 3.55-3.73 gears might be too high then. Like I was telling sherif, I don’t play on going faster than 65 on the highway. Unless of course I was break the rear tires from time to time. I do want to take advance of the high RPMs though. Just trying to figure out what’s a “tried and true” setup no matter the price. I’ve been debating on ordering the Pertronix/duraspark dizzy or just go all out on the ICE ignition made in Aus. I just haven’t seen enough reviews on them to know if it’s worth the $1200. Thank you guys!!

It really depends on your goals for your car. Dual plane intakes are more street friendly (better low-end response) while single plane intakes provide top end performance. Either will work with the right combination of engine parts and driveline mods.
Blue Thunder makes a dual plane intake that works well on the 351C 4V heads. If you have Ram Air, though, you may have clearance issues. The Edelbrock Air Gap intake is designed to work on both 2V and 4V heads and has decent dyno numbers, according to some online reviewers -- do a Google search and see for yourself. I run an Edelbrock 351 4V Performer RPM since it was what was available back then. No complaints. There's a few others out there from Offenhauser and Weiand, but I'll defer to other's opinions on these.
There are several good ignition systems to consider. If you're running a carburetor I like the Ford Duraspark 1 setup. There are different Pertronix setups members on here use -- some have opinions on these.
If you're planning to go fuel injection ask some of the members on here which ignition systems work with EFI.
Stall speed depends on you cam profile and gear ratio. You'll want to do your homework on these to get a combination that works well before spending your money on anything.
You need to think about a cam that will help you take advantage of the 4V heads. Many are converting to roller cams for the benefits provided. Again, you need to think about how you want to use your car and choose a cam that helps achieve your goals.
Also, consider what gear ratio will compliment your combination and objective.
Finally, ask plenty of questions on here. We are fortunate to have some knowledgeable straight shooters that will give you some honest feedback.

ya that’s the issue I see, after a ton of research I’ve noticed there isn’t many options if you want to have your hood functional :/. The good thing is I have a edel performer intake sitting around but I was kinda discouraged using it since the intake ports are much smaller. I guess I’ll just have to go with that.

Thank you for your time and knowledge sheriff. I’ve got a long way to go but able and willing. My dad bought this mustang new and kept it ever since. I wanna make him proud and also scare him a bit on his first ride

 

[AcesArneson]

Before you buy another part really ask yourself exactly what you want from this engine when it is finished. It will save you from wasting time and money. Those heads will flow way more air than you will likely need but choking them off with a tight intake will kill any performance you desire. Think about getting the intake ported if the flow numbers are not high enough for your desired horsepower. And use port stuffers on those 4V heads to keep the flow going to the cylinder. Talk to some old timers about design issues too, if you are sending it in for a rebuild. These old things have some real oiling issues that can be overcome in a good shop if the guy knows Clevelands. The heads hold back way too much oil at high rpm so you need good head work to keep it flowing back. If you are thinking of EFI you can also look at a transmission upgrade to a 4speed auto if that’s your game. Tons of decisions to make so ask yourself what you really want.

 

[73FastBk]

Before you buy another part really ask yourself exactly what you want from this engine when it is finished. It will save you from wasting time and money. Those heads will flow way more air than you will likely need but choking them off with a tight intake will kill any performance you desire. Think about getting the intake ported if the flow numbers are not high enough for your desired horsepower. And use port stuffers on those 4V heads to keep the flow going to the cylinder. Talk to some old timers about design issues too, if you are sending it in for a rebuild. These old things have some real oiling issues that can be overcome in a good shop if the guy knows Clevelands. The heads hold back way too much oil at high rpm so you need good head work to keep it flowing back. If you are thinking of EFI you can also look at a transmission upgrade to a 4speed auto if that’s your game. Tons of decisions to make so ask yourself what you really want.

Ya that’s the fear, I wanna make sure I get most things right now before it’s out back together. I shop Im taking it to is a classic mustang shop, I did hear about the oil issues. I’ll make sure to bring that up in the build! Im option to any option tbh, my main priority is to wake the engine up a bet but without killing the reliability. I want to drive this regularly to the fire station when I work. So many 4-5k miles a year.

 

[AcesArneson]

Ya that’s the fear, I wanna make sure I get most things right now before it’s out back together. I shop Im taking it to is a classic mustang shop, I did hear about the oil issues. I’ll make sure to bring that up in the build! Im option to any option tbh, my main priority is to wake the engine up a bet but without killing the reliability. I want to drive this regularly to the fire station when I work. So many 4-5k miles a year.

Ok if you’re looking for Drive ability really consider the port stuffers. Talk to Price Motorsports, Mary can send you a set. They glue right in. I know it seems counter-intuitive to reduce space in the intake but trust me, there is WAY too much space there for a daily driver to perform like a monster occasionally. Check the numbers on your intake. I would think you are looking for 400 hp which is fairly easy with these things. Compare the factory CFM with what is needed with your bore and stroke to see if you’re in the ballpark but I think you’ll be fine as long as it is a 4V intake. Hopefully it’s dual plane so you have some bottom end terror to exhibit. These things are torque monsters so if you are looking for a setup to roast the tires in your midrange of 2500-4500 it’s best not to overplay the top end. It works as a system so if you want good low and mid-range power use some shorty or mid length headers with a cam designed to open in this range and you will be more than pleased with the driveability as well as the ability to knock you back in the seat. The long plenum of the Ram Air nostrils plays to low and midrange power too. Keeps it tight and builds velocity which really helps build rpm with power. Just let the mechanic know what your target hp is and where you want your peak power then he can guide you towards cam, liftersWhatever you need. Incidentally I went to my builder with dreams of making 450hp out of a 2V with 2V heads and he said no problem. I got greedy later on when parts were on back order for the valves I needed and just ordered new aluminum heads instead. Then the cam billet was delayed and I got more greedy and decided to go with extra lift a sacrifice a bit of drivability for some extra hp. Should come out on the dyno around 530hp next week when he is finished. Can’t wait.