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 Post subject: Cam selection help?
PostPosted: Sun Mar 18, 2018 12:42 pm 
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Hi! I'm new to this site and 351C engines in general. I have been studying and am down to cam selection. Sorry if this has been beaten to death so forgive me for that! I did attempt to search several times! II just couldn't find anything like my specific build.

I have a 67 Mustang coupe this build is going in. It has a 4 speed wide ratio top loader and a 3.50 LS 9 inch.

I have built the bottom end stock with original flat tops with two valve reliefs.

The heads have been reworked with Ferrea Stainless 2.19 and 1.71 valves. 1.73 roller rockers and and aftermarket springs and retainers good to about .570 lift. this is all in 1970 4V Heads. I am using the '70 4V intake with a 4 hole spacer and a 650 DP along with long tube headers and the 2.25 inch dual exhaust already on the car.

Now the question. I have three cams. Which is best for my setup.

1: Summit 282/292 adv, 218/228 @ .050, .509 lift with a 114 LSA

2: Elgin 292/302 adv, 214/224 @ .050, .512/.538 lift with 112 LSA

3: Summit 288/288 adv, 228/228 @ .050, .554 lift with 112 LSA

Number 1 is in the engine now on the stand. Number 2 is in the box on the shelf, and I would have to buy number 3.

The main things I am worried about are detonation with the smaller cams and clearance issue like P/V with the larger one.

This is a street car. I don't plan on doing any racing. It is going to be a fun weekend cruiser.

Thanks in advance for any help!


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 Post subject: Re: Cam selection help?
PostPosted: Sun Mar 18, 2018 2:07 pm 
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Joined: Mon Oct 29, 2012 9:05 am
Posts: 2417
All of those cams are small for what you're doing with the exception of 3, but you need a duration split on a Cleveland head.

Couple of questions....

1. Do you know the exact compression ratio?
2. Do you have power brakes?
3. Where would you like the horsepower to peak? 5500? 6000?

I will tell you first off that you need more duration and a tighter LSA.

You are correct that the smaller cams could cause pinging/detonation but it’s less of a risk with a long advertised duration hydraulic roller. That's the first hurdle we have to get over. All-in-all, all the parameters have to be scrutinized and juggled to make everything work.

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 Post subject: Re: Cam selection help?
PostPosted: Sun Mar 18, 2018 5:26 pm 
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I haven't actually cc'd the chambers but going by the compressed thickness of my head gaskets and everything I could measure I am around 10.4 to 10.5:1 The heads were stock and they were only cleaned up. No major milling done.

I figured the first two were too small but I already had them since this started as a 2V build. I picked up the 4V heads for $75 and that changed my plans! Of course I had to buy valves and rework them but I am still in it pretty cheap all things considered.

If cam 3 is the only one of the three viable then that is what I will use. It belongs to a friend of mine and he only wants $50 for it! My main concern there is any clearance issues. Is .554 safe with the stock '70 flat tops?

Thank you again for the help!


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 Post subject: Re: Cam selection help?
PostPosted: Sun Mar 18, 2018 5:29 pm 
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I can give you my recommendations but a $50 cam (as well as $75 heads) is a good deal.

You normally don’t have exhaust valve clearance issues with a Cleveland and I don’t expect .550” lift cam to give you problems.

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 Post subject: Re: Cam selection help?
PostPosted: Sun Mar 18, 2018 8:03 pm 
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Joined: Tue Jun 02, 2015 2:28 pm
Posts: 216
50.00$ of something you will hate can be just one more cam on the shelf...I have my share...
Time wasted..... you could be doing something better......... like.... titley winks

We all try too make the right choice the first time....Off the shelf cams can make this very difficult.

If you are looking to low dollar the build NO.3 is the one for me.


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 Post subject: Re: Cam selection help?
PostPosted: Mon Mar 19, 2018 4:05 am 
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As stated I am new to 351Cs in general. I've built 302s, 351Ws, and FEs but never a Cleveland. I will certainly listen to any advice from you guys! What cam(s) would be best for my setup?

I have manual steering and brakes. Along with everything stated above.


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 Post subject: Re: Cam selection help?
PostPosted: Mon Mar 19, 2018 4:06 am 
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Are you wanting a hydraulic roller or flat tappet?

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brent@lykinsmotorsports.com


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 Post subject: Re: Cam selection help?
PostPosted: Mon Mar 19, 2018 5:18 am 
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For a 10.5:1 compression ratio, you need a really lazy lobe, other wise you could put yourself into a situation with pump gas.

Clevelands like a generous duration split and the 4V heads will want a little more overlap, especially on a lower rpm engine. Otherwise, you'll be a little short on power under 6000-6500.

My recommendation would be a hydraulic roller as I just don't think you could get to a favorable situation with a hydraulic flat tappet:

283/291 advertised, 227/235 @ .050", 109 LSA, 105 ICL, .555"/.565" lift. This camshaft will have 69° of overlap, which will help with the intake port volume of the Cleveland 4V head. Since you don't have power brakes, we can ask for a little more overlap.

The jist of 4V Cleveland cam selection is this: the exhaust side is very poor in comparison to the intake side, so you need a generous amount of duration split. The intake port volume is HUGE. These days we know that a high flowing small volume port is the best scenario; in the 60's, Ford made everything as big as they could. In a race engine, it's not an issue because rpm keeps the momentum up. However, in a lower rpm street car, trying to get a large amount of air/fuel moving can be very frustrating. Air/fuel has a momentum just like anything else and it takes effort on the engine's part to make it move.

To combat all of this, we use the exhaust side to pull on the intake side. It's called scavenging. A single pattern camshaft with a long LSA (same duration on intake/exhaust) will not allow the degree of scavenging that we need. In addition a shorter ICL will help low rpm manners including throttle response.

There are very, very few off-the-shelf Cleveland camshafts that are optimal. The reason for that is because cam grinders (Comp, Crane, Lunati, Crower, etc, etc.) all have a group of lobes and they just copy that group of lobes to whatever camshaft they're working with, whether it's for a BBF, Cleveland, SBC, small Mopar, Buick, etc, etc. If you thumb through a cam catalog, you will notice that the same camshaft is pretty much offered for every engine family....with the exact same specs. Engines are not universal. They all have differences that command different specs. The Cleveland is one of the most eclectic.

I am not a camshaft grinder, but I send camshafts all over the world for the engines that I specialize in. I have either Comp Cams or Bullet grind them for me. This particular camshaft in a billet steel core would cost $399. It's expensive, but it would be optimal for your engine's combination.

In addition, you will gain a whole lot of power by upgrading that 650 to a 750. :)

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brent@lykinsmotorsports.com


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 Post subject: Re: Cam selection help?
PostPosted: Mon Mar 19, 2018 11:07 am 
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Joined: Wed Oct 31, 2012 11:24 am
Posts: 283
SELL all three cams you already have to someone with EFI. BUY the cam that Brent has suggested. It will work great. The 351C 4V head is overlap dependent as Brent mentioned . I found that out 40+ years ago


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 Post subject: Re: Cam selection help?
PostPosted: Mon Mar 19, 2018 1:50 pm 
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Joined: Tue Jun 02, 2015 2:28 pm
Posts: 216
The 650 carb. will have very little fun factor and as you move up in the Cleveland food chain..
you will find 750+far better and needed in the fun factor.

You are already looking at better intakes ?(Don't lie)
It happens to all of us....


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