Cleveland exh.

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Steve.k
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Cleveland exh.

Post by Steve.k » Tue Sep 12, 2017 4:06 pm

We have been working on cleveland exh port. So far we are sitting about 248 @.700 with floor raised over .500 and the valve boss removed! Head guy says without milling and installing full plate he doubts there is anymore? Also what gains could be seen raising exh cfm from say 220 to 248 all things being equal?for what it's worth my pro stock plated heads flowed 244@800

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Re: Cleveland exh.

Post by DaveMcLain » Tue Sep 12, 2017 6:18 pm

I remember back in 1980 Jack Roush telling us that the port plate modification was worth about 50 horsepower on a Cleveland engine but it also might have helped to justify the cost of the heads which were about $6000 for a pair from him. I think that it depends on the chassis and if it causes you to have to compromise the headers it probably is best to just turn it in the head and get it over with.

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Re: Cleveland exh.

Post by Steve.k » Tue Sep 12, 2017 7:01 pm

50hp wow thats huge. Very cool info. The 6000 back then was nuts.

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Re: Cleveland exh.

Post by mag2555 » Wed Sep 13, 2017 7:57 am

What size Throat are you at ?
What size at the flange?
What air flow does the port pick up with a 45 degree bent tube on it?

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Re: Cleveland exh.

Post by piston guy » Wed Sep 13, 2017 11:39 am

Steve ,
The track will tell you if you've improved the head. I don't mean to be rude at all. I've had several conversations with retired Ford engineers that developed the heads and engines back "in the day" . They all laugh ( literally) when I ask about flow numbers and why the head "benches" so poorly. The general comment is the head will never show stellar numbers on a flow bench because it isn't reality. They claim exhaust scavenging is critical to making the head work and that isn't replicated on a flow bench that simply "blows air" out past the static valve. Exhaust pulses in the header tube obviously help to "pull" the next charge . If that could be implemented , the flow numbers would change by a good amount is their comment.
Modifying the heads to "high port" configuration changes the exhaust flow to a more "normal" situation ( a nice "arc" versus an over 90* sharp downturn) and the flow bench responds favorably.

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Re: Cleveland exh.

Post by mag2555 » Thu Sep 14, 2017 8:31 am

Piston guy if I might refere you to at least these 3 pages I will post up from a wel known person on cylinders Heads as opposed to the 60s Ford engineers and there propensity for oversized ports that you have talked with.

Please note that the order of the first two pages I posted should be reversed, sorry!
You do not have the required permissions to view the files attached to this post.

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Re: Cleveland exh.

Post by piston guy » Thu Sep 14, 2017 12:20 pm

Thanks for the post but NONE of it is 351C cylinder head specific. Different engineers were used for the 255 engines , both wedge and DOHC. The Westlake head was fine "for the day" and better than anything available back then. The best Ford had was the C6FE "GT40" iron head which topped out at about 250 CFM intake flow. IF it were THAT superior , it would have changed the way "wedge" headed small blocks heads were made. Nothing today is made like the Westlake , coincidence? An "off the shelf AFR 185 will make MORE horsepower without all of the oddball stuff those heads require.
The 351C is not a typical head. Virtually everybody complains about the exhaust port. Those that have figured it out run well with it , those that don't try to make it into a Chevy port. When the late Smokey Yunick designed the SK 42624 aluminum 351C head for use at Indy as a "stock block" , he left the exhaust port alone and altered the intake so it would not go turbulent. Unfortunately we can't ask him why he didn't rework the exhaust. Knowing the original design intent ( right or wrong) has helped me make more power with the head over the last 47 years of racing with them. Camshaft and valve spring advancements have also helped.

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Re: Cleveland exh.

Post by DaveMcLain » Thu Sep 14, 2017 1:49 pm

piston guy wrote:Thanks for the post but NONE of it is 351C cylinder head specific. Different engineers were used for the 255 engines , both wedge and DOHC. The Westlake head was fine "for the day" and better than anything available back then. The best Ford had was the C6FE "GT40" iron head which topped out at about 250 CFM intake flow. IF it were THAT superior , it would have changed the way "wedge" headed small blocks heads were made. Nothing today is made like the Westlake , coincidence? An "off the shelf AFR 185 will make MORE horsepower without all of the oddball stuff those heads require.
The 351C is not a typical head. Virtually everybody complains about the exhaust port. Those that have figured it out run well with it , those that don't try to make it into a Chevy port. When the late Smokey Yunick designed the SK 42624 aluminum 351C head for use at Indy as a "stock block" , he left the exhaust port alone and altered the intake so it would not go turbulent. Unfortunately we can't ask him why he didn't rework the exhaust. Knowing the original design intent ( right or wrong) has helped me make more power with the head over the last 47 years of racing with them. Camshaft and valve spring advancements have also helped.
In my opinion, a problem with the 351C exhaust port, 4V in particular is that it gets very large very quickly which locks you into having to use a header primary that's also large which limits what you can do in that area of the engine combo. I think that the designers of the engine were simply doing what they thought was best with the design given the technology and engine packaging that they had to work with. Overall they did a great job and I'd hate to try to do better.

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Re: Cleveland exh.

Post by Steve.k » Fri Sep 15, 2017 10:44 am

Thanks guys. The ford exh is a funnel shaped port and i think the gas expansion excels in this style port as hp goes up. Had a blower motor guy tell me they shape the port so the exiting gas has lots of room to expand. They do not care of shape, I think this maybe the theory behind this port also. We just spent two days dynoing a hyd flat tappet iron headed open chamber street motor. After fighting a gremlin that ended up comp hyd lifters bleeding down we mustered up 471hp@6000 and 415tq@5100. The owner didnt want to rev past 6000 but the engine would rev to 7000. I know the the motor wouldve clicked over 500hp as the hp curve was still headed north. This was a 9.5 comp open chamber head with the small valves. Edelbrock torker intake. Surprised me as well as owner. He was hoping for 425hp.

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Re: Cleveland exh.

Post by piston guy » Fri Sep 15, 2017 2:32 pm

Nice work Steve,
There are more guys out there that would have made 425 or less than your great results. the Cleveland is a tricky engine to make power with. Once you figure out what it likes , it responds with power , until then it acts like a turd.

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Re: Cleveland exh.

Post by treyrags » Fri Sep 15, 2017 3:14 pm

Valve events and lift are very important with the Cleveland
Image

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Re: Cleveland exh.

Post by Daniel Jones » Fri Sep 15, 2017 4:16 pm

> Once you figure out what it likes , it responds with power

Any tricks or approaches you'd like to share?

Thanks,
Dan Jones

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Re: Cleveland exh.

Post by piston guy » Fri Sep 15, 2017 6:37 pm

Listen to George Pence :wink:

Steve.k
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Re: Cleveland exh.

Post by Steve.k » Fri Sep 15, 2017 7:53 pm

Ahhh yes George. Good guy. You dont happen to work at racetec?

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Re: Cleveland exh.

Post by Steve.k » Sun Sep 17, 2017 9:59 am

Dan the motor is a flat top 9.5 racetec piston with ported oc small valve 4vheads. Ported torker intake and a comp xe274h cam. Stock rods and crank. We tried with tapered spacer but motor lost 8hp in bottom to mid. We tried 2" super comp headers but lost 11hp to about 5100 then made 5 more at 6000. This engine is far from exotic to say the least.It does have mpg windsge tray and small ring package. At 6000 the curve was still headed straight up but the owner didnt want to rev past 6000. Ive run stock rods many years past 7000 no issues.

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