Looking for a few tips on porting 351c 4v heads

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bob460
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Re: Looking for a few tips on porting 351c 4v heads

Post by bob460 »

Kazoom wrote: Sat Mar 13, 2021 9:37 pm :roll: im ...LMAO... too that your crying over a =D>...!DECADE OLD!... =D> pump gas street eng mag article #-o

... Bravo! :lol: :lol: :lol:
Who's crying your the donkey that posted it, trying to show how good they are, i asked for the most power you can make out of these heads.........and this is what you give me......must be killer heads if no one has made more power than the 730hp. :oops: :oops: :lol:

The 225 chi makes an easy 760hp on a 434ci , .680 lift solid street roller @6800 on pump gas.
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Re: Looking for a few tips on porting 351c 4v heads

Post by KnightEngines »

The problem is not with the flow or power potential, it's with the recycled coke can material they're made of, lacklustre heat treat, cheap ass guide & seat material etc.
Check the hardness after they've run for a bit, see how quick the guides wear & how the valves hammer out the seats.
If you're lucky the seat inserts won't fall out.
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Re: Looking for a few tips on porting 351c 4v heads

Post by Momus »

Kazoom wrote: Sun Mar 14, 2021 1:05 am my god all the crying :lol: :lol: :lol: haters will bash no matter what is posted, but...

arnt you guys happy that I am happy with my AVG XTC-R 351 head purchase :shock:

I just love that they have 4VB T/A ports so that I can use my 4V intakes :wink:
See how long the valve gear threads in the top deck last while you are at it.

Secondary aluminium used.
bob460
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Re: Looking for a few tips on porting 351c 4v heads

Post by bob460 »

FACT is SM/PC copy everyone's else's work and how they get away with it is beyond me. No brains to design there own stuff.........just after a quick buck.

A poor man pay's twice and SM/PC is a perfect fit for you Kazoom.......good luck making over 730hp and surviving...you must like playing Russian roulette i guess..... :lol:
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Re: Looking for a few tips on porting 351c 4v heads

Post by bob460 »

So they didn't copy the JON KAASE BOSS HEMI HEAD also......... :^o
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Re: Looking for a few tips on porting 351c 4v heads

Post by Steve.k »

What most people don’t understand about the Cleveland intake port is it has a severe dip in bottom of runner right where manifold mates to head. Most pro stock guys were trying to level this dip to keep the fuel in suspension at high rpm. They were not making the port smaller. Once the dips and bends were fixed the port ended up around 248 cc. I have a pro stock set here of Paul JENKINS. Been measured a few times. This dip is really apparent with the period correct ur19 manifold.
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Re: Looking for a few tips on porting 351c 4v heads

Post by 1972ho »

Steve can you post some pictures of the said Pro stock cylinder head intake port,and do you know if the heads flowed more are the same as a filled runner port.Thanks
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Re: Looking for a few tips on porting 351c 4v heads

Post by Steve.k »

1972ho wrote: Tue Jun 22, 2021 10:48 am Steve can you post some pictures of the said Pro stock cylinder head intake port,and do you know if the heads flowed more are the same as a filled runner port.Thanks
Here is flow sheet on heads. I will get you pics of manifold head combo. The heads have intake port roof raised and the floor lifted. As does the manifold at entrance of port. I’ve talked numerous times to Paul and the main purpose was to lift floor to get rid of the dip while still maintaining a good csa. He also would build up the epoxy on cylinder wall side to help turn the flow towards center of valve. He said the belief at time was the bigger valve was shrouded. They mostly used boss302 heads as they had 2.25 valves to start and tighter chambers. They later went to ti 2.19 as the ford valves would split. I recently put a set of 4v heads on a 400 block and you need spacers to fit the 9.2 intakes. This really amplified the look of the dip with 1” extra plate. I hadn’t paid much attention to it before. When you look at a newer design like blue thunder3.60 or 4.3 , chi3v pro they raised the floor and redesigned manifold to reduce this dip. The set of bt heads i have I believe are close to 237 cc I’ll check sheets. The straighter shot afforded a little less csa to get same results in flow. I have got as good or better flow with porting stock port but these were on 7300 rpm engines and we didn’t think we had fuel separation issues. The prostock engines were spinning 9600. If you notice the exh side it flows 244 I’ve only been able to hit 220 ish max on stock exh port without a plate.
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Re: Looking for a few tips on porting 351c 4v heads

Post by Steve.k »

B477C8F5-4455-4392-BC25-ADE2BF339754.png
Here is intake runner. Note how thin top of port is as this was from lifting roof. There are a lot of misconceptions that they were making the ports smaller as they were to big. Thats bullshit! In the end the csa of port was usually a lot bigger than as cast. If you get a chance to watch Morgans webinar he explains about how important a straight shot is and especially the floor before short turn. Once you understand what he’s talking about its easy to understand what the ps boys were doing. That said the Cleveland stock head can be made to make excellent power and tq and even lower rpm, contrary to what all the nay sayers think.
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Re: Looking for a few tips on porting 351c 4v heads

Post by 1972ho »

Those are really different from any modified cleveland port that I’ve ever seen.Thanks for posting 😎😎
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Re: Looking for a few tips on porting 351c 4v heads

Post by Steve.k »

The manifold butts up to the head like that and travels up tunnel ram to fill the dog leg. The manifold is hogged way thin to get the cross section back from filling. I’ll get pics from the two intakes. One is new (untouched)the other-is pro stocked. Huge difference in size. If anyone tells you they filled to make smaller they don’t know what they talking about.Paul was from Daytona and worked a fair bit with Dyno Don. He told me Don used his flow bench before Jon worked with him. If Jons still comes on maybe he can elaborate. I know Morgan said guys like Roush used the stock style port but stuck a wing on floor to speed the air up to keep fuel in suspension.I have a set of these heads at Tim Halstead’s in Ohio. He’s going to build a replica engine and Dyno a couple of sets to see if the theories made difference on dyno.
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Re: Looking for a few tips on porting 351c 4v heads

Post by Steve.k »

8B402C90-1183-4537-9645-D5634DC479B6.jpeg
F3FDA748-ED96-4F09-A52B-E6836A20B313.jpeg
A53F151D-89C3-4BCF-9457-7A6ED1AB981D.png
Here is a chi 4v head on a 400 with spacers. Note the drop from valve to port mouth spacer in between then up into intake tract. The ps guys were eliminating that droop.
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Re: Looking for a few tips on porting 351c 4v heads

Post by Steve.k »

48771D38-384D-42C6-82C1-878DF9D15D3E.png
Here is intake manifold port. Note in top pics the difference in plenum entry to port. That Ol intake is well used and needs some attention. But its cool to see.
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Re: Looking for a few tips on porting 351c 4v heads

Post by FPV_GTp »

Steve.k wrote: Tue Jun 22, 2021 3:18 pm 48771D38-384D-42C6-82C1-878DF9D15D3E.png
Here is intake manifold port. Note in top pics the difference in plenum entry to port. That Ol intake is well used and needs some attention. But its cool to see.

Very cool indeed! thankyou for sharing Steve , am i reading this right? throat diameter of 2.18 with a 2.19" valve at 99% ??? i haven't subtracted the valve steam of 0.341" away !
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Re: Looking for a few tips on porting 351c 4v heads

Post by Danoh1 »

Wow. Just finished reading all 19 pages. Lots of info.

I hope the OP found success with his build. Stone stock Cleveland heads actually work pretty well.

I run stone stock, unported, un-touched 1970 351C 4V CC heads on a 12:1 “old school” Boss 302. 4 inch bore. 3 inch stroke. Holman Moody dual plane high rise intake. Solid flat tappet cam, just under .600 lift. BG prepped Holley 750. Made 430 HP on engine dyno . Ran for almost 18 years with a few freshen ups along the way. Vintage Trans Am racecar. I use the MPG intake plates.

The engine is finally getting new .020 pistons and all new everything else. Heads still un ported. New valve guides going in. Changing the cam up just a little. Expect 450 or so this time around. But probably won’t be able to dyno it.
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