bbc 461cid, peanut port heads. what to expect? - Chevelle Tech
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post #1 of 38 (permalink) Old Jun 14th, 19, 2:11 PM Thread Starter
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Jani Heino
 
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bbc 461cid, peanut port heads. what to expect?

Hi, have been reading old peanut port threads here and got inspiration to build one for myself. This engine is going to my boat, Chris craft Stinger 260. I dont if this thread belong here but i do know that this forum has the most knowledge for this kind of build. I am new member here and have many questions to ask. Heads are 360 casting with stock size ferrea stainless valves int: 2.065 exh: 1.725. pocket ported with multi angle seats, intake valve back is rounded not 30 degree.

Flow numbers 28", good port

0.100= 65.5 cfm

0.200= 137.5 cfm

0.300= 206 cfm

0.400= 239.7 cfm

0.500= 256.6 cfm

0.600= 255.1 cfm


Other parts


-Block, gm 454 4bolt, bored .030 over, line honed, bore notched.
-Crank, gm nodular cast, 039 casting
-Pistons, speed pro l2349F forged. -29.4cc dome
-Rods, scat I-beam with 7/16 bolts
-Rockers, crane gold 1.7
-Valve springs, comp 924-16

-Intake, 2 Options, edelbrock performer rpm 2.0 or performer 2.0.
-Carb, rochester q-jet 750cfm from 454 mercruiser
-Camshaft, ??????


Time has come to deside what cam to use and where i set my compressio ratio. after unshrouding the valves my combustion chamber is approx 120cc, that puts my compression approx 10.3 to 1. speed pro pistons has plenty of material to shave of if needed. The first question is what is safe maximum dynamic compression ratio to use. I live in europe and our fuel is EURO 98e 5% ethanol.



Cam 1. Isky mega 270/270, .050: 221/221, lift: 0.549/0.549, lobe 108. overlap 54 deg. dynamic comression with my combo 8.34



Cam 2. Lunati street master 275/275, .050: 225/225, lift: 0.560/0.560, lobe 108. overlap 59 deg. dynamic compression with my combo 8.1


When started this build, i was hoping to get 450hp-500hp engine with good low end torque and peak hp in 5100-5300rpm range(cast cranksahft). What you guys think, what kind of numbers i should expect?


Before unshrouding the valves, intake flow was 260cfm @ 0.500 and [email protected] 0.600.
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post #2 of 38 (permalink) Old Jun 14th, 19, 5:54 PM
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Re: bbc 461cid, peanut port heads. what to expect?

Should go good, my no compression 461with 236 heads goes [email protected] I would use the RPM Performer but but an 850 what ever one it, that's the one that has worked the best so far for me. Isky mega cams are a little outdated but make real good power. Back in the late 80's I used the 280 mega cam and it pulled fantastic. Your combo should make for a fast boat.
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post #3 of 38 (permalink) Old Jun 14th, 19, 7:15 PM
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Re: bbc 461cid, peanut port heads. what to expect?

Hi Jani.
I am not a boat guy other than a reluctant passenger. Over the years I've listened to many stories about engines in boats and longevity; especially when run under load and higher RPM.
May I suggest you seek out some of the marine expertise that is out there. There are a few folks here that have marine experience and hopefully they will chime in.

But also take the time to seek out marine engine forums that may have a wealth of knowledge to share.

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Current Engine VortecPro 460 (513 HP) Original is resting
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post #4 of 38 (permalink) Old Jun 14th, 19, 7:42 PM
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Dan
 
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Re: bbc 461cid, peanut port heads. what to expect?

Not sure how it would run in a boat, but I just installed a PP motor in my 69 Chevelle and absolutely LOVE it! It has incredible throttle response and great low end torque . I think you'll enjoy it!
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post #5 of 38 (permalink) Old Jun 14th, 19, 9:52 PM
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Re: bbc 461cid, peanut port heads. what to expect?

That is a heavy boat and many had twin 5.7 engines in them.
Doing a single BBC would save some weight.
I really do not think the 2 cams would have that much power difference between them but I would go for the smaller one just for the fact you need the TQ and the higher dynamic compression may get you a tiny bit more of that in the RPM range that you will most likely be in.

I run ridiculous high DCR in my street cars on 91 octane fuel and pull heavy loads with them if you think 5000 extra pounds over vehicle weight is heavy. I do not even consider DCR as a number worth computing.
But it is there and computable.

If you have not stuck it all together yet you will benefit from roughing up the intake runners in the heads to keep fuel atomized a bit better than a smooth port.

The sharp edges on the piston tops in the valve relief area and any machined sharp edges should be smoothed ..320 or 400 grit sandpaper wrapped around your finger and sanding the sharp edges is all it takes.
Do also remove the sharp edge on the combustion chamber.

Helps Keep preignition at bay.

Good luck to you and Hope your outdrive is the strong one I think the Bravo is the stronger one vs the Alpha.
I am sure you have been around that block.
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post #6 of 38 (permalink) Old Jun 14th, 19, 10:10 PM
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Re: bbc 461cid, peanut port heads. what to expect?

Jani, BillK, one of the moderators here and a machine shop owner, builds marine engines and can probably give you some straight advice on your combo, PM him and good luck!
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post #7 of 38 (permalink) Old Jun 14th, 19, 11:04 PM Thread Starter
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Lots of good info👍 so the low end torque should be fine with either of those cams. It sounds that i have been over looking how important the DCR is, always tought it should be in 8.0-8.5 range in street engine. If i remember right even David Wizard didint mention anything about DCR in his book. There was a chart telling the right SCR for the ammount cam overlap.
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post #8 of 38 (permalink) Old Jun 14th, 19, 11:15 PM Thread Starter
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Here is few pictures of the valve unshrounding that took the 16cfm from the intake flow, but it made the exhaust flow better.
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post #9 of 38 (permalink) Old Jun 15th, 19, 10:20 AM
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Re: bbc 461cid, peanut port heads. what to expect?

The only thing that jumps out as to why you lost cfm on the intake side is something David Vizard mentioned in one of his videos on you tube the area on the Vortec head near the flat deck portion of the combustion chamber is quite large and if you port it larger unshrouding the intake valve more the upper CFM will be less.

He actually put some clay in that area and flowed the head again and picked up much more air flow and the head did not back up.
Looks like your unshrouding opened that area up on the BBC head.

What is happening is the air comes out of the port in a swirl pattern and when you open that area it tries to make the air swirl the opposite direction and that hurts the flow.

The air coming across the short turn into the bowl..Maybe a short turn tweak can fix it to some extent.
Watch the Vizard videos on porting Vortec heads and you should find that.

Here is a picture I scribbled showing the area you do not want to open up. Which when unshrouding you did open up.

Now this is on a vortec head and may also hold true on a BBC or other head. You decide..I do not have a flow bench.
I must pay each time I have heads flowed.
When i did open that area on old school SBC heads I would gain nothing and lost 3 cfm on a 461 many years ago.
Could have been from that.
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post #10 of 38 (permalink) Old Jun 15th, 19, 12:06 PM
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Re: bbc 461cid, peanut port heads. what to expect?

Quote:
Originally Posted by Janih View Post
Here is few pictures of the valve unshrounding that took the 16cfm from the intake flow, but it made the exhaust flow better.
The reason you lost flow on the intake side is those valves look sunk to me. Just recut them for a bigger valve 2.19 if you have the 2.06 you will get the flow back. Sinking valves is the worst thing you can do to a head.
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post #11 of 38 (permalink) Old Jun 15th, 19, 2:05 PM Thread Starter
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It is always nice to open the book after modifications 😂 it was like number 5, now it is like number 4.
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post #12 of 38 (permalink) Old Jun 15th, 19, 2:25 PM
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Re: bbc 461cid, peanut port heads. what to expect?

I would not worry so much about it and stick it together and run it.
Flow bench can't dupiclate what happens in a port with reversion etc.

If you end up needing more power then stroke it. and possibly test heads and other things then.
You may love it as is for now.
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post #13 of 38 (permalink) Old Jun 15th, 19, 5:06 PM Thread Starter
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Jeff, you are so right. I almost called to my machine shop to replace intake valves to 2.19", but I will leave the heads as they are now and let dyno tell the numbers. When i get my heads back, i could do some flow testing with both intakes the performer and the RPM, just to find out is there any benefits of the Rpm design in this level. I could use the Rpm in my next large oval port build. Here is a good comparison, measured at the same flowbench.

Edelbrock e-street 290cc stock, @left. My peanuts @right. Good ports 28"


e-street my peanuts +/-

0.100 56 65.5 +9.5
0.200 117 137.6 +20
0.300 177 206 +19
0.400 223 239.2 +17.8
0.500 248 256.6 +8.6
0.600 268 255.1 -12.9

Would be nice to see some dyno sheets from 454 with stock e-street heads and mild cam; 220°-230°intake duration.
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post #14 of 38 (permalink) Old Jun 15th, 19, 8:16 PM
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Re: bbc 461cid, peanut port heads. what to expect?

Quote:
Originally Posted by Janih View Post
Jeff, you are so right. I almost called to my machine shop to replace intake valves to 2.19", but I will leave the heads as they are now and let dyno tell the numbers. When i get my heads back, i could do some flow testing with both intakes the performer and the RPM, just to find out is there any benefits of the Rpm design in this level. I could use the Rpm in my next large oval port build. Here is a good comparison, measured at the same flowbench.

Edelbrock e-street 290cc stock, @left. My peanuts @right. Good ports 28"


e-street my peanuts +/-

0.100 56 65.5 +9.5
0.200 117 137.6 +20
0.300 177 206 +19
0.400 223 239.2 +17.8
0.500 248 256.6 +8.6
0.600 268 255.1 -12.9

Would be nice to see some dyno sheets from 454 with stock e-street heads and mild cam; 220°-230°intake duration.
PP heads do flow well to about .550 on the intake side. Which port did you flow the long or short intake runners? Like Jeff says stick it together and run it. Your low and mid lift numbers are very good and that's where your power will be made from as if you have a cam that max lift is .500 it's only there once in the cycle, from .200 to let's say .450 it there twice. What were your exhaust numbers?
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post #15 of 38 (permalink) Old Jun 16th, 19, 4:56 AM Thread Starter
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Re: bbc 461cid, peanut port heads. what to expect?

Quote:
Originally Posted by 68Chevele View Post
PP heads do flow well to about .550 on the intake side. Which port did you flow the long or short intake runners? Like Jeff says stick it together and run it. Your low and mid lift numbers are very good and that's where your power will be made from as if you have a cam that max lift is .500 it's only there once in the cycle, from .200 to let's say .450 it there twice. What were your exhaust numbers?
heads are ported by another person. Before i send the heads to be ported, i cleaned/smoothened one long runner and short runner, approx 1/5" below the seat and the short turn radius by myself, exhaust runner i left stock, stock valves/seats.

..........long runner.........short runner.............exhaust

0.100........65.....................62.5.......... ............50
0.200.......144...................154............. ...........94
0.300.......207.5................211.............. ..........128
0.400.......243...................233............. ...........157
0.500.......263...................244.5........... ..........174
0.550.......266...................251............. ...........180
0.600.......266...................252.5........... ..........185

Next step, valve unshrounding, stock intake valve with 30deg backcut. stock exhaust valve/ unported runner.

0.100.......68....................71.6............ ............59.2
0.200......146...................154.............. ..........115
0.300......208.5.................206.............. ..........144
0.400......235.5.................229.............. ..........164.5
0.500......250....................243............. ...........178
0.550......250....................247.7........... ...........180
0.600......250....................252.4........... ...........181.7

All these flow tests was done by me and my friend, with superflow 110 bench. After all this, the heads were ported by another person, and he gave me the results, only the long runner which is measured with another superflow 110 bench. Dont want to compare results between 2 different flowbenches, but when I get my heads back, I will do the final tests with the same flowbench that these above tests were done.
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