cast dart 165cc test head for novice

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steve cowan
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cast dart 165cc test head for novice

Post by steve cowan »

gentlemen,
i have a dart cast 165cc wissota class head i bought bare from summit at xmas time,i am using it as a test head as far as port sizing,valve seat angles,valve shapes etc.
i dont want to destroy the head as i get very attached to items i pay good money for,i am thinking is it possible that dart port shapes and sizing is comparable due to patent design ??.what i mean by this is are the dart cast series ports shape the same but only change in CSA as per foundry casting.
i have my flow bench which has port flow analyzer v 3.5B pro version software.
For a person at my level which is NEWBIE this software is complex and has a lot of features and my reasoning to buy the big bench and pro software was because i can grow into the system over time and the software corrects itself for temp,baro,humidity,depression corrected etc,by the manufacture it is recommended to run all the testing to 28'',i have a sharp edge orifice plate supplied to me for that bench,inlet and exhaust pitot tubes.
there has been big discussions here about calibration plates etc but i dont have enough experience to even comment on the subject maybe a conversation for me a couple of years down the track when i am more confussed.
anyhow,i have read here about being careful about chasing CFM numbers,the rabbit hole deal and can of worm etc and all that is great advice,but i think as i am new to the flow bench i need to see cfm numbers and all the relations within,on my other thread (215 dart 383 sbc) the discussion came up about porting using CSA as the mainframe of a port,i find this interesting.
i am going to put up some pictures of where i am this week on this deal and talk about blinking and the night is gone,man this is a blackhole for time.
i want to make it clear that i did not flow intake with a radius bend and i tried using clay and playdo but kept getting sucked into the port as depression increased,one of the parameter the software has it can compensate for port entry exhaust exit with or without a pipe etc,i do not have a proper valve opening tool so i jury rigged as best as possible using a jesel oncar tool and dial indicator so please dont be critical on me at the moment as it is about learning the bench and its features,over time i will be making or purchasing equipment as required,not a
dart 170 cast head 011.JPG
lot available here in australia so will be sourced from USA.
dart 170 cast head 007.JPG
dart 170 cast head 001.JPG
dart 170 cast head 009.JPG
port flow ananlyzer 001.JPG
port flow ananlyzer 001.JPG
port flow ananlyzer 003.JPG
port flow analyser 001.JPG
001.JPG
003.JPG
the first two pictures of flow are the same,if you look on the later pictures i checked port velocity at the apex of the short turn holding the pitot tube along the floor on the divider side of the port,the flow bench take 10 points of data to come up with a average.
the question i have is at 0.600'' lift max lift there is nearly 400 ft/sec on the SSR i suspect this is to fast ???????
to slow the air at the SSR is it a case of opening pinch,raising roof,opening window area or all of the above.
any advice appriciated and please be kind to me as i am only trying to learn,if not give me both barrels lol
thanks
steve c
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steve c
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Re: cast dart 165cc test head for novice

Post by steve cowan »

forgot to mention i have not checked a as cast port yet,have not checked the exhaust just wanted to share what i have at the moment.
i checked intake with no valve went 214
with the valve at 0.600'' went 217 cfm is this because the air went turbulent out of the seat area??? thanks
steve c
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Re: cast dart 165cc test head for novice

Post by B Original »

I see in the second and third picture is where I would start. Do a 30 degree back cut on the intake valves only.

3rd picture the seats on the intake here is one of the cutters that works good for me for the seat and throat.

If you have to use stones try to emulate as close as you can.
ift-4556-hp.jpg
use a cut like this for the top cut.
ft-5121a-hp.jpg
Flow balls are Golden for finding the chamber section to de-shroud and clearance.
Easy to make your own find a 1/4 check ball or ball out of a failed bearing and attach a tig wire to it.
flow balls.jpg
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Re: cast dart 165cc test head for novice

Post by statsystems »

Never use a radius on an intake seat, even if it flows more.

If you only test at 28 inches you won't learn much.

A flow bench is a tool. You can make it lie. Just because a port flows more on the bench doesn't mean it will make more power. See the first sentence.
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Re: cast dart 165cc test head for novice

Post by GARY C »

steve cowan wrote: Fri Apr 27, 2018 4:25 pm forgot to mention i have not checked a as cast port yet,have not checked the exhaust just wanted to share what i have at the moment.
i checked intake with no valve went 214
with the valve at 0.600'' went 217 cfm is this because the air went turbulent out of the seat area??? thanks
Did you put a valve in from the top to account for the stem or no valve at all?
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Re: cast dart 165cc test head for novice

Post by Scotthatch »

Everything said so far is right.

My two cents

If you are starting out hit up local shops looking for heads that they think are trashed ..one end blown up or cracked badly ... stuff they will just give you... you don't ever need it to run but you need practice testing and cutting on heads .... and get your friends to bring stuff to test ... you need time on the bench testing anyway

Next I would stick to 28 inch to start with ... air has sound and movement keep your ears open and probe around you will learn to feel the pull on a prob ... one of the best porters I know I swear has done it so long he can see the air move ....

Also do some testing with the intake on the head a lot of times the intake needs more work then the head does

Lastly I will say there is stuff you will see on the bench that never helps on the dyno and places you can cut that will make a few more HP but never shows up on the bench ... it takes a long time running from bench to dyno to learn that and most of the time 90% of the best flow ever will get the job done anyway
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Re: cast dart 165cc test head for novice

Post by B Original »

statsystems wrote: Fri Apr 27, 2018 5:07 pm Never use a radius on an intake seat, even if it flows more.

If you only test at 28 inches you won't learn much.

A flow bench is a tool. You can make it lie. Just because a port flows more on the bench doesn't mean it will make more power. See the first sentence.
Genuinely Interested in what you have to say STATSYS please teach. Want to understand how the radius affects differently from the flat cut 45 or where the radius comes up short. I always lap the seat on final prep this may soften the radius but not by much I am sure.
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Re: cast dart 165cc test head for novice

Post by groberts101 »

steve cowan wrote: Fri Apr 27, 2018 4:22 pm the question i have is at 0.600'' lift max lift there is nearly 400 ft/sec on the SSR i suspect this is to fast ???????
to slow the air at the SSR is it a case of opening pinch,raising roof,opening window area or all of the above.
any advice appriciated and please be kind to me as i am only trying to learn,if not give me both barrels lol
thanks
steve c
yes that it far too fast.. especially considering the final application the other bigger brother castings will be used on. And yes you can cause detached flow and turbulence to lose flow without a valve in place. First time I did it I thought flow would almost double without it in the way. Had to retest several times because I couldn't believe it. lol

Sometimes you end up doing all that to settle the short side down but I would start by thinning the guide area first. Reflow and see what effects from that alone. opening the pinch's width without lowering the floor any. Can also thin up the dividing wall to gain more width there as well. This will show you what each incremental changes impact will be further into the port. If the entry is too narrow it just sets the likely already too narrow apex's floor width up for an even harder time getting things settled back down before dumping flow over the SSR. In reality that casting will never allow you the flow potential that you need for the real deal, but the tricks to get where you need to be on the other larger casting will still likely be similarly effected.

I also would NOT add a 30° backcut to the intake valve for your other high rpm race application either. If not already there from the factory, I'd just flow it without a backcut first and then I'd push towards a 34-35° backcut angle and keep the underside radius smaller and flatter. IOW, no tulip shapes for that lower SSR as it will jiust eat up valuable real estate. Use the backcut to shrink the seating surface down to about the same size as the seat you intend on using. If you want to really get fancy you can even try another valve with double backcuts.

EDIT.. sorry for the slow uptake, Steve. I see the valves now. The backcut stuff is more a fine tuning aid than a deal breaker one way or the other. Usually best used in a manner that accentuates the ports natural strengths for its intended application. ie: lower lifts, higher lifts, slight reductions in reversion, etc, etc.
Last edited by groberts101 on Fri Apr 27, 2018 6:18 pm, edited 1 time in total.
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Re: cast dart 165cc test head for novice

Post by groberts101 »

B Original wrote: Fri Apr 27, 2018 6:00 pm
statsystems wrote: Fri Apr 27, 2018 5:07 pm Never use a radius on an intake seat, even if it flows more.

If you only test at 28 inches you won't learn much.

A flow bench is a tool. You can make it lie. Just because a port flows more on the bench doesn't mean it will make more power. See the first sentence.
Genuinely Interested in what you have to say STATSYS please teach. Want to understand how the radius affects differently from the flat cut 45 or where the radius comes up short. I always lap the seat on final prep this may soften the radius but not by much I am sure.
I'm sure he'll eventually comment bit I'm guessing the likely reason why he is telling you that is because it's very well known that a radius flows more air but doesn't actually "grab the fuel" and help atomization. Basically, intake is a wet port and exhaust is a dry port so what works for one in a real running motor doesn't necessarily work well for the other.
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Re: cast dart 165cc test head for novice

Post by af2 »

groberts101 wrote: Fri Apr 27, 2018 6:14 pm
B Original wrote: Fri Apr 27, 2018 6:00 pm
statsystems wrote: Fri Apr 27, 2018 5:07 pm Never use a radius on an intake seat, even if it flows more.

If you only test at 28 inches you won't learn much.

A flow bench is a tool. You can make it lie. Just because a port flows more on the bench doesn't mean it will make more power. See the first sentence.
Genuinely Interested in what you have to say STATSYS please teach. Want to understand how the radius affects differently from the flat cut 45 or where the radius comes up short. I always lap the seat on final prep this may soften the radius but not by much I am sure.
I'm sure he'll eventually comment bit I'm guessing the likely reason why he is telling you that is because it's very well known that a radius flows more air but doesn't actually "grab the fuel" and help atomization. Basically, intake is a wet port and exhaust is a dry port so what works for one in a real running motor doesn't necessarily work well for the other.
Shear is a better word.
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Re: cast dart 165cc test head for novice

Post by groberts101 »

af2 wrote: Fri Apr 27, 2018 6:18 pm
groberts101 wrote: Fri Apr 27, 2018 6:14 pm
B Original wrote: Fri Apr 27, 2018 6:00 pm
Genuinely Interested in what you have to say STATSYS please teach. Want to understand how the radius affects differently from the flat cut 45 or where the radius comes up short. I always lap the seat on final prep this may soften the radius but not by much I am sure.
I'm sure he'll eventually comment bit I'm guessing the likely reason why he is telling you that is because it's very well known that a radius flows more air but doesn't actually "grab the fuel" and help atomization. Basically, intake is a wet port and exhaust is a dry port so what works for one in a real running motor doesn't necessarily work well for the other.
Shear is a better word.
yes sir it surely is. :D

The "grabbing action" is likely better relegated to the lower cuts as the first one to get ahold of the flow is likely the most important one to worry about if the port is already struggling to keep things under control.
Last edited by groberts101 on Fri Apr 27, 2018 6:21 pm, edited 1 time in total.
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Re: cast dart 165cc test head for novice

Post by user-30257 »

B Original wrote: Fri Apr 27, 2018 5:00 pm I see in the second and third picture is where I would start. Do a 30 degree back cut on the intake valves.
why not back cut the valve to the same angle as the top cut for starts?
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Re: cast dart 165cc test head for novice

Post by B Original »

Headguy wrote: Fri Apr 27, 2018 6:20 pm
B Original wrote: Fri Apr 27, 2018 5:00 pm I see in the second and third picture is where I would start. Do a 30 degree back cut on the intake valves.
why not back cut the valve to the same angle as the top cut for starts?
Huhh Back cut implies its the second cut on the back side of the intake?
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Re: cast dart 165cc test head for novice

Post by GARY C »

Interestingly a serdie multi angle cutter looks surprisingly like a radius, this is a 167 cc head that pro top line did in the mid to late 90's as a stock replacement, the cutter was designed for stock type classes where porting is not allowed and is usually used in conjunction with a bowl hog cutter, testing done to develop it showed more power with no back cut on the valve which also reduces flow on the bench.

These had a 2.055/1.6 valve because I had an old set laying around and with what I call a clean up port job flowed around 240 at .500 lift and stayed there, worked good with a 262 hyd flat cam and 1.6 rocker.
Sorry all I have is a cpl of flip phone photos.
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Re: cast dart 165cc test head for novice

Post by B Original »

groberts101 wrote: Fri Apr 27, 2018 6:19 pm
af2 wrote: Fri Apr 27, 2018 6:18 pm
groberts101 wrote: Fri Apr 27, 2018 6:14 pm

I'm sure he'll eventually comment bit I'm guessing the likely reason why he is telling you that is because it's very well known that a radius flows more air but doesn't actually "grab the fuel" and help atomization. Basically, intake is a wet port and exhaust is a dry port so what works for one in a real running motor doesn't necessarily work well for the other.
Shear is a better word.
yes sir it surely is. :D

The "grabbing action" is likely better relegated to the lower cuts as the first one to get ahold of the flow is likely the most important one to worry about if the port is already struggling to keep things under control.
In a moderately well designed port wouldn't you expect the flow to approach and sometimes pass supersonic as it goes past the seat section minimizing the shear or grab effect?
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