Ported Dart pro 1 pre platinum

[Carnut1]

Carnut1,

Did you hunt up a picture of the EQ23 50 cc head combustion chambers with 2.02"/1.60" valves that you asked me about a while back?

I don't know much about chambers, but, IMHO, they look great! 50 cc's and flat-tops or slight dish for the win.

A 400 block, a 6.25" long rod, 4.155" b x 3.00" s = 325" engine here! Like a hopped up 302 Z-28 motor is all. Rpm the sucker to the moon!

Got's ta buy my pistons....

pdq67

The ones I found did look really nice. I like how they do their chambers. That is a solid head design. I really like how that engine is coming together. That bore and stroke is the one I was hoping you would use. Thanks, Charlie

[randy331]

Where I am now at .7" lift. I feel the valve job could be improved but that would require sinking the seats a bit. Any input about valvetrain issues and if it is worth the headaches would be appreciated. Thanks, Charlie

What headaches would be involved sinking the valve some?

Randy

[KnightEngines]

No headaches, sink the valves, set up the springs with shims or offset locks or offset retainers - whatever, gotta do it anyway.
Pushrod length will change, rockers will sit higher on studs (studs can be shimmed up with hardened washers if need be) - all stuff that needs to be checked when building an engine anyway.

I routinely sink seats, on just about every head they sit too high in the chamber.

[Carnut1]

That is what I have been thinking. Heads need a flat mill at least anyway. The valvetrain will all be new and custom so sink em. Thanks, Charlie

[KnightEngines]

Let us know what you have decided in the way of valve sizing & seat angle - we can advise on a suitable valve job.

[randy331]

Heads need a flat mill at least anyway.

Angle mill only, unless rules don't allow it.

Randy

[MadBill]

Where I am now at .7" lift. I feel the valve job could be improved but that would require sinking the seats a bit. Any input about valvetrain issues and if it is worth the headaches would be appreciated. Thanks, Charlie

What headaches would be involved sinking the valve some?

Randy

Sinking a 2.02" valve by 0.050" will add 2.6 cc of chamber volume.

[pdq67]

Carnut1,

Did you hunt up a picture of the EQ23 50 cc head combustion chambers with 2.02"/1.60" valves that you asked me about a while back?

I don't know much about chambers, but, IMHO, they look great! 50 cc's and flat-tops or slight dish for the win.

A 400 block, a 6.25" long rod, 4.155" b x 3.00" s = 325" engine here! Like a hopped up 302 Z-28 motor is all. Rpm the sucker to the moon!

Got's ta buy my pistons....

pdq67

The ones I found did look really nice. I like how they do their chambers. That is a solid head design. I really like how that engine is coming together. That bore and stroke is the one I was hoping you would use. Thanks, Charlie

Charlie,

You ever drive or ride in a '58 Impala or a cheaper Bisq. with a hopped up 348 in it?? Like a 350 hp jobber, "trips", and all.

It will trip your trigger!!

I got to drive Gene's '58 Imp one time at speed, and I'm talking way above 70 mph! Like a 100 or so mph for miles and the big SOB floated like a boat on the water. But we could drive like that back about '63 or '64 or so!!

Jerry had a '58 Bisq. with I think the later 350 hp engine in it, (trips and all), and I am here to tell you that it was scary at speed! 110 mph by the speedo in 2nd gear sort of scary.

We left La plate, MO one afternoon after Jerry pissing, "Barney Fife", off and went over the SFRR overpass north out of town on three tires at like 90 or so and Jerry just laughed and kicked it up to 125 mph as we left town on three wheels.

We were running 125 mph when he shut it down and it took a 1/2 hour for the rim to cool off. so he could change tires.

Later that week, Jerry got a ticket in the mail to come to Court, cost him $75 that time..

Damned "W" engines would run..... Old fashioned as they are to this day...

My .060" over, 11.5 to 1, 409 with trip's ran like a small block on steroids!!

pdq67

[Carnut1]

No experiance with the "w" engine but some with 331's. The valve job for the sunk port #1 2.08" 40 / 45 / 60 / 75. Thanks, Charlie

[badassracing]

I'm gonna ramble a little about 50 deg (& other steeper angle) valve seats here for a bit, maybe clear up a little confusion, maybe add to it.
This is just my take on it & I am a long, long way from an expert on the matter.

To explain how a 50 deg seat works I'll take it to the extreme a bit - just to emphasise it.
Imagine you have a regular 45 deg valve seat cut for a 2.08" valve with a 60 deg bottom cut, it's cut to the edge of the valve & .040" wide.
Now take a 1.98" valve & cut a 60 deg face on it.
It'll go into the same seat & seal on the bottom cut - so nothing else has changed.
Off course that 1.98" valve is sitting deeper in the seat & is smaller in dia, so at low lift the curtain area is reduced & it flows less. Curtain area will remain smaller than the larger valve, but before the convergence point you start to get the effect where that smaller valve is not 'in the way' as much - the air has to turn less to get around it.
That has a few benefits, firstly it'll flow more raw cfm due to less restriction from the valve head, secondly it'll allow velocity to remain higher further into the chamber - energy in the incoming charge is not being wasted diverting around that 2.08" valve, that ties in with pressure recovery. Thirdly the air coming in over the short turn is less likely to skip across the back of the valve & out the long turn or sides - the valve being less in the way gives a straighter path out the short turn side, so the valve is seeing more equal flow around it's circumference.

Now if we look at longer duration cams required for an engine to turn higher rpm we realise that the valve is actually opening before the ideal time in order to be open far enough when peak demand occurs - it's the nature of the beast, when they invent a square lobe it won't be a problem, but for now it is.
So that loss of low lift flow can be advantageous, with the larger valve (& therefore larger curtain area at low lift) flow is often too much, if you combine the larger raw flow available with the negative pressure pulse coming from the exhaust port as the intake opens you can see you'll get a 'gulp' of air & then the airflow slows (or stalls) until the piston gets on it's way down the bore & the draw on the valve starts again.
With a 50 deg seat & reduced low lift flow that 'gulp' will be extended in duration & the stall in airflow reduced - evening out the draw on the valve & resulting in higher velocity into the cylinder & through the port being developed earlier & giving a better 'head start' as peak demand occurs.

All these benefits can be seen with NO CHANGE to the seat, just a smaller valve sealing on the bottom cut.
Off course a 60 deg seat would have a very limited life span & is not practical in 99% of applications, so we split the difference & get a % of the benfits with a 50 deg seat & modified top & bottom cut angles to mimic the seat required for a larger valve whilst giving a 50 deg sealing face.

You can also see some of the benefits of a steeper seat while retaining a 45 deg seat (for durability purposes) by simply running a smaller valve, steeper bottom cut, larger thoat % & steeper top cuts - if the 45 deg seat is extended well past the actual valve& also functions as the top cut you can fool the engine into thinking it has close to 50 deg seats while maintaining a 45 deg seat.
Doesn't work as well as actual 50 deg seats tho.

Now, flow bench results - on the bench all you'll see is a reduction in low lift flow & a slight increase in high lift flow.
But that is not a running engine pulling 6000+rpm, it's just a vacuum motor pulling air through a valve at constant depression & fixed lift - it in no way mimics the dynamics of an actual engine.
You can only 'see' the benefits of the steeper valve seats by visualising the dynamic engine doing it's thing, or putting it on a dyno, or racing it.

If you notice I'm talking about engines with relatively long duration cams turning fairly high rpm & making good HP/ci, the benefits of a 50 deg seat mostly just apply to this type of engine, lower rpm, smaller cammed stuff sees less or no benefit from steeper seats & reduced valve job life is a bigger downside than any small benefit.

Very nice post.

Thanks for the thread Charlie...there's some good info in here.

[JoePorting]

Nothing kills flow numbers like milling. Expect to lose around 3 CFM per .010" milled across each flow level.

[KnightEngines]

Not if the seats are sunk more than the heads are milled...........

You'll only start loosing flow when you start getting into the valve job, with the seats sunk he won't be milling anywhere near as much off the heads to get those CC's back as compared to how much the seats are sunk.

[Biteme]

Nothing kills flow numbers like milling. Expect to lose around 3 CFM per .010" milled across each flow level.

Would that be because of pressure recovery out the short side?
Possible one of the reasons sinking the seat a tad helps?

[pdq67]

I have often wanted to plunge cut the chambers for bigger valves.

Say -605 heads out to 2.02"/1.60" valves is all.

But keep the small chambers as much as possible to keep the compression up.

This is why I bought my EQ23 50 cc heads so I wouldn't have to do this..

And right, they have a beautiful chamber....

Us short stroke motor guys have a problem building compression with the heads we have to deal with. 265, 272, 283, 301 and such is all..

pdq67

[wyrmrider]

sinking the valves can loose flow dbl check