EQ 23 SB Chevy Heads- Home porting costs for CNC results.

[Dusty]

Originally Posted by bowtie421regal85

this is a very interesting article. i was wondering whether you or dave could help me with a question? i have a stroker small block 400. it has a 3.875 stroke 4340 eagle forged crank shaft, 6"eagle h beam rod, and JE forged 13.3/1 40 over pistons. i beleive it comes out to 422.7 ci. the block has splayed billet caps

but my question is would the 50cc combustion chambered 235cc version work? or would that raise the compression to much? or would i have to change the pistons? if so since my rotating assembly is already balanced would i be better off getting bigger combustion chambers? with the bigger combustion chambers would the heads flow as good? i have a set of the old dart pro 1 230's but want to get a better head if this is the eq head is not the best option to accomplish this any suggestions we be greatly appreciated. i have just came gfn i have already seen some information packed writings you and dave rock!! any help the two of you could give me would be great keep up the good work.




sorry to write so many questions but also i have a stock suspension buick regal this motor is going in and th400 tranny,coan converter 5000 stahl,it has a 8.5 grand national rear end with a posi unit 4.56 gear and 28 by 13.50 quick time pro tire, hoping to get the car down to 3100# could you recommend a cam for the eq heads? if you don't recommend these heads for me. how about if i have the pro 1's ported? what cam would you recommend? i know this is a lot of ?, but if you could help m,e out i would appreciate it every cam place recommends something way diffrent from the next it's frustrating, and picking a head is tough the eq's sound innovative if i was togo with them would they bennefit from a 2.10 intake valve. so if you can point me in the right direction for the best 23* head and cam.

it would be a big help thanks

Those Dart heads are probably 64ish cc which would put you at a ridiculous compression. The 50cc chamber is definitely more advanced in the flame propagation department, mostly it makes it easy to get a flat top in a 350 not so much a problem with a 400. Funny you should mention that motor as I have a 400 and I'm building a very similar engine. I can't recommend a cam for you not comfortable enough with that yet especially once you throw lots of compression and big inches into the equation.

[Mwilson]

great looking heads, May fit my budget.

[bnio]

I was wondering if you would still comment on this test. Did you do any probing of the port to check port velocities? It would be interesting to see what they were if you have them. With those flow numbers I would assume they must be on the higher side with such a small volume intake port. Also do you have any info on the min cross section section of these heads? Port velocity is something that you never see details about when the heads are tested on the bench but it is a very important aspect of how the head is working.

[FlowSpecialist]

Excellent article Dusty and nice job on the heads. One thing I'd like to comment on is the valve seat widths. You say those are 60 thou. That's very narrow for valves as big as these and what the flowbench tells you isn't always the full story as far as power output goes.

The valve seats not only have to flow well but they have to seal well, last a reasonable time and perform the vital job of removing heat from the valve heads. Any heat that doesn't get dissipated through the seat or guide ends up heating up the incoming charge and reducing VE. Now you might at first think that this is mainly going to be an exhaust valve issue but the inlet valves, albeit running at lower temperatures, have perhaps 50% to 2/3 more surface area than the exhausts and in terms of total heat capacity can be the main problem in the chamber.

Wide seats might not give you the best high lift flow figures (although if you get the seat geometry right they can flow pretty darn well) but they do a much better job of removing that heat and preserving engine efficiency.

I've done back to back tests over the years on a number of occasions and increasing the seat width can literally transform how an engine runs. More torque at low/mid rpm, better emissions and a big hp boost at the top end.

Many years ago I had a customer come to me with a short (1/4 mile) oval track Ford Pinto 2L motor that had to stay in one gear throughout the race. Corner speed was about 50% of the speed at the end of the straight which meant a good spread of torque was needed over about 50% of the engine's rpm band. His problem was the cam they were using to get good top end power and straightline speed wasn't pulling out of the corners. They asked me for advice on a milder cam choice.

I said first thing is let me look at the head and see what's been done for you. They couldn't understand what the head had to do with anything but sent it to me anyway. As expected it had very narrow seat widths as per most race engine builders over here who think narrow seats are the real deal. There was enough material left to recut them from 1mm wide to 2mm wide (42mm inlet valve) and a minor bit of tidying up in the throat area.

Next race day I got a very excited call from their mobile phone. The engine now had not only more top end bhp but so much low rpm grunt it wasn't just pulling out of the corners it was spinning the wheels out of them. They eventually ended up going to an even higher diff ratio to get more speed at the end of the straight. The cam choice they had didn't even need looking at.

Valve seats are about the most critical part of the cylinder head as far as power goes. Flowbenches are part of the story but sometimes you have to go past what they tell you to get engines to work at their best. With valves of this size you want seats at least 2mm wide and maybe wider. Have a look at Bill Jenkins Chevy book and talk to DV about it. I think he'll back me up.

Dave

[Dusty]

We haven't had problems with that seat width. We've beaten them on the dyno on two engines with nitrous and the third current engine (406) has cracked but the heads still keep on keepin on.