I'd like to thank everyone that helped me decide on the compression ratio for my current project on this thread: Ported and Milled Vortec heads on stock 350

As mentioned this is not my engine and as a result of the comments; I will take a conservative approach with compression. The chambers measured 65cc before milling, target after milling 62cc. Estimated compression ratio as follows, 0.5 less than my original target:

Cylinder Head Volume (cc) 62
Piston Head Volume (cc) 10
Gasket Thickness (in.) 0.026
Gasket Bore (in.) 4.166
Cylinder Bore Diameter (in.) 4.0
Deck Clearance (in.) 0.030
Stroke (in.) 3.48
STATIC COMPRESSION RATIO 9.53:1

Two Singh grooves were cut in the chambers as shown, I will post better pictures after the mill and valve job.

I understand the theory of the singh grooves, but it seems that this is just the opposite of the effect of polishing a combustion chamber. As I understand it, these grooves are made to create turbulance from the squish area. Let me know if you notice any difference. Why not just design a head with a convoluted squish area. I'm sure I don't have a thorough understanding of the process so I may be totally wrong. Enlighten us!!!

If you're ever at the beach, dig a trench with your heel in the sand near where the waves reach their highest. When the water retreats, it falls into that groove and rushes back. Where the returning water hits the water line it creates a lot of turbulence.

A flat quench area is like a book that you set down on the table. The air is forced out in a flat space. Cutting the grooves makes two points of intensified flow out of the quench area just like that channel in the sand. Its just a way to add more turbulence to the quench process.

Curtis is absolutely right, I did a test, lets call it privative wet flow. I put a gasket on a grooved head and placed a piece of plexi glass with a hole in it over the squish area. With a low pressure parts washer, I blew solvent into the hole; some of the solvent blew out of the squish window, the rest exited out of the groove in a stream. I concluded, with this groove as a guide, you can decide where you want the concentrated squish to flow. Now I cut them in many directions trying to decide what works best.

I've been doing this for over two years, at first with the direction of Somender Singh. Some folk’s say this won't work, I have never heard that from someone that has tried it!

Automotive breath, I won't hijack the thread, but if you have any links or tech on Singh's grooves, I'd love to hear it via PM or email. I have a set of Vortecs going to the machine shop this week and this has been a consideration of mine. I like the benefits but I wouldn't have the first clue as to where to start cutting.

Curtis, contact me at automotivebreath@hotmail.com

The best information got wiped out when this site crashed: turbobricks

My good friends at mpgresearch love what it does for fuel economy.

I have a TBI iron head 350 running on 87 octane at 10:1 compression towing my race car.

I have done over 30 engines, mostly race cars, details will follow, I have a torque convertyer to change for the turkey drags !

how deep and wide? triangle or rounded cut?

how deep and wide? This is difficult to answer because it widens and contours into the chamber.

triangle or rounded cut? I have done both, round is less likely to develop cracks, by the way,I have never seen one crack.

If this is a stock Vortec head, you can just count on the heads cracking. They are so thin that I can't imagine them not forming a crack out the exhaust seat right into your groove you've put in that already miserably thin deck.

I hope you defy the odds, but they are against you. I hope you didn't run that right up against the fire ring of the gasket.


Nairb

Hi Naiab, I sure hope you're wrong about the cracks, I never cracked a head before.

I don't consider these heads thin, the 083 heads on my TBI truck shown are thinner with a 0.050" mill and a 0.030" deep groove, the thickness at the groove bottom is less than .200". These vortecs are thicker to begine with and I'm being very conservative with a 0.030" mill, should be plenty thick enough for a mild street engine.

These grooves end 0.080" short of the fire ring to relieve pressure at the bore, it works wonders to help control detonation and to prevent carbon contamination of the oil, I do this to all of my race engines.

If there stock vortecs, I have to side with Nairb. I`ve seen Vortecs come into my former machinists shop, they were run hot once, and not very hot at that, one had 5 cracks, there was a crack from the water jacket out, where it`s a really thin area that`s obvious to the naked eye, the other area a crack developed was on the quench pad of the number 2 chamber.
We ordered some vortec heads from RHS, they were very heavy castings with real thick decks.

Here's a picture after the mill and valve job, these are production vortec heads 062 castings. The chambers ended up at 60cc, final compression ratio will be calculated when the deck hight is measured.

I seem to recall something in one of those articles from last year that Singh said the piston-to-head clearance had to be kept to around .070" to get any benefit with the grooves.

Anybody remember this, or has my feeble brain gone flatulent again?

Hi jimfulco,
I have had several discussions via email with Somender Singh on that subject.

With grooves and a large squish to bore ratio > 25% squish area with minimal detonation as the primary objective; his recommendation was between 0.050" to 0.70" piston to head clearance at engine assembly. Of course there are many variables to consider like intended RPM range and such.

Most people running with out grooves tend to go with a very tight piston to head clearance to eliminate detonation. This difference has been and will continue to be the subject of countless discussions.

In this example using a dish piston, the squish to bore ratio is very low, it is advantageous to tighten the clearance to generate more squish action.

Some of this may be my own general opinions, I hope I haven't mis quoted him.

Thanks for the update. After lots of studying, I am totally convinced they work. And will be using them on my new SBF heads.
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