3.0L Head Porting
 

Hello,

I plan the rebuilt of a 930/10 3.0L engine (70,4x95mm) with 9.5:1 J&E pistons, DC40 cams, 40 IDAs with 36mm venturis and single ignition. Its in a 70% fast road/ 30% track car with 2150lbs. With the DC40 cams I assume it'll have the HP peak at around 6,5-6,5k RPMs.

This engine has the late SC heads with small 34/35mm I/E ports. What would you recommend the intakes to be ported? 38mm?

Many thanks,
Christian

Sell the heads you have and get a set of Carrera heads, the work is already done. But you do need PMO insulators so you can mount to the heads without leaks as the intake part of the head is shorter.
Bruce

Bruce,

As these heads were recently refurbished I want to continue using them with a ported intake. But how large should the intake be ported?

Thanks,
Christian

small port 3 liter heads are fine

Hi,

Bruce's idea is really the best one as you'd get good cost recovery on your current heads.

JMHO, but 34mm ports on a 3.0 with those cams is a bit small and you'll see power drop off over 6K. I would be using either Carrera or early SC heads.

That said, one cannot replicate the flow by simply opening up your current SC heads to 39mm. There are major differences in airflow around the guide boss and in the throat. We have flowed all of these heads on the bench to discover the differences, even after extensive work with the Bridgeport mill. We finally digitized the early SC heads and now we can CNC the small-port versions to flow as good or better (more consistently) as big-port factory SC heads.

Please let me know if I can help.

Hi Steve,

You are of course right in terms of 'best case' solutions, especially since I had you do my heads. I will say one thing: driving Jeff Higgins 3 liter MFI car with small port heads and 36mm 'S' MFI made me a believer in terms of seat of the pants performance. His cams are roughly equivalent to DC40s and that sucker pulls all the way to 7K.

This is the reason I suggest that given that he already has the heads, it really isn't a big deal.

Thanks Steve and Kenik for you thoughts on this - now its 1:1 regarding the porting question on my engine configuration :confused:

What max HP would you expect from this engine?

Thanks,
Christian

Don't forget that Steve's the expert - I am just a hack. All I can offer is my seat of the pants opinions where he can actually give you experience. :)