MP Hemi head porting, HP improvement?

I have a 540 I HEMI, 4.360” bore, 4.5” stroke. It is a street car, 4,100 lb. 3.54 gear with GV. The cam is 248/254 @ .050 with .580 net lift solid roller 112 lobe separation. 10.5 CR.
cruising rpm is 2,500-3,000.
How much power will a good street port make on a MP aluminum head? the engine made 635 HP @ 5,900 rpm, Teardown revealed horrible bore finish, no way the rings were sealing. Along with other issues. All is fixed, I am keeping the cam etc. Just clean up of the valve pocket of the head, and port match.
I don’t feel the need for the Victor head, I am not after max power. But while we are at it, the heads are getting a “street” port job.
What is your experience?

MCH ported my MP Eddy heads several years ago. My engine specs are very similar to yours. I broke my engine in on the local speed shop engine dyno. So here's my combo;

540" Hemi, 10.25cr +/-, 250* sft cam, .565 .547 lift, 2 1/4" headers, Indy single plane intake, and Thumper's 1050 Dominator. Made 697hp @ 6,800 and was pulling vacuum. The single plane made 11 more hp at the top, but lost 30+ lbs of torque through the range to the Indy dual plane back-to-back. So, I am running the dual plane in the car.

70 Cuda, primarily street car, 518od, 4,000 converter, 3.91 gears, 3,850lbs with me and gas. Have made a few passes at the local 1/8 mile track on a test and tune night. Not enough runs to dial it all in and with plenty of spinning, it ran 1.68 60', 7.16 @ 98.5. Clearly high 6s and 100+ is within easy reach with a little suspension tuning and a little practice.

Hemi heads, for a mild engine flow pretty good. Out of the box MP heads usually flow around 375cfm which is more than my EZ1 Indy wedge heads.....Should be able to make over 700hp with them....

Your cam is holding you back more than anything......Port matching helps, what intake and carb?

Which head flows this much?

WIth the large intake valve or the 2.25” intake ?

MP 2.25 valve heads should be in that range. My Canfield 2.4 valve heads flow 458cfm....For the money the Eddy heads are pretty good too.....

I am running an MP “marine” dual carb dual plane with two 750 Hollies

Here is the intake set up. I made the stainless 3/8 lines, and the air cleaner to get cool air through the RO23 hood scoop

Uuuuhhhh........... not even close.

I thought they were more in the 330 cfm range?

MCH cnc ported my MP heads back in 2006 and they flow right at 430 cfm.

I tested two heads from two different pairs.....355-375 has been our experience with the MP heads. What have you found?

I was waiting for you to reply.

I had a head flowed - flowed 318 OOTB

This is the Eddy head made for and sold through Mopar Performance back a few years ago.

I don’t think I’ve ever flowed a pre-Edelbrock MP aluminum Hemi head in its “ootb” form, but with a valve job and bowl blend by Jeff at MCH...... it was 317@.700.
Normal “full porting”, no tubes 365@.700.

Without digging through my notes I want to say the Edelbrock version was right around 320...... ootb.
(Found my notes 317 ootb, 323 with 3 minute blend)

A really nice original 559 head with the seats touched up and Manley valves was 311.

The best of the stock type MP heads I’ve tested was the latest version of the 559-M head, which went 335.
The earlier version had a flatter floor and approach to the bowl/short turn, and ootb it was like 315.

Indy SR head with a valve job and mild bowl blend is 337.

I’d have to really dig deep to find some numbers on a stock type stage V head....... but my recollection is, without porting, they’re right in the mix with these other heads.

The MP Edelbrock head with a basic clean up of the entire port ends up in the 350’s.
A more serious effort, but still no “tubes” gets you another 20cfm.

A normal “full porting”(no tubes) of the later 559-m is also in the 370’s.

Full cnc port job on an original 559 head from MCH, with some tubes, right about 400cfm.

Edelbrock Victor -ootb = 400cfm
Recut seats and blend 420.

Of the “stock type” hemi heads, I like the Ede made MP heads the best.

Here are the OOTB numbers provided to me by Chrysler Engineering circa 2008.

110-M heads are the '06, Edelbrock/MP are the '07.

They seem to agree with the 317-320+ ballpark, right in there....

I expect given the source of this information somebody will throw darts at it, and that's okay with me.

One thing I’ve noticed with hemi heads more than anything else I’ve tested...... on a flow bench that has a “back wall” (like the SF-600), if you don’t turn the head around when you flow the ex ports, the numbers will be noticeably lower.

Most of the stuff I’ve tested, turning the head around does almost nothing.

Also........ the Hemi heads seem to pick up noticeably with a flow tube on the exhaust.

That being said, the ootb numbers for the Ede made MP head, ex facing the wall and no tube is around 185 on my bench, and like in the graphs...... it gets there at a pretty low lift.

With the normal full port, ex port facing out, 2-1/8” flow tube attached, you’re in the 260 range by about .500 lift...... then it just stays there as the lift increases.

The victor with the valve job and bowl blend, also with the ex facing out and flow tube attached is in the 300@.700 lift range.

Anyone ever try a BBC 2.25" valve in a Hemi? It killed the flow up to around .700" lift and then it was about the same. I tried it just to see how it would work. It didn't.

Which head is the MP P5153875 in you comments above?

I've always believe the formula of 2 HP per CFM, except on all out race motors where you can achieve 2 1/4 to 2.5 HP per C.I. N/A

I bought the first set of Indy 426SR heads that Indy CNCd. I wasn't to impressed and sent them to Modern Cylinder Head to have them ported. I requested they flow them before and after. On a 4.32 bore they flowed 361.2@.800. Jeff never did port them, he finally did a bowl blend and valve job. They then flowed 386.2@.800. The heads were 210 CC's on the intake port as delivered from Indy and measured 213cc's after Jeff sent them back to me.
I bought a set of Indy Hi-Po heads, they feature a 2.4" intake valve and the I take port measures 266cc's. I had them flowed locally and the intake went 443 corrected@.700. (his bench couldn't do them at .800).
IMO the Hi-Po heads will make at least 100 more hp than my 426 SR's but for my current package they aren't a very good fit. They have poor port velocity down low and my torque numbers suffer drastically. They want lots of rpm to work and the hp peak was north of 7000.

These:



One of the 370cfm sets I did went on a 12.5:1 496 and made right around 800hp.

You’re around 600 cubes too, right?

Just proves that not every combo benefits from “bigger” heads.

Yep, 605 inches. With some other changes they might work better for me. For now though I am going to put the SR's back on, they are a much more street friendly package. The SR's made 764.3 ftlbs@3527rpm at the start of the pull. From 4100 to 5500 rpm they made 800 ftlbs. + Peaking at 4818rpm producing 818.4ftlbs.

Thanks for all the info. We “cleaned up” the ports, worked on the short side radius. We will flow test them, then put the engine on the Dino and see what we have. Port velocity is more important on this STREET car as it spends most of it’s time cruising at 2,500-3,000 rpm. I will post results in a few weeks.

+1 for CNC ported SRs on a 604. I'll have track numbers soon.