190cc alloy heads will they make a difference?

[Bruceynz]

Hi Guys,

My friend has changed his plans and now has asked me if I am interested in his speed master heads, 68cc chambers, CNC machined 190cc intake runners. 2.02 intake valves and 1.6 exhaust.

Mopar Chrysler SB 318 360 190cc 68cc CNC Hyd-FT Complete Aluminum Cylinder Heads

Anyway he says the intake ports are as big as the ports on his alloy 440 heads. Although comp will be up a little bit over the stock heads the flow is much greatly improved, am I going to notice quite a lot of improvement over my mild 360 with stock heads?

My engine is a stock rebuild type deal by previous owner so I have a low comp mopar pig, as much as I love mopar I despise the way they made them low comp and all the balancing drama you have to go through to change anything But I still am a mopar man and I know why it was done and it was never a performance engine and its me who is wanting to change its intended use from a mopar work horse to a spirited performer!

attached photo shows 360 head in the middle and 440 on the outside.

Thanks
Bruce

 

[80mirada]

Those are too big for a stock short block. If you could get them cheap they would be good for a stroker motor

 

[Bruceynz]

yeah they are a big head alright, I remember ford did something similar and put super big ports on a 302V8 and called it the boss 302 but it struggled down low with slow air speed.

Interesting point to think about, the new 5.7 hemi with the eagle heads is 220cc intake ports which is even bigger than the heads my friend has, how does that work? 220cc must mean more airflow?

 

[Aspen500]

I agree with 80mirada. You would lose all low end torque, throttle response and driveability with ports that size on a stock engine.

That's why the Ford Boss 429 was such a pooch on the street but was fine for superspeedway use at sustained higher rpm, the ports were gigantic. The 426 Hemi is sort of in the same boat also. Great for Daytona but not so much on the street.

 

[80mirada]

Gen 3 Hemi has more of the port in the head, and it is a fairly straight port with modestly sized valves

 

[Bruceynz]

So what you guys are basically saying is they are only suitable for a 408 stroker?

 

[80mirada]

Or a high compression 360 with a stiffer gear and loose convertor.

 

[kkritsilas]

Ford liked big ports and valves. They did it with the Boss 302 (essentially a motor built to win at Trans Am), and again with the 351 Cleveland (had valves bigger than some big blocks) and with the 429. All of those engines really only came alive at very high RPMs. Boss 302s and 429s were street versions of a race engine, and were not that great a street engine. The 351 Cleveland was never the success that it might have been suggested from the specs.

I guess a lot of that is true of the Chevy 302 in the first generation Camaros, and even the Gen 2 Hemi. Before anybody gets on my case about my statement about the Gen 2 Hemi, just ask yourself this: in a daily driven street car, would you take a Gen 2 Hemi, or a 440 6 Pack/Barrel?

 

[BudW]

Let me ask this question: What are your plans for this car?

If a smooth running daily driven car (or close to it) I would stay more with what you have (with some tweaking).
If planning on having the car throttle wide open most of its life and NOT driving around town all day (no daily stop and go driving) and you do have a fairly large cubic inch small block, then those heads may be a great addition to your family.

On a daily driven car or one you “might” loan out to your significant other, you/they won’t be happy because all low end lower will be sacrificed (and transferred completely to the upper RPM range).

I will tell you this, those heads would be great for a full time road racing car or something else that will see full throttle and high RPM’s a lot.

Someone spent a lot of money to get them ported!

 

[Bruceynz]

Hi Bud,

Speed master sell the heads CNC'ed straight out of the shop. I just got the option to buy the heads for what they cost my friend and he will through in the xe275 cam, ferrera 2.02 and 1.6 valves. That's how it all started, he is going 440 now and his 360 getting a turbo with iron heads. So the alloy heads are up for sale.

 

[Bruceynz]

Bud - speed master sell a 170cc head, 2.02/1.6 65cc chamber size. I don't want to turn my car into an unpleasant car to drive so would these be a better option, on a 360? 3cc smaller in chamber volume compared to the 190cc, this will help with comp. Same size valves and flow should be much better than stock open heads.

Mopar Chrysler SB 318 360 170cc 65cc Hydr-FT Complete Aluminum Cylinder Heads

Thanks
Bruce

 

[80mirada]

Those work well on stock short blocks . They are a clone of Edelbrock RPM heads, but are very nice.

 

[Bruceynz]

using the summit comp ratio calc it comes out at this:
I am not sure how far my piston are below deck but my friend has his mid 70s 360 apart and he said they are 150 down the hole, I had a camera in mine the other day and I would say I am worse than 150!

 

[BudW]

I don’t think you want to hear my answer.
Is the engine already in car?

Compression ratio is a big deal. Not enough, it won’t run well. Too much, and without proper grade fuel, it will pre-detonate (not good).
The only way to find out, is to remove a cylinder head and measure existing cylinder head chamber, existing piston depth and head gasket thickness. With that knowledge, you can determine existing compression ratio. Also, can compare combustion chamber on old head vs. new head.

The only other way I know it can be done is to tilt engine and perform a CC measurement test in car (something I don’t think has been performed before - or possible as far as that goes).

Without knowing where you are at, measurement wise, any and all talk about upgrades won’t tell you a thing.

My gut is telling me the 150 measurement at TDC is wrong, but hey, I wasn’t there and can’t prove it - so going by those numbers, I have a suspicion that you may need more than just cylinder heads to fix car with (may require higher compression pistons, as well).

Experience has told me not to take anyone’s word on compression ratios. Measure, measure and re-measure - that way you will know. Otherwise you might end up with more of a mismatch than you currently have.

 

[Bruceynz]

this is a photo of my friends engine at tdc, I know you can't measure but you can see its pretty low

and my engine inside with a we camera at tdc, if the gasket is 40 thou she is well down the bore!

 

[BudW]

Too many unknown variables for me to suggest or recommend.
Your assumptions may be spot on – or may be slightly off (or way off).
The other short block has dished pistons (most 360's I've worked on were dished).

I like this calculator because it also includes the top piston ring gap:
Compression Ratio Calculator | Tools | Diamond Racing Pistons

Another place to for a good read (about SCR vs. DCR) is:
Dynamic CR

The attached pictures are calculations I made 2½ years ago. I did get custom pistons made for both big block engines (different specs for each) and my final calculations details are on a far more complex spreadsheet at home (before ordering the custom, non-returnable, pistons). I’m at work now, so don’t have access to that spreadsheet.

Note: I didn't make this for other people to read. It is for example use only.
Before ordering pistons, I CC'd the cylinder heads and measured my head gaskets and a few other things.
After the coatings, the custom pistons (two sets) and rings cost me slightly under to $2,000 US.

Yes, I know it is more work, but there are somethings I only want to do once, and that is engine rebuilds. In ten years or so, I won’t mind going through the process again – but until then, I want it right the first time and I will know that all aspects are working together (intake, camshaft, exhaust, ignition timing, etc.).
It would be another story if I broke it (insert smiley face).

BudW