Hesco ACH for my build

[Jim K in PA]

G'day. Just joined after lurking for quite a while.

Might as well get to the punch line. Will the Hesco ACH allow me to run higher compression (S&D) with 87-89 octane? My goal is to make as efficient a stroker as possible, with the goal of long term durability, power, and efficiency (in that order). I will spend the $$ if it will accomplish what I want.

So, there is a big lumbering query without much other info, so fire away and I will fill in the rest of the blanks.

[SilverXJ]

The ACH should allow you to run more compression using lower octane fuel. What makes this possible is the lower combustion chamber temp provided by the characteristics of aluminum. Roller rockers will also help you reduce the temps further. I don't have any personal knowledge but this is what I have heard from a few sources.

[Jim K in PA]

Thanks silver. I know my first post was too vague in many ways. I have built engines before (mostly big Pontiac stuff). I am VERY familiar with high compression engines with iron heads and the issues with detonation, even running 93 octane. I am also aware that the aluminum head provides much better heat transfer to the water jacket, reducing hot spots and detonation. I guess my question should have been, if I build my stroker with an ACH, how much compression can I run and still use 87-89 octane fuel?

I don't see how/why rocker arms of any type would influence detonation, unless IVC angle is changed with a roller cam profile which then affects dynamic compression. I am welcome to explanation otherwise, however.

As unrealistic as it may be, my goal is to build a 4.6/4.7 stroker with an ACH to get as close as possible to the power and efficiency of a stock GM 4.8L Gen IV V8. If I don't build a stroker, that is the engine I would replace my stock 4.0 with. I really DO NOT want to do the V8 swap though.

BTW - the rig the stroker would be motivating is a 2005 Wrangler Rubicon Unlimited. 33" tires (255/85), 4.11 gear, 6 speed with 0.84 OD. The rig will have a RTT and rack on top, as well as armor, bumpers, winch, 31 gallon fuel tank, extra fuel cans, OBA (York 210 with 2 tanks), second spare, recovery gear, camping gear, and two middle aged fools in the front seats. I figure trip weight will be 5800-6000#. It is also a DD, so knock 1k# off that figure for daily use. As you can see, wind resistance, and weight, will make long trips through the Rockies, Andes, and even the Poconos an unpleasant, boring chore. I don't want to do 100mph, but I would like to get to 65mph before the next fuel stop.

I suppose a call to Bennie at Hesco is in order. I was just hoping to get some feedback from anyone else who may have built a stroker for the street with an ACH from Hesco.

[SilverXJ]

I don't see how/why rocker arms of any type would influence detonation, unless IVC angle is changed with a roller cam profile which then affects dynamic compression. I am welcome to explanation otherwise, however.

It has nothing to do with valve timing. The rollers do not heat up the oil nor add heat to the valve as much as a standard rocker.

[Jim K in PA]

It has nothing to do with valve timing. The rollers do not heat up the oil nor add heat to the valve as much as a standard rocker.

Interesting - I would love to see some data on that, because the very small amont of valve train friction is not going to add much heat, especially compared to the enormous heat load from combustion. If there were enough friction in the valve train to cause substantial metal and oil heating, the components would not last very long.

[Jim K in PA]

Nobody running an aluminum head on a street driven stroker here? I know they are rare, and mostly utilized on bulds with forced induction. I am confident that the ACH will help me achieve what I want, but was hoping for some real world feedback, especially from a durability and efficiency perspective.

[Antifreeze2]

I'm running an aluminum valve cover on a yet to be stroked 4.0 and it significantly reduces heat on the top end. To the point where I may get a heat extractor hood to further help this cooling effect. I only wish I had numbers to back it up. Point being, a $100 valve cover may save the $500+ cost of roller rockers.

[SilverXJ]

Except you still have the stock rockers with their short comings. And the valve cover isn't pulling heat away from the combustion chamber via the valves. I am sure it isn't a whole lot but you are replacing sliding interfaces (rocker arm pivot and rocker arm to valve) with rolling interfaces. And every little bit helps.