Power Points 2

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POSTED ON October 30, 2017

Last issue we brought you the build-up on a very special 429 Smallblock Ford. This issue it hits the dyno.

Essentially, the premise of this engine was to build a motor in which all its collective parts were harmonised and synchronised. Leon Withnell from A1 Hi Performance built this engine for himself as part of his ongoing R&D programme and the aim was to pay extremely close attention to every aspect of its design and construction process to minimise internal frictional losses and maximise horsepower at the flywheel. For a full description of the theory and practice of building such a remarkable engine see Part 1 in Volume 20, Number 4.

On C&R Motorsports Development’s Superflow 902 engine dyno, the motor did not disappoint, producing 805.6hp at 7250rpm and 636.5lbs/ ft of torque at 5650rpm on VP109 unleaded fuel. What’s more, the 429 averaged 705hp and 613lbs/ft between 4550rpm and 7550rpm. The monstrous torque curve is almost horizontal for 1500rpm. In the last article, Leon was expecting the engine to approach 1.90hp/cubic-inch, so when the actual peak figure was 1.878hp/cubic-inch – so close to those predicted after all the painstaking measurement, calculation and modeling – we thought it would be a good idea to ask Leon a few questions and gauge his opinion about the engine.

PSC:
Before you began ordering parts or building the engine you started a computer model of the 429, what was involved with regards to entering the relevant data into the software to achieve accurate real world results?

LW:
First, I look at the rev range, piston speed at the estimated peak torque and horsepower rpm and flow demand requirements. This is followed by Brake Mean Effective Pressure (BMEP), Indicated Mean Effective Pressure (IMEP) and Volumetric Efficiency (VE) and consideration of friction for rotating components such as the bearings, valvetrain, piston rings and oil pump. IMEP minus BMEP can also be used to give anindication of an engine’s internal frictional losses. In this case the engine runs a 4.185 bore, 3.900 stroke, 6.00 rod, 2.750 main bearing and a 1.850 big end bearing. It has a 390cfm flow demand, 223 BMEP and a 116% VE.

PSC:
Now that the engine has been on the dyno, how close were the results from the computer model’s predictions to the actual water brake results?

LW:
The computer simulation was within 15 horsepower and 10 foot-pounds of the actual dyno result. I believe this slight difference is related to windage issues.

PSC:
Was there any other data that you collected while on dyno that would help you in future engine projects?

LW:
Yes, some sample probes were utilised to aid in understanding intake air velocity and they inadvertently lead to the discovery of some other important information.

PSC:
You have been engine building for many years and it seems from all of your engines that we have featured over that time that you have explored different
aspects of producing power (from dynamic cylinder pressure to reducing internal parasitic losses) and that each of those aspects is incorporated into your next engine in an evolutionary process. What have you learned from developing this engine that will be carried forward into the next engine you build?

LW:
Obviously, you try to use the best parts available but in the best possible combination. So, efficiency ie: piston ring packages, valvetrain, camshaft type and the like would be the key things I will carry forward from this engine’s development and testing. Every engine I build is different because ultimately cost is always the overriding factor. In our current economic environment you have to offer a better quality product that dyno numbers don’t necessarily reflect ie: sharp throttle response, excellent drivability, good engine vacuum for brakes but also exceptional torque and horsepower compared to other, cheaper alternatives. So, to answer your question, I just keep pushing boundaries and know there’s always a better way, that’s what I learnt.

PSC:
You have spent a great deal of time on the flowbench developing the CHI Cleveland ports. However, the air the cylinder actually sees is influenced also
by the carburettor and, importantly, the intake manifold. A huge amount of work also went into the intake manifold on the 429 – were you able to minimise the manifold’s restriction to cylinder head airflow? What was the nett effect on flow with the manifold bolted to the cylinder head?

LW:
One fatal flaw in cylinder head flow testing is that without the full induction system connected you are not seeing the full picture (sort of seeing a tree but not the forest) and most of the time a significant loss occurs when the manifold is added to the head on the flow bench. So, when in combination with low compression et cetera, a head that could make 500 horsepower or use around 250cfm at 28- inches only makes 470 horsepower when the untested intake manifold is used on dyno. In the case of the modified manifold I used with the 429 that was not an issue.

PSC:
Earlier in the project you had three intake manifolds to test when the engine went on dyno. Why did you only run the current manifold for your testing?

LW:
Pretty simple, with the latter [the manifold used on dyno] I achieved no loss in flow, it actually went up and intake velocity (remember that velocity, velocity…) was where I wanted it to be. By simply looking at it you can see a straight line of sight to the cylinders with very little loss of flow through curvature of the runners and the runner length fitted the rpm range I desired.

PSC:
The engine produced 805hp, almost 1.9hp per cubic inch, were you satisfied with that power level?

LW:
You are never satisfied, 10 minutes after leaving the dyno you think I should have done this or that. In the context of this engine some minor adjustments to crosssectional areas, tappet settings and the oil pan would have netted further gains.

PSC:
Why did you opt not to fit a vacuum pump to the motor and what would the expected gains be if you had?

LW:
A good question. I didn’t fit a vacuum pump because the one I do have is part of the structure in the T-Series AU car the engine is destined for and it is difficult to remove. However, not having a vacuum pump did hurt the final result a little, maybe by five to ten foot-pounds and ten horsepower. Clearly, with wet sumps you want the oil as far away as possible from the rotating assembly but you are restricted by the chassis and sump clearance. fabricated
a windscraper that ran really close to the rotating assembly and it worked well but built up pressure beneath it and a correctly fitted vacuum pump would have made a difference.

PSC:
In the first half of this article, run in Volume 20, Number 4, you revealed that a significant part of this engine’s design revolved around reducing windage
within the engine. Were those efforts successful and do you think there are still areas that could be improved upon?

LW:
As I said earlier, yes and no. In regards to the rotating diameter of the crank et cetera, yes but with the oil pan I would say a limited result.

PSC:
An 800hp manifold and cylinder head combination for the street is a serious package that would be very popular with most Ford engine owners and racers. Are there any plans to market this proven combination? If so, what would be the estimated cost?

LW:
The head package has been available for some time from CHI, I only made minor changes to the heads as they come. The manifold was exceptional and would make a bunch more power on a race-only deal. I was impressed by the consistency of the spark plug readings from cylinder to cylinder, so I intend to manufacture it immediately together with Scott at CHI as I see it as a logical way to go. Cost wise, I would expect no change from what CHI already do, maybe a little more for the manifold and depending on valvetrain requirements so from $4500.

PSC:
You paid a great deal of attention to the issue of exhaust gas reversion in this engine. What are the major contributing factors that create reversion?

LW:
Hot cams, big heads and exhaust systems in street strip cars almost always create reversion ie: LS3 Chev and large port Cleveland. If you think about residual exhaust in the cylinder during overlap at say 13-psi and 12.9-psi in the header pipe, when the intake valve opens to reveal 12.6- psi in the intake port, that residual exhaust heads straight into the intake port (notable by the dark stain) and as the piston changes direction this exhaust residual dilutes the intake accordingly. So, in effect, it costs torque and horsepower. The problem you have with low rpm engines is that there is so little intake air velocity, piston speed wave pressure induction and exhaust scavenge to work with, which is why I took so much interest in the US Engine Master programme. I think the results stand up.

PSC:
You have now been building engines for over 25 years, if you had the opportunity, who would you thank for their help along the way?

LW:
So many people over time but some people I would highlight are the guys at Performance Modifications: Brian Sadler, Danny, Paul and Ben who, over these years, have provided massive insight to me and more importantly, the racing fraternity as a whole. I believe that recognition is deserved.

The 429 has an imposing presence on the dyno and incorporates a huge amount of effort to minimise internal frictional losses.The lines in red show the power and torque from the new 429 compared to a tough 429 Windsor Leon built eight years ago – no comparison really!The figures speak for themselves with this engine.

A huge amount of work went into building the custom intake manifold which actually added flow when bolted to the heads.

Leon from A1 Hi Performance stands with the 800hp monster.

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