SLC 24 Howard Jones

Howard Jones

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Engine coming together. Short block altogether. There's a lot of work in putting an engine together from selected parts that are not necessarily all from the same vendor. Everything needs to be sized and machined to fit together correctly. But in the end, you have a correctly balanced and properly assembled engine. The AFR heads were pretty close but still got a 2 thou skim to correct the head mating surfaces. My guy said that, again they were pretty close, but we wanted to do a 5-angle job on them and make sure everything was the same cylinder to cylinder. All the valve springs were correct rates and all the valves were the same length. So in short AFR heads were very close out of the box.

The Callies crank and rods were balanced and the Mahle pistons were together "dead on" the same weight. The rods were balanced end to end which is a process of ballanceing rods that is more complicated than I want to explain here. What was interesting is they were really nearly perfect and required very little modification.

So next is to put the heads on and finish assembling the engine, Then dyno time! Yea!

I also called Kennedy Engineering to talk to them about my clutch. I found out I could increase the clamping capacity from what I had now, max torque 530 ft/lbs, to 670 with a change to a 6-puck friction disk. Great! that saves some money. I'll post some pictures of that when it gets here.
 

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Neil

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Engine coming together. Short block altogether. There's a lot of work in putting an engine together from selected parts that are not necessarily all from the same vendor. Everything needs to be sized and machined to fit together correctly. But in the end, you have a correctly balanced and properly assembled engine. The AFR heads were pretty close but still got a 2 thou skip to correct the head mating surfaces. My guy said that again they were pretty close but we wanted to do a 5-angle job on them and make sure everything was the same cylinder to cylinder. \All the valve springs were correct rates and all the valves were the same length. So in short AFR heads were very close out of the box.

The Callies crank and rods were balanced and the Mahle pistons were together "dead on" the same weight. The rods were balanced end to end which is a process of ballanceing rods that is more complicated than I want to explain here. What was interesting is they were really nearly perfect and required very little modification.

So next is to put the heads on and finish assembling the engine, Then dyno time! Yea!

I also called Kennedy Engineering to talk to them about my clutch. I found out I could increase the clamping capacity from what I had now, max torque 530 ft/lbs, to 670 with a change to a 6-puck friction disk. Great! that saves some money. I'll post some pictures of that when it gets here.
I think your new 6-puck clutch disk from Kennedy is what I'm now using in my Donovan. The photo is a comparison between a stock Porsche organic disk and the K
IMG_20190118_113942190.jpg
EP sintered metallic disk.

I'm also assembling another aluminum block Donovan right now. My Lunati crank is at Gary's Machine Shop to be skim-cut on the crank counterweight throws and then re-balanced. A 4" stroke small-block Chevy is pushing things and there is a tiny bit of interference with the bottom of the piston skirts. Trimming off a little off the crank counterweights should solve that problem. The final displacement will be 408 CID. I have a pair of fully-assembled Brodix Dash-12 heads for it but I may use a pair of Chevy Bow Tie 18 degree heads. Those are bare heads so I'm not sure it is worth the expense of adding valves, springs, rocker arms, & valve seats to use those 18 degree heads. They can generate 700+ BHP in a prepared block.
 

Howard Jones

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Neil, I'm using a Dart SHP block, a 4.125 bore diameter, and a 3.75 stroke 6-inch rod. I think you are correct those look like what I have for a clutch. I looked at Brodrix heads for this motor but settled on the APR heads because my engine guy told me that they were still using good quality pieces, like springs, retainers, and valves. Much of the budget heads (I don't put Brodrix in this category) are, while fine for street engines, for the most part, not suitable for track sustained rpms.
 
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Neil

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Neil, I'm using a Dart SHP block, a 4.125 bore diameter, and a 3.75 stroke 6-inch rod. I think you are correct those look like what I have for a clutch. I looked at Brodrix heads for this motor but settled on the APR heads because my engine guy told me that they were still using good quality pieces, like springs, retainers, and valves. Much of the budget heads (I don't put Brodrix in this category) are, while fine for street engines, for the most part, not suitable for track sustained rpms.
I agree. APR heads have a very good reputation! The Brodix dash-12 heads I have are ones that were manufactured back when Brodix -12s were used on most of the fastest sprint cars.
I am quite pleased with that KEP clutch disk in my car. It is unusual for a sintered metallic disk to have a spring center and marcel. This makes engagement smooth and it is far easier to drive than "grabby" solid discs.
 

Howard Jones

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Howard Jones

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I have tried everything I can think of. I cannot get it right side up. My 49 dollar camera never does this. Just the 500 dollar Iphone.
 

Randy V

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Odd…. Let’s see if my edit works…
BTW - that’s a very strange exhaust setup on the dyno…
IMG_2723.jpeg
 

Howard Jones

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Here's the final dyno chart after we took about 50HP out with jetting and timing. The best guess is it would make well north of 600HP with a different intake and 850 carb. Here's the 400 (top) compared to the 350.
 

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Randy V

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Interesting dyno charts. Did you capture A/F ratios? Curious about the dip in torque down low when she starts out pretty high.
 

Howard Jones

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Randy, these are interesting:

These are the final run data. Look at AFR and manifold vac. Do you see what happened as the carb just couldn't flow enough air? This engine ran the carb out of flow at about 4400 rpms. You can see that the man vac was good until right about then and after 4500 or so the engine just keeps pulling vac all the way out past 6500.

We added a main jet size and took out 2 degrees of timing before this final run to constrain power. The one before power continued to climb to 560 at 6000 rpms where he stopped the run. Even then as the man vac kept dropping the AFR kept solid at (12.9-1) - (13-1). On the posted final run he held AFR to 12.5 or so and you can see the effect of the larger jet size.

Dillon said this engine will make easy 600HP at about 7000 with an 850 and a different intake manifold. His rpm limit is due to the hyd rollers. But the gearbox man ( California Motor Sports ) wanted me to hold torque to "500 or so".

The early rpm area of the curve is influenced by the way the dyno adds load after the throttle is opened. This is an interesting dyno setup. Samson Racing Engines is an approved SCCA TA-1 and TA-2 engine supplier. Dylan told me that to meet the SCCA-approved engine output standard he had to reduce his apparent power output by about 25-30 HP at the 550HP level. All of the suppliers were required to send a spec engine and dyno data to the SCCA to be analyzed. Then a correction factor was applied to each approved vendor to level power outputs across the board.
 

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Randy V

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It is interesting.. AF1 / AF2 - are these left and right banks? Curious why the delta between the two.
What is the CFM of that carb?

12.5 is pretty much a gold standard. Dropping to 11.5 (rich) seems to stick in my craw a bit when the other was still 12.5..
So he starts loading it down at 3600 And things go a little wonky (Carb issue? Air bleed size?)

Rather than pulling timing and having to make changes to jetting to reduce power, Have you thought of just reducing overall flow and keeping the engine ”happier“ in the lower RPM band? I’m presuming your timing is locked by about 3,000 RPM.

Not trying To really second guess your strategy - just curious…
 

Howard Jones

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There are two lambda sensors one in each collector. As we began testing Dillon noted that one of the early jet changes didn't seem to make as much difference as it should so he began to suspect the leaky exhaust issue. We then did a couple of timing changes before going back to the AFR tuning because he was confident that the observed 11 to 12 range was okay for the time being. As suspected because the collectors are up high we were unable to bolt on the rest of the exhaust system and had to use flexible pipe to get the exhaust gasses around the equipment. Once he got serious about the final AFR tune we sealed up one with several raps of exhaust wrap and saw that the AFR went up about .7 of a point. This data came from one side "sealed" and the other left simply with the collector stuck into the flex pipe to see if the wrap helped. Since it did the other side was sealed and the next run confirmed that both heads were producing very similar AFR readings.

These runs were also with my homemade air filter housing. It cost 3-4HP with back-to-back tests.

This motor is running a 750 double-pumper Protect carb on a low profile single-plane Weiand intake. The Engine gained nearly 40HP by going to 34 degrees total advance from 32 degrees total advance that we left it at. We lost about 20 more with carb changes that got us to right at 12.4 -12.5 at max power from 12.8. The best number we saw was 560 abet at a lower RPM.

The advance curve is all in at about 2500 PRMs.

I want to drive the car and see what I have. This motor makes at least 100 more ft/lbs of torque everywhere on the curve. That's pretty much what I wanted to do as well as make about a 100HP more and have it hold well out past where the other motor started to lay down past 5800 or so.
 

Randy V

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Thanks for the explanations… It all makes sense to me now.
I think you’re right on the 850 CFM Carb also.
You’ve got a mountain of torque there for the weight of your car - it’s going to be fun to drive!
 

Howard Jones

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As it was explained to me, The intake manifold vacuum should read about (-.2) - (-.3) inch/vac with the throttle wide open. As you can see it does right at the point it is fully opened and full power is asked for. Then the engine begins to add revs and almost immediately the intake manifold vacuum begins to increase until it is well above that at 4000-4100. From then on it just continues to pull more vac, until it gets to the point that the power is limited by airflow.

Dylan said "No matter how much more fuel we give it now ( when we were at 550 ish), power will continue to fall off as revs climb, and the vacuum will continue to increase. This is exactly what a restrictor plate motor looks like. The valve timing on this engine (cam specs) is intended to run out to 7000 and then begin to fall off just like yours does at 6000. You can see hp/cin begins to flatten out right there. With more air, it would continue to make more hp/in until it became cam-limited at 7000, more than likely about 600-620 or 1.5 hp/inch. That's about it for pump gas on a hot day. After that fuel quality, cam/ valve train, and compression ratio would need to go up but then you would have a sprint car motor, 900 hp/ and more than 2 hp/inch "

I learned a lot from building this motor.
 
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Howard Jones

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So with a lot more power, I decided to add an oil cooler to the gearbox. This is the same pump I have on my GT40 with a slightly larger cooler. It's a Tilton 12V positive displacement type of pump. I located it next to the gearbox on my homemade mount which also serves as an anchor point for one of the GRBX cables. It draws oil from the drain fitting on the bottom of the GRBX through an inline filter and then from the pump returns to two points on the transaxle. One above the R&P and the other on the rear cover. It is manually activated from the instrument panel and protected with a 10 Amp circuit breaker.

Here are some pictures and a description from Summit.

 

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