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Experience w/mini-starters?

Curious if anyone here has any prior experience with mini-starters. These are high torque, geared starter motors primarily for high performance street or strip cars.

Some background-
BBC 454 punched out 0.060 with stock stroke, gapless rings, performance camshaft running around 12:1 static compression. Dynamic compression is higher due to amount of ignition advance. Stock starters have always struggled to start this engine even when cold. Verified no spring bind or other mechanical issues. When heat soaked, forgetaboutit. Running 1000 CCA battery with 2 ft of 1/0 cable on both feeds.

Looking at getting a mini-starter. Figure minimum of 180 ft/lb torque. Two choices stand out from Powermaster; the Master Torque or Power Max Plus for BBC w/168 tooth flexplate and staggered mount.

Anyone have any experience with Hitachi style v Denso form factors? Which do you prefer and why?

Both produce same torque @ 180 ftlb. However, one is geared at 3.7:1 and the other is 3.25:1. Not big difference. However, one is rated @ 1.8 HP (1.4kW) and the other is 2.5 HP (1.8kW). I don’t want to load the battery more than necessary so does it make any sense to choose the higher power rating if they have the same torque rating?

If Your battery can deliver 1000 CCA, I’ll go straight for the 2,5 hp. You’ll still be way inside the battery capacity.
Be sure the cables can sustain a load of up to 800 amps. In some cases bigger IS better and also check for possible weak links in the supply line.

Way back in time, when I was an apprentice, at school we did some tests on starters which included amp. consumption on starters turning an engine and a locked starter.
I still have the paperwork from that and a 1 hp starter turning an engine at 0 C. used around 100 amps and the same completely locked starter went up to 300 amps.

I can’t figure out how you determine needed wire dimensions over there. Here (EU) we use the guide - 8 amps per square mm. copper max load.

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I have used the Powermaster but primarily for weight reduction. The engine only had a CR of 10.3:1 and the heavy wound-field starter did OK when cool and a bit weak when hot.

The Powermaster did fine cool and just OK when hot.

Other issues played with the hot-start. Like headers wrapped closely around the starter! Add to that a 12 ft length of 1/0 cable and a ground at the back of the car. All conspired to give poor hot performance. Running another 12 feet of 1/0 up to the block helped a lot - steel has quite a bit more resistance than copper and a Ford remote solenoid pretty much cured the hot start issues.

I agree with @anon86613489 - 2.5 hp starter. A 12:1 big block is a tough ask for any starter! Go big!

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Thanks for the replies!
I messed up, I actually have 2/0 cable and it’s copper. Short run, battery is up front. Current delivery should not be an issue at this point.

It does have ceramic coated headers so heat soak is an issue but the existing starter can hardly start the engine even when cold.

Yeah, the Powermaster has significant weight reduction @ ~11lbs. Street/Strip car w/all metal body so not worried as much about weight from that perspective as holding it up there to install :wink:

Mustangman, that is interesting experience with hot/cold performance with Powermaster. Do you recall, was that the Hitachi or Denso style unit?

Seems the consensus is go big! I’m a fan of that as well. My only concern is that the output power (torque rating) is the same for both units so it would seem one is simply more efficient at delivering power over the other. Or am I thinking about this wrong? I could step up to 200+ ftlb of torque with a 2.5HP starter motor in the Hitachi version…

asterix, the 2/0 cables should not have more than 0.25V drop @ 800A. The supply side is closer to 3.5ft and the ground is 2ft. Another important aspect I should have mentioned earlier- I have an HEI which is sensitive to voltage drop.

Thanks again for your experience and advice!

Yes, kinda. If the 2,5 hp has the ratio of 3,25:1 and the 1,8 hp has the ratio of 3,7:1, that could equal the amount of torque measured, but the 2,5 hp would rotate the crank at higher speed. This is just a VERY simple explanation.

Sounds about perfekt as I can’t see You ever even get close to 800 amps.

Ah, I think I get it now. The ratios and HP numbers are reversed from what you have there. The 3.25:1 is 1.8HP and the 3.7:1 is the 2.5HP unit. I definitely want higher rotational speed to get it started as quickly as possible…

If I get enough stalled attempts even the 2/0 cables start getting warm :wink:

That’s why I wrote:ít was a very simple explanation. There’s more to it than that. The rotational speed of the starter itself, the numbers of teeths on the drive gear which effects the overall ratio and efficiency of the unit in general. Only the seller can tell You the speed of the drive gear.

That would worry me a bit. In “my” calculations, the wires should be AT LEAST 100 square mm. copper (same as 10 x10 mm), is that something similar to Yours? If smaller, time for a hefty upgrade. Heat and resistance is Your enemy.

Down here in the near illiterate south zeroes have long been referred to as “ought” in situations like wire gauge and it was noted using 0s as in double ought = 00. Of course buying buckshot is a much more typical reason for using the term.

That would be equivalent to 4/0 cable! Going to a 7/16" stud would be impossible. Not to mention just bending it into position.

2/0 is 67.4 mm2 and the OEM 4ga is approximately 25 mm2.

For continuous duty, I would agree with that assessment but for short duty starter use, the cable should be more than adequate. I think the starter motor may only be 1kW (junk aftermarket apparently) and that is contributing to the stall and high current draw. When successfully cranking, it’s only dropping 0.2 volts at the starter.

That’s right. It’s abbreviated in wiring charts and diagrams as 1/0, 2/0, 3/0 etc for clarity. Much harder to read and discern 0, 00, 000, 0000. It’s still pronounced “two aught” when speaking it…

I’m sorry, I do not know whether it was Hitachi or Denso. The Powermaster permanent magnet starter did OK as long as I used the remote solenoid for the starter current.

I think the hot start was that the solenoid was very close to the header. Even with heat wrap on the header it was still an issue. When I raced it, I was regularly seeing 240 F water temps and 290 F oil temps. For endurance races, the fuel stops required the engine to be off so hot starts were required. Even a short stop put a lot of heat soak into it.

Yeah, that’s toasty!

FWIW, after looking over offerings from Powermaster, Proform and MSD, I went with the Dynaforce from MSD even though it was the more expensive option at around $360. 3HP motor and 4:1 gearing. Plus, it was red powdercoated :wink:

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I use a Denso mini starter on one of my DT466E engines on a fleet vehicle, and have in the past used them on non-electronic 7.3L diesels.
They work fantastic, and I don’t fear near as much lifting it above my head to install it, lol


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I want to thank you guys for taking the time to help.

No doubt. I probably read a dozen various technical pieces that explained in various detail, some excrutiating :wink: but you guys really helped clarify the main points to consider. Plus your personal experience is invaluable to me.

It’s not easy at all to make apples-apples comparison due to all the variables but I think I made the right choice for my situation. Will know in a couple days…

Have you made the voltage measurements I usually suggest, from the terminal to the starter case during attempted cranking? There’s lots of unexpected places voltage drops can occur in either of the two wires going to the starter, and those measurements will show definitely if a voltage drop is the cause of the fails to crank. I suspect in your case it’s not a voltage drop problem, but better to spend a half an hour to make sure than replacing the starter motor only to find out that’s not the problem. If the two different starters have the same torque but different KW specs, I think the one with the higher KW spec may be more sensitive to voltage drops in the wiring and grounds, if that’s a concern.

Do people today still use remotely mounted For solenoids on Chevy’s like we did in the old days so the hear wouldn’t affect the solenoid?

Ford parts on a Chevy?!? I hope your tongue or fingers did not snap off while saying or typing that…

Seriously though, one Ford part is tucked away inside the trunk of this car- an inertia switch for the electric fuel pump. Done many years ago, that was the easiest and most economical way to accomplish that. Buy one from a junkyard car and install it (in a way that no one can see the cross-pollination). :slight_smile:

I’m familiar with that practice of divorced solenoids from years back. Typically now, people replace the wiring to avoid voltage drops, heat shield/blanket both starter and exhaust and buy higher power starters and starters made from aluminum bodies and permanent magnets to overcome the issues of those days.

My problem is not with the solenoid even when hot. The motor is susceptible to heat soak more than the solenoid. That’s been verified by voltage measurements at the starter motor as mentioned above. And, it’s just plain too wimpy for the task.

Well, the results are in. The MSD Dynaforce is installed and could not be more pleased with the performance. This engine has never cranked this well. Amazing cranking power from this small starter. Chokeless carb w/mechanical secondaries can be finicky cold but this starter wheels engine over so fast it starts in 2-3 seconds ice cold. I can hardly let go of the key fast enough when hot. No heat soak issue whatsoever. I had to clock it to clear engine and headers and just barely clears both. Sounds really cool winding down with 4:1 gearing.

Btw- removed starter was OEM Delco not some cheap aftermarket unit I thought I put on it last time…

Good for you. Starter problems are really annoying. Glad you got it resolved.

Not sure what you mean? If it is a smaller package (i.e. mini-starter), I wouldn’t have guessed there’d be any fitment issues.

Although smaller, the motor is offset from center due to the gearing between motor and pinion gear. The oem is direct drive inline assembly. To help fitment they have various holes drilled in mounting block to allow rotation for best fit. Remove screws, rotate assembly and reinstall screws in new location = clocking.

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If you remember this post, I wanted to provide a long overdue update.
No wonder the old starter was having difficulty. Check out the pic below. The red circles are around the contact points for the solenoid providing power to the motor. The disc is doing it’s job to rotate and disburse the contact events around the entire circumference to extend life. However, look at how small the contact patches are on all parts for such high current demands. No wonder it didn’t last very long…