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Question for ya'll regarding a Mechman alternator - was the Mechman alternator housing/bolt placement location in the exact same spot as the stock OEM alternator? My Mech 250amp has a bigger housing (dog ears wider apart), requires a larger belt, and is a really tight fit next to the radiator overflow tank.
We compared mine with another Vette that had one - my MM is definitely larger than the other Vette's Mechman...
Is this what everyone experienced too? I'll talk with Bret, was just curious what others experienced. Perhaps the 170 amp is smaller?
Yeah, my MM 170 amp was, if anything, slightly smaller and easier to reinstall that the stocker. Didn’t realize that the 250 amp was bigger, but that makes sense.
But I don’t get why it would need a longer belt, if the pulley is the same size, unless it’s offset outboard a bit?
Look at the bright side Mitch, now you can start bragging on here that, “My Mechman is bigger than yours!
Sammy, I would brag that way, but my Mechman is on the bench!
Finally talked with Bret! Man, what CS! Great guy, absolutely just a great guy...He did say his pulley is a tad smaller (to get higher speed/amps at idle), so the belt will have slightly more room. I've already ordered a slightly smaller belt!
Yeah, my housing was a larger size. So I just bought one from Bret, and will deal with the other to the best outcome. He walked my through reading belt sizing and much more, spent 45 minutes on the phone with me! Felt bad to take so much of his time, but he insisted,,,
Originally Posted by Sphurley
I have the 170 and it was an exact replacement size wise.
Originally Posted by CI GS
Yeah, my MM 170 amp was, if anything, slightly smaller and easier to reinstall that the stocker. Didn’t realize that the 250 amp was bigger, but that makes sense.
But I don’t get why it would need a longer belt, if the pulley is the same size, unless it’s offset outboard a bit?
Look at the bright side Mitch, now you can start bragging on here that, “My Mechman is bigger than yours!
Last edited by Chiselchst; 07-11-2019 at 04:53 PM.
Sammy, I would brag that way, but my Mechman is on the bench!
Finally talked with Bret! Man, what CS! Great guy, absolutely just a great guy...He did say his pulley is a tad smaller (to get higher speed/amps at idle), so the belt will have slightly more room. I've already ordered a slightly smaller belt!
Yeah, my housing was a larger size. So I just bought one from Bret, and will deal with the other to the best outcome. He walked my through reading belt sizing and much more, spent 45 minutes on the phone with me! Felt bad to take so much of his time, but he insisted,,,
Glad to hear that you’re getting it sorted. Bret is absolutely a fantastic guy to deal with. I’ve really had many good experiences with many vendors that I found on here, including Bret, BTR, IW, DSX, Hinson, and CCA, to name a few. And without help from people like Carson, Jody, Christopher aka “subfloor” and a bunch of others, including, hell yes, even that oldmotorhead guy (don’t tell him I said so though), I would’ve had to pack it up years ago.
Did anyone get a shorter serp belt when they put their Mechman alternator on?
I've purchased a couple of smaller belts, and a belt measuring tool. Am I wasting my time trying to get the *exact* belt fit I had from CPR?
Pulley is like 1/4" smaller, LOL...
Did anyone get a shorter serp belt when they put their Mechman alternator on?
I've purchased a couple of smaller belts, and a belt measuring tool. Am I wasting my time trying to get the *exact* belt fit I had from CPR?
Pulley is like 1/4" smaller, LOL...
I didn’t notice a difference in diameter with the Mechman I installed, but then again, I really didn’t look, tbh.
As to whether you need a smaller belt, that will depend on belt stretch and the amount of range your tensioner has with the current belt. There’s only one way to tell - put the belt on and see where the tensioner is sitting. If you’re running a regular belt, you want it nearly resting on the stop at fully closed (compressed). If it’s an RPM belt, you want it somewhere in the middle of the tensioner’s range, because those belts are so damn stiff that when you ease off from a WOT pull, they tend to snap back and slam the tensioner against the stop, which either upsets and dumps the belt and/or destroys the tensioner (and sometimes other **** as well - ask me how I know). If it looks good, then just test it and see if you get belt slip. With the limited range of the stock tensioner, getting the right length belt on there is critical.
Speaking of tensioners, I’m not sure if I ever posted a pic of the AC Delco tensioner that I’m running now, which seems to be holding up better than the previous Dayco versions, after destroying two of those. Basically I crossed referenced the part # of the Dayco unit and it gave me an AC Delco number equivalent, and I took the chance and ordered it from Rockauto for like $48. I had to devise a stop for this as well, since it has the same wide range of motion of the Dayco. It was much easier to do a proper stop on this one, since it has a nice wide flat shoulder on the arm. So far (knock on wood) it’s working. Here’s what it looks like:
Thanks Sammy.
I've never seen that tensioner!
I have a couple of tensioners I picked up but never one like that.
I'm not able to use the RPM belt, they don't have a lot in my size (99", or 2510).
Thanks Sammy.
I've never seen that tensioner!
I have a couple of tensioners I picked up but never one like that.
I'm not able to use the RPM belt, they don't have a lot in my size (99", or 2510).
I actually bought one at Amazon for $8, and one for $16
The car currently has a NAPA Micro-V 080991 / 8PK2517.
I'll try a 98.6"/8PK2505 belt first.
Without you wrenching, this place kind of slows down a lot LOL
No worries Mitch. I don’t think there’s a tensioner in existence that I haven’t seen, in my quest to find one that works, lol. Hopefully this one will hold up now and I can focus on other things like suspension tuning, etc.
And don’t worry about not finding an RPM belt, they’re more trouble than they’re worth, from my experience. They need to be exactly the right length, which is easy if you have an adjustable tensioner to put it where it needs to be in the spring tensioner. We don’t have that option with our setup.
BTW: If you can’t find the exact length belt, you can always try to go with a larger idler or tensioner pulley. I’m assuming that the 8-rib tensioner pulley you’re running is the standard IW “Corvette” 8-rib pulley, which is 2.69” in dia., iirc. They also have a larger one, like what I’m running now, which is 3.00” in dia. I only bought that because I needed a quick replacement and that was all Summit had in stock. Mine is very slightly damaged from kissing the Magnuson idler when the last tensioner jammed down on the stop (from me running too small a belt). In fact, if you need to buy the larger one to get your belt to fit properly, I’ll gladly buy the one you have now off you as a spare and pay for shipping. Looks like those come in handy for me!
I haven’t been doing any wrenching lately, on account of being in Germany with the wife for the last three weeks. Heading back home tomorrow though, and I’ve got two cars to prep for our next event on the 27th, so I’m sure I’ll be wrenching again soon.
Going to have my ls3 in for a tune in Aug. I have the 84mm pulley on my Heartbeat, 602 rwhp and 540 rwt The dyno said 10lbs of boost. I have a 81mm pulley for the upper but don't want to blow the engine, What say you guys. Stock heads, Pat g. cam 220/242 .626/598 119lsa +4. And supporting parts. 1 7/8 long tubes. 3" pipes back to axle.
Your numbers seem low for what you have. I think you have passed the limit for the I assume stock TB is limiting you. Spinning the SC is just making more heat.
I have a HB w/93mm pulley, no cam, Z06 manifolds and cats, and make 554/507 on 91octane no meth.
Your numbers seem low for what you have. I think you have passed the limit for the I assume stock TB is limiting you. Spinning the SC is just making more heat.
I have a HB w/93mm pulley, no cam, Z06 manifolds and cats, and make 554/507 on 91octane no meth.
Yes many have said the number are about 20 to 30hp low for what I have done. Hence why I'am having it tuned by someone else. Some Idle problems I continue to have. And yes it is stock TB. On 92 octane pump gas
Go for it Scotty! Yeah, your numbers are a dab low.....on average, with an average dynojet, on an average day, with an average tuner, with average quality gas. Do you detect a trend there? Do a before and after dyno. That will tell the story. I'm betting you'll see another 15 hp and tq everywhere along the curve.
With your cam being at -7 degrees of overlap, you should have absolutely no idle/drivability issues. If you get an improvement in manners and a nice power increase, it will all be worth it. Best of luck to you!
Go for it Scotty! Yeah, your numbers are a dab low.....on average, with an average dynojet, on an average day, with an average tuner, with average quality gas. Do you detect a trend there? Do a before and after dyno. That will tell the story. I'm betting you'll see another 15 hp and tq everywhere along the curve.
With your cam being at -7 degrees of overlap, you should have absolutely no idle/drivability issues. If you get an improvement in manners and a nice power increase, it will all be worth it. Best of luck to you!
Glad you chimed in, After all I still remember Our first phone call we had on who to do my cam 3 years ago. Will a 91mm put me at 11pounds if in fact the tuner said it was at ten pounds when he did the last dyno run 3 years ago. Would I be pushing to much into those stock cylinders? Will ask the new tuner to what he thinks also. Has anyone in the twin Cities used CJ Tuners in ST Paul?
(ETA - listen to Old Motorhead, LOL). BTW I thought Rodney might might claim it's due to you driving it naked, LOL...
Since dyno numbers vary, I would not be too upset with those numbers, seems reasonable? Was it a Mustang dyno by chance?
Mine did 661 on 91 octane, the difference being; larger cam, OD tensioner with 87mm (10# boost [my boost would be would be higher if not for ported heads, slightly less restrictive exhaust & larger cam]), PRC ported heads. 2" headers, full 3" Corsa ZR1 exhaust through axle backs (now with full 3" B/P BBE). I'm going to guess I'd have 1-2 lbs more boost without the ported heads and a smaller cam, and 2.5" axle backs? My request to Pat G was to try to keep boost low to minimize belt slip, FWIW.
I did pick up ~90 whp when on e85 with same set up, I think you'd see similar improvements. E85 is safer, as it helps the keep the combustion chambers cooler (lower BTU value, more fuel required), helping to fight off detonation...
On the reliability front - many on this forum have reliably ran at that power level / vs. octane...
My opinion, worth what you paid
Originally Posted by scottg
Going to have my ls3 in for a tune in Aug. I have the 84mm pulley on my Heartbeat, 602 rwhp and 540 rwt The dyno said 10lbs of boost. I have a 81mm pulley for the upper but don't want to blow the engine, What say you guys. Stock heads, Pat g. cam 220/242 .626/598 119lsa +4. And supporting parts. 1 7/8 long tubes. 3" pipes back to axle.
Last edited by Chiselchst; 07-28-2019 at 12:50 PM.
(ETA - listen to Old Motorhead, LOL). BTW I thought Rodney might might claim it's due to you driving it naked, LOL...
Since dyno numbers vary, I would not be too upset with those numbers, seems reasonable? Was it a Mustang dyno by chance?
Mine did 661 on 91 octane, the difference being; larger cam, OD tensioner with 87mm (10# boost [my boost would be would be higher if not for ported heads, slightly less restrictive exhaust & larger cam]), PRC ported heads. 2" headers, full 3" Corsa ZR1 exhaust through axle backs (now with full 3" B/P BBE). I'm going to guess I'd have 1-2 lbs more boost without the ported heads and a smaller cam, and 2.5" axle backs? My request to Pat G was to try to keep boost low to minimize belt slip, FWIW.
I did pick up ~90 whp when on e85 with same set up, I think you'd see similar improvements. E85 is safer, as it helps the keep the combustion chambers cooler (lower BTU value, more fuel required), helping to fight off detonation...
On the reliability front - many on this forum have reliably ran at that power level / vs. octane...
My opinion, worth what you paid
Thanks Mitch
I know of one guy on a certain island that is still yelling some colorful names at Rodney. e85 won't work this year. I will see if this new tune will make me happy. It was a Dyno tune
A bigger throttle body will definitely help. I measured 4" of vacuum between the throttle body and the snout on my Heartbeat rig with 81mm pulley. Get rid of that vacuum and boost/airflow/power will go up. The only way to get rid of that is with a bigger throttle body. Don't know if anyone makes a snout to accomplish that though. Maybe Sammy will chime in.....unless he's somewhere with several of those cute little drinks with umbrellas in them....It's a Caribbean thing.
That doesn't mean that there's a wall there though. Just that the smaller the pulley you use, the greater the restriction. It will still make more power with a smaller pulley.
And Scotty, my boost peaked at 10psi at around 3000 rpm. 9.5psi everywhere else along the curve. My cam was bigger on the intake and smaller on the exhaust vs yours. Haven't a clue whether that makes any difference or not. Make sure you have the proper size belt(s) before you go to the dyno. I'd look at what you're running now and get the next size shorter. Maybe even the next two sizes shorter.
Last edited by old motorhead; 07-28-2019 at 01:52 PM.
07-05-2019, 08:48 PM
