SS124A

Today at the shop we had to change a timing belt on a Honda..
An while thinking how lucky we are to never have to do this to our own engines I realised that we could machine or adapt some pulleys to work on the rotary..

What I am proposing is a COGGED pulley kit for 78-85 engines (maybe more years later).
Consisting of a main, water pump, and alternator pulley.

All will use a Cogged pullet, like a timing belt.

A couple thoughts, I have issues with even my double pulleys at high RPM...
I know of Honda's that see 12-13K

Please post if you are interested, or if you have suggestions etc.

85rotarypower

That would be a great alternative to a dual belt system. The only problem is that the belt is exposed to the elements and anything that goes through an engine bay. I would worry about it coming off since there is nothing on the pullies to retain the belt. If you could solve this problem, you could have a seller there.

mar3

iTrader: (8)

Just copy the design off of the gilmer belts found on super chargers like those made by Weiand in the 6-71 and up category...

alien_rx7

In the "How-To Modify Your RX-7" book from HPbooks it shows a couple of race-prepped engines with cogged pulleys on everything but the alternator which still had a regular pulley but had been moved to the bracket the A/C use to be attached to and only had the belt running from it to the main pulley. The cogged belt on the rest of the stuff also had a tensioner on it just above the water pump attached to the area around the thermostat housing.

mar3

iTrader: (8)

That's a pretty rare book, BTW

Lotus00

I think it would be pretty sweet, I would probably get some if they didnt cost too much

jayroc

Theres a set that someone sells on ebay that I see occasionally. he wants something like 350-400 for the set if I recall, though.

RacerX7fb

Someone posted one here a few weeks ago.. looked sweet all billet... and cost around $300

mar3

iTrader: (8)

lol...the virtual mantra of all those roaming the 1stgen tech corner...

jayroc

I'd like a set myself. If you can make them cheaper than this ebay guy, then I'd buy a set.
http://cgi.ebay.com/ebaymotors/ws/eB...category=38656

Ah, and presumably, you'd adjust it out at the alternator just like the old belt.

wwilliam54

if i could get a main pulley that had a clutch that keep it under 6500 i'd be satisfied

Rx7carl

As youve seen, theres already someone out there making these. Theyre not just on ebay, I believe guru makes a kit.

SS124A

yeah, and that kit costs a fortune. Wonder which alloy the pullies are... Prolly heavy heavy 4140

Rx7carl

Thats a good point. I dunno what they are made of, nor what they weigh. I'd suggest you make them underdrive for the racers. They would be an excellent solution for running an s/c.

SS124A

Carl,
The problem with that is, atleast in IT :
17.1.4.d.1.n
... Type of od accesory drive (eg. V-belt, toothed belt, etc) shall remain as stock.

My plan was to make a kit for far less than $100 shipped! That would be optimal for street engines and for race classes where there are no restrictions

So let me know what class you are in, and I'll check (or you prolly know) what the requirements are.

Rx7carl

I didnt mean for IT racers. I know I cant use it (IT7). But EP, GT2, GT3, drag racers and street rods could all use it.

SS124A

yeah ok, I am going to go through the gears, and pulleys parts bin at the shop. I have a few ideas for gears that will work.

My only concern so far is mounting a tensioner to constantly tension the belt at high RPM. I am thinking that i could make a bracket that would mount to the three upper left side of the water pump housings.

I have to go to work, so now it is killing me to not get to experiment until tomorrow..

Please keep posting ideas, and I'll postmy progress

Carl, how many road-races a year do you attend?

I plan on having 2 engines this year, one crazy b-ported 12A with LW flywheel, the pulleys, webers etc..

and another tite stock engine for road-racing.

My point is, even for the racer, they could switch the system on and off in less than 1/2 hour. if they drive their car on the street or autoX.

Lt. Dan

Don't we have to be careful taking the Main Pulley off?

Dan

frstgen12a

it would be good if someone made a cheaper kit - not something i have on my priority list - but if someone had a cheaper one I'd probably scoop it up - as long as the price didnt affect the quality. underdriving would be nice too

alien_rx7

Yes, there is a certain procedure one must follow when taking it off otherwise risk damage to the ring bearing that is in there. I think the procedure is just making sure there clutch pedal is pushed in while you're doing the work but I could be mistaken so find the correct procedure before doing the work.

Lt. Dan

My point was that I don't really want a kit that I have to constantly install and remove....

Dan

SS124A

Dan,
DO you road-race?

mar3

iTrader: (8)

Will Lt.Dan and Carl please answer this guy before the Superbowl? Before you ask, I do one or two road "races" a year based on what the DFW club can arrange with MSR, a road course down here....it's not a real race, we just get to go as fast as we want on the 1.7 miler for a day...I might do 1 or 2 ERS events when SSixpeed can get me to go out, but I always end up in a class where if you deviate from stock in the slightest, you're in there with "shell cars and bars" modifieds...still a cog gear system that was adaptable to ANY combination of main, water pump, air pump, alternator, air conditioner compressor or power steering pump that might be on a 1stgen RX-7 would be interesting....

And tax refund time is just around the corner, too....

pratch

Carl used to do 10+ a year. I'm pretty sure as the year moves on he'll be getting active. I can't answer for him, but there's a ballpark figure for you.

Rx7carl

I'm hoping to do 4-6 races this year, depending on $ and time. I didnt do hardly anything last year.

Theres nothing to removing the main pulley as long as you only remove the pulley and not the hub. Just put the engine at TDC, unbolt, bolt on new one.