We are in the middle of another Renny rebuild and thought we would post a few pics to share. The motor was in running condition but suffered a damaged pilot bearing and E-shaft due to a botched clutch job. The car is located in Florida so we made arrangements for the engine to be shipped. Needless to say, a full rebuild was the logical decision made.

We planned on ordering a new E-shaft but found a used one that passed our inspections. The pics below are from the inspection and ultra sonic cleaning of the shaft. We resurfaced the irons and are using new rotor housings to ensure the engine will have the same sealing power and service life as it had when brand new. Of course we had to clean up the ports a bit, and added some coatings in there with our stud kit as well to add some extra efficiency. I will take a few more pics of the build and post them later perhaps.

It's always satisfying when owners decide to do proper rebuilds, and we are very confident this engine will perform great for him.

 

Stud kit ? Tell me more .


Also : what is the deal with resurfacing ? How much can you safely take off ?

 

We have developed a stud kit for RX-7's and 8's that replaces the stock tension bolts in the engine. Many people are unaware of how much stock bolts stretch if reused during a rebuild. An experiment we tell people to try is torque their new rebuild down with the old T-bolts and then let sit over night. Come back later to double check the torque setting and see if it is still the same. An added bonus is cost. The studs we offer are cheaper than a new set of stock bolts. There is more info on studs here.

http://turblown.net/store/index.php?productID=82

Renesis irons are a bit different than RX-7 irons when it comes to resurfacing. You don't have to worry about decreasing the height of the water jacket seal grooves. This makes some irons that would be 'borderline' for an ordinary 13B, become salvageable if you have a high amount of stepped wear. Other than that there are no major clearances that will be affected. We generally take off .003" of an inch or until all wear grooves are removed.

 

I see in your blurb on the stud kit you say they are "a must for turbocharged" engines . My understanding was that dowelling would be far superior to just putting better studs in ?

My engine builder told me not to resurface the irons due to the limited depth of the hardened layer .....

 

I have read the opposite "studs are better than dowels" since they remove less material from the plates, which weakens the castings?

so when do you make the decision to open a "good" running motor for a rebuild?
I have a 2nd motor that has 30000km could be effected by low compression as it is a early production motor so far it is ok.

I'm worried about refreshing the motor since rebuilds can turn up problems and the parts list quickly grows and so does the rebuild cost.

 

Resurfacing the irons does remove the nitrated surface. Most of our rebuilds are performance orientated and we value sealing power over a 150k mile engine longevity. Its far cheaper to resurface vs replacing irons.

Its the same thing when rebuilding a piston engine; you hone the cylinder bores.

 

You are correct that adding extra dowels does remove material and weaken the plates. The extra dowels are always added around the tension bolt holes which have less meat around them. Then you bore the hole out and that area gets even smaller. I have seen the irons around extra dowels crack, and if the machining isn't done correctly it is almost guaranteed. I am not against extra dowels, I have done them before.

The biggest thing the studs limit is engine expansion on its axis line. If you ever run a turbo engine on a engine dyno and put a strain gauge on it, you will see the engine will expand during a pull with the oem bolts. It will not with our stud kit.

P.S. MM runs our studs in his latest engine

 

^ and mine (well, next time anyway, )

 

wonder if MM would care to give us some feedback since doing this ......

 

lol ive looked at those studs many many times. It was one of those things i wanted for my next engine.

 

I just heard back from these guys today;

http://www.blackmambarotarybug.com/

the oem bolts were coming loose after just one pass, no longer a problem with our stud kit

The Falken Drift Cars also run our stud kits too...

 

So the big question here is...how much can/should we torque these bolts down to? And can the stock tension bolt o-ring/seals reliably withstand the additional torque for long?
I've seen 45 ft-lbs up to 50 ft-lbs (race only), but what's the sweet spot for a street/strip setup where we can benefit the most from the increased clamping force (by way of the increased torque) that these bolts offer us?
Last thing, what about the stock outer tension bolts that are still used, do we torque them down the same as the studs or go with the stock torque specs?

 

like - is it holding up any better than previous engines ....

 

Back in the early years ALL warranty claims for Coolant Seals failures the Factory insisted all Side Housings (irons) be resurfaced...every one. (10A, 12A, 13B).

And naturally all new small parts, interestingly we Never replaced Rotors, if they were not damaged they were cleaned and reused, in some cases Oversized Corner Seals (0.2 and 0.003) (10A, 12A) were used after Reaming the Rotor Corner Seal inset with our Factory Reamer Jig Set.

 

/\ the irons on my latest rebuild had some deepish grooves - ( could just feel with your fingernail ) . They went back in . The engine was hard to start and had poor vacuum initially but went on to get better and better - good as new now.

 

Ouch.

Well, I am the one that BEATS on the engine!
And, be fair, putting the Turblown studs into the iron was one of the things that I did participate in when the motor was rebuilt.

That said, I don't know what kind of feedback I could give other than:

a) The studs seem very substantial
b) They were installed with absolutely NO incident
c) In my opinion, they could only be an improvement; and
d) I haven't nuked the motor, so I can't tell you if they are awesome or if I am just "lucky"

My last four motors all came apart for different reasons, all of which were not related to tuning, so it is difficult to quantify and durability claims.
I will definitely be using them from now on. That might be and indication that is worth something, I suppose.

 

And what did you guys end up torquing them down to?

 

Cheers , will look at this agian if i ever have to do another rebuild .
FWIW - neither of my engine failures was related to tuning either .

 

On a street driven car I recommend 32 ft lbs, including the OEM bolts used in conjunction with the kit. 50 ft lbs can be done on a race only application where the engine will be broken down ever so often. At 50 ft lbs you will see increased side seal groove wear on the side plates. Yes the stock o-ring'd sealing washers hold up just fine, even at 50 ft lbs.

 

A Pictured of the Brand New Coated Rotor Housings

 

Coated with what

 

A semi synthetic thermal barrier & oil attraction coating that we offer.

http://www.turblown.net/store/index.php?productID=98

More assembly photos

 

This is a pretty interesting thread about replacing the stock tension bolts with something more substantial. Before I had my REW block rebuilt this was something that I had looked into and will be something that I upgrade the next time around as I decide to see how well things would hold up with the stock tension bolts.

 

Very nice rebuild picture. Very clean

 

Below is our standard procedure of pumping the entire engine full of oil before it is spun over. We use a small external oil pump that we have built. When a new engine, or an engine that has been sitting for a long time is first started it takes a while to fill all the cavities( takes over 2 quarts to fill the engine!). During this time you experience a lot of engine bearing wear on uncoated bearings. We finish with a compression test. This is the highest we have ever seen for a rebuilt renesis. Its going to be Stellar once broken in.