Top end rebuild 3.2

[turbochad]

Well I did it, I missed 5th gear on the straight at HPR and went into 3rd instead at 6 grand in 4th (110 mph) on a free lap day a week ago. Needless to say the tach went well beyond the last digit before I caught it. I drove the car in another four sessions after that and it ran great, I thought I dodged a bullet, not so. On the ride back home I noticed a miss under light load and took it to my local shop (Storz) for a leakdown. Four bent valves. Three cylinders were 20% and one was in the mid 80's. The car ran consistent 2:18s with four bent valves, bad alignment, and a driver that can't shift.

The car has 92K miles so the guides were not so great anyway. Lots of oil in the exhaust ports. So Bob and I have been talking about what should be done and here is the list so far.

Rebuild the heads with
New Valves
New Guides
New Exhaust studs
HD valve springs
964 cams

Re-ring the pistons, (P/C's are in spec.- Nicasil)
Recondition the rods
New rod bearings
New ARP rod bolts

Transmission rebuild (1st and second syncros are weak)
Lightweight aluminum clutch setup
Resurface the flywheel
Thinking of Torque Bias Diff (GT Trans)

Have we missed anything? Anyone else have suggestions about what else we should do while we are in there (can't afford new 98's unless someone has a good set to sell). The motor has Dilivar head studs on the bottom and they look perfect. Bob thought we should just leave them. I will take some pics and post them later tonight but the rod journals look great and the other internals look really nice for 92K miles. I appreciate any comments.
Regards,
Chad

End of day pic of my car (Gaga) and Michael Wachholz 944 T

[Jim Garfield]

Sounds like what I've been thinking about when I do the top end, I think that about covers it unless you dig deeper. I'm curious about what kind of ballpark estimate you got for the engine, minus the transmission work?

[turbochad]

They mic'd the P/C's and they are well within spec, barely worn it seems. everything is looking good. I don't really have an estimate, Bob just gave me a range based on options. I'm expecting the engine to be somewhere between 5 and 8k and the trans to be 3 without LSD or 5k with plus the clutch.

[911st]

Just my two cents.

If you run any time trials cams can put you in a faster or modified class.

I do not think there is much to 964 cams on a 3.2 unless it possibly has euro compression.

If need, playing with the valve timing can move the power band up or down a bit.

At best such a cam change might cost a little TQ and pick up a little upper rpm HP. Probably will not effect lap times.

I could be wrong.

Might consider replacing the timing chains when apart. I had a motor come apart with 170k on it and the chains stretched enough to require replacement of the cam sprockets. Might keep that from happening. Or, there might be a measurement you can check.

[porschenut]

Hey Chad, sorry to hear about the mishap! It's amazing how such a simple mistake can be so costly. The repair is about half the value of the car!

I know it would only add to the expense, but if you've thought about close ratio gear sets, at least for 2 thru 4, now's a real good time to be doing that. It would feel like gaining 50 bhp while keeping you emissions-compliant. That's what I'm going to do next time my tranny gets pulled.

I've been dealing with Bob and Mike at Storz for years, and they're very fair with their pricing so I agree with your choice of shops. Keep us posted on your progress.

[Rodsrsr]

+1 on new chains as well. I found out that mine were stretched so far that they were making contact with the case! Anyway dont feel bad about the missed shift, it's what caused me to do a top end rebuild as well (plus a freah pair of 20/21 web cams)

[turbochad]

Originally Posted by porschenut

Hey Chad, sorry to hear about the mishap! It's amazing how such a simple mistake can be so costly. The repair is about half the value of the car!

I know it would only add to the expense, but if you've thought about close ratio gear sets, at least for 2 thru 4, now's a real good time to be doing that. It would feel like gaining 50 bhp while keeping you emissions-compliant. That's what I'm going to do next time my tranny gets pulled.

I've been dealing with Bob and Mike at Storz for years, and they're very fair with their pricing so I agree with your choice of shops. Keep us posted on your progress.

The close ratio gears is a great suggestions and one that we have touched on. Any suggestions on what gear sets for 2-4? I know that it is a lot of money but I don't plan on ever getting rid of this car, so doing it right is a priority. I want to daily drive it for a couple of years then turn it into a dedicated track, club race car. Bob and Mike are great, and their shop is only blocks from my house. I typically like to do motors myself but this one needs to be done in a hurry. I am now driving my 30K mint condition '90 928 and there is snow on the ground, ouch.
Regards,
Chad

[turbochad]

Originally Posted by 911st

Just my two cents.

If you run any time trials cams can put you in a faster or modified class.

I do not think there is much to 964 cams on a 3.2 unless it possibly has euro compression.

If need, playing with the valve timing can move the power band up or down a bit.

At best such a cam change might cost a little TQ and pick up a little upper rpm HP. Probably will not effect lap times.

I could be wrong.

Might consider replacing the timing chains when apart. I had a motor come apart with 170k on it and the chains stretched enough to require replacement of the cam sprockets. Might keep that from happening. Or, there might be a measurement you can check.

My understanding is that regrinding 3.2 cams to 964 specs (increased duration) is a good combination with the Wong chip and sport exhaust where the rev limit has been increased to 6,800rpm. I am upgrading the springs and rod bolts to ensure reliability. You may be right, it may not affect lap times as horsepower plays less of a role than the driver

I will make sure Bob checks the chains and sprockets for stretch or wear.

[porschenut]

Here are a couple of interesting threads on optional gear ratios. Another option is swapping the 8:31 for a 7:31, which is cheaper but may be less reliable especially if you eventually increase the hp output of your engine.

915 Modifications

7/31 Ring and Pinion into an '81 915? Help

[JeremyD]

If you have emissions considerations - I would not go much more than a 20/21 cam - if no emissions I would go with the 993 SS cams and Steve Wong chip. They produce a nice flat torque curve - and should work well with a lighter flywheel

[Steve@Rennsport]

Originally Posted by turbochad

The car has 92K miles so the guides were not so great anyway. Lots of oil in the exhaust ports. So Bob and I have been talking about what should be done and here is the list so far.

Rebuild the heads with
New Valves
New Guides
New Exhaust studs
HD valve springs
964 cams

If I might add,.........

Be VERY careful about your choice for valve springs: many are overly stiff and have seat pressures that really accelerate wear on cam sprockets, chains, idlers and intermediate shaft gears. I would also replace the OEM sintered metal valve spring retainers with Titanium ones for durability.

Transmission rebuild (1st and second syncros are weak)
Lightweight aluminum clutch setup
Resurface the flywheel
Thinking of Torque Bias Diff (GT Trans)

For track use, an LSD is FAR FAR better than a TBD.

I would strongly recommend replacing the old-style Dilavar head studs while you are there. To do otherwise would be a poor decision.

JMHO, of course.

[turbochad]

Steve,
I appreciate all your input.

I am not sure what springs Bob ordered but I know he is getting them from Walt at CE. I believe he also ordered ti retainers. I'll check with him regarding the specs.

I am getting an LSD, and appreciate your comment.

I mentioned to him the idea of replacing the lower studs and he didn't seem to concerned about it. What studs should I go with?
Regards,
Chad

[Wil Ferch]

Didn't read all the responses...but as to head studs, there are 2 schools of thought...noting that "factory" is top-twelve steel, and bottom-twelve old style Dilivar:

1.) Use ALL steel ( Porsche...ARP, like you mentioned)
2.) use ALL LATEST Dilivar..993 full-thread ( 993.101.170.51)

I'd go with 2.)....as they have the dual-benefit of the originally-intended expansion/contraction rates like the aluminum case and that they are not prone to break like the older style.

[AlfonsoR]

Originally Posted by Steve@Rennsport

If I might add,.........

Be VERY careful about your choice for valve springs: many are overly stiff and have seat pressures that really accelerate wear on cam sprockets, chains, idlers and intermediate shaft gears. I would also replace the OEM sintered metal valve spring retainers with Titanium ones for durability.


For track use, an LSD is FAR FAR better than a TBD.

I would strongly recommend replacing the old-style Dilavar head studs while you are there. To do otherwise would be a poor decision.

JMHO, of course.

Steve, what are the valve springs you recommend for a 964 cam? Would the recommended springs be safe to use on a stock 3.2 if you haven't done the cam upgrade yet?

Thanks

[Grady Clay]

I guess this a ‘me too’ post.

Me too on replacing the head studs.
I too would choose the 993 Dilavar over the steel studs but either are far better than leaving things alone.

Carefully decide on a LSD clutch set-up. Use the 12-disc version as it will last much longer than the 4-disc. I like them shimmed ‘tight’ spec. They do take periodic maintenance.

Yes, replace the chains and photo-document the condition of the cam sprockets. Replace the chain ramps and install rebuild kits in the Carrera tensioners.

The reason some like the stiffer valve springs it to protect from valve float when you over-rev (again?). The price you pay is greater valve and seat wear, accelerated guide wear, more wear on rockers & cam lobes, greater wear on chains, sprockets, idler, ramps, jackshaft bearings in the crankcase and even the tensioners. Wear on the rockers and cam lobes can be significant if you have restricted cam oil flow.

The Ti retainers are a good idea.

I have used my stock valve springs set at stock height to above 9000 rpm with 935 Sprint cams with no float. It is not quite apples & apples as I use the lighter 935 rockers.

Not to rub salt in your wound, some WEVO shift pieces and all new bushings might be in order.

If you are considering cams, gear ratios and the like, carefully go through the rules with several racers who know how the rules are interpreted. If you car considering mods that move your class, think through all the mods necessary to put you in the class you want.

Keep in mind that if you continue as a ‘daily’ it will need to pass emissions – including the ‘drive-by’ IR ‘sniffers’.

Also, look at who is competing in those classes. You want to race with knowledgeable people.

If you are going to make this change, do it right and not step-by-step.

I would want a car that competes (legally) in PCA Club Racing, SCCA Regional, (RMVR with an older 911), NASA and possibly more.

Something else to consider: Build yourself a spare hot-rod engine and geared transmission. (Have gears for HPR, Pueblo, LaJunta, etc.) Once you have the technique down, an ‘R&R’ can be done in a short Saturday with time left for chassis maintenance and your self ‘pre-tech’. This also solves the emissions issue.

Best,
Grady

[gregwils]

Let me apologize in advance for a minor, temporary hijack, but this caught my eye.

"and install rebuild kits in the Carrera tensioners."

Is there a part number for this, couldn't find it in the catalog? Or can you just call Pelican to request it? Thanks.

[turbochad]

Grady,
As usual that was a lot to chew on, but I am listening and will take to heart what you said. At this phase in the cars life as a daily driver/ track toy, racing is not in the cards, for the car or me. In three to four years I plan to move on to another daily driver and turn this car into a club race car, but I am driving it daily because it has been my life's dream to drive an aircooled 911 every day.

Between now and then I plan to accumulate the knowledge on and off the track to be proficient in the decisions you speak of, and I really hope I get to spend more time with you at breakfast (Breakfast Club) to discuss these things in detail (I'll take notes). I need more time to learn how to set up the car and understand the classes, rules, etc.

993 Head studs, Done. I have a hard time when I look at 993 head studs understanding how an all threaded stud it better. It seems that they would stretch and crack in the valley of the threads, unless they somehow act as a coiled spring. In my life doing VW motors and until now I had not even heard of fully threaded studs. I can accept that one's understanding of physics and reality don't always mesh, so I'll do it, but I hope someone can explain to me the physics of the threaded stud.

I will likely do the heavier springs just as insurance knowing the valve train will suffer more wear and rob some power. I want to do the cams for the extra power now knowing that this will not be the motor I use for racing. I have no idea what class I want to get into at this point and I would likely change my mind in a couple of years when I do it anyway. I will build another motor myself or refresh this one (within the class rules) when I change it over to full time track duty, that will be fun.

I am now looking for a 12 plate LSD, I understand the maintenance.

I will have Bob put in new chains, ramps and rebuild the tensioners, I didn't look at the sprockets, but Bob said they look good.

The salt is burning, it is hard to admit that I did this.......I am also thinking about the Wevo gate setup, but the miss shift was an anomaly that had a lot to do with the high closing speed pass I had to make with a slow car that signaled the pass left (one line) then swerved to that same side. I had to change course back to the right, upshift (I was at 6K in fourth), and decide where I was going to brake because I was now off line going into turn 4. I didn't panic, but I did make a bad shift as a result of many decisions needing to be made at once. Lesson learned. Bushings and coupler are all good and the shift feel is good for stock.

I run stock HE's a single SS magnaflow high flow sport cat with a 2.5" straight through SS magnaflow muffler, twin out. The car passed emissions easily with a Wong chip and this exhaust. I understand that the higher duration cam will change things, but Bob says it will pass, so I will trust it unless I hear differently from you.

Thanks for taking the time to help.
Regards,
Chad

[911st]

Just wondering, did you have traction problems out of a corner with your open diff?

I had an old worn factory LSD in my 85 and never had any traction issues. Just wondering .

I know they are very important in tight AutoX corners.


Just a note. I suspect the more cam you have the more the motor will respond and benefit from exhaust tuning.