General build questions - 81 SC

motogman · 10-30-2020, 09:42 AM

I am going to use this thread to ask my questions and get input on my engine project.

I have the heads off and am down to the cylinders and pistons which I am about to remove without taking this pistons out of sleeves (at least not yet). As a matter of interest in looking at these pics there are 5 broken head studs - and yes the car had been running well without the phut-phut noise often heard when I took the motor out for a clutch issue. I think it had run a fairly long time in this condition.

I am interested in any expert observations or comments about what you see thus far...

#1-2-3 - dirty and cleaned pics - 4 studs missing and lots of blow by on this side.

#4-5-6 - note strange scribe marks - any ideas, also #5 missing 1 stud but appears there was no blow by as this is the uncleaned condition.

Flat6pac · 10-30-2020, 10:38 AM

You need to pull the P&Cs to see the total trouble you have.
Knowing if you can pull the broken studs with out machinist help is a major concern
If you need to pull stubs broken below level the case generally has to disassemble because of slag from the removal getting inside.
40 years, it’s time for a cleaning and reseal anyway.
Bruce

motogman · 10-30-2020, 12:17 PM

I am guessing this is not the first time this motor has been apart but I do not have any history on the car. One reason I suspect this is the strange scribe marks on the tops of the bores - see '17' on bore 4 and '23' on bore 5 for example (see pic). I would not think this 'factory'? Can anyone comment?

Can one tell from the type or look of the adhesive between the case halves if that joint is 'factory' or or not?

Dpmulvan · 10-31-2020, 04:11 AM

Tear it down, your going to have to replace all case studs anyway. I’m thinking 5 stud isn’t missing but broke off in case. Those scribe marks are not factory.

motogman · 11-01-2020, 01:42 PM

At first look I thought the cams were good but with a bit closer scrutiny I find this pitting on the intake lobes on the 4-5-6 side. Only the 4 lifter seems to have a little damage.

After reading some threads, it seems the 456 side is more prone to cam damage than the 123 side (this may or may not be the case, it just seemed like more reports of this on the right side).

I am assuming these need to be resurfaced, ground and hardened. Since only 1 cam has this wear - do I just have the one redone? (Of course if I change profile both need it). What about rockers - do those get a similar redo? All or just the one with damage?

Please add your comments and recommendations.

Does the 964 cam grind work OK in an otherwise stock 3.0 CIS motor? Does anything else have to change? What is the difference in performance from the stock cam profile and something else (while I am doing it)? Keeping in mind this is a basic - stock or close to that build.

Also any recommendations on shops to get this work done?

boyt911sc · boyt911sc's Garage

I have good news for you. A few days ago, I met Ian Carpenter when he came to visit me and had a chance to get a ride in his beautifully backdated SC car. The motor starts and idles like any typical 3.0 liter SC. The motor runs very smooth but wait till you give it some gas! It accelerated and pulled like an SC motor in steroids! I have rebuilt more than a dozen SC engines and none came close to this one.

The collaboration of William Knight and Ian Carpenter (Icarp) have demonstrated that this new cam referred as M1 is an excellent upgrade for 3.0 liter CIS engine. BTW, I had rebuilt 6 engines with 964 cams but more impressed by this M1 cams. I will be building a motor with M1 cams very soon.

This is a very interesting cam I like to explore further. I don’t know William Knight except reading about his vast experience in Engine Rebuilding in this forum. And met Ian Carpenter, another successful professional engine rebuilder and spent some time talking about CIS in general. These M1 cams are for people with CIS that want to upgrade their CIS motor performance without spending a lot of money.

Contact William Knight or Ian Carpenter (Icarp) for detail.

Tony

motogman · 11-02-2020, 07:29 AM

Good lead. Thanks.

Oh... I can feel my self slipping down a slippery slope...

garment · garment's Garage

If the M1 cams are as interesting as Tony says they are (and I have no doubt they are!) I am going to want a set myself...

icarp · icarp's Garage

I am Ian Carpenter ,
The cams you have are not usable in my opinion.
I will be in So Cal prior to Thanksgiving , Any one up for a drive up the crest?
Then in Napa for the bird
How can I help? link to the discussion. 3.0 rebuild for performance advice

Icarp

KNIGHTRACE · KNIGHTRACE's Garage

I have M1 cams coming in soon. I can also have the. rockers fixed if you need. My email is KNIGHTRACE@MAC.COM 615.969.4917 William Knight
P.S. glad to help if you have questions, I would do the rod bearings you do not have to split the case to do this.

ahh911 · 11-11-2020, 07:34 AM

To add,
ARP rod bolts at arp torque specs, or re-use the existing ones or buy Porsche replacement bolts and nuts at the Porsche spec of 55Nm. Make sure you measure the old ones and new ones carefully in the center "fat" coupling section. OE ones can be nasty big and dangerous if you're not aware.
Phil

motogman · 11-12-2020, 10:25 AM

Quote:

Originally Posted by ahh911

To add,
ARP rod bolts at arp torque specs, or re-use the existing ones or buy Porsche replacement bolts and nuts at the Porsche spec of 55Nm. Make sure you measure the old ones and new ones carefully in the center "fat" coupling section. OE ones can be nasty big and dangerous if you're not aware.
Phil

Thanks for the input - can you clarify a couple of things...

Is reusing rod bolts an acceptable practice?

Are Porsche replacement bolts OK - this is not a race/high rev motor?

How are "fat" bolts dangerous?

Thanks

ahh911 · 12:22 PM

Is reusing rod bolts an acceptable practice?

Are Porsche replacement bolts OK - this is not a race/high rev motor?

How are "fat" bolts dangerous?

1) I would have re-used the rod bolts. Based on several inputs, one being there was no evidence of over-revving where there was piston valve interaction, two the timing chain wasn't stretched as some other members have seen, that to me means a hard life, just these two alone gave some clues. Then, upon inspection, every rod bolt measured within 1 thousands inch of each other ( I think it was 1 thou, because I was amazed, I may have written it down, not sure), if one had stretched significantly I would have seen it.

Here is what I would do if I had to do it over again and this is what I recommend: remove all the rod bolts, measure each one. The stock ones are simple to measure as the ends are very square. Careful not to knock the bolt ends as you tap them out, but even if you did, you'll figure out a means of cleaning up and measuring. Then, once all are labelled and measured, tighten them up to 55Nm, release and re-measure. If they haven't changed length you are good. I would have done this, but I tried a test with one of them all the way to 70 Nm, they didn't stretch even then, I still didn't want to re-use it. I would not have run the 70Nm (don't ask) test but I'd already bought new bolts and didn't know how terrible they would be. I think the original bolts are excellent quality, as most orig parts on the car. To answer you question, if it doesn't permanently stretch at torque, then your're ok. 10mm rod bolts only!

2. Not 100% sure about new Porsche bolts, I heard they were better but not firsthand experience.

3. I don't know, there is a drawing, mine were 4 thou out I believe, there was no way they'd be tapped or pulled in as intended.

Rod bolt diameter New vs Orig and Junction

Phil

mikedsilva · 11-14-2020, 01:28 PM

Looks like you have Alusil cylinders and matching pistons.

Quote:

Originally Posted by motogman

mikedsilva · 11-14-2020, 01:29 PM

btw - we have 1 car running the M1 cam here in Australia now..
and it's the smoothest 3.0 I've ever driven; spins like an electric motor!

KNIGHTRACE · KNIGHTRACE's Garage

Mike thanks for the information, I recently drove a clients car with a 3 liter low compression small port engine with the M1 cam. It really made an amazing improvement. It had an honest 225 hp to 230 hp and stock he said it was 180 hp. He drove across the country and averaged 28 mpg. It was impressive. The cam was designed to work with the cis piston. William Knight
knightrace@mac.com

motogman · 11-16-2020, 04:06 PM

Question on chain replacement...

How is the chain wear evaluated to determine if replacement is needed?

I am not too keen on the replacement chain with the link.

ahh911 · 11-16-2020, 04:57 PM

I just looked at the tensioner, when it's compressed all the way the wide part is below the housing lip so a holding pin can be put in place. Mine sits 1/8 inch above the lip. Also hunt around for pictures, the chain when stretched will be on the left side close to the top of the chain housing, on the right side the timing chain tensioner sprocket I believe comes closer to touching... something, don't remember. I looked at lots of pictures, then compressed the cylinder and compared it to when it had the chain on. I guess a weak tensioner will make it look like the chain is ok, but that was not my case and pulling the chain up by hand had no further effect, within reason. I've seen some chain stretch pictures on this forum and they are pretty obvious.

Phil

motogman · 11-23-2020, 06:53 AM

I am now working on cleaning and checking the piston oil squirters. After research many threads, I seem to only find examples of checking these when the cases are split - which I do not plan to do.

It seems feasible to do the check without splitting the cases. What all needs to be blocked and where is the best opening to inject cleaner and air pressure to check these without splitting the case?

KNIGHTRACE · KNIGHTRACE's Garage

I have used the master link no issues, WK