911T rebuild and mild upgrade
 

I've got a few questions for the rebuilding group.

I'm planning on a low budget rebuild of my bone stock '70 911T targa with about 90K on the clock. I've had this car for 10 years now, would never dream of getting rid of it. It's just not getting enough use due to a tired motor.

I want to do a mild refresh of the T motor without breaking the bank (I know..ha, ha). Been collecting parts as I could, and just now building up the motivation to drop the engine/trans and get going. Here's the plan:

Swap out the T cams and pistons with E cams and E mahle pistons I've picked up through the years, all showing little to no wear. Question: Should I reuse the original cast iron cyls., or use a set of alloy cyls. that I got with the pistons? I assume the car won't have oil squirters as it's a 1970, and I'm not planning to add them (unless the cost is nominal...again ha..ha), but remember this is not a track car, just a driver. Also, do I have to get new lifters if mine are ok, or will they pretty much screw up the cam lobes of the different cam? Can I get the lobes treated to help break in to the lifters?

Heads go to a machine shop for valve regrind, new guides and seals installed. I'm fortunate to have an excellent local shop and know the machinist is more than capable of the work. I welcome any pointers I can share with him, as he's probably never done 911 heads before. No other work is planned with the heads.

Assume I'll need new crank and big end bearings, also chain guides, but that's all I'm planning on. Is this a bad assumption? BTW, I picked up a nice intermediate shaft that I could put in if mine's worn, but from what I've read that may have been a waste of money as the case is probably the worn part, if anything. Newer oil pump will go in too.

New oil return tubes and seals all around. That's about it. No plan to replace much else like head studs unless I screw something up. I won't be doing the chain tensioner oil upgrade. I've already replaced originals with the mechanical tensioners, and have no issue with adjusting the chains every couple years. The car doesn't get driven all that much. I know this description of work will make the porsche purists cringe, but hey it's my car not theirs...and I'm really serious of doing this on some kind of budget.

Hopefully I can get some confirmation that what I planning (especially the P&C swap) is at least not a bad idea, plus get a few insights along the way of specifics to watch out for, or other tricks not included in the engine rebuild book, possibly suggestions for changes to the jets on the Zeniths.
Thanks,
Larry

Use the Biral Barrels that came with the pistons.
Plan on opening the venturies to 30 or 31 mm, you will want to rejet the carburettors anyway.
I would also put in well refurbed mechanical chain tensioners using the latest refurb kit with the spring loaded check valve.
For the rest: As long as the job is performed in a really proper way you will be fine with the solution and will have a much more vivid motor.

Larrydrop, lifters aren't an issue as the rocker arms ride directly on the cams and don't have lifters like OHV engines do. It's a good idea to have the rocker arms refaced so that you have new surfaces to "wear in" to the new cams. They can be rebushed if they are sloppy on the rocker shafts. CGARR and others can do this work.

Apologies for the slow reply to posts, family in town for the weekend.
Thanks for the terminology correction....I knew they were not lifters as in the post, but guess I reverted to non-mechanical valve terms.

Thanks for the tip on the rocker arms! Good to know I don't have to have the cams treated to wear back into the rockers. I'll plan on having them all re-faced, and rebushing as needed for sure.

In looking at the camshaft parts on the Pelican site it seems like the oil line restriction kit and intermediate shaft bearings, a couple things I hadn't necessarily planned on doing, should be included on the to do list. What do you think?

Thanks for the post. Apologies for the slow reply..family in town for the weekend.

I'll plan on using the birals. I'll definitely check out the new tensioner kits.

Also thinking I should just plan on new timing chains as I don't really know how to gauge wear on mine. What do you think?

Lastly, I'm actually toying around with a "quick turn around " option of just doing heads, P/C, timing chain work, and not spitting the case. I figure rod bearings can still be replaced with this option. I'd get back to a full rebuild in a couple years. Am I crazy for thinking along these lines?

It's easier to split the case and you're already getting all the seals for the bottom in the seals kit. Cutting chain, balancing the rods while getting the bearings and bolts changed..you're not saving any time.
Bruce

What do you plan to have done to the case? Many here believe that if a mag case is split, it will require being decked and align bored.

As for your crank, I'd not make any assumptions. It's possible it may be fine. If the bearings are in spec, you can have the crank polished and replace the races. If you have to replace it, start shopping now. They are getting harder to come by.

Good luck keeping the budget in check. I couldn't do it.

MHO. Get your cues about the crank and crank bearings from the appearance of the other internals (rod bearings, interior cleanliness, cam/cylinder wear, etc.). The T engine was the least stressed engine Porsche made (6 cylinder). Once the case is split, popular opinion is on the side of line-boring, case savers and other mods. I would consider replacing the T heads with later model versions with larger valves and ports to better match the E cams and pistons. Heads have to be reconditioned anyways.

Add'l budgeting can be a topic at this point in time. Sometimes, the slippery slope of rebuilding an early engine intersects that of a later model engine that could result in a more powerful, longer-lasting engine at comparable cost.

Sherwood

Sherwood, if the engine is made of original components it has got the same valve sizes which have been used from 2,2L through 2,7L (this one should be a 2,2), these are OK.

Larry, if the case is bone dry it may work to leave it close. Just open the rod bearings and conclude from their state of wear if its worth opening to also do the mains, facing your statement to do a full rebuilt anyway later (why?).
However my experience on a huge # of T rebuilt is chances are quite good that they are not distorted and can be reassambled as they are without facing and line boring. This would lead me to do the full job and split while in there.
Re chain tensioners i meant to use the std hydraulic non oil fed ones and to do a refurb with the latest refurb kit for these ones.

Thanks. I stand corrected. I incorrectly assumed it was an early 911T (e.g. '68-69').

Sherwood

Thanks for the advice everyone.
I was on the fence about splitting the case, thinking of the proverbial can of worms that may result. Bruce and crummasel have pretty much talked me out of the easy road, plus I can't claim my case to be close to bone dry. Although most seepage does seem to come from oil line connections, there is no doubt a little coming from the case. This being the second early 911 I've owned, I'm used to keeping a bag of oil dry handy

Engine is the stock 2.2L with Zeniths, so I'm encouraged to hear that my efforts to modestly pump up performance with E components won't be thwarted by the smaller valves of the 2.0L.

On the topic of valves; with new guides will I now be able to run straight no-lead gas in this engine, or will there still be an issue with exhaust valve heat transfer and valve lands in the head?

Question for the group: what oil pressure on cold start up would you consider "normal" for an early 2.2L? I've always been a little concerned that my oil pump has some wear, and that was one of the motivating factors for opening up the case. Is oil pump wear a common problem for an 80-100K motor? I know gauge readings are notoriously inaccurate, but mine reads approx. 80 cold, and 40-50 hot (at say 2500+ rpm). Do you think that's ok? Temp on the car typically stays 180 F if not sitting in traffic and 75 degrees F or less ambient temp. It will creep up on a warm day for sure, or sitting in traffic, but I don't think it's ever gone over 210.

I've usually got the engine spinning to keep pressure up and air moving if stuck in traffic for awhile, which fortunately doesn't happen very often where I live....with the exception being the Woodward Ave. dream cruise that's just around the corner (August 16) here in Detroit.

BTW, if you ever have reason to be through the Detroit area 3rd week in August or want to make a special trip I highly recommend checking out the dream cruise. It has to be the largest show and drive of collectable cars in the world. I liken it to going to Vegas for a car guy...everyone should do it at least once. There's always a good showing each year for our favorite marque.

Thanks,
Larry

No probs with unleaded fuel.
New valve guides are not worn (evident, no? ;-) ) but will also have better wear properties compared to the original ones.
See to get them mounted as concentric as possible and try to avoid excessive valve seat regrinding.

Thanks crummasel.
I'm assuming valve guides will be worn and needing replacement, but seems you are suggesting I inspect and only replace if needed?
I have not read up on this particular topic yet. I'd be grateful for your take on acceptable wear to leave the valve guide in service, either qualitative or quantitative.
(Is any noticeable looseness unacceptable, or is there a value I could use a dial indicator to measure?)

Porsche specifies the mounting tolerance to be within:
In .03...057 mm
Ex .05....077 mm
with a max wear of
In .15mm
Ex .2mm
However with 90K (miles i guess) i think they are close to having head it, depending on the previous usage and temperatures the engine had.
If your plans are to be perfect i would change them, if plans are to go reasonable i'd measure them properly and then decide.
Also inspect the valve stems for wear.