Restart of the big block Z

[Michael]

Some of you have been following my progress since at least the 20th century. There – is that sufficiently pompous? After inveterate blunders, rebuilds, disassemblies and sallies at improvement, the 461 is now finally installed in my Z.

 

As of 6 pm EST, 17 April 2011, the big-block roars back to life! Have not driven it yet – still need to bleed the clutch and to fill the gearbox with fluid. But after some fiddling with the carb, the engine achieved a stable idle at 850 rpm, without too much coughing or apoplectic shaking. A bittersweet achievement, as the lifters clank unpleasantly and the timing is troublesome to adjust. No great flaws, nothing that a little enlightened patience can’t fix. But the disappointment is that now having driven newer and more refined cars, I’ve lost the youthful urges for the visceral thumping of loud mufflers, large cam and so forth. However powerful it may be, there is less joy than disaffection. I find no elation, no relief, no self-satisfied feeling of achievement, even if this time the rockers really are oiling (they may not be), the freeze plugs are holding, and the exhaust is no longer brown.

 

My next build, if there will be one, will not be a traditional American V8. Henceforth my enthusiasm for these engines will be purely passive. Perhaps I’ll attempt to turbocharge my Miata, or maybe swap in a silky fuel-injected V6. Something that gets more than 7 mpg and doesn’t require a helmet just to drive around the block.

 

But now comes the pedestrian task of better tuning, sorting out the electricals. Don’t wire your kill switch to the battery positive cable – it does nothing while the alternator is charging. I know, because in a panic I had to kill the engine, and even outright removing the battery failed to achieve this. The only solution was to pull the ignition wires from the distributor!

[emeraldlion]

But more seriously, it is quite sad that you have been so at a loss for enjoyment with the results. Sorry to hear it. Edited April 18, 2011 by emeraldlion

[Michael]

Finally drove the thing this afternoon.

 

Main impressions... the power is fine, but lacks the impact of outright rocket thrust. Perhaps my standards are unrealistic. With the close-ratio gearbox, more time is wasted in shifting than in actual acceleration; best results are starting in second gear, and immediately shifting into 5th. RPMs rise so quickly that I almost certainly over-revved the engine on several occasions. With four over-stretched rod bolts, this does not bespeak a comforting feeling.

 

The good news is that this time, my safety-wired rosette of bolts holding the adjustable timing-sprocket seems to be holding, and there is no embarrassment of said bolts backing out and grinding into the timing cover. Speaking of timing, the engine likes around 12 degrees at 900 rpm (with vacuum advanced plugged). It starts relatively easily in the warm weather that has finally visited us in Ohio. This (the easy starting, not the weather) is a welcome improvement over the trouble that I had circa 2006, when I last seriously worked on the engine.

 

My colleague and I took video of the "first drive", or thought that we had; sadly, the camera was on the wrong mode, and instead of amateur video, we have amateur images of weeds growing along my driveway. In a few weeks we'll try again, and I'll try to upload something to a video hosting site.

 

Bottom line - yes, it's nice to have finally overcome the vast plethora of seemingly trifling difficulties that plagued this effort for over a decade, combining in their vile cabal to quell whatever urge one musters to make progress. But as I posted some weeks ago, the completion is anticlimactic. When I was in my mid-20s, I wanted brutal acceleration at all costs, convenience, reliability and everything else be damned. Now, approaching 40, I'd prefer the easy litheness of my Miata combined with the unhurried thrust and poise of my M3, but instead what I have is a Japanese muscle car. It's basically a Chevelle 454SS, minus 1200 lbs.

 

Where to next? For as long as I have garage space, the Z will remain parked within, to occasionally be trotted out for a mild day's tilting at windmills. Maybe some day I'll take it to a chassis dyno for the obligatory bragging rights (or plaintive consternation over making 100hp less than Desktop Dyno is predicting - few things are so depressing as a great theory, so long oblivious to practical criticism, defeated by a 10-minute experiment).

 

My advice to prospective swappers: keep it mild. And any operation so extensive as to keep your car on jackstands for over a few weeks, is best delayed until you're a wizened old man, doting in retirement on empty acres, empty save for weeds and field-mice, silent save for mating calls of toads rejoicing in the incessant rains of languishing spring.

[emeraldlion]

You know, this really is a great post. I think( do to the nature of the addiction) most of us here "snowball" our plans and dreams for the car. It seems great to have these cars and dreams of a big block would be great, but I think there is a lot to be said for the average swap that doesn't go wild. I've been ragged a little for not going with anything bigger than my little 283 chevy, but I want to have it mostly reliable and easy driving other than balls to the wall power.

[DavyZ]

Michael, I have followed everything you have gone through with the car over this past decade--has it really been that long??? My gosh, how time flies. I am still working on my car and have actually made some progress in the past few months. Good to see yours is finally driving

 

If I have anything to add to your advice it is this: get a rust free car to begin with that doesn't need paint or anything else. In fact, just buy a converted V8Z from Craigslist and be done with it...

 

Thanks for the updates--I am surprised that the power is less than awesome, figuring on the power to weight ratio...

 

Davy

[Pyro]

big blocks need lots of timing, even mild ones.

 

plug you vacuum advance into a manifold vacuum source (not a ported source). You need vacuum advance!

 

set total timing to 40 (at 4000 rpm with no vacuum advance).

 

would be nice to have 15 to 20 at idle, then get another 10 from the vacuum advance to make 30 at idle. This will make around 50 when you rev it up in neutral (no load).

 

crane makes a vacuum advance that is adjustable.

 

You will be surprised by the power difference if you make these changes.

 

readjust the idle speed and idle mixture after the timing adjustments. You will find the engine smells much cleaner and gets better mpg and has better throttle response with more timing.

 

here is a nice timing write up for a small black chevy. skip to the end of the paper to see what i'm talking about. BBC need more timing than a SBC due to wider pistons and slow flame travel.

 

http://www.corvette-restoration.com/resources/technical_papers/Timing101.pdf

Edited May 15, 2011 by Pyro

[Mikelly]

Wow... Just wow...

 

Reading this makes me think back a ways... Started mine up in the last two weeks as well... Earth must have been tilting on axis... Funny how times change the older we get... Love all the cars I have that I can drive. Not so sure how much I still "love" my Zcar... Hoping that actually driving it will rekindle the flame...

 

Good luck with your project Michael, and how about those Miatas... Gotta love them... We do ours!!

Mike

[Drax240z]

I've been following since the early days too Michael, glad to see you still fighting with the BB... I'm with Mike Kelly, starting to love the drivable cars more than the project cars! Argh!

[Michael]

Thanks to everyone for their encouragement and words of congratulation! To be sure, I'm less disappointed than disenchanted. If my current result were to have been obtained 1-2 years after starting, I would be fairly pleased. The reason for my jaded disaffection is that a dozen years is too long just to reach where I'm at. I don't mind having spent the money for my "lessons" on what I really want and what the engineering compromises entail. I do however mind the time spent and the opportunity-cost, in terms of other cars to hypothetically have tried, on account of the Datsun having monopolized my vehicular attention.

 

video uploaded to You-Tube:

 

Issues to which to attend in the immediate term:

- compression test. Is the horse pulling the car with every leg?

- more advance for ignition system (currently 16 BTDC at 850 rpm (vacuum disconnected), linearly increasing to 30 BTDC at 3000 rpm, and that's it). I might try a Megasquirt-type of setup with the distributor gutted to serve merely as a device connecting the camshaft to the oil pump. I am not impressed with MSD/Crane/Mallory/Accel/Pertronix topical fixes to the GM HEI. The current generation of MSD digital ignition is an intriguing alternative, but there has been too much derogatory evidence against MSD.

- figure out why it's backfiring upon release of the gas pedal. Sounds as if lots of unburned hydrocarbons are going down the headers!

- solve oil-seepage problem through intake cover bolt holes.

- figure out why the carburetor firehoses fuel into the venturis upon the gentlest application of throttle... or get a new carburetor. I'm not even sure that the vacuum secondaries are opening on this carb... or why I have a carb with vacuum secondaries in the first place!

 

Longer-term issues:

- new tires (these are maybe 20 years old, if not older).

- if all goes well, dyno tuning.

- if all goes even better, G-force T5 transmission.

 

It is amazing how much of the manners of an engine depend on seemingly superficial aspects of tuning... spark, fuel, and that sort of thing. I mean, I spent years and years worrying about combustion chamber design, dynamic compression ratio, head port geometry and intake charge speed, piston speed and rod/stroke ratio... but in the final analysis, that's all ancillary crap. Well, not outright crap, but the best cylinder head design in the world won't compensate for incorrect timing or a carburetor that pukes fuel.

 

The Miata is a wimpy little hairdresser's car, as a local friend remarked. But I enjoy the smiles-per-gallon and am warming to the idea of turbocharging it via a turnkey kit (BEGI or Flyin' Miata).

[Pyro]

try 26 degrees initial with 40 total. (just add 10 more).

[rsicard]

Michael:

 

You are very accurate in your assessment

 

" Well, not outright crap, but the best cylinder head design in the world won't compensate for incorrect timing or a carburetor that pukes fuel."

 

All of which you have said is true. After having rebuilt and driven a Chev Big Block with modified factory fuel injection, they like 40 degrees + advance for ignition timing. That in itself should tell the story of the inefficiency of that engine design. The fellow that designed by the small block back in mid 1950s had a design that was WELL AHEAD of its time. The only thing really improved is the cylinder head designs and advent of multi-port fuel injection which GM screwed up until the LT-1 came about with very precise ignition and fuel injection timing.

[kamikaZeS30]

Sounds like you've been down a long road, Michael. But, I think you can at least take pride in the fact that you've, for the most part, finished what you started. Which, sad to say, is a lot more than what most people who set out to complete an ambitious project can say. And, I can't imagine that a big-block Z is really "disenchanting," then again, I'm 27, not 37.

 

I have both a 1991 Mazda Flamboyant Hairdresser's car--eerrr, I mean, Miata and a 1971 240Z w/ a 383 V8 swap. I really like both cars for different reasons. I just spent over $7000 on my Z over the past year for the v8 swap and related drive-train/suspension items. I spent about $800 on the Miata, for some basic maintenance stuff, some new stereo components, aftermarket shocks and springs. I don't know which I can say that I get more "smiles-per-gallon" from, probably because it's difficult to flex those muscles under the kind of acceleration G-forces I experience in the Z.

 

The one thing the Miata does have over the Z is that I don't have to explain to potential passengers why they smell gas when they roll down the window.

[Mikelly]

Michael, We did a Flyin' Miata instal on my youngest son's car... Don't go with the voodoo controller. It's junk. Do a megasquirt or the Hydra for control of the system. Otherwise, their kit is very well made and comes with pretty much everything you'd expect to need. Their phone support is very good as well. And I know some hate the Miata, but it's like a timex wrist watch (of which I own as well). We hammer on it at the track, bring it home, park it, and don't drive it much until the next track event... gas it up and go... Can't beat that kind of reliability.

 

As to the other issues, I'm with you fully... Shouldn't have taken as long for me to do mine either. I just hope the reward justified the aggrevation and stress my build has put on my "already stressful" life.

 

Mike

Edited June 26, 2011 by Mikelly

[Michael]

Mike - is your Z now running more or less to your satisfaction? Did you finish the 383, or have your switched to an LS-family engine?

 

I performed some more fiddling. Checked static compression; it's 167 psi to 172 psi across all cylinders. In the process I discovered that one of the ignition wires had a short, so for the past 2 months I had a V7. Then I realized that the #2 and #4 ignition wires were crossed - so really I had a V5! For good measure, I added 10 more degrees of timing by rotating the distributor, following Pyro's suggestion. Now the car definitely feels better. The backfiring is gone, the engine feels smoother and power has of course improved. The carb is OK, though I still have no proof that the vacuum secondaries are opening under load. Best method for burnouts is to start in 3rd gear, rev the engine to all of 1500 rpm, dump the clutch and then punch the throttle. This leaves a satisfying cloud of tire smoke. In fairness, the result is not entirely due to prodigious engine torque... the tires are around 20 years old. I almost never leave my own driveway, preferring to avoid the risks of public roads (having a long paved driveway helps). Now I'm searching for a better ignition control system... and a helmet! The driver's head is surrounded by roll cage tubing, and I mistrust even the most sophisticated padding. One panicked swerve to avoid an Ohio groundhog or raccoon, and I'd get a nasty left-brain indentation.

 

We need to have a Datsun reunion, maybe at the geographic halfway point. Get AAA to tow 200 miles, then drive the remaining 50 miles.

 

The Miata might be getting a used Jackson Racing supercharger with "powercard", if the Craigslist gods listen to my supplications.

 

Question for the cognoscenti: short of driving around with a mirror on a stick, or going to a chassis dyno, how does one determine whether the carburetor's vacuum secondaries are indeed opening under load?

[Pyro]

put a small piece of paper in the secondary hole.

 

drive it hard

 

stop and look for the paper

 

if it is gone then the secondaries are opening.

[Michael]

Did the paper-test... Drove the car at moderate speeds (up to 50 mph), mostly doing burnouts in various gears (first through fourth), up to 5500 rpm or so. Result: wad of paper stuffed adjacent to one of the secondary throttle blades is completely intact.

 

One other result: with the secondary thus (slightly) open, idle jumped from it usual ~1000 rpm to 1300 rpm.

 

I now have around 12 miles on the odometer since my most recent rebuild. These are mostly burnouts in my driveway. Today I drove around the neighborhood, venturing onto public roads. The car is uncomfortably loud, but is otherwise fairly settled and responsive (and that's driving on only the primaries, ha ha!). It still spews oil past the timing cover - likely culprit is the front crank oil seal. As a bonus, the bouts of sporadic hard braking seems to have loosened the front-right caliper, so that now the car brakes evenly, without dragging severely to the left.

 

More observations on the Doug Nash 5-speed: aggressive upshifts with clutch-dumps are actually pretty smooth, as if the transmission were built specifically for such driving in mind. Intentionally brutal driving results in smoother response than if one tries to drive this like a normal street car; that is to say, leisurely shifts cause bogging and requires the operator to "hunt" for the proper gear, while wantonly abusive gear-banging is rewarded with crisp, precise engagement. Reverse is still a problem - the shifter loves to pop out of reverse, especially if blipping the throttle.

[Pyro]

i guess a wad of paper would work if it is small enough. But I would use a small flat piece around 1/4" x 1/4".

 

what carb are you using??

[Michael]

1/2" x 1" piece of office printer paper, folded to form a 1/4" x 1" strip.

 

The carb is a Holley 4160-style vacuum secondary, 750 CFM, bought new from Summit Racing in 1998. "Mods" are removal of the choke plate and filing of the throttle blade shafts/screws for some nominal increase in flow. I am now contemplating a Race Demon 750 or 850. The intake manifold, by the way, is an Edelbrock Performer RPM oval-port, stock except for minor port-matching to the heads.

[Pyro]

That is a good carb. I use on on my 454 in my 70 c10 and my 350 in my 71 240.

 

if the secondaries aren't working then either the big diaphragm is busted (or not installed right) or the oil ring where the diaphragm housing bolts to the main carb body is leaking.

 

an easy fix. I would try fixing what you got first. for 20 bucks you should be able to fix it.

 

and try a smaller piece of paper. one layer of 1/4" x 1/4" should do it.

[DRIVEN]

Another trick to verify secondary opening on a Holley is to put a paper clip on the diaphragm rod. Make sure it's pushed all the way up. Make a WOT run and check to see if it was forced lower on the rod as the diaphragm moved up. Make sense?

 

One other thing. I've had really really good results using Quadrajets originally on Cadillac 425s and 500s. The advantages are mechanical secondaries and (on the 425's) an electric choke. The throttle response is superior to most Holleys. I run one on my 413 and it still even pulls down 20MPG. The U-Pull-It yards around here are full of them and since old people don't drive that much, they usually have pretty tight throttle shafts. I know, there isn't typically much love for the Qjet but I've always had pretty good experiences. Just throwing it out there.