Valve job.. ’57 Maserati 3500GT

Posted on April 7th, 2013 by Dave under Austin Healey, auto restoration.

You’ve probably already seen some pictures of this car herein previously. According to Maserati build records only two of these cars were built in 1957, so it’s VERY rare!. Here’s another look.. click on photo to enlarge-arrow back to text.

1957 Maserati 3500GT Paris show car-really!

Well, as good as it looks, I became concerned that the car simply was making too much induction noise at highway speeds to make it a comfortable “touring” car. I let it go for awhile until the owner and his wife both agreed to let me at least check the cam timing to see if it was off to the degree that valve overlap would allow poor filling and emptying of the cylinders yielding a lot of  Ross Perot like sucking noise. Well to my surprise the timing was a few degrees advanced on the exhaust cam, but probably not enough to cause the symptom we were experiencing.

Most manufacturers have very clear and well defined marking showing where the engine should be timed for optimum daily usage. There are many variants to this setting for specific racing needs. Maserati, and now this is my wild ass guess, ran in  the engines before delivering to the end user, and this one being the “Factory” show car that year probably had Guido or some engineer do a little extra tuning. I say this because the marks on the cams that should coincide with the marks on the retaining caps were hand scribed with an electric pencil and labeled “PM” with an arrow.  See photo:  followup note: no, I’m told by all the experts that this was the way they all were..

Factory markings?

I felt that the engine “ran” pretty well as it was and rather than spend many hours to set the exhaust cam to where one would think it belonged I decided to check some other parameters for the issue. First was to check the compression reading, note to self: (ALWAYS DO THIS FIRST YOU HARD HEAD) well, the reading were horrible, 5 cylinders were at 60PSI or less and only one cylinder managed to get to 100PSI.  The compression ratio for this beautiful engine is only 8.2 to 1, nevertheless, even at Albuquerque’s altitude I would expect no less than 150PSI on all 6 cylinders.  The carbs were “chuffing” out air at various RPM’s, not unlike many 911 Porches tend to do. I’d recently had a friends TR4 with a similar presentation and that was severely receded valve seats. The seats are generally pressed in and are the seat upon which the face of the valves rest to allow the pressure of compression to occur as the piston moves. Warnings of seat recession was widely spread with the demise of leaded fuels, but that never really materialized except in a few racing engines that weren’t properly built with hardened seats and valves to handle the new unleaded fuels. Remember that “valve jobs” were the most common repair and bread and butter of shops before unleaded fuels. Now I see maybe one or two a year.. sigh..

OK, so the owner gave me the go ahead to pull the head off as see what exactly was causing the lack of compression. First the valve clearances were all over the map. The Factory called for 0.1 mm (0.004″) intake and 0.2 mm (0.008″) exhaust. The readings were as wide as 0.013 to 0.0, only 2 or 3 of the 12 were close.. The valve clearances are set by means of hardened discs of different thicknesses between the valve stem and an upside down “bucket” that is opened as the cam lobe rotates.  Well, the good news is that the seats don’t appear to have much recession, but they will have to be reground and the valve faces will need to be re-cut. I have not pulled the valves out of the head yet so I can’t report on the condition of the valve guides, springs etc. Here’s a shot or two of the removed head, block, and all the miserable silicon that some previous mechanic used to keep the coolant from leaking out.  Tedious job to remove it..

wet liner cylinders, tiny brass(?) combustion seals, Silicon mess...

Head and Carbs on the bench..

top side with cams still in place- note dual spark plug design

note difference in operating temp of these valves.

Next, I’ll disassemble the remaining removable bits from the head and deliver it to the machine shop…  The head is at the machine shop for their part of the job. Parts are ordered and I spent several tedious hours today cleaning up the block deck and liners of all the silicon schmutz and gasket remnants.

cleaned and ready to re-seal and add coolant gasket

The starter has been sent to the re-builder to check for condition. All the new compression may be more than a tired starter can handle and it’s a PITA to remove when the carbs are installed.. ditto the oil filter..

While the head is at the machine shop I’ve started to do some general clean up and repairs to other under the hood items. First on my list was to blast the 2 exhaust headers and then coat them with a graphite product I’ve used for many years with nice results. One of the headers was wrapped with heat cloth tape the other none. Turns out there was a reason. The rear wrapped one was nearly cracked in half on the underside (luckily). Being of cast iron construction they are problematic to repair without special  mostly Nickel alloy rods or high silver content brazing wire, which I happen to use for the bicycle department. Here are some pictures of this process.

Badly cracked rear header-click on this

Raw repair prior to surfacing

Double click on this one above. There must be about 3 troy oz. of silver in that repair..

finished and coated front side

finished and coated backside with repair

Then I spent the rest of the day removing the old paint and cleaning up the cam covers of casting flash and other imperfections. I polished the raised lettering and outlines and finished with a new coat of black “wrinkle” paint as was original. The owner wants the letters painted red as was done previously, but I may try to talk him out of that, as I think the black and polished aluminum looks classy enough. We’ll see.

restored to like new--well, almost..

So I’ve been pondering this next picture. It is a straight edge laid across the tops of the wet liners with the copper “fire ring” sitting in it’s normal position. The gap you see back to the deck is nominally 0.087″ which is huge in my thinking of what the outside perimeter gasket to seal the coolant jacket, is capable of. Perhaps this is why there was so much silicon used by the previous builder. I haven’t received the new gasket set yet, so I’m in the dark until they arrive. The old one is visible in the earlier picture of the underside of the head and I think we can all agree that it isn’t that thick.. a conundrum..

wow..tiny text.. click on twice?

The most simple (cost effective) solution is to have a shim or spacer, whatever one cares to call it, water jet cut and surface ground out of sheet aluminum to the correct thickness. This will return the deck height to the same as the wet liner height.  I can use the rubber perimeter coolant seal as a template as the spacer is not terribly dimensionally critical except for the thickness. This will also correct the overall height of the cams which will bring the valve timing back to original. Pretty sure that I can have it done locally, another plus.

Yesterday I cleaned up and painted the cam cover end plates, oil filler and tach drive plate.

More assembly prep work..

In the process of changing the oil filter cartridge..

old oil filter cartridge

I found this along with a fair quantity of silicon

collapsed internally

sealant remnants that had migrated into the lubrication pathways.. The filter had imploded and was not filtering much of anything. God only knows how much of the filter material has migrated and is possibly blocking the oil passages or bearing feeders… what next?

Yesterday I bought a sheet of 3031 Aluminum sheet at 20 Ga or 0.032″. I was hoping for 19 Ga (0.036″) but couldn’t find it locally. Nevertheless, it’s in the hands of the water jet operator along with the template for the spacer. I’m confident that with a light coating of sealant on both sides plus the OEM gasket the height will be within the allowable factory variation spec. (+/- 0.1mm [0.004″]) Regardless, it will be FAR better than what I started with..

Here’s a couple more shots of the cleaned up engine bay, the water pump and the very unique leather wrapped oil line.

Driver's side

passenger side

Water pump

Leather wrapped oil line for dash gauge

The owner dropped by with a couple hardback Maserati books and I found a picture of the early 3500 engine and in my meager attempts to bring the car back to it’s  original appearance I noticed that the water pump was also black wrinkle paint finished, like it is now..

Factory finish for the water pump

still waiting for the machine shop to finish…

Here’s  today’s new issue. The old tach drive cable had broken at the engine end. The female screw cap that mated to the male cam cover plate had broken at some point and the cap was replaced with workable bracket that kept the cable inserted into the back of the cam. The new cable and housing look to be just the ticket, but the overall length of the square cable is too long. Ask any instrument repair shop and they will tell you that the maximum insertion into the back of a mechanical tach or speedometer is 3/8″.  This new one is ~ 7/8″ too long and would instantly ruin the tach. Plus it has no retaining collar to keep the cable from migrating into the tach. Luckily we have a nationally respected instrument repair shop (MoMa) about a mile from me. I’ll run them both over this morning and confer with Margaret and Joey and see what the best fix is. Here’s some comparative photos.

top=old / bottom= new

top=correct insertion length, bottom too long! Note collar on top cable

engine drive ends. Note missing retaining flange on top cable.

Finally got back to work on the Maserati this last week. I got two versions of the water jet cut spacer. One was 0.032″ the other was 0.40″. Here’s what it looks like..

Head spacer and gasket

And while that was being cut I managed to get a factory fan. It has 6 blades, the car has some Japanese single blade, no doubt why an electric fan had been added. The new fan was taller than the radiator shroud which was dead flat. I un-soldered it and and beat it into submission on a sandbag and then English wheeled it into a fairly pleasing radius that cleared the blades. Hmm, the “program” won’t upload the shroud picture I want, so here’s how it used to look instead..note that the blade it pushing up on thee shroud.

A bit of a clearance problem...

The machine shop finally called and informed me that they would need 6 new intakes, 6 new exhausts and 12 new guides.. apparently the seats were acceptable. It was decided beforehand that they would disassemble the moving parts of the head so they could measure stem lengths and insertions etc., should they ultimately set the valve lash at their establishment. I ended up doing it since I’ve done many similar heads before and they hadn’t. The two numbers they provided for each bank were useless.. It took nearly 14 hours to get them to plus 0.002″ of the factory spec. An extra 0.001″ was to allow for the seating in of the pads and valve seats. This was the machine shops idea and sounded like a reasonable idea. It took this long because my assortment of shim pads was mostly from Jaguar heads and their pads tend to be much thinner that these Italian ones. So I had to spend many extra hours using my old Sioux valve grinder to grind thick pads to the correct thickness..  After a good nights sleep and with some help from my pal Bruce (HVAC expert) we installed the head perimeter shim atop a coat of Yamabond (a product for sealing the crank case halves of a motorcycle). It goes on evenly and it cures slowly giving us plenty of time to install the rubber perimeter seal (~0.075″) and the 13  (0.050″) ball bearings that nest in precut holes in the rubber seal. These are to keep the rubber seal from squishing out under the 100 ft lb torque applied to the head (I stopped at 95 ft lb) So, after hooking up fuel lines, oil lines, power lines,water lines, linkage, Ex manifolds and the cam covers, cap, tach drive and sundry other time consuming tasks I got the old oil and coolant drained out. Almost ready but, I forgot that I had to reposition the cam timing so the opening and closing was at factory spec. Remember I’d thought this was the issue causing the loud induction noise.

Splined keeper and pin for cam adjustments.

Here’s a look at the new valves..

The green thing is just holding the head for it's picture.

So now for the “bad” news…. I checked the compression before starting the engine and to my disbelief it was nearly as bad as when this project was started. A second confirmation with a leak by tester showed that even with new valves there was up to 75% leakage. Mostly it turns out through cracks throughout the head it self. I pressurized the cooling system and had coolant coming out the exhaust ports. Couldn’t see it on the intake side due to the big Weber’s, but I could hear the air escaping…. Well, what the f… do you do now? Just the previous day I’d informed the owner I expected to see another 100HP.. We weren’t able to “pressure check” the head when it was off because there were just too many holes to start with. I’m thinking that that cracked exhaust manifold may have been caused by the coolant leaking into it. Maybe? Anyway, I put some sealant (Alumiseal) in the radiator and fired it up. Started on the 2nd rotation. Ran it through a couple heat cycles while I picked up and put away nearly every tool in my tool boxes. Then I took it for a short test drive…. Unbelievable is all I can say. This thing flat ass runs. About 90KPH in one block and only half throttle. This engine doesn’t need any stinking compression… I can only imagine if it was at 100%. Yikes! OK I digress. I had the owners come drive it and before it ran out of gas on them they confirmed that it was mega better and quieter too. ;~)

Note: Now that all the dust has settled..I went back today (after it’s been driven 50 miles, head re-torqued, etc.) I got out the compression gauge and checked it with the engine at just off idle and the readings were 150PSI, so that confirms my thinking that the valve overlap was just too much to overcome at cranking speed. I feel better and it will certainly ease any fears of near future problems for the owner..Happy days.

Here’s the new look, well here’s the before pic..

Engine compartment ~Oct. 2012

After the valve job/clean up May 2013

Dolled up 1

Dolled up 2

don't mix up the ignition leads!

Dolled up 3

So what are we going to do about the engine..? Nothing for a while. There are some 3500 heads out there at reasonable prices, my choice is to find a complete engine to rebuild, but the Paris Car show provenance may negate my wishes.. Let’s play it by ear.

I need to install some seat belts (5 point harnesses if I had my way ;~)) and fix some steering wheel cracks… otherwise this story is a wrap. Feel free to email me ( About on the home page or leave comments below)

This was a fun one… dave

PS Let me add a few comments about driving this car. First I can only start to imagine the visceral thoughts that Moss and Fangio and other top Formula I and sports racers must have experienced using this power plant in a race car chassis. Did I mention this is a completely tubular frame? Boosted giant Alfin drums on all 4 corners and a gear box that begs to be shifted just for the sheer joy of it. The torque is prodigious for an Italian car and the engine noises are priceless. It will rev to 8000 RPM… happily (note to owner No, I didn’t push it that far). Did I mention it is an all aluminum body? Absolutely no body roll in fast corners and a nice steering ratio once under way. The Maserati brothers did well with this design. Hope some of you get an opportunity to get a drive or ride in one of these drop dead gorgeous cars..


And as an added bonus, here’s a U Tube clip a friend sent me of this very car a year or two before the current owner bought it at auction.

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