High Performance Head Swap

S

Sparks

Brian Mattson
You've heard this before, but Matt is definitely THE MAN! :worship::worship:

I've just installed one of his High Performance Cylinder Heads on my 85 Bertone. What an amazing transformation! Nothing subtle about it....seat of pants initial testing puts the horsepower peak about 1,000 rpm higher, and there's a lot more there. :eek:mg: :eek:mg: The exhaust system is still stock, although the cat "fell off" this morning, and had to be replaced with a test pipe. An obvious improvement. I took my serious mechanic friend for a ride, and he was amazed how strong it pulls right up to 7,000 revs.

My next step is to improve the exhaust, so I picked up a 1974 stock 4 into 2 manifold. I plan to run dual downpipes noticeably longer than the stockers, and join them into a collector before a single pipe in/out MagnaFlow. I chose MagnaFlow because they have the widest variety of sizes in stainless steel mufflers, plus they have offerings in the smaller pipe diameters that will be required.

The head swap took one month, but I cleaned & painted many of the parts, plus putting in a new water pump, all new hoses, and Euro style clamps.

Now it's time to ride, and enjoy our short summer! :):sun::excited:

Brian, "in da UP"
 
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Euro style Clamps?

What are Euro style clamps?

I am looking for hose clamps that are type "d" as opposed to gear clamps. These tighten with a machine screw pulling on two tabs on the side of the clamp. Closer to the originals.

I have found a gear clamp that has an internal metal band to give continuous protection to the hose, but like the aesthetics of the old style. Can not find them though. Perhaps the ones you used will work.

Congratulations on your head upgrade.

Paul Davock
 
Euro Style Hose Clamps

Hi Paul,

The clamps I use look very close to the original, i.e., they have the two parallel wires. The difference is that the Fiat ones have a screw that spreads the ends, whereas mine have a screw that pulls them together. Actually, they're standard British parts that I bought from Moss Motors. (I used them on my Jags & MG's). The wire clamps look much more original, but are more difficult to install than the usual strap/worm gear type. The problem is that when you pick one that seems right, and goes on easily, it will run out of travel. (Either initially, or after some time). The answer is to buy one size smaller, and "force" it on. I find that lubricating them with Armorall spray makes thing much easier.

I used Moss # 326-440 for the large hoses, and # 635-060 for heater hoses. They have many more sizes available.

Brian, "in da UP"
 
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Nix Pics

Unfortunately, the Hi-Po head looks identical to the stocker, so nothing original to show.

I will be photo documenting the new exhaust system, though. I plan to tune the secondary (down) pipes so the system peaks at, or slightly above, the torque peak. Hopefully, when upshifting, it will drop right onto a torque peak & pull strongly. Should help cruising also.

Brian, "in da UP"
 
Thanks for the Kudos Brian!

We put our best mojo into that one for you (lol).

Glad that it's behaving the way you want it.

Would be interested to hear if you had to do any tweaking / remapping of the AFM.

-M
 
Tweaking the AFM

I haven't done any tweaks yet.....I thought I had a F/A meter lined up, but no luck. Your AFM flap test sounds very similar to the "test pin" built into British SU carbs. Push it in slightly (raising the piston) to test. If the engine slows down, it's too lean. If it speeds up, it's too rich. I've tuned my MG's & Jags that way since the 60's, with no problems.

Brian, "in da UP"
 
I found the screw and wire style clamps are good at annoying me and putting deep marks in the hoses, they are much harder to get off and on than the worm gear strap type. My favourite ones so far are the "t-bolt" type.
 
Cam timing gear

Hello Brian,

congratulation for your head swap!
Midwest-Bayless web site they recommend to use an adjustable cam timing gear with Performance Cylinder Head Assy.
Do you replace the original Cam Gear ? If yes by which product?

Thanks
 
Cam Timing Gear

Hello Yves,

You may want to speak to Matt about this, but here's what I observed. The head & cam box millings caused the cam timing to lag by about 6 degrees. As the toothed sprocket has 8 degrees per tooth spacing, by moving the cam up by one tooth, the timing ends up being advanced by 2 degrees. Matt claims that the engine peaks out at 3 to 4 degrees advanced, so the difference between that and the two degrees I saw is not enough to warrant an adjustable timing pulley. So I'm running the stock one, and am happy with that.

Brian, "in da UP"
 
I'm planning to do exactly the same thing with my Bayless cam/cam box setting, once I get the head work done. :D
 
Original Gear Cam

Brian,
I'm happy to learn that the original gear cam work with the performance head.

At iddle is the engine run smoothly?
Do you keep the original exhaust manifold also?

All those question because I'm interested also by that Head Assy from Matt. I'm a weekend driver I just want to put some pep in that engine.

Thanks
 
Idle / Exhaust

The idle is just what I was hoping it would be. There is an audible syncopated loping to the idle, but nothing that causes problems. There is no lag or stumbling coming off idle, and response is smooth. Although the normal idle is spec'd as 800-900 rpm, I run mine a bit higher.

I am using the stock exhaust system presently, although the old cat "fell off" & got replaced with a test pipe. I have obtained a 1974, 4 into 2 exhaust maniflod, which I have been working on. It now has all new studs, has had the runners cleaned out, and I have increased the output opening from 1.25" stock to 1.375". (This is the internal diameter of the 1.5" OD S/S tubing that I'm going to use for the downpipes). The length of the downpipes will be increased & they will go into a S/S collecter with a 1.75" outlet. A Magnaflow S/S muffler with 1.75" in/out will complete the set-up. Hopefully, the system will peak midway between the torque & horsepower peaks.

Brian, "in da UP"
 
Sparks said:
I am using the stock exhaust system presently, although the old cat "fell off" & got replaced with a test pipe. I have obtained a 1974, 4 into 2 exhaust maniflod, which I have been working on. It now has all new studs, has had the runners cleaned out, and I have increased the output opening from 1.25" stock to 1.375".
Brian, "in da UP"
Click to expand...

Brian,

Did you just cut off the output pipe and weld on a bigger one ? Is there and internal stuff to deal with?
 
Exhaust Manifold Output

Hi Robert,

I used a mill grinder (like a Dremel tool on steroids) to mill the outlet openings & smooth the entry into them from the individual runners. As the internal runners are the same diameter as the head passages, I didn't do anything to them, outside of cleaning & polishing a bit. But when they come together in pairs, the outlet diameter was only 1/8" larger than each runner, so I opened this up by another 1/8" to 1 3/8". This allows for increasing the down tubes from 1 3/8" to 1 1/2" OD, assuming 1/16" wall tubing and matched openings.

Be careful with the mill grinder, as it takes metal off rather quickly at 25,000 rpm (and be sure to use extra eye protection, not just ordinary eyeglasses!). I used a 1 3/8" OD washer as a template to keep the openings round. A rotary sandpaper drum polished it up.

Brian, "in da UP"
 
Dyno?

Any chance of getting some numbers after the upgrades?

I'm hopping this kind of upgrade can put off an engine swap for more umph.

BrianM
 
Dyno....no such luck

One of the drawbacks of being way out in the sticks..... I do have a favorite short straight stretch of road with excellent visibility way away from anyone that I use for reference. Only have to watch for deer.... I've given up drag starts many years ago; only use rolling starts now. Stock X reached a little over 80mph. Head swap only, 90-95mph. Test pipe & AFM tweak brought it up to an even 100mph.

More important is the general feel while everyday driving. Where the stock configuration was peaking a little over 5,000 revs, it now starts pulling strongly at 5,000 up to at least 6,500, and shifting at 7,000 allows a drop right back in the strong pull. It feels like a whole different machine..:eek:mg:...Reminds me of my 1974 Alfa 2 litres (both Spider & Bertone coupe). The X is only 1.5 liters, but the same free-revving, strong pulling is there, with the X having even more revs. This is plenty of motor for me, while the new exhaust should make it even sweeter....:thumbsup:

Brian, "in da UP"
 
1.5inch downpipes are good, but make the collector larger than 1.75inch... I usually use 2.25inch and use mandrel bends up to the muffler too. 2.25 inch in / out muffler on 1500's works very well... but drop the tailpipe size back to 2inch and then the noise level will still be accepable and without any droning at highway speeds.

Getting rid of the super restrictive single out exhaust manifold and front pipe will transform the car, alone its good for around 8hp, coupled with a freeflowing exhaust - even more!

Here's a couple of pics of how I do it. (tailpipe isn't fitted)






SteveC
 
Exhaust System

Hello Steve,

Thanks very much for your response, especially the pictures! I'm glad to have inputs from someone who's done it already. The hp numbers sound great.

I envisioned a system just like this, same pipe dress and all. I have two question/comments & please do not take these as criticism, this is my first attempt at a custom exhaust....

I was planning to have the collector end right where the original cat ended, in the stock spring loaded "orbital (?)" coupler, or perhaps some other flex coupler. Your direct connection looks much simpler; have you had any breakage/fatigue problems?

The 1.75" collector outlet came from comments in the "Headers by Ed" website, www.headersbyed.com. There is much good info here, but I am referring particularly to the "Header Parts" bullet, sub-heading "Formed Collectors...(page 3)." He talks about the ratio between the total area of the inlet pipes divided by the collector output area. For street use, he recommends: " Street Use = 1.7 and up; Street/Strip = 1.4 to 1.7; Competition: avoid ratios under 1.1.....At 1:1 there is no change in areas and the collector's secondary scavenging effect is non-existent!". Going through the math, taking into account ID's, the 1.5" inlets would want a 1 5/8" collector for Street, or 1.75" max collector for Street/Strip, or a 2" for Competition. This is where I got my number. Once past the collector, the diameter could open back up to reduce restriction, although my initial thought was to keep it constant. Like I said, this is my first "design" so I'm looking for inputs.

Thanks,

Brian, "in da UP"
 
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