95 Berlinetta weight reduction and modifications.

After doing what I could with the ports I sent the heads to Stephan at Lesco (because of comments/praise I read from Rifledriver)

We agreed it may be worth the effort to go slightly oversize on the valves to allow room on the seat for a multi angle valve job.

So he installed CHE guides and had Ferrea make new valves.

Intake original- 26.5mm Ferrea- 27.25mm

Exhaust original- 28.5mm Ferrea- 29.15mm

I liked the result of the exhaust valve job.





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The intake valve job left the valve to throat percent smaller than I wanted and I felt a too abrupt transition.

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They offered to cut another angle into it but I decided I could do it myself so that's what I did. I broke the bottom 60deg cut with a 75deg cutter then blended the bottom of the 75deg cut into the port.

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Next, I didn't like the loose fit of the valve springs (inner and outer) to the retainer.

It's ideal they fit perfectly with a slight interference rather than having room to slop around.

Thankfully Ed at CHE precision was willing to take this on and he made new retainers out of titanium (Ti-17) that are not only lighter but locate the valve springs perfectly.

 

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No I don't think I will need them with the stock camshafts.

 

I may have mentioned it before but what I'm doing applies to probably no one. As far as the engine is concerned, I'm focusing on high rpm power. Basically, don't do anything I'm doing.
I'm just sharing for those that may be interested.

So going back a bit I re-assembled the heads and re-installed on the engine. Used Murray Glegg head gaskets.

Also had some underdrive pulleys made to reduce accessory rpm. (alternator/water pump/power steering) A/C unchanged.

Before doing so, I CC'd the chambers and compression ratio -now- after milling the heads and slightly larger custom valves is 11.5-1.

All things but mainly vehicle weight, driving style, compression ratio,multi angle valve job and other head work influenced my decision on cam timing.

Further- you can run less overlap with higher compression as less -dead- space exists (so less space for residual exhaust gas that needs to be cleared by -overlap-)

-slightly- larger valves but much more importantly multi-angle valve job will increase low lift flow during overlap. (so again less overlap needed)

And of course with higher static compression and no other changes, cylinder pressure may get out of hand at low/mid rpm resulting in detonation. (if someone were to drive it like a tow truck and not like me)--- loading it heavily/high throttle input at low/mid rpm instead of downshifting.

That being said, I retarded the intake cams 2 degrees and advanced the exhaust cams 2 degrees. Reduces overlap and slightly reduces cylinder pressure at lower/mid rpm.

-Trades low/mid rpm torque for high rpm power.

-Delays start of compression cycle (compression cycle starting at IVC) to reduce low/mid rpm dynamic compression.

So original cam timing-

Intake valve open- 16 deg btdc
Intake valve close- 42 deg abdc (center valve 10deg retarded)
Exhaust valve open- 56 deg bbdc
Exhaust valve close- 16 deg atdc

Now-

Intake valve open- 14 deg btdc
Intake valve close- 44 deg abdc (of course center valve still 10deg retarded)
Exhaust valve open- 58 bbdc
Exhaust valve close-14 deg atdc

With increased static compression ratio and altered cam timing, cranking compression is 210-220psi. This doesn't mean much other than the delayed intake valve closing may compensate for increase static compression at lower rpm as cranking compression is similar to original. (or to say in another way, if I put the cams back to stock, cranking compression would likely be higher/higher than what you would expect from a stock engine).

Next that I installed was rebuilt clutch and lightweight flywheel from hill engineering. Along with that, a new quill shaft from hill engineering.

Replaced a bunch of common items of course and now I've fixtured the headers and started to build replacements. As I mentioned earlier, focus on high rpm power so I'm starting with custom flanges that are angled upward to match the cylinder head exhaust port angle and using larger radius tubing.

Also- drastically reducing the primary length. Original 22.5" Now 16.25"

Increasing secondary length. Original 5" now 7".

And using merge collectors everywhere.

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Thanks guys.

My notes on the clutch weight is-

original clutch/flywheel- 25.2lbs

lightweight flywheel, rebuilt clutch with sprung hub- 17.4lbs

Fwiw, Hill engineering does not recommend using this flywheel on the street. I thought it may not be bad on my car due to the weight reduction.

Pete, I don't think it will have a drastic difference, just a slight amount. I would like to shift it at 9100. (and any rpm over stock is not going to help timing belt life)

As for compression, no I didn't lower the piston in the cylinder/measure/CC so to your point, it's half a point higher than whatever it started at. I would be surprised if actual compression was lower than advertised on these giving the cranking compression numbers and power output.

 

Pete, thanks and I agree that for best performance even with the stock engine 9000 would be better than the current rev limit. Also agreed on the timing belts. I may revise my thoughts after running it on the dyno if it seems to be happy with more rpm. (no signs of valvetrain instability)

 

Thanks everyone.

I finished that header and looked at it for a few days. Thought to myself, I think I can make it with bigger radius tubing. Also thought, if I put in enough time in the design I can make it more aesthetically pleasing.

The larger radius tubing means a lot in terms of flow. If you look at many headers available they have a very tight radius bends for some of the tubes and larger radius for others. Most still better than the originals. (Some are worse)

So, I decided now was the time so I cut the header into pieces, ordered new material and started over.....

 

The larger radius tubing added more difficulty than I expected.

Original headers are 2" centerline radius so a 180 degree bend is 5.625 outside diameter

The first header I built was 2.5" centerline radius so 6.625 outside diameter.

These are 3" centerline radius so 7.625 outside diameter.

Primary length now 17" and secondary 8". They are all exactly the same length.

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Thanks!

 

Some progress

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