Thread: Project Sebring GT Spyder

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Thanks Whiplash. Glad you're enjoying it.

I bought this engine as a "practically new" piece that had only been test run. Up until now I had never been able to verify any of that story. I was pleased to find that the lower end did actually look brand new. There was no staining or other signs to indicate that it had many hours of run time. The parts looked like they had just came out of the box. The cam showed no signs of wear. So far, I'm pleased.



While I'm tempted to just hook it up and run it, not having any real history on it makes me cautious. The story that came with this engine makes me suspicious of it's history. Also, the hot rodder in me just won't me let run it as is. You know, the little devil on your shoulder that keeps saying "Hot rod it!!!". The early LS engines had some faults that were corrected in later engines. This is a first year engine and I have a few upgrades planned.

It may sound crazy to some, but my plans are to tear it down and inspect everything. Hopefully I'll wind up with a pile of fairly new parts. Then I can reassemble it with the upgrades and be reasonably confident that it will hold together. So far these are my planned changes:

I picked up a set of older CNC ported heads for a good price. They will accept a higher lift than the stock heads and should really improve the breathing. I need to CC them to verify chamber volume.

The rod bolts on the early engines are known to be weak. I'll swap them out for ARP's and have the big ends checked for roundness. I talked to a reputable machine shop and they told me it could be done without pulling the pistons off the rods (they are press fit). He said they will sometimes have to hone them slightly with the ARP bolts.

The oil pump will most likely be changed to a Melling. The early pumps supposedly have cavitation issues and can lose suction at high RPM's.

The cam will get changed. Right now I'm looking at around 224@.050 with somewhere about .580 - .600 lift and 112* lobe separation. The heads will handle more than that, but that has been identified on several forums as a good daily driver type cam for an LS and manual trans. The cam will most likely be a Howard's, but I'm open to suggestions. You out there Tech?

The trunions on the rocker arms will be upgraded for the extra load the cam will put on them.

The cam swap will require the cam position sensor be moved to the timing cover with an LS2 cover and timing gear.

The valley cover will be swapped to an LS6 part. The PCV was moved from the valve covers to the valley cover on that engine to solve a small oil consumption issue.

The LS1 intake is being swapped out for an LS6 to better support what the heads can flow. I also picked up an 80mm BBK throttle body. It's just a little larger than stock, but is "supposed" to flow 30% more. That's according to BBK. I'll also be using a larger 5 wire mass air flow sensor and plumbing cold air to the intake.

I'm going to go to a full return type fuel system and the injectors will be resized.

I have found a tuner within 60 miles that has a good chassis dyno. His dyno can do road simulation tuning and not just full throttle pulls. That's important to me since I want to drive this car like a stocker on the highway. His reputation is good, so I'm willing to take a chance. That's the reason for the rod bolts and oil pump swap. Hopefully, to keep it together on the dyno. It'll probably get pulled on harder there than I ever will. FWIW - My tuner thinks this combo should put about 400 HP(maybe a little more) to the rollers. That should be fun in a 2500 lb car.

He is going to do an initial "safe" tune so that I can break the engine in before we thrash it. That's real important to me. Dyno's scare the crap out of me. I know they are necessary, but I personally know of more than one person that had mechanical carnage on a dyno. Beating on an new unbroken in engine never really sounded like a good idea to me. Looks like I better make sure the driveshaft is up to it.

I've already started collecting some of the parts for the upgrades. I like engine work and I'm looking forward to it. I still have a lot more work to do before I get there though. Guess I better get back to building.

just read thru your build, man you are completely redesigning your chassis/suspension, it looks very sturdy. Nice work. I did rings and bearings on my 5.3 last winter, I wasn't after anymore HP for my stude project, I'll just be happy when I hear it run OK. The LS engines are such a pain to put back together, nothing like a small block chevy or ford of old. Also they are super finicky about the block and head gasket surfaces or those metal gaskets won't seal.

Thanks V8. The chassis on this car couldn't handle the power of a very low power SBC. I had to make some improvements if I wanted to have more power.

I know what you mean about the LS engine assembly. I've been studying them as much as I can. They are certainly different than the older engines I'm used to. My engine is a very early one and can't use the MLS head gaskets. I'm limited to the graphite gaskets. There is a notch in the heads that prevents using the later gaskets.

I had my heads shaved by an old machinist who apparently was not up on the newer ls motors and decided they were not smooth enough for the mls so I used the graphite just to be safe. the guy could not get the cam bearings in right, he kept insisting they were right but when I looked with a mirror they were not lined up with the holes, ended up taking it to another shop to do it. I would recommend checking them to be sure.

Originally Posted by johnboy

Don't wish to digress from the theme of your thread; but couldn't let that remark go by without commenting on it:
A good friend of mine has a Sunbeam Tiger, I've been in it several times, but Ian has never allowed me to drive it. (Perhaps he doesn't trust me? I wonder why!)
I can vouch for the fact that they go like a scalded cat, and stick to the road like dogs**t to your shoe.
A real 'fun' car!
They're almost as much fun as the Cobra!
(...and Ian has never driven that!)

Understand the Tiger is for sale..

Originally Posted by Kiwidreamer

Understand the Tiger is for sale..

How much

A few comments-------don't resize LS fractured cap rods unless you have the OVERSIZED OD bearings-----

Issue of oil pump cavitation is internet hearsay

Many bolts in modern engines are torque to yield and need to be replaced after torqueing only ONE time

Many torque values are torque to an ft lb valve then certain number of degrees rotation after that

Thread lube/ sealer usage is an EXTREMELY important issue

Front/rear covers (crank seal) alignment needs special procedure to insure sealing-----

If using high lift cam with high spring pressures modify rockers with the better roller bearing/pivot shafts

What is the point of the new fasteners needing to be replaced after a single use?

Things like that feel like a manufacturing scam to me.

From an engineering viewpoint, it sounds as if the nominal torque value takes the fastener into its plastic region; Young's modulus. Just doesn't seem like a smart way to do businesses.

Between the expensive throw away bolts and expensive gaskets it doesn't make you want to tear into one of these things unless you have to.

Just remember the new technology invoved with aluminum engines-termal expansion is huge and you need to contain those combustion pressures/heat if your going to change heat to torque----------- and sealing up the new thinner oils does take more precise methods-------

As for the bolts---------if they weren't tightened into an area that did the job you would be blowing out the gaskets-----and without a very PRECISE method guys would be over stressing the block threads -remember its now aluminum, not cast iron---------The old rule of thumb about 1 1/2 times diameter for thread length engagement was left behind in the 90s-or 3 decades ago------or last century---------

Most of these bolts in question are torque to yield and are designed to stretch to add pre-load through the fastner. That being said, they can or do stretch and will break or be weak and not do their job.

Hotrod 46, the inside of that engine does look very nice.

Its really all about the threads in the aluminum blocks( or other components) for many years aircraft was where alum was used to save weight and components had helicoils installed from the intial build-----wasn't used as a repair as is commonly thought-------altho the use of heli coils as an excellent repair did develope over years.

Today the use of torque to yield and throw away after on use is a process to protect the bigger, more complicated , more expensive parts and throwing away used bolts is cheaper than repairing pulled out threads and the results of that-blown gaskets, leaks, etc, etc

After a little research on torque to yield bolts, it appears that my initial assessment was correct: the fastener is taken into the plastic region: it stretches past the point from which it will recover.

And they (bolt) should fail-saving the block!!!!!!!!