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 Post subject: Early GT4 build
PostPosted: Sat Feb 06, 2016 8:25 pm 
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Posts: 166
Kinda double posting here, put a thread over at the other site.
Basically took a core motor in for the build that went to OZ, turns out the core engine is a '74 complete with what looks to be the LM 'sprint pak' or somesuch. Crazy BIG cams, ported heads and manifold, 35-36-37-38 series carbs, odd lightened rods, the rod casting is not the same as the stock rods I've pulled from a dozen or more engines over the last decade. thinner beam, smaller small end and the large end is tapered or dull "knife edged", they've been shaved and balanced along with each one exactly the same weight, I've got a 0.01 gram scale and they all are exact, even the rod bolts are all exactly 40.00 grams, I grabbed the box of bolts I have from the other teardowns, those all varied between 40~41 grams. The pistons that were in this engine were all hand scribed with weight and bore size, each one had a bit of grinding to get them all the same.

When I'm not so lazy I'll get more pics up.

The steel liners were trashed, they came out corroded badly, took 3 days in the sonic tank to get the scale out. I had a set of NOS nikasil liners laying about so I used those instead of sourcing steel ones. New 11:1 narrow pin boss pistons, found a Co in Italy that specializes in pistons and they do excellent custom stuff.

I need to profile the cams, they have differing prelim data when I checked them on the bench to P6 cams. I get over 300* duration. need to dig up the notes I made. The cams are in series, 107188-189-190-191 but not stamped with a P6 as normally found. So either it's an LM engine or it's sporting LM bits.


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 Post subject: Re: Early GT4 build
PostPosted: Sun Feb 07, 2016 8:22 am 
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Posts: 4250
Madhatter wrote:
Kinda double posting here, put a thread over at the other site.


I do the same thing...different places tend to discuss different things.

Very cool for a core.....did it run when it came in? Is this a straight up rebuild?

I can see the wide lobes even in the pics. That alone tends to make the low end poor but coupled with big port and carbs I'd expect an exceptionally poor low to mid range. The Michelotto cars used 208 heads I'm told and I had one of those heads here because the guy who owned it was scratching his own head looking at how small the ports and valves where. After playing with it without a bit I mated it to a 308 intake, went up to a 38mm intake valve I think it was and got about exactly 308 peak flow but way more low lift flow and about 60% higher port velocity and dynomation was saying with stock carbs and p6 cams it would make in the 320-330hp range with better than stock low end which shocked the guy. Anyway once you plug everything into the simulator I think you'll find with those heads it will want less duration to be very happy on the street.

Interesting on the rods balancing. Do the caps alone all match too? I suspect they will. Matching total rods weights is a pain but getting them matched end to end is way more a pain. I'd never tried it before the franken12 and it took a long time and the methods I found on youtube to end weight the rods simply didn't work, at least not with my scale. The best I could do end to end was +/-0.25g but got the totals within my scale's limit. I went to pickup everything from the shop that balanced the crank damper and new flywheel done they had the shock "are the reciprocating parts were exactly the same, we've never seen that before......".


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 Post subject: Re: Early GT4 build
PostPosted: Sun Feb 07, 2016 5:22 pm 
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Joined: Wed Jan 14, 2015 1:27 am
Posts: 166
Yep all caps match, and the rods are balanced end to end. Where material was removed vary a lot too, most it was on the sides but some only had the bottom rib ground on. I've never seen this on a 308 let alone a production Ferrari.

Doing some digging on the part numbers at what not on the engine I came across this page:
http://www.dino-gt4-registry.com/08020.htm

The engine I have shares all the same data. This engine though came up from Australia.

The carbs are soaking at the moment, I don't think they've been run in a decade or more, varnish city! Once de-varnished a bit I'll strip them down and run them thru the ultrasonic tank. cad plate all the steel bits and reassemble.

Engine had not been running that I could see or tell.

Pretty much a std re-build, it's far too early of a block to modify for the 3.5 or 4L builds.


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 Post subject: Re: Early GT4 build
PostPosted: Sun Feb 07, 2016 6:46 pm 
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Posts: 4250
So a very rare car somewhere has lost it's engine :shock:

Or perhaps it was a replacement, let's hope. Either way its very cool to find stuff like that.

Is the block different then the later ones? I always thought all 308 blocks were basically the same.


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 Post subject: Re: Early GT4 build
PostPosted: Sun Feb 07, 2016 7:51 pm 
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Posts: 166
The crank was balanced and ground and you could tell it had a fair amount of tweaking done to it, unfortunately the journals are scored and would require an undersize to use again. I have a bunch of great OEM cranks to choose from the 3.5 and 4L builds so I did not use the original one.

The block is not very different visually, the front cover is of course the old inboard bearing one. The block did require heating to install the liners, it checked to spec per the WSM but on the tight end. From the dozen or so other 308 blocks the liners practically fall out and fall in, so that was different.

Just measured the intake cam, 0.370" lift
duration at lift,
386* @ .01"
296* @ .02"
264* @ .05"


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 Post subject: Re: Early GT4 build
PostPosted: Sun Feb 07, 2016 10:50 pm 
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Madhatter wrote:
264* @ .05"


That's not crazy duration. My H-D roadrace engine with similar bore and stroke to the 308 was 270 ...close and it idled pretty well but with type slide carbs.


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 Post subject: Re: Early GT4 build
PostPosted: Sun Feb 07, 2016 11:14 pm 
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Joined: Wed Jan 14, 2015 1:27 am
Posts: 166
No not crazy in the grand scheme of cams. However it doesn't match the specs for the P6 cams that I have.

P6:
duration at .01", .02", .05" & lift
- Intake 291 268 243 (.365 new)
- Ex 285 261 233 (.340 new)


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 Post subject: Re: Early GT4 build
PostPosted: Sun Feb 07, 2016 11:25 pm 
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Joined: Thu Jan 01, 2015 6:47 pm
Posts: 4250
I have the same lift at .365 but 370 @.050 duration....which is probably wrong and is at 0.5mm which matches your 0.02" number.


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