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I know you want to stay as stock as possible on appearance, but one thing that I believe will hold back your combo will be the standard exhaust manifold.
I run extractors in my cars, but I have swapped my motor into a car with standard exhaust manifolds (still with dual exhaust) and it felt like a slug compared to in my car. No other changes to engine or carb. The standard exhaust manifolds are fine for a low rev torquey motor as suited to the GMH mantra of the 308 being the weekend boat hauler.
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 1 user thanked Sandaro for this useful post.
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Apparently a DCR over 8:5-1 needs a very high octane fuel otherwise it’s prone to detonation. Some use @50 thou close. When I use @50 IVC of 32 degrees I get around the same as your result, 9.:5-1 DCR. Using the advertised valve closing of 64’ degrees I get 8:2.1. I noticed today, on this Aussie calculator below, if i press on the 308 reference listed with other common Aussie motors it auto fills the specs in the tables and I make the slight adjustments to match my motor. Further down the page, it has a list of common cams. If I press on the 666 cam, which is the same as my cam, it also auto fills. This give automatically gives a DCR of 8:2.1. This calculator uses the advertised ABDC 270’ and ATDC 280’ which means the cam is in reality fully closed at 64 degrees not 32. This make sense I guess, a cam can’t in reality be closed if the valve is open @0.050”. https://pcengines.com.au...VKWHHWkKNntv4Bi9zYU8-tEVEdited by user Sunday, 27 April 2025 9:01:21 PM(UTC)
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j.williams |
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The reason I want to keep it looking original is it’s a very original survivor. I agree it would improve the performance some more with extractors.
Only looking to get a little better performance out of it. Even though it’s a 308 it’s only got a lsd banjo. Don’t want to go to far and be snapping axles every time I put the boot into it. |
j.williams |
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