Tetraboost on Lower Compression V8 - Worth It?

P6Jon

New Member
So I just recently bought my 1974 P6B. I’ve only been able to take it out once so far with our current fuel shortage, but filled up with Esso 99 octane (ethanol free) before a nice 40 mile drive. Ran beautifully, no pinking or any problems from what I could tell.

I’ve come across Tetraboost, which will add TEL to unleaded. In my case, I could make 101 octane ethanol free fuel, so a genuine 5 star.

I know it’s been discussed plenty on here, but I can’t see any advice about the later 9.25:1 V8s like mine. Is it worth it really worth it, and more importantly could it actually do any harm, or is the worst case scenario it’s a total waste of money but I have peace of mind?
 
It won't do any harm, the higher cr engines were designed for 5 star, and will notice the benefit, the lower cr engines less so.
 
It won't do any harm, the higher cr engines were designed for 5 star, and will notice the benefit, the lower cr engines less so.

Thanks Harvey. I think it’s just the peace of mind that makes an “additive” worth it, but Tetraboost definitely stands out as it’s not really an additive. I’ve always said aluminium heads don’t need additives, but I’ve never owned a car this nice so I think I’ll eat my own words now! :LOL:
 
I had a 289 Mustang with cast iron heads with no valve seat inserts, I was concerned initially about valve seat recession, a chat with a cylinder head specialist dispelled my fears. The car had solid lifters and a valve lash of 0.022" cold / 0.018" hot. I set the lash at the time I rebuilt the engine, I ran the engine on super unleaded for six years and never needed to re set the valve lash. There was no recession.

A Rover V8 has hardened valve seat inserts, there will not be any problem with unleaded.

If you wish to mix up the equivalent of 5 star fuel fine, but you will only benefit if you advance the ignition timing accordingly, otherwise it will not make any difference to performance.
 
A Rover V8 has hardened valve seat inserts, there will not be any problem with unleaded.

If you wish to mix up the equivalent of 5 star fuel fine, but you will only benefit if you advance the ignition timing accordingly, otherwise it will not make any difference to performance.

I personally don’t think an aluminium head would require lead replacement either, and the lack of posts about V8 valve recession on this forum probably confirms that. But I’ll err on the side of caution I think, as there is definitely debate about it and it’s only a few pence extra per litre!

Valvemaster certainly is much cheaper though and also comes highly recommended. It’s undoubtedly much safer to store and handle too. So I might use that instead.
 
I've used mine on unleaded 91 for the 20 plus years, no problems to report.
 
I have been running my 3500S on standard 4Star, as available from any petrol station ( before the current shortage!) and no observable problems. Various mechanics have tunes the engine over my ownership, and I guess the ignition has be re-times for this fuel.
I did once consider fitting 'unleaded' heads, but looking at the cost, decided to put it off until I had problems.
It is my understanding that valve seat recession is wot if you spend long periods cruising at full speed, whihc is not how I drive. HOpefully I can go on driving the car like this.
 
Thanks for all the replies. I think I’ll carry on as I started, and as I did in my old Jaguar XJ6 with an aluminium head, and just use super unleaded without any additives. If I come into any trouble, well the worst that happens is the head gets rebuilt better than new with even harder valve seats, so not the end of the world :D
 
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