Unleaded petrol

[johnpower]

I am reconditioning a Ford 302 engine manufactured in 1978 and I am fitting new valves but regrinding the original valve seats. Will the engine run on unleaded petrol or will the valve seats need replacing?

[mike huddart]

, Dear John,...yes, valve seats need replacing, why not put bigger valves in at the same time, while you,re making bigger holes for the vave seats, you might as well make some even bigger ones and get a performance hike for the cost of a set of valves.... a decent set (16) of stainless valves is about £80....Mike

[mike huddart]

Dear John, I have had second thoughts on your heads, you really should fit new seats, they rely on the valve rotaters fo exhaust seat cooling, but by the time you add all the costs up youre getting close to the cost of an aftermarket set of heads. For a mild spec engine and low mileage, you should be OK as is. Do the sums first!....Mike

[dingocooke]

Mike you've probably forgotten more about yank V8's than Ill ever know, but I always assumed that, as unleaded was the only fuel available post 1972 in USA, that any engine built after that would be fine (valve seats wise) running unleaded.

[mike huddart]

Yes,youre quite right, I am the worlds leading expert on american engines and have most of the best smart alec answers to just about anything on V8s. Hoever I don,t know everything about petrol but know enough to know whatever they put in american petrol (gas) in 1972, they don,t put in now. So whatever they made exhaust seats of in 1978, induction hardened or whatever, won,t cut the mustard now.Just about every 70,s 80,s marine Ford we see. has severly rescest and/or cracked seats. However John isn,t going to sea in his Cobra so should survive OK without converting his heads.If he was planning on something serious, towing a caravan or Le Mans 24 hrs etc then hardened seats and bronze guide inserts would be a must .....Mike

[wilf]

Mike - is it the more severe duty cycle for marine engines that causes worse valve seat recession?

[dingocooke]

Originally Posted by mike huddart

Yes,youre quite right, I am the worlds leading expert on american engines and have most of the best smart alec answers to just about anything on V8s. Hoever I don,t know everything about petrol but know enough to know whatever they put in american petrol (gas) in 1972, they don,t put in now. So whatever they made exhaust seats of in 1978, induction hardened or whatever, won,t cut the mustard now.Just about every 70,s 80,s marine Ford we see. has severly rescest and/or cracked seats. However John isn,t going to sea in his Cobra so should survive OK without converting his heads.If he was planning on something serious, towing a caravan or Le Mans 24 hrs etc then hardened seats and bronze guide inserts would be a must .....Mike

Good answer Mike!! Ta for the info

[mike huddart]

Wilf, re. marine engines, its because their always under heavy load, particularly pulling skiers, like the 82 351w we did last year, all the exhaust valves had sunk over .200" and 6 where cracked. Similar problems with other HD use ,racing ,towing etc , but not as bad........Mike