Controversial question - I hope! Is there a better type of cylinder head than an Ally 9E to use on my Mag engined trials car. Phoenix crank, Pigsty trials cam and indeed built by them about 12 years ago. I get about 125 psi and 30 bhp now,not sure how that calculates as a compression ratio?
I was thinking of changing to a new Ricardo one, will there be any more power for my money?
(20-11-2017, 10:02 AM)bobthompson Wrote: Controversial question - I hope! Is there a better type of cylinder head than an Ally 9E to use on my Mag engined trials car. Phoenix crank, Pigsty trials cam and indeed built by them about 12 years ago. I get about 125 psi and 30 bhp now,not sure how that calculates as a compression ratio?
I was thinking of changing to a new Ricardo one, will there be any more power for my money?
According to Stuart Bonney in a 2006 paper 'Compression Ratios and Cylinder Compression Testing in Ford N Series Tractors'- compression pressure checked with a Compression Tester will be 17 to 20 times the compression ratio with a standard street type cam.
If you take an average of 18.5 for a 6.2 : 1 CR you get 115 PSI at a cranking speed of 120 rpm (The Ford specification)
20-11-2017, 12:49 PM (This post was last modified: 20-11-2017, 01:19 PM by Speedex750.)
Hi Bob,
I too would suggest you stick with what you've got. At 30hp and decent compressions you're right on the money. Any of the new cylinder heads, good and well made that they are, wouldn't give you much more, you probably wouldn't feel the difference on a section. If you're trialling through the VSCC you couldn't use any of the sixties heads as well as they wouldn't be eligible. If you're after a little more bottom end and mid range power/torque you could try getting the compression up a little by skimming the head to the limit of the valve lift and ensuring the pistons are topping to the deck of the block. Other than that; if the head is installed and you're not having gasket or plug problems; in my humble opinion you're best sticking with what you've got.
Photos of heads old and new are shown the Speedex site.
20-11-2017, 09:55 PM (This post was last modified: 20-11-2017, 09:57 PM by bobthompson.)
(20-11-2017, 12:49 PM)Speedex750 Wrote: Hi Bob,
I too would suggest you stick with what you've got. At 30hp and decent compressions you're right on the money. Any of the new cylinder heads, good and well made that they are, wouldn't give you much more, you probably wouldn't feel the difference on a section. If you're trialling through the VSCC you couldn't use any of the sixties heads as well as they wouldn't be eligible. If you're after a little more bottom end and mid range power/torque you could try getting the compression up a little by skimming the head to the limit of the valve lift and ensuring the pistons are topping to the deck of the block. Other than that; if the head is installed and you're not having gasket or plug problems; in my humble opinion you're best sticking with what you've got.
Photos of heads old and new are shown the Speedex site.
Dave
(20-11-2017, 09:55 PM)bobthompson Wrote:
(20-11-2017, 12:49 PM)Speedex750 Wrote: Hi Bob,
I too would suggest you stick with what you've got. At 30hp and decent compressions you're right on the money. Any of the new cylinder heads, good and well made that they are, wouldn't give you much more, you probably wouldn't feel the difference on a section. If you're trialling through the VSCC you couldn't use any of the sixties heads as well as they wouldn't be eligible. If you're after a little more bottom end and mid range power/torque you could try getting the compression up a little by skimming the head to the limit of the valve lift and ensuring the pistons are topping to the deck of the block. Other than that; if the head is installed and you're not having gasket or plug problems; in my humble opinion you're best sticking with what you've got.
Photos of heads old and new are shown the Speedex site.
Dave
Thanks Dave - it was looking at the Speedex site that made me wonder if it was worthwhile changing after all.
Great picture and shows the difference clearly, but is there enough difference in performance to make it worth putting my hand in my pocket?
That is the big question.........
05-01-2018, 08:35 PM (This post was last modified: 05-01-2018, 08:59 PM by Steve Jones.)
Without any doubt, yes. At least that's my experience and I've got Ricardo heads on three engines. The only issue (if it is one) is that with the plugs being over the valves, you can't put the proverbial pencil down the hole to identify TDC.
