I have read that the heads from '77 and newer are better than the previous years. Would there be any noticeable improvements on my '74 250 with 45k miles on it if I were to swap it to a newer style head?
Eons ago I replaced the head on my '75 Granada 250 with one from '77, couldn't tell a difference. YMMV.
Could it be related to the hardened seats on the later 70's vehicles with the transition to unleaded fuel? Certainly if you are rebuilding an older head and go with the correct seats and valves, then that would be moot. As far as any other changes to the head, no idea here.
Best bang for the buck to a 250 is swap to a pre-emission (69-72) timing gear set and playing with the advance springs inside the distributor. The '77-'80 head came with larger intake log, 1240cc v 1345cc flat log/ 1420cc hex log. The 77--up 6 cyl also has larger intake valves, 1.659" v 1.75" Will they be a noticeable improvement with just a head swap? You will notice a little, but your passenger might not notice anything different
actually an older small block six head with smaller combustion chambers would add to Compression Ratio and increase performance. .. improvement with the larger valves would be incremental, but valve job could could be opportunity to squeeze some easily available performance out of the restricted 250. The anvil strong small block six 250 with simple upgrades will add drivability to the Maverick experience. .. all stock cylinder heads produced between 1963 to 1968, had approximately 52cc combustion chambers, while the cylinder heads produced from 1969 onward had approximately 62cc combustion chambers....key is to measure carefully and record the results, then mill the head accordingly to obtain the desired compression ratio. Typically, milling the head .010" will result in an approximate reduction in volume of 2cc's. For example: if your cylinder head currently has 62cc chambers, and you want 52cc's, you would need to mill .050" off the head to reduce the chamber volume by 10cc's. ... with a little more compression , back-cut valves, DSII upgrades, maybe carb tune or swap', 250 can be optimized . hav fun Stock 250 with minor engine mods and Vortech Supercharger added for improved Maverick drivability: .
