So here is an odd problem. Just bought a 56 F-100 with a Y-block. Engine appears to be an amalgamation of parts. Block code is for a 54 - 256 Merc. Distributor is from a 1960 model, and most curious is that the 1-4 cylinder head has 1:54 rocker arms and the 5-8 side has 1:43's. Haven't driven it enough to notice an issue as we are having difficulty getting it to maintain idle. Doesn't run much below 1,000 rpm. I saw somewhere on the forum that someone is making 1:54 replacements. Can anyone tell me where I can find them? Also anyone have a feel for what the affect of having each bank with a different lift? Maybe not a big deal, but having OCD tendencies, I'd like them to be the same, and I'd prefer to go with the greater lift if possible.
Y - Block Rocker arms
- Thread starter rwoodcock
- Start date
Motorhead6
Senior Member
You will not notice a problem with the different ratio arms. That said, it would be a bit of a waste to put 1:54 arms on a 256 cid engine. Most Y-block engines will have the 1:43's. The 312's used the larger ratio arms.
What carb are you using? The early Fords require a correct distributor to match with the original carbs. That won't affect idle, but the performance will suffer. If you have a late model intake manifold with the original 256 heads, you may have a mismatch that causes a vacuum leak. That will never allow your engine to run smoothly below about 1,000 RPM as you stated. The fact that you have 1:54 rocker arms on one side may indicate a later model head there.
A '56 F100 deserves at least a 292cid engine with the correct carb/dist combination; either both early carb/dist or late carb/dist. I would change it out for the correct engine and use the dist you have with a late model carb.
You can find the 1:54 arms on e-bay or give John Mummert a call. He has a web site. www.ford-y-block.com
What carb are you using? The early Fords require a correct distributor to match with the original carbs. That won't affect idle, but the performance will suffer. If you have a late model intake manifold with the original 256 heads, you may have a mismatch that causes a vacuum leak. That will never allow your engine to run smoothly below about 1,000 RPM as you stated. The fact that you have 1:54 rocker arms on one side may indicate a later model head there.
A '56 F100 deserves at least a 292cid engine with the correct carb/dist combination; either both early carb/dist or late carb/dist. I would change it out for the correct engine and use the dist you have with a late model carb.
You can find the 1:54 arms on e-bay or give John Mummert a call. He has a web site. www.ford-y-block.com
Thanks for the information. When I bought it I was told it was a 292, but the block has a CBY code. I suspect they may have bored/stoked the engine. I'm tearing it down to investigate, the rockers were the 1st thing I noticed. It does have 57 T bird aluminum valve covers, ram horn exhaust, electric fuel pump, and a 2 barrel. I was also told it had a vacuum leak, but have not been able to find it, which started the tear down process.
Y-Blockhead
Well-known member
If your concerned about the different rocker ratios you could put all the 1.54's on the intakes and all the 1.43's on the exhaust.
Motorhead6
Senior Member
The vacuum leak is probably from the mis-matched intake manifold to head. One of the heads may be early Y-block and the other (the one with the larger ratio rockers) late model. You haven't given a clue as to the intake. This will not work. Both heads and intake must be matched; either early(i.e. 249/256) or late. The Mummert site has a chart with all of the casting numbers for heads, blocks and intake as a reference.
Thanks for the feedback. I'm in the process of disassembling the top of the engine to look at the numbers and determine what I do have. Engine is in the truck and I'm having trouble finding and seeing the head codes with the exhaust maniforlds on. I'll be doing that over the weekend. Good thought about how to use the rockers I have. Going to call Mummert today for a price and go from there. I'll post my findings after it's diasssembled and see if it generates any more questions I need help with. Appreciate the insight.