chevygod Posted February 28 Share Posted February 28 Hi All, Looked high and low, cannot find an accurate image that show the difference in size, length, or shape of the lever arms on small block and big block fuel pumps. I'm chasing fuel supply issues on a 454 and will be buying a new pump, but want to know what I currently have, and what I have bought in the past and see if it was right or wrong. Thank you for any input, Tom Quote Link to comment Share on other sites More sharing options...
MC1of80 Posted February 28 Share Posted February 28 Both work on each other. Usually though the big block and high performance small blocks had the "canister" type pumps. The lower body of the pump is bigger. What is done to your 454 and what is it doing that you feel it's pump related? 2 Quote Link to comment Share on other sites More sharing options...
Scott S. Posted February 29 Share Posted February 29 Hey Tom, Are you using a "W" block or Mark 4 block ? Rumour is that the Mark 4 uses a different pump, whereas the "W" uses the same one as a small block except with a bigger holding tank and discharge fittings. Hope that helps, and welcome to the machine. 1 Quote Link to comment Share on other sites More sharing options...
chevygod Posted March 5 Author Share Posted March 5 All, sorry for the late reply, lot of catching up on other projects and this was set aside. Thomas, I also thought that they were interchangeable, and had run SB pumps on 402's and 454's with them usually working until this instance, which promoted the research. I then found many folks pointing to the SBC pumps having a different lever arm that the BBC pumps. Looking deeply at what the application listings show, there is some sort of major difference. Scott, this is a Mark 4 454 from a 70's truck (I was told). So it's a normal BBC. I have a original 402 70 Monte, with what was probably a BBC lever pump. Not driven, needed a pump when the one on it started to leak badly, so i threw on a spare 305 pump, with out comparing the arms. It starts and runs short distances fine. Has not seen major open road driving. The 454 I'm currently dealing with is in my 70 Concours Wagon, it had a pump on it when i bought the car, dunno the exact type, but it failed, so I bought a "correct" 3 port big can 72 and up 454 pump at O'Reilly's. Did not compare the arm. Ran somewhat good, but sometimes had a dead spot above 45mph. Didn't pressure check anything, took it off and took it back and was given another. Same thing. I needed a 3 port pump, so borrowed the pump off my 72 Monte, 350 engine, 3 port. Put it on and it ran great for weeks. So bought a new one (72 SBC 3 port at O'Reilly's) and installed it. This pump has run well until recently, which is what started this investigation. The motor now has started to sign off at about 35mph. I have also swapped good running carbs around trying to narrow this down, one raised the point of stumble but it's still there. What I've found online is that an SBC pump on Big Block will sometimes work but usually results in low or no pressure, BBC on Small Block may work but many ended up with a bent or broken lever arm. Also, some pointed out that older AC Delco pumps had a W on the arm if it was a BBC pump. Neglecting all of the differences in shape and port size and quantity, many pointed to the arms being differently sized, so that is why I am trying to find a good comparison of the lever arms. I wonder now if the supposed BBC pumps I got earlier had incorrect arms, and maybe the reason some of the small block pumps I've had would work is because the arm is in between small block and big block sizing. I am also going to be trying to measure the fuel pump lobe offset and therefore the push rod travel, just to make sure I am not losing the lobe on the cam. Thank you all, Tom Quote Link to comment Share on other sites More sharing options...
Scott S. Posted March 5 Share Posted March 5 Just a thought, not meaning to add to the variables, but the rod between the cam lobe and the pump arm could also add to the mystery. Quote Link to comment Share on other sites More sharing options...
Scott S. Posted March 5 Share Posted March 5 Hey Tom, I found a couple images on a Holley affiliated website that might be of some help.... Top one is for a small block.. Scott. 3 Quote Link to comment Share on other sites More sharing options...
Rob Peters Posted March 5 Share Posted March 5 47 minutes ago, Scott S. said: Hey Tom, I found a couple images on a Holley affiliated website that might be of some help.... Top one is for a small block.. Scott. Whoa.... That pump lever looks to be chrome.... that could be a deviation from factory correct and could throw someone into another judging class. rob 1 5 Quote Link to comment Share on other sites More sharing options...
jft69z Posted March 5 Share Posted March 5 5 minutes ago, Rob Peters said: Whoa.... That pump lever looks to be chrome.... that could be a deviation from factory correct and could throw someone into another judging class. rob Good catch. I'll bring the video borescope camera to Carlisle. 1 3 Quote Link to comment Share on other sites More sharing options...
Dtret Posted March 5 Share Posted March 5 59 minutes ago, jft69z said: Good catch. I'll bring the video borescope camera to Carlisle. As long as that’s all you plan on using it for. A lot of gator aid and cleaning solution going on here later. No double checking for cleanliness. 1 Quote Link to comment Share on other sites More sharing options...
chevygod Posted March 6 Author Share Posted March 6 Hi Scott, I am going to look at pushrod length. However, the pics of the arms are exactly what I was looking for. Those give a good indication of the differences. Thank YOU! And the plating is probably bright zinc, but still incorrect, hah! Best regards, Tom Quote Link to comment Share on other sites More sharing options...
jft69z Posted March 6 Share Posted March 6 17 hours ago, Dtret said: As long as that’s all you plan on using it for. A lot of gator aid and cleaning solution going on here later. No double checking for cleanliness. Reminds me of an old joke... Q: What's the worst part about rectal thermometers? A: The taste. 🤮 3 Quote Link to comment Share on other sites More sharing options...
Scott S. Posted March 6 Share Posted March 6 18 hours ago, chevygod said: Hi Scott, I am going to look at pushrod length. However, the pics of the arms are exactly what I was looking for. Those give a good indication of the differences. Thank YOU! And the plating is probably bright zinc, but still incorrect, hah! Best regards, Tom Hi Tom... These are both aftermarket "high performance" replacement items. I don't think G.M. makes them, but, like you said, they should give you an idea of the difference.... The push rod should be 5.75" long by 0.50" dia. Same rod for both big and small blocks. Scott. Quote Link to comment Share on other sites More sharing options...
Scott S. Posted March 6 Share Posted March 6 3 hours ago, jft69z said: Reminds me of an old joke... Q: What's the worst part about rectal thermometers? A: The taste. 🤮 But the best part is the nurse administering the test. 1 Quote Link to comment Share on other sites More sharing options...
Leghome Posted March 6 Share Posted March 6 I am glad you tried but don't even wanted to think about trying it 5 hours ago, jft69z said: Reminds me of an old joke... Q: What's the worst part about rectal thermometers? A: The taste. 🤮 1 Quote Link to comment Share on other sites More sharing options...
jft69z Posted March 6 Share Posted March 6 10 minutes ago, Leghome said: I am glad you tried but don't even wanted to think about trying it I didn't try that... 1 Quote Link to comment Share on other sites More sharing options...
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