The Great Pumpkin - '71 Duster
Lots of rain here this weekend so I made some progress on rebuilding the 416" yesterday. After looking at the box for almost a year, I finally hung my new set of higher compression pistons on to the rods. This was a big step that I was actually kind of dreading.
Like anyone who has dealt with them, I detest Spriolox. It took me about five pistons (two locks per piston) before I was able to get them in efficiently without gouging up the inside of the wrist pin bore with the screwdriver tip. There always seems to be a point around the circumference where the lock just kind of hangs. You have to position it so it will flex and then you can work it down into the slot but it's not easy to get it there consistently, it's like a 'feel' type thing. There is nothing I could physically recognize about the process that was helpful to decrease the effort and do-overs until I realized the outside tangent of the lock had to be at a very specific angle at the same point every time. If I did this all the time I'd be better at it but once a year does not provide the muscle memory needed. It went painfully slow and I hate marring new parts but I had a method that I stuck to and eventually got it done with a minimum of destruction.
So the new slugs (Diamond 51008) are almost the same as the previous ones (Diamond 51410) but the new ones are flat tops while the previous ones were -21.5cc dish. Same compression height of 1.457". I think the flat tops might weigh a few grams more but it's probably negligible. I've spoken to several knowledgeable people and they all said there was no need to rebalance the rotating assembly which saves me a lot of hassle and money. Theoretically they should be the same zero deck as the previous ones.
I am going to transfer the existing rings from the old pistons to the flat tops. I spoke to Total Seal about it directly and they said it was fine to do that since the engine was only broken in and ran a few times on the dyno. I am very happy not to have to file new rings. This piston swap worked out pretty well!
I'm not quite ready to put the pistons in yet though. The block will need to be thoroughly cleaned before the crank goes back in. I may have mentioned a few posts back about needing to change the rod bearings as they were fairly scuffed up when I took it apart. Thankfully the mains seemed OK.
Not sure where all the dirt came from between building it and putting it on the dyno eight years ago but let's just say I didn't have a clean room at my old house and then it sat for a long time without being perfectly sealed up. I am using a 5 gallon bucket of real-deal parts washing solvent to clean stuff this time around. I need to be careful with it and not splash on any painted surfaces, it is nasty. When each piston and rod assembly was done they went back in the plastic shipping bags until I am ready to install them.
To be clear, the reason for swapping pistons is because I have a fancy new set of aluminum heads. Not sure if I've mentioned that here yet. I started the process of acquiring these particular parts almost exactly a year ago. Due to a lack of availability of certain parts because of supply chain issues and then waiting to get them machined properly, it took the better part of eight months for them to be finished and delivered. Honestly, they are things of beauty though and it was worth the wait. I don't know the flow numbers off hand but let's just say it's enough to make the kind of power that could push the stock block to it's limit.
Once the choice was made to go that route, it no longer made sense to stay with the dished pistons since the aluminum will tolerate a higher compression ratio. That obviously created a snowball effect - more squeeze changes the combustion dynamics so I've upgraded the cam to a 263/268 @ .050" solid roller. It never ends.
The hope is that the new combination of almost one point higher compression, the solid roller cam, larger headers and a somewhat "better" intake (Victor vs. Holley Strip Dominator, the Victor has a bigger plenum) should easily net a significant power increase over the previous combo of parts. It remains to be seen what the changes will do exactly but I'm betting there should be at least a 50-60hp gain over the previous 500hp number, maybe even more. The guy that did the heads thinks the car should be in the 10.20-10.30 1/4 mile range when all is said and done. I think I've created a bit of a monster.
More to come.
Lots of rain here this weekend so I made some progress on rebuilding the 416" yesterday. After looking at the box for almost a year, I finally hung my new set of higher compression pistons on to the rods. This was a big step that I was actually kind of dreading.
Like anyone who has dealt with them, I detest Spriolox. It took me about five pistons (two locks per piston) before I was able to get them in efficiently without gouging up the inside of the wrist pin bore with the screwdriver tip. There always seems to be a point around the circumference where the lock just kind of hangs. You have to position it so it will flex and then you can work it down into the slot but it's not easy to get it there consistently, it's like a 'feel' type thing. There is nothing I could physically recognize about the process that was helpful to decrease the effort and do-overs until I realized the outside tangent of the lock had to be at a very specific angle at the same point every time. If I did this all the time I'd be better at it but once a year does not provide the muscle memory needed. It went painfully slow and I hate marring new parts but I had a method that I stuck to and eventually got it done with a minimum of destruction.
So the new slugs (Diamond 51008) are almost the same as the previous ones (Diamond 51410) but the new ones are flat tops while the previous ones were -21.5cc dish. Same compression height of 1.457". I think the flat tops might weigh a few grams more but it's probably negligible. I've spoken to several knowledgeable people and they all said there was no need to rebalance the rotating assembly which saves me a lot of hassle and money. Theoretically they should be the same zero deck as the previous ones.
I am going to transfer the existing rings from the old pistons to the flat tops. I spoke to Total Seal about it directly and they said it was fine to do that since the engine was only broken in and ran a few times on the dyno. I am very happy not to have to file new rings. This piston swap worked out pretty well!
I'm not quite ready to put the pistons in yet though. The block will need to be thoroughly cleaned before the crank goes back in. I may have mentioned a few posts back about needing to change the rod bearings as they were fairly scuffed up when I took it apart. Thankfully the mains seemed OK.
Not sure where all the dirt came from between building it and putting it on the dyno eight years ago but let's just say I didn't have a clean room at my old house and then it sat for a long time without being perfectly sealed up. I am using a 5 gallon bucket of real-deal parts washing solvent to clean stuff this time around. I need to be careful with it and not splash on any painted surfaces, it is nasty. When each piston and rod assembly was done they went back in the plastic shipping bags until I am ready to install them.
To be clear, the reason for swapping pistons is because I have a fancy new set of aluminum heads. Not sure if I've mentioned that here yet. I started the process of acquiring these particular parts almost exactly a year ago. Due to a lack of availability of certain parts because of supply chain issues and then waiting to get them machined properly, it took the better part of eight months for them to be finished and delivered. Honestly, they are things of beauty though and it was worth the wait. I don't know the flow numbers off hand but let's just say it's enough to make the kind of power that could push the stock block to it's limit.
Once the choice was made to go that route, it no longer made sense to stay with the dished pistons since the aluminum will tolerate a higher compression ratio. That obviously created a snowball effect - more squeeze changes the combustion dynamics so I've upgraded the cam to a 263/268 @ .050" solid roller. It never ends.
The hope is that the new combination of almost one point higher compression, the solid roller cam, larger headers and a somewhat "better" intake (Victor vs. Holley Strip Dominator, the Victor has a bigger plenum) should easily net a significant power increase over the previous combo of parts. It remains to be seen what the changes will do exactly but I'm betting there should be at least a 50-60hp gain over the previous 500hp number, maybe even more. The guy that did the heads thinks the car should be in the 10.20-10.30 1/4 mile range when all is said and done. I think I've created a bit of a monster.
More to come.
