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Heads and cam ?
- Thread starter polara383500
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polara383500
Member
It could take a yr to build it but when it’s done it’s gonna be a bad convertible!
It made perfect sense.
twostick
Senior Member
I wouldn't panic just yet. Unless it has a LOT of miles on the shortblock I would either put the new heads on and drive it for the time being or find a used 906 or 452 head and put that on it.
I would seriously doubt those marks are anything other than that. It takes a pretty serious divot to cause any structural compromise to the central mass of the piston top.
Case in point: I had a 429 Ford many moons ago that dropped an intake valve. The head came off it and the piston drove it deep into the seat on its edge which left an equally deep 3rd valve relief in the piston.
I was on a job 300 miles from home so the next day I went to the local scrap yard and bought a used head off a 460 LTD cop car and installed that with a new head gasket and figured I'd be lucky if it made it out of town.
I drove that truck and beat it mercilessly for a year after that until I melted 3 pistons out of it one night being a little drunk and a lot stupid.
There was about 1.5" of the circumference of the piston at the rear gone. You could see between the inside of the rings and the piston.
One of the pistons was the one with the 3rd valve relief. It was none the worse for wear after all that time.
Kevin
polara383500
Member
Not sure on what it has on it for miles! Odom says 61 the way it looks could be 161,000 the heads had new fel-pro head gaskets so it’s already be apart before and don’t know why!!
twostick
Senior Member
polara383500
Member
130 on must of driver and 121 in two 90 in one and 130 passenger!
From the tone of the comments, it seems that the "bad convertible" will very possibly demonstrate how "bad" it might be with the stroker motor in it. No problem with that, except that you'll be dealing with a unit-body car rather than a "full-frame" car. What difference might that make? On a hard launch, with littrle wheel spin, the engine's torque can put some "twist" into the body structure itself. Even on non-convertibles, that's why some "street cars" carry ONE front wheel and not both front wheels after launch at the drag strip. If they carry both front wheels evenly, then the car most probably has a full roll cage and a structure to tie the two "frames" together in the middle.
I've seen come Chrysler product convertibles which have developed stress cracks where the rh quarter panel attaches to the center body panel between the quarter panels. I was told this was a trait of such cars. This was years ago well before the populary of stroker motors even existed, so those stress cracks were with 440/375 motors. The particular car was a '70 Coronet R/T convertible.
Wonder what those little wedges are for at the rear of the door frame, above the striker bolt? To help limit body flex during normal operation. Almost all convertibles have them, even non-Unibody cars, AND Unibody cars with t-tops (think '77-'81 Camaro/Firebird cars . . . which could stand some sub-frame connectors without any t-tops, anyway). NOT to forget the real possibility that the frictions in the TF would need upgrading to handle the additional torque, OR upgrades to the rear suspension so all launches are good ones.
No desire to dampen your dreams, but there might be some side issues that need to be considered/fixed so that your end result is as good as it needs to be.
When you get the engine out and look at it, remember that you're looking at an engine "with wear", which might not look good to you, but as it was running decently well before hand, things don't have to look "perfect" to give good performance. PlastiGage the main and rod bearings to see where those clearances are. "Marks" on the cyl wall, unless you can hang a fingernail in them, can usually be honed out (ref "Reignited" YouTube channel where he does that on a Gen III Hemi). IF there were no "cold start piston knocks", then the piston-to-cyl wall clearance might still be decent. I know there might be a desire to condemn what you have, as evidence that it needs that stroker kit in it, but to some eyes, a "used motor" might look "worn out" when it's not. BTAIM
As for the head, it might just need a valve job, with new gaskets/seals and such. Might get somebody to Zyglow the piston crown to check for cracks. Or some other method to check for cracks on non-iron engine pieces.
In the end, your money, your dreams.
Just some respectful thoughts,
CBODY67
I've seen come Chrysler product convertibles which have developed stress cracks where the rh quarter panel attaches to the center body panel between the quarter panels. I was told this was a trait of such cars. This was years ago well before the populary of stroker motors even existed, so those stress cracks were with 440/375 motors. The particular car was a '70 Coronet R/T convertible.
Wonder what those little wedges are for at the rear of the door frame, above the striker bolt? To help limit body flex during normal operation. Almost all convertibles have them, even non-Unibody cars, AND Unibody cars with t-tops (think '77-'81 Camaro/Firebird cars . . . which could stand some sub-frame connectors without any t-tops, anyway). NOT to forget the real possibility that the frictions in the TF would need upgrading to handle the additional torque, OR upgrades to the rear suspension so all launches are good ones.
No desire to dampen your dreams, but there might be some side issues that need to be considered/fixed so that your end result is as good as it needs to be.
When you get the engine out and look at it, remember that you're looking at an engine "with wear", which might not look good to you, but as it was running decently well before hand, things don't have to look "perfect" to give good performance. PlastiGage the main and rod bearings to see where those clearances are. "Marks" on the cyl wall, unless you can hang a fingernail in them, can usually be honed out (ref "Reignited" YouTube channel where he does that on a Gen III Hemi). IF there were no "cold start piston knocks", then the piston-to-cyl wall clearance might still be decent. I know there might be a desire to condemn what you have, as evidence that it needs that stroker kit in it, but to some eyes, a "used motor" might look "worn out" when it's not. BTAIM
As for the head, it might just need a valve job, with new gaskets/seals and such. Might get somebody to Zyglow the piston crown to check for cracks. Or some other method to check for cracks on non-iron engine pieces.
In the end, your money, your dreams.
Just some respectful thoughts,
CBODY67
I have a professionally built 520" stroked 440 in a '68 Sport Fury. Building a really good stroker is not cheap and there are a lot of things that come into play besides building an engine. You need to have a strong transmission with the right torque converter for your set up. The fuel delivery system will need to be upgraded as will the exhaust and cooling system. I love my stroker. I built it for street and strip use but there are pros and cons. I have other C Body's with stock engines to drive if I want to take a long trip, which is not something I can do with my Sport Fury as it has 3.73 rear gears and a short tire.
If you decide you want to go the stoker route and want someone else to build the engine and have the right machine work done look at the Facebook page for Auto Services of Old Saybrook (Connecticut). Not around the corner from you but within a few hours from you.
CBody67 brings up some good points. Even with traction limited G70/15 bias ply tires on my car (raced in a stock appearing, stock tire class) the left front wheel gets lifted up pretty good on launch.
If you decide you want to go the stoker route and want someone else to build the engine and have the right machine work done look at the Facebook page for Auto Services of Old Saybrook (Connecticut). Not around the corner from you but within a few hours from you.
CBody67 brings up some good points. Even with traction limited G70/15 bias ply tires on my car (raced in a stock appearing, stock tire class) the left front wheel gets lifted up pretty good on launch.
polara383500
Member
With it being a vert I’m not gonna want to do a lot under the car to stuff everything up!
After thinking about it I’m gonna pulled the motor this wk and see what the bottom it looks like! If bottom end is good might just by a rebuild kit .30 after go back stock with a cam. I might be able to do that rt quicker! The heads I have there not worth the repair so I was just gonna go the stealth heads rt too!
I don't know if your Polara is a 67 or a 68. Keep in mind that 67 & 68 used different heads and went from a closed chamber to an open chamber design.
polara383500
Member
It’s a 68! A buddy said there open and told me to go closed!
The open chamber heads also came with the 1.74" exhaust valves, which only appeared on the '67 440/375 motor before that. Which would make that '67 motor the only one with that valve size in a closed chamber head, from the factory (other than some specific race motors). Otherwise, the closed chamber heads would require machinng to replace the stock 1.60" exhaust valves with the larger 1.74" exhaust valves. The intakes were 2.08" on both combustion chambers.
More-evolved technology now indicates that a "closed chamber" situation can have more beneficial turbulance for a better "burn", it seems. Have not seen any real documentation of increased power, that I know of. David Vizzard's book on Small Block Chevys details why the closed chamber can work better and be more tolerant of higher compression ratios without detonation. FWIW
Enjoy!
CBODY67
More-evolved technology now indicates that a "closed chamber" situation can have more beneficial turbulance for a better "burn", it seems. Have not seen any real documentation of increased power, that I know of. David Vizzard's book on Small Block Chevys details why the closed chamber can work better and be more tolerant of higher compression ratios without detonation. FWIW
Enjoy!
CBODY67
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