DuPuis Family Cobra Build

Discussion in 'Hangar Talk' started by Ted DuPuis, Aug 3, 2018.

  1. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Camshaft arrived!

    87D6D0D9-90CF-43D3-B0B0-384D3A9F32D1.jpeg
     
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  2. tmyers

    tmyers En-Route

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    I can almost hear that nice lope at idle

    Sent from my SM-N920V using Tapatalk
     
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  3. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    108 lobe separation angle, so it should lope just fine.

    In looking through the documentation from Isky, they have another cam with the same LSA and same lift, but more duration. So if I decide that this cam is too small (which I think may happen, although we'll see) there's a natural upgrade I can go to.
     
  4. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Yesterday I made another order from Summit Racing, getting started on the fuel system.

    I decided to use those Ford QC adapter fittings to then move to a standard -AN style. Reason being, no matter how old this car gets, those fittings will be easy to take off. Also by the time I looked at buying the new Ford parts (or replicas thereof), it was going to end up costing the same or more to do that vs. what I'm able to do with parts from Summit for a custom setup. So in the end, I think it suits what I want better. I'll have to buy some more fittings I'm sure, but this will be better all around.

    I also ordered ARP head studs (which are required for this intake as there's no room to put bolts in), an ARP driveshaft for the oil pump (that's a known weak point on 351s), an oil pump, some gaskets, and other goodies.

    The oil pump I went with a standard volume Melling. Melling makes good quality oil pumps. High volume oil pumps have become all the rage, however the more I read into them the more I didn't want one. Couple reasons:

    1) The high volume oil pump flows more oil (duh). This takes more horsepower, to the tune of around 6 HP on a 351 according to some references I saw. By itself, this is irrelevant if it's the right thing to do for engine longevity.

    2) For an engine with normal (non-race) clearances like this one, a high volume oil pump can actually end up trying to push too much oil through the tight passages on the engine, and result in problems even including engine failure.

    So in this case it seemed the best thing to do was buy a new oil pump with standard volume that's a good pump, and put that on the engine.

    Building wise, what I need to do next is figure out my piston-to-valve clearance. This is easy because the springs on the heads actually are double springs with a smaller/weaker internal spring. Al I need to do is disassemble one intake and one exhaust valve, reassemble with the single weak spring, and then use my adjustable pushrod to get the valve lash to 0 and turn the engine over a couple times, while also having my dial indicator set up to measure the clearance. Given that the engine is using dished pistons rather that pistons with valve reliefs, using the clay method doesn't do me any good. The clay helps to make sure the valves aren't too close to the reliefs. All I care about is how far I have before I hit anything. Once I get that all confirmed to be good, I can torque down the heads, lube up the cam with the appropriate assembly lube, and install it permanently with the lifters. Oh, and order the correct length pushrods. I'm specifically leaving some things in my Summit cart (and not ordering them) to make sure I can always hit that free shipping they offer on orders over $100. :)

    One thing that I'm really coming to appreciate on the benefit of buying a crate engine vs. building it yourself is the calendar time aspect that it takes to build something right. Unless you're an engine shop that builds these things for a living and has lots of parts around or else building an engine you've built before and can have a parts list you just buy, you have to make a bunch of orders on specific parts to get what you want. Some things have lead time, but others you just can't order until you get to that part in the process. The pushrods are a great example. I can't order those until I measure to make sure I get the correct length. I could, but I'd probably be wrong. The other issue is that valve lash settings are for a hot engine, not a cold one, and those settings will change due to the expansion rates of iron block, aluminum heads, and all the other metal parts in between. I found this article:

    https://www.onedirt.com/tech/engine/rockin-lash-setting-valves-cold-hot-lash-settings/

    Which uses data from Crane, but probably a good starting point, that suggests that subtracting 0.006" from the hot lash spec should be a good starting point for me. Given that I have pedestal rockers and thus want get it right the first time, this would indicate going for an 0.014" cold lash instead of the 0.020" hot lash spec'd by Isky.

    Another decision I'm coming up on is oil. Isky sends a nice page of information regarding what they recommend for oil on a flat tappet cam (and specifically a flat tappet solid lifter cam like mine). However, it's outdated. It suggests Brad Penn motor oil, Pennzoil GTP Racing Oil, or Valvoline Racing Oil (and specifically calls out NOT Valvoline VR-1). They say all of these have the appropriate levels of Zinc (ZDDP) additive which is important for my flat tappet cam. Also, don't use synthetic oil according to Isky.

    Fine. Only problem: None of those oils exist anymore. Brad Penn oil is semi-symthetic, Pennzoil GTP isn't sold anymore (I can only find Pennzoil GT oil), and Valvoline only sells "VR-1 Racing Oil".

    The other option they recommend is going with a conventional mineral oil and putting in zinc additive/supplement.

    ATK recommended 10W-30 oil (although I want to call to talk to them about this some more) which seems reasonable on a 351 that was originally built in the 80s. Brad Penn oil is available in 10W-30 (mail order only from what I can find), but the Valoline VR-1 that's commonly available in auto parts stores seems to bottom out at 20W-50. I don't mind ordering oil, but I do tend to agree with Isky that I don't want to go for synthetic in this engine, so that makes me think I probably am going to be best off going with a good conventional 10W-30 (or maybe 10W-40) and then zinc additive each oil change.

    Last night Laurie came home from work and got to see the Cobra with the rear suspension bolted up, wheels and tires on, steering rack attached, pedalbox and master cylinder on, and a whole lot of boxes gone from the garage. It's a huge amount of visual progress since she left for work, and she said "Wow, this is really looking like a car." Like me, she really loved how good the big tires look in back. It's exciting - this really is looking more like a car, and although vroom-vroom noises are over a month away, they're definitely impending.
     
  5. SoonerAviator

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    FWIW, I run Castrol GTX HD-30 (straight 30w) in our 351w for the boat. Doesn't burn any appreciable amount of oil, but then again it only sees 20-30hrs of run time a season.
     
  6. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    I was thinking of going GTX 10W-30/40 and the Zinc additive. I think that might be the way to go.
     
  7. Zeldman

    Zeldman Touchdown! Greaser!

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    On the oil pump, I hope you plan on disassembling the pump to check for FOD inside and clearances. And for broken teeth on the gears. I found that once, and I have found metal filings as well. Melling has always been my choice for pumps.

    For my engines I always rounded out any sharp corners inside the pump where the oil flows to reduce cavitation at higher RPM. I never used high volume pumps either, because after deburring and cleaning up the corners I found the oil volume to be just fine.
     
  8. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    I was planning on opening up the pump to look for those bits for sure. I've also heard of some people having issues with the screws holding the cover on coming off and having problems there, so I was going to check it and make sure to reassemble with red loctite on the screws, plus follow the suggestion of pre-priming the pump with vasoline.
     
  9. SoonerAviator

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    You can prime it with a cordless drill prior to installing the distributor if you like.
     
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  10. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Yes, I was intending on that.
     
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  11. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Managed to get a few minutes in the garage tonight and I got the engine mostly set up to check piston-to-valve clearance. There's a few aspects to this step in the process. Put the cam in (although only for the first time, not the last time), put the head gasket on, put the head on, put a few head bolts in to snug it down (but don't torque it down). Put in a couple of lifters, the adjustable pushrod, and snug everything up, and of course the timing gear.

    Since the valve springs are double springs, I removed the outer springs from those valves to put less pressure on the adjustable pushrod as well as make it easier for me to move the rocker and valve to determine the clearance. I'm not sure of the exact spring pressure of the inner spring. It's not one of those super light springs specifically for checking valve clearance, but it's light enough that I can compress it by hand to figure out the clearance. Because I'm using a dished piston I'm going to go specifically with the dial indicator method of clearance checking and not use modeling clay. Since I don't have valve reliefs I don't need to see how close to the edge of those I am.

    Putting the timing gears on was fun. I looked through the instructions and the crank gear has keyways for +/- 4 degrees. My thought is that depending on how much clearance I have for the standard/centered up, I may try with the 4 degrees advanced and retarded just to see how that impacts the piston to valve clearance. This cam is probably a bit on the small side and going to be tending towards lower end torque between the tighter lobe separation angle and relatively conservative lift and duration. Because of that I may consider installing the cam at the 4 degrees retarded keyway just to try to push things up a bit in the RPM band if the clearances will allow it. I'm not concerned with degreeing the cam in this case. Something more to think on.

    If I can get to it in the next few days (and it's not a rush, so I may not) I'll see if I can find out what my clearance numbers are and pull the cam out to lube it up and install it permanently.

    [​IMG]

    [​IMG]
     
  12. 455 Bravo Uniform

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    Why would clay not work on those pistons Ted?
     
  13. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    There's no reason why it wouldn't work, it's just that there's no benefit to it with dished pistons vs. doing the dial indicator method. With the dial indicator I can get a more precise measurement of what the clearance is. The clay primarily offers a benefit if you have valve reliefs in a flat-top or domed piston, and need to know how close or far you are from reaching the edge of those reliefs. In this case the valves will be right about in the center of the dish, and there's not a lateral clearance issue I'm concerned with.
     
  14. Zeldman

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    Cool..!!! Blower pistons.!!!

    (almost)
     
  15. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    My real preference was to go with piston relief flat top or domed pistons to push the compression up to about 10.5:1. As it is it's around 9.6:1. Lower than I want but it'll suffice and the other option was going to be to spend a lot more money on a custom short block build or a higher end off-the-shelf build that was going to get rid of a lot of the cost savings that I got from this.

    I've had a few friends tell me I should put forced induction on the engine, but that doesn't match what I'm going for with this build at all.

    Part of me thinks I've missed my calling building custom cars/engines. I am enjoying it.
     
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  16. SCCutler

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    This is simply awesome.
     
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  17. Zeldman

    Zeldman Touchdown! Greaser!

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    I agree, a blower sticking up out of the hood of a Cobra just isn't right.

    I enjoyed it too until I started doing it for a living, same with racing and flying...:lol::lol:
     
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  18. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    I am enjoying it. :)

    I've seen it done on some of the FFR replicas. I'm pretty open to people doing whatever it is they feel like with these cars, and I had given it some thought just because one of my bucket list goals is building a car that has a big blower sticking out of the hood. Although as I told @Rgbeard I think a good option for that would be building a 6-71 blown 6.0L+ V12 for his Jaguar XJ-S.

    The old saying... take your two favorite things, make one your career and one your hobby. I've more or less done that. Of course with aviation, even if it's your career, it's also generally your hobby to some extent.

    I've been thinking more about the cam timing and I think I want to give the Isky tech folks a call to get some input on the cam timing they recommend given my setup and goals. This is a situation where getting it right the first time isn't critical per se, but it is always nice.
     
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  19. SCCutler

    SCCutler Administrator Management Council Member PoA Supporter

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    So, Ted, we’ve discussed a hot rod Town Car.

    But, how about a Mark III? I love how he shifts with the column shifter. Bet the AC works, too!
     
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  20. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    That's great. I love land yachts, especially ones that are made to still be stupidly fast while maintaining the luxury features.
     
  21. Sac Arrow

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    He never leaves second though, as far as I can tell.
     
  22. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Wouldn't surprise me if that thing has 3.08 or 2.73 gears in it. Top of 2nd is probably pretty quick...
     
  23. EppyGA

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    First, second and drive. Watch again.
     
  24. Sac Arrow

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    Okay I watched again full screen on the laptop. I thought he might have been clutching but I see he's doing left foot braking.
     
  25. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Tonight I got the valve clearances checked to my satisfaction. Intake and exhaust were both over 0.100" lift. Exhaust side was more like 0.150" or better. In the end I had to remove both valve springs to check it as at max lift I wasn't able to get even the inner valve spring to compress very much beyond the max lift. That makes sense - with these rockers the max lift should be .507" and the max lift of the springs is supposed to be something around .570". Still a plenty safe margin, but to make sure I have .100" or more piston-to-valve clearance, it wouldn't suffice. So I pulled the valve spring and just checked that way. With sufficient clearance, I'm happy, so I put the second head on and snugged it down so I could put the spark plugs in both heads and cover up the ports. It was getting late by that point (I pulled the rams off the dozer) so I called it a night. The heads aren't torqued down but I may do that tomorrow.
     
  26. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    The current state of the engine.

    2757FF91-751B-4330-A849-7E36B2C17C4D.jpeg
     
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  27. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Not a hugely productive night on the Cobra. I had to put the hot tub back together (finally fixed the leaks on it... for now...) and then one of the kids had a nap in the afternoon and so she wouldn't go to sleep. And she also didn't want to be in the garage. Can't blame her fully - it's after 10 PM and it's still 85 degrees with 70% humidity. It'd be a nice night to take the Cobra on a drive, if it was ready.

    But I did get two things accomplished regarding the cam. First one is that I installed it with assembly lube, now having gotten the measurements done. I couldn't find the cam gear bolt so I didn't put the cam gear on, but the cam itself is in. I was then going to work on the head bolts or something else, but I was getting complaints from the little one.

    The other thing I got accomplished was a phone call to Isky tech support to ask about some specifics on installing the cam with my engine and if I should mess with the timing or not. The guy sounded like an older fellow who knew his stuff. His advice was to install the cam straight up, but that he'd recommend running the valve lash a little on the tight side, which would help give me a hair more effective duration and lift. Logical advice, especially when combined with my 1.7:1 rockers. With aluminum heads I was going to need to run a bit tighter than spec cold anyway, so I'll probably aim for on the side of 0.010" or a hair less when cold vs. the 0.022" when hot spec. That should put me something in the 0.014-0.017" hot range - that whole aluminum and steel expanding at different rates thing. That ought to be about right. The tricks of working with old school stuff - part of why I wanted solid lifters instead of hydraulic.
     
  28. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Did some more thinking and planning while I was sleeping last night.

    It's coming up on time to do another order from Summit Racing. I've decided that I want to order an ARP cam bolt. Seems silly not to for the $4 it costs. I also need to order pushrods once I measure the appropriate length to order. So I think what I'd like to do this evening is get the cam gear on (although obviously not bolted/torqued down), torque the heads down, and then I'd like to do the work to get the pushrod length figured out. Then just keep pushing forward on things. That'll probably take the evening but I can also blueprint and install the oil pump if I have time.
     
  29. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Made some more progress on the engine this evening. I got the heads torqued down, the cam gears on (but not torqued). Lifters pre-lubed and installed. Then I started doing the work to figure out what size pushrod I'm going to need. I ended up measuring 8.104" which gets my lash a hair on the tight side. Of course, 8.104" isn't a standard length pushrod, but 8.100" is. So I'm thinking that the thing to do is order a set of 8.100" pushrods and then start from there to see how the clearances fall. Given that 8.104" got me a hair tighter than what I wanted, 8.100" might get me about perfect, or at least close enough. Working with pedestal mount rockers is making life harder here, though, since I can't adjust the things just by using an adjustment nut. I will be buying hardened pushrods even though I don't have guide plates, just because I like things to be beefier

    I was going to open up the oil pump to see how that looked inside, but I also realized that I didn't have the ARP oil pump bolts that I wanted, so I need to order those, too. Another Summit order tomorrow it looks like. I can still take apart the oil pump to inspect it, of course, but I wouldn't be able to put it back on, so I'm less motivated.

    I could put the intake manifold on now, but I think I'd rather wait until I get the valvetrain assembled just so I can clearly see that the pushrods are properly seated and make sure that all the clearances are correct.

    Tomorrow I might take apart the oil pump and then might also take the plenum off the intake manifold to make sure there aren't any shavings I need to worry about in there.
     
  30. 455 Bravo Uniform

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    Are the rockers shaft mounted? With no adjustment?

    I ran adjustable pushrods on my stock shaft non-adjustable rocker Buick. 12.0s@110mph with hundreds of passes, never came out of adjustment. Something to consider.
     
  31. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    They're pedestal mounted rockers. So to adjust them you have to put shims underneath. Shims are available, of course, but the smallest shim I've seen is 0.010" which I think will result in a pretty significant increase in lash.

    I've got an adjustable checking pushrod but my understanding is that you're not supposed to use that in a running engine. I haven't seen adjustable pushrods for these engines that are intended to be run, but if you're aware of any then I'm definitely interested.
     
  32. 455 Bravo Uniform

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    Here’s a start, but you may need to do some calling around to get a set the right length, or custom built:
    http://www.taperformance.com/products.asp?cat=438
    Probably not price competitive for Fords, but back when a set of adjustable roller rockers for a Buick were $500, these were the ticket.