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A visit to the machine shop...

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  #46  
Old 03-10-2014, 06:17 PM
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The intake is an Offenhauser C-Series.

Assuming the shop has everything ready Saturday a.m. I should have it assembled this weekend. Then a week or two to decide on which shop and collect everything I need for the break-in/test session.
 
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  #47  
Old 03-11-2014, 01:01 AM
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What size carbs are you planning on trying?
 
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  #48  
Old 03-12-2014, 06:57 AM
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I acquired desktop dyno and been pLaying. I agree that the 268 won't be too different from stock, however there will be a idle, and the difference between the lsa/lc will drop the trq a smidge and raise the hp that smidge. Also it moves the peak up about 500 rpm

I'm REALLY liking the Howard 263. It can be used with stock springs and has a -7 overlap. So it will have an idle, nut as noticeable as the comp 268 though. Do you know of anybody who has used it?
 
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Old 03-12-2014, 04:46 PM
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I don't believe the 268h cam will idle any differently than the stock cam. They have the exact same duration and LSA, so the same amount of valve overlap except the Comp cam has steeper ramps and is advanced 10. The DD program I've got shows more tq at low rpm with the 268h cam.

Whether or not there's a noticeable difference between equivalent Howardm Isky, Comp, Crower, whatever cams is debatable. One or two degrees of duration or lobe separation isn't going to change much. I ended up getting the 268h because I don't believe there's $200-300 difference between it and the Isky 262.

That Howards cam has less overlap than stock. It should idle lower if anything.
 
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Old 03-12-2014, 07:36 PM
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How is overlap measured? Stock has a -26 and the higher duration such as a 270 and up go to a 1 overlap
 
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  #51  
Old 03-12-2014, 08:30 PM
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Between when the intake valve opens and the exhaust valve closes. Check the seat to seat timing figures. The stock cam and 268h have the same 48 overlap but the actual valve timing is advanced 10 with the 268h.
 
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Old 03-12-2014, 10:06 PM
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Is there a way to measure that or calculate it? From a .050 lift since most places don't list that
 
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Old 03-13-2014, 04:17 PM
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  #54  
Old 03-13-2014, 04:41 PM
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Correct me if I'm wrong, but it shows the turbo cam with a 114, so the higher the degree, the less overlap? Because you would want the turbo cam to close the intake to build pressure.
And the big cams with high lifts, have lower numbers, and would have more of a like.

If I'm missing something please tell me I've spent the last few weeks underwater on cams and am trying to learn it as best as I can.

I really appreciate all the information you have given me. I've learned a lot.
 
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  #55  
Old 03-13-2014, 05:27 PM
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With a turbo you want to close the exhaust valve earlier to keep the intake charge from blowing out the tailpipe. The intake charge, especially boosted, has enough momentum to keep cramming the cylinder even after the piston starts back up in the bore.

Higher LSA number reduces valve overlap. Computer friendly cams have 114-116 LSA because the MAP sensor need a smooth vacuum signal.

LSA in and of itself doesn't determine whether or not a cam will have a choppy idle. Duration and LSA determine when valve events take place and the amount of overlap.

As far as how a cam will perform, when the intake valve closes is the biggest factor. Plug some intake closing numbers into a dynamic compression calculator. The stock cam closes at 70 ABDC. Comp 268h at 60, 260h at 56, 252h at 52. The 252h gives about 1/2" more effective stroke than the stock cam and bumps compression ~.5 point.
 
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  #56  
Old 03-14-2014, 03:28 PM
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Fingers crossed everything will be ready tomorrow. I'd been meaning to drop an old Offy C intake I picked up with a welder to get a cracked off mounting tab repaired. That way I won't have to break down the Bronco to run the dyno test. Had to take a day off today anyway and the welding shop is just up the street from the machine shop. They were working on my head when I got there.

I wish there was an easy, off-the-shelf solution for an engine cradle to fit a 300. Banging around in the back of a truck on a tire is no way for a new engine to travel.
 
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  #57  
Old 03-14-2014, 05:34 PM
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One of the better ways I've found to transport the 300 is to take a wooden pallet and remove the center plank. Then, the oil pan will rest between the outer two planks and the front and rear of the engine on the two end 4x4s. Seems to work pretty well.
 
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Old 03-16-2014, 02:08 AM
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what is your take on the c and dp intakes? which do you think is better and why?
 
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  #59  
Old 03-16-2014, 08:17 AM
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I don't have any experience with the DP but anecdotes I've seen from people who switched from a DP to the C style were "I'm not switching back". I got the C because I found one for $80 about ten years ago. And another I picked up for $40 because it has a busted off ear.
 
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  #60  
Old 03-16-2014, 08:27 AM
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Picked up the short block yesterday but when I got home and unwrapped it noticed something very screwy.

The shop told me the block had been decked .010" previously. It needed to be resurfaced anyway and since it's bored to 4.060" and can't be bored again we decided to take the pistons to zero deck.

They're not at zero deck. Now here's the screwy part.

10.000" - standard deck height minus
(6.2097") - rod length
(1.99") - 1/2 stroke
(1.767") - compression height of pistons per the manufacturer equals
.0333" - piston below deck with a new, un-machined block.

I measured the pistons in the short block at .0345" below deck.

How in the blue hell can that be? They're further below deck than if they were installed in a fresh block.

It was too late Saturday for me to call the shop when I got around to fooling with the engine but as of now I am very confused.
 
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