regular headers work with a tall deck engine? - Chevelle Tech
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post #1 of 17 (permalink) Old Jan 30th, 07, 5:09 PM Thread Starter
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regular headers work with a tall deck engine?

I am looking at a tall deck 427 engine that is for sale and I am considering buying it to put in a chevelle or nova. Will standard deck headers work and just be closer to the floor, or are special headers needed? This is a supposedly performance built engine, are there aftermarket forged pistons for these engines or just the factory style heavy 4 ring style?

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post #2 of 17 (permalink) Old Jan 30th, 07, 5:30 PM
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Re: regular headers work with a tall deck engine?

the answer depends on the car its used in,and the brand and part number of the headers used, even the cylinder heads, effect the results as some heads have the exhaust ports raised as much as 7/8" higher on the heads in relation to the block deck even on a standard block, Ive had standard headers fit with zero problems Ive also had them be totally un-useable, and its not just the floor to collector clearance at times its the stearing/suspension or frame , even the starter or oil filter or clutch linkage that became the problem.
if youve got a decent welder and some fabrication skills most problems are reasonably easy to work around, but you may want to build custom headers in some cases.
Im sure your aware that there header flanges and collectors available in kits to build your own custom headers and that you can cut/splice and recoat standard headers
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post #3 of 17 (permalink) Old Jan 30th, 07, 6:16 PM Thread Starter
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Re: regular headers work with a tall deck engine?

This engine has factory style oval port heads so the exhaust port will be as normal, I am just wondering how much wider the engine will sit compared to a regular passenger engine, not sure how much extra room there is in a chevelle chassis for the bigger engine with headers.
My biggest concern is the pistons, the seller really doesnt know what parts are in the engine, only that they are forged pistons according to him..so I am just wondering if there are aftermarket pistons for this engine or just the factory ones..and if the aftermarket ones would need a longer rod to be used. Would a regular 427 piston work just by using longer rods?

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post #4 of 17 (permalink) Old Jan 30th, 07, 6:31 PM
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Re: regular headers work with a tall deck engine?

the correct rod length depends on the deck height and piston compression height and stroke of the crank, normally tall deck blocks use a differant tall piston,you can use stock 427 low deck pistons WITH a longer than standard connecting rod in the tall deck block, you need to know 2 of the three to find the third, heres some calculators to play with, keep in mind the tall decks 0.4" taller deck, ie 9.8" vs 10.2" so if a standard deck piston for a 427 with its 3.76" stroke and 6.135" rod are used the added 0.4 " taller bore and the rod needs to be 6.535" or .4" taller


1/2 stroke plus rod center to center length plus compression height should be very close to deck height






http://www.kb-silvolite.com/calc.php?action=piston_comp

http://www.kb-silvolite.com/calc.php?action=deck

http://www.kb-silvolite.com/calc.php?action=piston

http://www.newcovenant.com/speedcraf...ssionratio.htm

http://www.kb-silvolite.com/forged.p...VY&EngSize=427
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Last edited by GRUMPYVETTE; Jan 30th, 07 at 6:52 PM.
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post #5 of 17 (permalink) Old Jan 30th, 07, 6:32 PM
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Re: regular headers work with a tall deck engine?

Dave...I have heard of a guy that runs a tall deck block in a 71 Elky, and has no clearance issues at all. Mr 4 speed knows who it is, maybe he will chime in. Im not sure about the pistons, but I looked into it one time past, I believe there are quite a few available. I have the name of a guy I know who has built several tall decks....if I can dig up his email, I'll pm it to you. John

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post #6 of 17 (permalink) Old Jan 30th, 07, 7:05 PM
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Re: regular headers work with a tall deck engine?

Hi Dave , Johnny O is correct I am running one in a 1971 gmc sprint same as el camino with no clearance issues ,please read this old post .

https://www.chevelles.com/forums/showthread.php?t=159317


Ask all question before building one , I also got a Cowl hood with RPM AIR GAP with two 1/2" each spacers

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post #7 of 17 (permalink) Old Jan 30th, 07, 8:02 PM Thread Starter
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Re: regular headers work with a tall deck engine?

Thanks for the info guys, let me see how it goes, I should know by the end of the weekend if I end up with it.

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post #8 of 17 (permalink) Old Jan 30th, 07, 10:05 PM
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Re: regular headers work with a tall deck engine?

I just picked up a tall deck block, brand new, prepped at 4.310 bore. Probably going to build it as a 6.8" rod 496 motor. Not sure what it's going in yet, but it was so reasonable I couldn't pass it up.

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post #9 of 17 (permalink) Old Jan 31st, 07, 12:29 PM
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Re: regular headers work with a tall deck engine?

A few months ago, I installed a set of Hooker Super comp headers ( the set with 2 1/8" primary tubes and 3.5" diameter collectors) into my 70 Chevelle with a tall deck 632 inch motor. The Passenger side only had to be dimpled with a ball peen hammer in one place for starter clearence ( and that was with a mini-starter at that), but the driver's side header had to be dimpled in five places to clear the frame, steering shaft ( on cylinders #3 and #5) and on cylinder #7 for control arm cross shaft nut clearence.

The steering shaft was the biggest obstacle.But I don't think that you engine will need the 2 1/8" primary tube diameter, so you can probably get the smaller Hooker headers and you might not have to dimple them as much as I did. I suspected that the tops of the collectors would be hitting the floor boards too, but on my car, they didn't, so that wasn't an issue.

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post #10 of 17 (permalink) Old May 24th, 20, 10:30 PM
 
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Re: regular headers work with a tall deck engine?

What cylinder heads did you run on that 632?
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post #11 of 17 (permalink) Old May 24th, 20, 11:23 PM
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Re: regular headers work with a tall deck engine?

If you paid attention to your geometry and trigonometry classes in school, you'd know this is easy to figure out. Block is a 90 V, that makes each bank 45 relative to the centerline drawn between the crankshaft and the camshaft.
We know the block is getting .400" taller at a 45 angle, so we can use basic Pythagorean theorem of A + B = C, and the 45 bank angle means we can work from an equilateral triangle. This means A and B are equal to each other, and the hypotenuse (C) is .400", or .16.
Half of .016 is .08, so A and B both equal .08.
Square root of .08 = √.282842"

Head moves up relative to the ground .283", and outward relative to cam/crank centerline by the same .283" with the tall deck block.
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post #12 of 17 (permalink) Old May 25th, 20, 12:27 AM
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Re: regular headers work with a tall deck engine?

13 year old thread!
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post #13 of 17 (permalink) Old May 25th, 20, 2:58 AM
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Re: regular headers work with a tall deck engine?

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post #14 of 17 (permalink) Old May 25th, 20, 5:12 PM
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Re: regular headers work with a tall deck engine?

oldie but goodie. kinda nice to see somebody doing the math. I'd round off those numbers to .300 both ways.

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post #15 of 17 (permalink) Old May 25th, 20, 6:19 PM
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Re: regular headers work with a tall deck engine?

Quote:
Originally Posted by Rmchevelle View Post
13 year old thread!
Yeah!!! What the heck???? I just wrote a two paragraph reply thinking that I'm helping the guy out!!! LOL Thanks for pointing out the expiration date of this obsolete thread, because I definitely wasn't even looking at that!!!

Quote:
Originally Posted by Tom Mobley View Post
oldie but goodie. kinda nice to see somebody doing the math. I'd round off those numbers to .300 both ways.
Well it also looks like someone rounded off the original thread date by 300 months.
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