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Old 11-28-2013, 06:26 PM
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454 cam phasing

I posted this question at chevelle.com but not much help there so far. Any advice from here would be welcome.

I have a 67 chevelle., 4 speed 3.55 rear 10.2:1 454,+.040, 049 heads with 11/32" stem 2.19/1.9 valves. total combustion chamber volume is 103cc with the speed pro domes and the iron heads, measured by burette.
I was running a xe268h as I was enjoying the tame idle and torque for a mostly street driven car, but detonation proved to be a problem and I popped the head gaskets on #2 and 7 cylinders. Blue fel pro permatorques and stock re-used head bolts may have been a mistake.
I am going to swap to a 282s comp solid flat tappet. I am wondering if I should retard the cam 4 degrees to reduce the bmep a little more.
With the 268h the intake closed at 60, producing a dynamic compression ratio of 8.48:1, but it rattled at about 2000-3000 rpm. limited the total timing to 34 degrees with a stop pin on the centrifigal and ran 94 octane.the bmep was peaking at 180 psi right at that rpm range according to desktop dyno. Wallace cranking calc says the cranking compression should have been 171, but it was closer to 175-180psi.
the 282s closes the intake at 67 which produces 8.04 dynamic, 160 psi cranking, and a bmep of 176-178 where it was 180 before with a peak of 180 at about 4000rpm.
I am wondering if I should retard the timing 4 degrees to close at 71
this would produce a dynamic of 7.79 with a cranking pressure of 154psi and a bmep of 174 where it was knocking with a peak of 176. would this be detrimental to performance?
thanks in advance for any input.

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Old 11-28-2013, 06:58 PM
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retarding the cam will make your torque curve slightly higher.what other equipment in on this engine?what were your A/Fs through the rpm range at WOT? do you have a good cooling system,,,,etc?whats your static timing,,,,more info is better
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Old 11-28-2013, 07:09 PM
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Quote:
Originally Posted by ratlover View Post
I posted this question at chevelle.com but not much help there so far. Any advice from here would be welcome.

I have a 67 chevelle., 4 speed 3.55 rear 10.2:1 454,+.040, 049 heads with 11/32" stem 2.19/1.9 valves. total combustion chamber volume is 103cc with the speed pro domes and the iron heads, measured by burette.
I was running a xe268h as I was enjoying the tame idle and torque for a mostly street driven car, but detonation proved to be a problem and I popped the head gaskets on #2 and 7 cylinders. Blue fel pro permatorques and stock re-used head bolts may have been a mistake.
I am going to swap to a 282s comp solid flat tappet. I am wondering if I should retard the cam 4 degrees to reduce the bmep a little more.
With the 268h the intake closed at 60, producing a dynamic compression ratio of 8.48:1, but it rattled at about 2000-3000 rpm. limited the total timing to 34 degrees with a stop pin on the centrifigal and ran 94 octane.the bmep was peaking at 180 psi right at that rpm range according to desktop dyno. Wallace cranking calc says the cranking compression should have been 171, but it was closer to 175-180psi.
the 282s closes the intake at 67 which produces 8.04 dynamic, 160 psi cranking, and a bmep of 176-178 where it was 180 before with a peak of 180 at about 4000rpm.
I am wondering if I should retard the timing 4 degrees to close at 71
this would produce a dynamic of 7.79 with a cranking pressure of 154psi and a bmep of 174 where it was knocking with a peak of 176. would this be detrimental to performance?
thanks in advance for any input.
I've used the Keith Black DCR calculator for years with good success. It requires the intake valve closing point at 0.050" tappet lift, plus 15 degrees.
Your 268H cam closes the intake valve at 35 degrees ABDC @0.050" and when plugged into the KB calculator, reveals a DCR of 9.004:1. With iron heads, it's no wonder the motor is spitting out the head gaskets. I won't recommend anything over 8.5 on the calc with iron heads and less than 9.0 with aluminum heads. I also always recommend a tight squish, 0.035" to 0.045".

The 282S closes the intake at 44 degrees ABDC @ 0.050" tappet lift and will produce a DCR of 8.531:1. If you installed it 2 degrees retarded, closing the intake valve at 46 degrees ABDC @0.050" tappet lift, the resulting DCR would be 8.416:1 and the motor should operate on pump gas without detonation. Of course, I still have no idea of your squish, so that will play into the equation also.

If it were mine and I had made the mistake of using iron heads with a 10.2:1 SCR, I would use a 2-piece timing cover when I went back together, along with drilling the cam sprocket for hollow dowels. That would make it easy to retard the cam another 2 degrees if you have detonation problems with the new cam.
http://www.summitracing.com/parts/clo-9-231/overview/

Drill the cam sprocket hole to 13/32" and use these bushings.....
http://www.summitracing.com/parts/cca-4760/overview/
It's very easy to get this wrong and advance the cam instead of retarding it. With the cam sprocket stationary, the cam itself should be rotated counter-clockwise to retard it, with the thinner part of the bushing on your left and the fatter part of the bushing on your right if you are changing the bushing with the cam pin straight up.

Here's the KB calculator.....
https://www.uempistons.com/index.php...ors&type=comp2

.

Last edited by techinspector1; 11-28-2013 at 07:26 PM.
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Old 11-28-2013, 07:16 PM
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I have a wideband 02 and it was consistent at 13:1 throughout the 2-6k rpm range. I have a aluminum crossflow and the temp never rose much above 180-190 f. Overheating was never an issue. I caught the head gasket early. I pulled the engine to get the headers recoated, and when I pulled the plugs there was a couple of wet ones. I paid close attention to the timing. I ran a silver and blue spring, put a stop pin to limit the advance and ran 8* direct port vac advance. Ignition timing was 16 initial and 34 total. It ran hard, but I was not sure if it was the weights on the centerforce clutch rattling a bit or detonation. Pistons show no signs of damage. Pulled them and checked the ring lands and rings all ok. plugs had no signs either.piston is about .008 down the hole with .040 thick gasket. could be a little tighter.Thanks for the replies by the way! I am surprised that the Wallace dynamic calculator would be that far off, but it calculates from intake closing point. I have a timing chain that has keyways cut for +4 or -4 so I am thinking it would be wise to try the -4 right out of the gate.

Last edited by ratlover; 11-28-2013 at 07:24 PM.
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Old 11-28-2013, 07:26 PM
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check the deck height like Richard posted. I dont like those center force clutches,Im surprised it lives behind a BB
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Old 11-28-2013, 07:35 PM
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Quote:
Originally Posted by ratlover View Post
I have a wideband 02 and it was consistent at 13:1 throughout the 2-6k rpm range. I have a aluminum crossflow and the temp never rose much above 180-190 f. Overheating was never an issue. I caught the head gasket early. I pulled the engine to get the headers recoated, and when I pulled the plugs there was a couple of wet ones. I paid close attention to the timing. I ran a silver and blue spring, put a stop pin to limit the advance and ran 8* direct port vac advance. Ignition timing was 16 initial and 34 total. It ran hard, but I was not sure if it was the weights on the centerforce clutch rattling a bit or detonation. Pistons show no signs of damage. Pulled them and checked the ring lands and rings all ok. plugs had no signs either.piston is about .008 down the hole with .040 thick gasket. could be a little tighter.Thanks for the replies by the way! I am surprised that the Wallace dynamic calculator would be that far off, but it calculates from intake closing point. I have a timing chain that has keyways cut for +4 or -4 so I am thinking it would be wise to try the -4 right out of the gate.
The following was copied from the website of Ken's Speed and Machine Shop, Inc.......

Pre-ignition/Detonation:
The porcelain shows up pre-ignition and detonation (timing/octane). It will not accurately reveal jetting/air/fuel ratios. To look for the first/beginning signs of detonation, search the white porcelain for tiny black specks or shiny specks of aluminum that have fused to the porcelain. When detonation occurs, part of the air/fuel mixture explodes instead of burning, the explosion is heard as a "metallic knock", this audible knock is the result of a sound shock-wave, and this shock wave travels back and forth across the clearance volume "disrupting" the cooler boundary layer gases that cover the entire clearance volume area. This disruption allows "more" heat to be transferred into parts, especially, domes/piston tops, along with the very rapid rise in pressure like a hammer blow, pistons can get torched with melted sides and holes!!! With the early signs of detonation, the shock-wave will also rattle rings causing the tiny amounts of oil that now gets by rings, to be fused to the white porcelain as tiny black specks, also fused as specks are soot that was clinging to clearance volume surfaces in the relatively "still-air" of the boundary layer. One step beyond the black specks, will be tiny specks/balls of aluminum coming off the pistons that will be fused to white porcelain,....the next step to be reached is occasional pieces of the porcelain being broken-off as detonation gets worse, etc. Soon after that are holes, blown head gaskets, broken connecting rods, etc.

"I am surprised that the Wallace dynamic calculator would be that far off, but it calculates from intake closing point.
So does the KB calculator, but it uses 0.050" closing instead of whatever number the Wallace calculator uses.
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Old 11-28-2013, 07:36 PM
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deck height is .008 down the hole. I wanted to zero deck the block but the machine shop owner said it was a bad idea. I guess he meant well and assumed that it was a gamble decking the block any more than necessary, as I was having the block bored at the same time and had not fit the crank and pistons to the block yet, even though I had the crank and pistons in for balancing..yeah whatever(the machine shop is a couple hundred miles round trip, wanted to get it done in one trip) I figure .048 quench is tolerable. spent $2k in machining and balancing and headwork. heads were planed as well.
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Old 11-28-2013, 07:41 PM
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ratlover,where are you in cnada? Thats quite a lot to spend on machine work? I budget up to 1200,usually under 1000
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Old 11-28-2013, 07:42 PM
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I will post some pics of the piston tops and plugs... let me know what you think. Only got a few hundred miles on the motor, maybe a couple dozen real hard flat out runs. Thanks for your assistance. I got the machining done in Nanaimo. They did nice work, but it was pricey as there are not many shops on the island That was for new guides and hardened seats on the heads as well.
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Old 11-28-2013, 07:43 PM
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Quote:
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I will post some pics of the piston tops and plugs... let me know what you think. Only got a few hundred miles on the motor, maybe a couple dozen real hard flat out runs. Thanks for your assistance.
You need a 10x lighted scope to look at the porcelain.
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Old 11-28-2013, 07:50 PM
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gotcha... I thought that was a little more visible to the naked eye. I will keep you posted. No black specs to the naked eye anyway. here's the Wallace link see what you think.
http://www.wallaceracing.com/dynamic-cr.php
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Old 11-28-2013, 08:17 PM
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rwenuts is a Nanaimo res,should talk to him,maybe buddy up and share local knowledge
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Old 11-28-2013, 08:36 PM
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definitely some black specs. you may be able to see them. No signs of damage on the pistons... I think!
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Old 11-28-2013, 08:48 PM
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Quote:
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I figure .048 quench is tolerable
Me too.
It's probably ideal, because of the heavier weight of components that eat up clearances more quickly than a small block.
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Old 11-28-2013, 08:49 PM
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definitely some black specs. you may be able to see them. No signs of damage on the pistons... I think!
Yep, you can see the oil on the insulator even without a 10x glass.
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