Stabbing a smaller cam in 454, need your opinion

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Machtuck
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Stabbing a smaller cam in 454, need your opinion

Post by Machtuck »

Street 454 runs really well but pings in the summerish time of the season. Cam is shelf Lunati hyd roller 231/239/ .600/.600 110. I’m sitting on 9.8 to 1 with 781 heads. 118 cc/ .020 shim and about .020 in the hole. ( i know, i should had zero decked).
Anyways, I’m doing some long distance cruising with the car and stabbing the old crane flat hyd flat tappet back in. Doing this also because i collapsed one of the roller lifters and it’s tapping pretty bad. Tried many things other than yanking lifters and rebuilding.
The specs on the flat tappet are 224/234 .525/.550 114.
My question is: I’m worried the pinging might be worse with the smaller duration cam hence greater cylinder pressure. Would removing the shim head gasket and replacing it with a .039 gasket be advisable? It would bring me down to around 9.5 to 1. I realize that the squish would not be a good if i did this. Am i splitting hairs here? Thanks for your input in advance.
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Re: Stabbing a smaller cam in 454, need your opinion

Post by BillK »

I am thinking the smaller cam would be worse. (9.5 to 1 should not be an issue.) Call Lunati or whoever you prefer and tell them the issue you are having and ask them to grind a cam that will work.. No way I would go backwards to a flat tappet camshaft.

Also you did not mention the rest of the combination ? Carb ? Distributor ? Vacuum advance ? Vacuum advance is a must on a street vehicle in my opinion. You simply cannot get the correct timing under all conditions without it.
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Re: Stabbing a smaller cam in 454, need your opinion

Post by My427stang »

Well the .020 in the hole and .020 shim is perfectly good for quench if that's where it is across the whole deck

Hard to say how it will do though without advertised duration on both cams and ICL. However, generally, the 110 LSA HR would be centered on 106, and the Crane flat tappet at 114 LSA should be on a 110 or 108 center. That is certainly to your advantage depending on the lobe design

You could go to a .030 gasket if it was still available, but I wouldn't go much looser than .050 total quench distance and where you are is pretty nice.

Post the advertised duration and intake centerlines for both cams first and we'll see where you are

Don't forget a little ignition timing work and the right mixture goes a long way too.

On edit ***** if your cam is the 278/290 adv and on 108, it should be fine on pump gas unless real lean, hot, or the timing curve is wrong for the application and better on fuel if it is in at 110, . The thing is, the Voodoo hyd roller on 106 should be good too, with the only exception being the Voodoo may dilute a little at low RPM with 10 degrees more overlap and pull a little harder on the port.

Best thing would be to post all the cam specs, as well as your timing curve, you should be just fine on pump gas with either of those cams
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Re: Stabbing a smaller cam in 454, need your opinion

Post by GARY C »

I would work on the tune to get rid of the ping before I would change the cam, any engine, cam, compression combo will ping if tune is wrong.

My guess is you need to address your fuel and timing curve, where ever it pings you either need less timing or more fuel at that point or both.
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Re: Stabbing a smaller cam in 454, need your opinion

Post by F-BIRD'88 »

Start by acessing the quality of the fuel used.
Inlet temps. Uneven afrs on cylinders vacuum leak.
Mech and vac adv timing. Replace or remove and clean the noisey hyd roller lifter.
Fix the cooling system.
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Re: Stabbing a smaller cam in 454, need your opinion

Post by travis »

I’d start with the simple stuff. Initial/total timing? Cranking compression? Does it run hot? Checked for vacuum leaks?

Neither cam should ping with that setup, unless your running it with 2.56 gears in a 4000 pound vehicle
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Re: Stabbing a smaller cam in 454, need your opinion

Post by Machtuck »

Thanks for the replies.

Crane Hi- Intensity 280/290 224/234 .525/.550 114 109/119. Hyd flat tappet. 80’s era cam. I realize nobody really likes this cam and it’s 114 lsa but it Worked really well for several years and lots of vacuum.

Voodoo. 282/290. 231/239. .600/.600. 110 lsa. 106 icl. Hyd roller.

Would keep this voodoo in but lifter is bad and i have a road trip planned.

Msd w/ vacuum advance. 22 initial. 36 total. I planted a screw in the mech advance to limit to 36 degrees. Currently have the vacuum advance unplugged.


4000 pound 72’ monte carlo. 2004r/2400 converter/ pwr brakes/ ac

Thanks for all of the replies guys!
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Re: Stabbing a smaller cam in 454, need your opinion

Post by F-BIRD'88 »

If that cam is a used cam get a different plan.

Fix/replace the hyd. Roller lifters and put some 92+ octane gas in the tank.
Reconnect the vacuum advance. Limit that to about 12-15 deg tops. Use champion rbl9y or 10y plugs.
Or cross ref brand.
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Re: Stabbing a smaller cam in 454, need your opinion

Post by travis »

Have you confirmed that it isn’t just a bent pushrod?

Another thought off the top of my head...will your current valve springs work with either cam? If they are proper springs for the roller they may be a little much for a flat tappet.

What gears do you have? Heavy car, OD trans...certainly more chance of pinging with iron heads if your rpms are too low.

Where is it pinging? Off idle, cruising speed?

It may be better to just replace the lifter (or lifters)?

22 initial seems a bit high to me, especially since neither cam is that big.
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Re: Stabbing a smaller cam in 454, need your opinion

Post by Geoff2 »

Make sure the engine is running as cool as possible. Cold air induction will help, as well as adding HP. Engine oil cooler will help also.
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Re: Stabbing a smaller cam in 454, need your opinion

Post by RevTheory »

Is this a common occurrence with a 9.8:1, iron-headed BBC? Nothing jumped out at me with that cam on a 106 ICL.
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Re: Stabbing a smaller cam in 454, need your opinion

Post by rebelrouser »

Not a guru by any means, but there is very reasonably priced engine software that can calculate timing curves for what ever fuel you are running taking into account your cam, compression etc. I have had good success in using a distributor machine to modify the distributor to match the computer generated timing curve, and it fixes all these issues. I have also used these types of programs when using EFI and boosted engines to calculate a curve under boost and using those numbers to set up the timing maps and again it seems top work very good. If you don't have a distributor machine, check the timing at 500 rpm increments and plot the curve on a piece of paper. I use performance trends software, but I am sure there are many others. I just fixed a ford with a 351 Cleveland with the same issues you are having, about an hour on the distributor machine and all is good.
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Re: Stabbing a smaller cam in 454, need your opinion

Post by ClassAct »

rebelrouser wrote: Fri Feb 15, 2019 8:58 am Not a guru by any means, but there is very reasonably priced engine software that can calculate timing curves for what ever fuel you are running taking into account your cam, compression etc. I have had good success in using a distributor machine to modify the distributor to match the computer generated timing curve, and it fixes all these issues. I have also used these types of programs when using EFI and boosted engines to calculate a curve under boost and using those numbers to set up the timing maps and again it seems top work very good. If you don't have a distributor machine, check the timing at 500 rpm increments and plot the curve on a piece of paper. I use performance trends software, but I am sure there are many others. I just fixed a ford with a 351 Cleveland with the same issues you are having, about an hour on the distributor machine and all is good.
Hey rebel, do you have a link to that software you speak of? I'm interested for sure.

TIA
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Re: Stabbing a smaller cam in 454, need your opinion

Post by My427stang »

So, pretty common story here, ignition timing and I think you confirmed it

However, the FT cam you have on 109 ICL should be ever so slightly more tolerant than the Voodoo on 106, but barely

That being said, your 22 degrees initial is likely the problem. I'd have to also assume that your 36 comes in quicker than 2900-3000.

With a Rat with a big chamber and heavy car, I'd be running a less aggressive curve. Likely 14-16 degrees initial (at the most), and a curve that gets me to 36-38 by about 2900-3000. You can always change springs again to sneak up on the best part throttle response versus rattle if it gets lazy

If you drew a graph with timing on one axis and RPM on the other, plotted your current advance curve versus the curve I recommend, you can see how a change in initial timing changes the whole curve and may be your only issue. Your 22 degrees is a bunch for either of those cams.

Of course, after that change, be sure to readjust the idle a/f, and make sure the engine isn't running on the transition circuit, if it is, open the secondaries a little and close the primaries
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Re: Stabbing a smaller cam in 454, need your opinion

Post by dustinm »

RevTheory wrote: Fri Feb 15, 2019 8:39 am Is this a common occurrence with a 9.8:1, iron-headed BBC? Nothing jumped out at me with that cam on a 106 ICL.
I have have multiple iron BBCs with 10:1 and cams 230 @ .050 - 240@ 0.050 and never had any pinging issues. I used to run 10% E 89 octane, I now run 92 since our base gas has changed and 10% E is 87.
I have ran 308, 331, 410 gears. The only thing I dont have vs OP is a lockup torque converter.
What rpms does this happen?
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