Thread: which Cam

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I am building a budget BBC with parts I have. Here is what I have so far. 454 bored 30 over with speed pro 340 domes pistons. Stock crank. Merlin World Grumpy Jenkins 119CC iron 320 runner rec port heads with 2.30-1.88 valves. Piston catalog states I should have right at 10.5 CR. Weiand Team G dual plane rec port intake. Engine is going in a 1955 Chevy Truck, auto trans with 3000 stall, Ford 9" with 4.11 gearing. I am not going to be racing this truck on the street or track. I want a cruiser with radical idle and low end power. I am going with the hyd roller cam. I am looking at the Lunati Voodoo #60213 Hyd roller. 241/249 625lift on 110/106. or the Lunati bootlegger 240/252 595lift on 108/104. What differences am I looking at between these two cams. Pros and cons of each.

one to 3 degrees and .030 lift?????????you won't notice any seat of the pants difference

I'm far from being the BBC guru on this forum, but I'll take a swing at it. There are aspects that I feel I must address before worrying about cam timing.

First off, unless you take precautions to prevent detonation, I think you're going to be disappointed when the motor pings on pump gas. Current thinking has the static compression ratio limited to 9.5:1 when using iron heads on pump gas. Iron heads just won't throw off enough heat from the chambers to prevent detonation like aluminum will. Of course, if you have access to quality fuel, like maybe E85, then it will not be a problem.

I'd be wonderin' how much that big 33cc dome would hinder flame propogation across the chamber and what it would do to squish as well. Speakin' of squish, did you plan to use the block at 9.800" with a steel shim gasket, such as the Mr. Gasket 1131G, or cut the decks for a composition gasket? 1.640" + 6.135" + 2.0" = 9.775" stack. Maybe your pistons are taller than that, but you did not bless us with that info, so I'm guessing.

I'd also be triple-checkin' piston to valve and piston to head clearances with clay.

On Wallace's calculator, I get 10.8:1 SCR and 0.045" squish using a shim gasket, 0.025" piston deck height and 9.800" decks.

Lunati 20110713 (old number 60213). LSA 110, intake centerline 106, intake closes 46.5 degrees ABDC. Intake closes too early for the 10.8:1 SCR, 106 ICL favors power in the lower rpm range, something you will not have with a 3000 stall converter.

Lunati 1140HR. LSA 108, intake centerline 104, intake closes at 44 degrees ABDC. Intake closes too early for the 10.8:1 SCR, 104 ICL heavily favors power in the lower rpm range.

Howards 120665-12. LSA 112, intake centerline 108, intake closes at 49.5 degrees ABDC. 3000-6500, lopey idle, broad mid-range power, 3000 stall. This would be my choice. I'd make provision on installation to retard the cam a couple of degrees after I ran it for a while and maybe saw the need for more top end. I like the offset cam sprocket bushings with a Cloyes aluminum 2-piece front cover, makes advancing or retarding a snap. This cam produces an 8.675:1 dynamic compression ratio on the KB calculator. That's maybe a little high for iron heads, but with good fuel, it should be a rocket. One last thought, I might use a little more converter with this cam, maybe a 10 inch, 3500 stall.

Whatever you do, DO NOT use a thicker composition gasket to lower static compression ratio. John Erb, chief engineer for Keith Black Pistons has stated that a builder will be better off with a slightly higher static compression ratio and a good tight squish (piston/head clearance with the gasket in place) than he will be with a slightly lower static compression ratio and a thicker gasket (wider squish).

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you can also grind a notch across top of dome so flame front from spark plug can get across the cylinder better

need to check piston to valve speed pros valve notch is just as forged not fly cut so every piston can very in depth . and need to know cc on heads and were piston is in or out of the deck as for cam i be looking on the 241/249 on 110 can run it on 106 or move it to 110 you may move the rpm band a 500 rpm but run it adv 4 built many this way for street with cams much like this. were the valve opens and shut.s matters but most all the time bbc like tight lsa . stall is fine intake works good . have used the gump heads there good but heavy to work on

yep---valve to piston clearance with those size valves (2.300 intake) will use up the the piston notch pretty fast---------and don't just check at tdc as clearance is much less as piston nears top of stroke just before and after tdc---

yep and the old speed pros were never cut for a big 2.300 intake that would be first on my list is fly cut them

Out here somewhere I have a holding fixture for cutting em in the mill----set up for angle milled heads angle and the compound because of the tilted stems---

Thanks for the replies, I was planning on checking the valve to piston clearance. I need to order my cam, lifters and push rods. To check the clearance I need to order a solid roller lifter in place of my hyd roller lifter right? If pistons do need to be flycut do I just mark them and take them to my machine shop or bust out the dremmel. Been a while since I built a motor and my usual machine shop closed so I will be using a new one I have never tried.

the push rod cup can be lower in the solid roller so you need lite test springs to test with the roller lifters . need to find the center of the fly cut that can be done by taking the head off a old valve and grind a center on it put head on with no valves in head them take punch and mark the pistons .i done it this way i have the BHJ piston vise i use to fly cut them on the mill

Hey!! What are the opinions on the 3000 rpm stall?, is that a little to high for the street(heat)? Would a 2200 to 2500 be better? Pete

My old 1984 454 crew cab with 4 10 gears did around 3000 at driving speeds so a 3000 stall will be slipping a lot on the street-----why have a big motor if your just goin to slip/slide the trans???? hook it up and use the torque of the engine, not the torque converter of the trans--------


and use modeling clay strips on the piston to check the clearance as you need to measure the radial clearance around the notch as well as the vertical-------


Isky has a good simple set up to notch pisstons in an assembled engine-

I was going to get a 3000 stall because that what the cam card said it needed. I would much rather have a lower stall for the street but not sure it would work or not. I planned on the modeling clay just still not sure how to set up valve rocker with the hyd lifter. I heard you can just use the hyd lifter just turn rocker nut down 1 full turn past 0 lash. Then turn motor over 2 full revolutions. Is this correct?

Well I answered my own question about valve set up by finding a good post on here about the subject. Now just need my parts. Still questioning my stall speed.

If you drop the stall speed, then you'll have to drop the cam timing. If you drop the cam timing, then you'll have to drop the static compression ratio. COMBINATION, COMBINATION, COMBINATION.

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