idle help

[lightning boy]

What is the compression height of the piston and what is the head gasket thickness?
Did you perform the compression test with the throttle all the way open and all the plugs removed?
Seems low.
Put a mighty vac on the brake booster and see if it holds. Trans vac line too.
How did the valve springs look on the #2 hole?

[73ss]

What is the compression height of the piston and what is the head gasket thickness? Machinist said pistons are 10 in the hole. I measured around .008", Hard for me to get a good measurement due to dome and piston rock at TDC. Head gasket is cometic, .040 thick.
Did you perform the compression test with the throttle all the way open and all the plugs removed?
Seems low. Yes
Put a mighty vac on the brake booster and see if it holds. Trans vac line too.  Brake booster good, OD trans no vac line.
How did the valve springs look on the #2 hole?  Springs & valves are great, Not sticking, Valves seal excellent on that hole. Rocker geometry is good.

I think this cam has too much overlap, card says 63.6 * overlap for advertised and 11.6* overlap at .050 lift.

[Cliff Ruggles]

What is the advertised duration and check point? 

The cam in my 455 is 289/308 @ .006" tappet lift, 112LSA and ICL at 109.5 and it makes 13.5" vacuum at 750rpms with only 10 degrees timing in it.  Cranking pressure is 198-200psi across the board..

230/246 @ .050" is not a big cam in that engine and with 114LSA it shouldn't  have a lot of overlap.

Late intake closing lowers cranking compression and will make the engine somewhat "lazy".  Even with that said that little cam in a near 500CID engine with 10 to 1 compression it should me idling with a LOT more vacuum and not having to run more than 10-12 degrees initial timing.

Something is fundamentally wrong someplace......IMHO......

[73ss]

I agree with your comments, Thanks for the tips. Some of the poor vacuum should be due to the #5 intake not sealing well. I don't see anywhere on the card at what lift they take the advertised duration at.

[tayto]

"Degrees of Duration" 284.6*/289.6*

[Kenth]

You will find measurements of the lobes, intake BHR233353 and exhaust BHR247360, here:

https://www.howardscams.com/sites/default/files/lobe%20list%20email%201-20-2014.pdf

HTH

[tayto]

guess my post got cut short... both howards cams i've installed the advertised duration was at .006" HTH.

[73ss]

Thanks for the replies, I think this cam would be better suited for a 454 with the stock heads. Any cam recomendations?

I took the head off with the leaky #5 valve and found that the valves have been floating, The intake valve kissed and took it out of round ever so slightly. Cant see it without a dial indicator. One of the spring shims got beat to hell as well. I installed the recommended howards springs that match this cam, Set them to the correct height, within a few thousands. I had 2 of the springs tested and they are about 20 ponds light on the seat pressure. I didn't realize I was getting into float, I've got a 6K rev limiter. It would start to break up just before 6K, I figured my rev limiter was off by a few hundred and it was valve float that was causing the breakup. Cam and springs are supposed to be good to 6400.
Looks like I'll be needing to replace all of the springs and a valve, Anybody have a trusted brand that they use?

[Cliff Ruggles]

Common problem running into issues at high RPM's with HR lifter set-ups.  Spring pressure may not be the answer and for sure that cam isn't making power past 6000rpm's in that application so really no need to rev it that high.

I've dyno'd plenty of big CID engines and a 230 @ .050" cam isn't making power in a 450-470cid engine must past 5500rpm's and some quit down around 5000-5200......

[73ss]

I talked with a tech at Howards and apparently the cam that I have is more for blower & nitrous use for a 454 and not a stroker, which he said is contributing the low psi on a compression test. Also the springs they listed are the minimum requirement. Would be nice if that was made clear in their catalog.

Anyhow he recommended a 243/249 @ .050. 640/640 lift. 112 LSA 108 centerline.

Lunati also has a similar grind: 240/245 @ .050. 612/612 lift 112 LSA 110 centerline.

Thoughts on these please.

[old cars]

David Vizard. These are tight LSA for BBC. Do not compare this to a Pontiac

[Cliff Ruggles]

"I talked with a tech at Howards and apparently the cam that I have is more for blower & nitrous use for a 454 and not a stroker, which he said is contributing the low psi on a compression test."

That statement really doesn't make any sense to me.  So the tiny cam on a wide LSA without much overlap makes "low" vacuum at idle speed on a stroked 489cid engine with 10 to 1 compression?

So tell me how going to a bigger cam on a tighter LSA is going to improve that deal?

I would suggest correcting your leaking valve issues and advancing the current cam to see if it helps some before jumping to a different cam and having to change valve springs, etc......

As far as the Vizard stuff goes I'm sure some folks do well with it.  I've ventured down that path a few times and wasn't overly impressed aside for the "raspy" idle quality, stinky exhaust and nitrous-like power curve punching a butt-load of power into the mid-range.  If those are your goals for the project then you may be happy with all that.

Related to the topic recently a customer called up here building a 454 Motorhome engine for his 1 ton dually and went that route.  I asked him why he thought going to a really tight LSA cam with the ICL clear down around 100 degrees was going to be a home-run in that application.  He very quickly snapped at me that Vizard does this all the time with excellent results plus he wanted TONS of low end torque and didn't care what the engine did at higher RPM's. 

Not wanting to be critical of others I didn't comment and sold him the parts needed to get his carb up to par.  He called back several times wanting tech help and was NOT happy at all with the 454 he built using one of those cams.  He kept screaming "turd" thru the phone and I guess it was all the carburetors fault instead of the poor cam choice.....FWIW.

Anyhow, these engines are sensitive to intake closing point, and overlap.  Doesn't matter if it's a Ford 460, Pontiac 455 or Chevy 454, they all respond in similar fashion and the camshaft is a BIG player in how well the engine works.  It should be very carefully chosen based on CID, the static compression ratio, head flow and intended use of the vehicle.

I see the results of this sort of thing a LOT here.  The first thing folks need to keep in mind is that an engine up around 500cid with pretty high compression is NOT going to be happy at all with a relatively "small" cam in it.  Just in shear terms of cylinder filling abilities alone using a cam that's a very good choice for a smaller engine isn't going to be the ideal cam for your much larger engine, all else being equal.........Cliff

[old cars]

David Vizard teamed up with Lunati Camshafts to have a series of cams ground to his specs .     Lunati – Flat tappet hydraulic custom ground on Voodoo lobes
                                             with lunati spring package and lifters
                               specs: 273 duration 107 LCA at 4 degrees advance
                                          227@.050 - valve lift .552 inch with 1.72 rockers
This is the one I used which was ground on Voodoo lobes , which are famous for making power. This is an agressive lobe and the builder must keep this in mind. David Vizard dyno tests on a a 460 cu in BBC     with prepped peanut port heads resulted with 450 ft lb torque at 2600 rpm and 550 ft lb at 3800 rpm, HP at 5600 rpm  was 512.
Peanut port heads are truck heads with ports of only about 250cc. These were often thought of as throw aways until some builders dyno tested these heads in nearly stock form only to find out they delivered nearly 500 hp. David Vizard did a pocket port with a 2.190 intake valve. Thats all. Of course a good valve job.
On a 468 cu in BBC build with stock Edelbrock E-Street heads , Victor Jr  intake,  and 850 Holley peak torque was 588 ft lbs and peak HP was 581. Same cam. A Holley 950 HP further boosted torque to 598 ft lbs and 599 HP.  And torque at 3000 rpm was 550 ft lbs. This was a 10:1 compression engine. With a port job to these heads and a flat mill to bring compression to 10.5, output climbed to 611 ft lbs and 626 hp. We have already reached a well built Stroker 496 cu in output with more camshaft.

I live in southern Ontario Canada where we have 2 drag strips close by.
 I have a friend with 1969 El Camino custom built 496 BBC who occasionally runs at the drags. The engine with AFR heads was dynoed at 630 hp. This car runs 11.4 at the strip with a 3:73 rear gear ratio . I have helped him out numerous times. He does not drive the car far because the fuel mileage is poor to say the least. I have another friend with a 1972 GTO 480 something pontiac stroker he built himself. He runs 11.3 at the drags and uses the car as a daily driver. This car has a 3.08 rear axle and gets decent fuel mileage with good manners. Very impressive true street car.
There is a trend these days to build a true street car and good HP with very good fuel mileage. My car is a 1975 Monte Carlo 454 BBC with peanut port heads that I use for touring and practically a daily driver in the summer. This is a 3900 lb car with a 2.73:1 rear axle and 400 turbo trans. Performance is outstanding in the lower rpm range on up. I get 15 mpg on the highway without trying hard. No I don’t have any time slips. My brother in law has a 1969 Chevelle 427 cu in 425 hp and 4:11 rear axle. This is an original car that he has owned since 1969. I have driven this many times. Those cars did not start making horse power until the upper rpm range and he shifts it at 7000 rpm. Although this car may be the envy of many it does not have the low rpm street performance of my Monte Carlo or the previously mentioned GTO, even with a 4:11 rear axle.
I don’t really care what camshaft people choose (unless I am building the engine.)

David Vizard was once asked his opinion on something. His answer was . “ I don’t have an opinion I have a dyno.”

[Cliff Ruggles]

I get involved with quite a few Pure Stock and FAST Class cars because they are required to use factory iron heads, stock intakes and Q-jet carburetors.  I've helped out quite a few folks with big block Chevy engine set-ups for both classes.

You'd be amazed at the power we've made with those "door stop" flat iron intake manifolds teamed up with factory iron heads.  One of the very first ones I got involved with was a 1970 Chevelle's 454 engine (stroked to 496).  I helped with the cam choice and did the Q-jet and factory points distributor for it.  He had the heads opened up for the larger 2.19/1.88 valves and some minor work in the bowls and short turns.  Dyno day came and he was getting all sorts of "flack" from the dyno shop he carried it to for testing.  They were FULL of under the breath rude comments telling him it wouldn't make chit for power and to get rid of the POS iron intake and Quadra-Junk carburetor sitting on it.  Keep in mind that the engine was totally "stock" in appearance by Class rules.  He told me that when they made the first pull on it that the dyno operator and his staff were dialing 911 and heading for the exit doors!  After giving him all sorts of crap about the parts being used it cranked out close to 600hp and over 600ft lbs torque on the very first pull!

The cam I selected for it was a custom ground HR Comp cam with XFI lobes and wide LSA to keep vacuum high and idle relatively smooth to meet class rules.  I don't remember the exact cam specs but it was in the 255-260 @ .050" range and around .650" lift at the valves.

I've never read one word of any posted literature or articles by Dave Vizard so can't comment on anything about any of that.

I will say that I've used PLENTY of tight LSA cams over the years with advanced ICL.  No problem making power with them, but the nasty idle quality, stinky exhaust and "reversion" we saw at low RPM's keeps me from going that direction with street engine builds. 

It's pretty rare if I'll use a cam with an LSA tighter than 112 degrees and ICL in the 108-110 range.  I also use higher compression and really tight squish with my street and street/strip engines plus good flowing heads and superb exhaust systems. 

Most "builders" use lower compression then try to bring back the lost power and efficiency by using smaller cams on tighter LSA's.  To each his own with that deal and to date I've never seen a rule book about any of this stuff, so do what you like and what makes you happy........

[old cars]

All beer is good beer some are just better than others.