Mrgadget

I have to tear down my 350, rod bearing we think.
When I had it rebuilt, the builder talked me into a Comp cam 268H, 218/218 .456 lift 110LS. I've been told by a lot of people, this is pretty mild.
I want to go with a little more cam, not huge, just a little more effective.
Also, I'm running a Weiand 142 supercharger at 5 psi.
After searching, I've come up with 2 that show more lift.

Compcam XE268H 224/230 .485/.490 110LS and

Lunati Voodoo #60103 227/233 .489/.504 110LS
Any comments likes or not likes?

Frank

Fun71

What is the compression ratio? Not what it's "supposed to be" but what is it really using actual measurements?

Mrgadget

Good question.........the engine builder said, it was right at 8.75:1, I can't verify it.
It was bored .030, so 355 cubes.

Octania

Pretty sure I had a poor experience with a 268H cam in a LC 403. When altered to HC via shaved #6 heads, and the ign tailored to suit, much better

1BOSS83

I'm running that Cam in a 70 350 with #6 heads. I'm not sure what you mean by "more effective." More lift may not mean all that much in your application; what valve train are you running?

cutlassefi

Even at just 5# none of those cams are the correct choice.
An Erson MP/2 would be perfect. Specs are 214/226@.050 on a 114 with .478/.493 lift. Perfect blower cam.

Mrgadget

Stock valve train.

Mrgadget

Well, thats what I was looking for........I had heard Erson was a good one but had trouble searching for one on their site.
Thanks for the info. What a great site when you've got a tech question.
Frank

I was thinking of putting 1.6:1 roller rockers on, since I've got the 46 year old ones on now,how does the Scorpion ones sound?

oldsmobiledave

Well today is a historic day. Mark & I agree on something.


Three days ago in a private message reply to Mr Gadget I recommended the same cam when he asked me which cam to run in his engine.


I am shocked. I better go have a beer.

cutlassefi

Lol!! It was bound to happen at some point! ;-)

olds 307 and 403

I have the 1.72 ratio Scorpion rocker arms, they are nice. Wow, this is freaky, you two agreeing.

Mrgadget

Yes you did, so being pretty inexperienced on cams, I put it out there........good to see the same results from two directions...........thanks to both of you.

Mrgadget

Now my last question............will the Scorpion 1.6:1 roller rockers be ok with the Erson cam?

svnt442

Yes. Same ratio as the stock ones so all you are doing is adding the roller efficiency to the valve train.

Mrgadget

I thought the stock rockers were 1.5:1........I've heard it stated both ways. Tried measuring my stock rockers with a caliper, wasn't a conclusive check, but seemed to be 1.5:1, if they are 1.6:1, I stand corrected.

svnt442

1.6 is the stock ratio. 1.5 is mostly a Chevy thing.

Fun71

Olds rockers are 1.6:1. Look at any cam specs and take the advertised valve lift, divide by 1.6, and you will get the published cam lobe lift.

Mrgadget

Got the head and piston cc'd yesterday........head 64cc, piston 23cc.
When we took the engine apart, expecting to see a bad rod bearing, but all looked good.....but my friend noticed the skirt on #8 looked very badly scored.
Removed the head and looked into the cylinder and it looked like the piston was cocked in the cylinder. When we took it out, it was badly scored. Went to have it cc'd and my machinist friend mic'd the piston, it was marked .030 for 4.087, actually mic'd at 4.065 which is a .010 over, there was the culprit. I'm amazed it lasted 2 years and really disappointed in the quality of the guy that did the engine build.
I'm going to see if this guy can get me another, correct .030 23cc piston, I am having trouble finding one. In case he can't get one for me, does anyone know where to get a 23cc dish piston.

A little long but so glad to have found the problem.......mismarked piston.

cutlassefi

If that's the piston that's scored then it's collapsed, not the wrong piston. Have your guy measure the ring land area. It's should be roughly .020 smaller than the bore size.
And the fact that it's #8 would leave me to believe it obviuously got hotter than the rest for some reason, i.e. Lean, timing, cooling.

Mrgadget

Here's a couple pics of the #8 piston.
So if it's more than .020 smaller, it has collapsed, is that right?

Mrgadget

Here's a couple pics of the #8 piston.
So if it's more than .020 smaller, it has collapsed, is that right?

One more pic.

Fun71

I ran your numbers through a compression ratio calculator. I had to guess at the piston-to-deck clearance (chose ~.020" as that seems to be the norm for unmilled block decks). Then taking into account cast aftermarket pistons are short on compression height (1.595" vs. 1.615") and typical Fel Pro head gaskets are ~.040" thick, your final compression ratio comes up as 7.9:1 so you may be able to use a bit more boost.

Mrgadget

Interesting, I also used one of the online calculators and came up with 8.28:1, maybe I should use a thinner gasket??
It seems as a .02 gasket raises the CR to about 8.6:1.

Mrgadget

Well, just got bcd from the guy who built the engine, and he took one look at the piston and said, that's a collapsed piston. Now I know he and Mark(Cutlassefi) don't know each other, but again same conclusion from 2 sources. He said it probably is advance in a cheap distributor not controlled well, he is providing me with a new distributor. And the piston is coming from Texas. Wow, I have to take back all I was thinking about him. Whew.

Fun71

Here's what I used to get 7.9:1 CR:

Bore = 4.087"
Stroke = 3.385"
Head volume = 64cc
Piston Dish = 23cc
Piston to deck clearance = .040" (.020" deck clearance + .020" for too short piston height)
Head Gasket thickness = .040"
Head gasket bore = 4.250"

oldsmobiledave

If the head is 64cc it has been milled as they are 68-69cc stock.

Mrgadget

Ok about to fire this engine up......question about oil and cam break in.
I've used Valvoline VR1 racing oil 40wt for years. Now to break in this new Erson MP2 cam, I was going to use the same oil......zddp, I think is around 1300ppm.
Would this be okay to use for the break in by itself or add a couple oz. of Lucas zinc additive at least for the 500 mile break in period.
Any comments or suggestions?
Thanks, Frank

marcar1993

I just broke in an erson cam (from mark, cutlassefi) and I used Joe Gibbs 15w50 breakin oil as the erson paperwork stated to use.

Mrgadget

Ok got my engine running and all sounds good so far.
Thanks for the cam info from Oldsmobiledave and Mark(Cutlassefi) and compression ratio and rocker info from Fun71.
But not without a couple surprises......my friend timed it at 10* and didn't like the huge advance at idle (was 42*) so he disconnected the VA and engine ran hot, normally was 195, then it was 225. He left, I reconnected the VA and temp came down to normal but adv was at 42*. after research I found my old dist. was set at 4 turns out, that might have caused me to lose that piston. My new dist. was also set at 4 turns out on the VA can, so I adjusted it out to 10 turns and adv is now 19* with manifold vac. Ran it to 3000 rpm and total adv is now 36*......I think I am real close to the right spot, temp it running at 190-195 with a 185 thermostat. The car runs very snappy now.

svnt442

The vacuum can will only pull the advance up under part throttle. Under full throttle the vacuum drops and the can does nothing. You want more vacuum at cruise to help with fuel economy. The 36° total should be mechanical advance, not tied in with the vacuum.

Mrgadget

Yes, I realize the vacuum drops off and centrifugal takes over as throttle is increased.
I thought 36* at cruise is good, is that correct?

svnt442

No.

Mrgadget

No?.............what is good ay cruise?

svnt442

I have seen numbers up to 52°. It all depends on the combination.

oldsmobiledave

Glad to hear that the Erson cam worked out. How about posting a video of the car so we can hear it!

olds 307 and 403

Since your car is boosted, it will need a very different advance curve. My normal 8 to 1 Olds V8's like nearly 60 degrees part throttle.

Mrgadget

Well, this was a little challenging, but here it is: