Ok, going with Scat rods. Now for the big question....which hydraulic roller to use. Machinist prefers Comp Cams. So that being said, which Comp Cams HR is the best choice for this motor? Car has 4.11s and close ratio 4 speed so don't need low end. I would like 14 inches of vacuum at 750 rpm and clean pull to say 6200+ rpm. (I like rpms). This car stays on back roads and never sees the highway. As always thanks in advance.

 

I would be here.....
https://www.summitracing.com/parts/cca-11-460-8

Jebby

 

Comp has some of the most advanced lobes in the industry. Having said that, I would stay away from their more aggressive lobe designs when spec'ing a cam for a street car. You're better off going with a less aggressive lobe and getting the lift you want from a 1.6 or 1.7 ratio rocker. You'll get more longevity out of your valvetrain that way.

As for the exact specs on the cam, I'd go with whatever your head porter recommends. For stock heads, Comp has a spec sheet you can fill out and they will recommend a cam for your setup. https://www.compcams.com/cam-recommendation-form

 

Comp cams are ok. Their roller lifters are better than ebay. But they ain't Morel. Also labeled Erson or Howards.

 

I like the grind that I posted......it will work awesome with the rec port heads......but I also recommend using it with Howards lifters.
The Magnum grind is a great street breather......and the ramps are lazier than an all out horsepower cam....easy on springs and components....idle all day.

Jebby

 

Not crazy about that company....if you have to get it on a steel core not the iron.

Wouldnt even consider a reason to reuse old pistons with all the work you have into it now.

It would be nice to see a solid roller in there and a decent head...or a very well ported set of irons its not going to be cheap though with all new valves, guides etc. A roller cam isnt original and I bet will help resale, same with heads.

After all youre building it for yourself not some mystery buyer? Youre spending $ so make it the way YOU want it.

 

Call Crower and give them the flow numbers on the heads along with the compression etc and have them custom design a solid roller... YOU WILL NOT BE DISAPPOINTED!
The service is so good from Dave Crower. I cannot offer more praise for his help. I understand engines and he explained why he did what he did and why he did it, he designs the closing ramps to let the valve down quickly to just above the seat and then down VERY SLOW onto the seats to keep from pounding them into the heads with higher spring pressures.
First cam I had them do was a 302 small block chevy - 636" lift solid roller - it made 350 ft# torque by 3000 rpm and made 517 hp @ 7200rpm
Extremely easy to drive and made 15" of vac at 950-1000 rpm idle.

 

sstonebraker, thanks for the Comp Cams recommendation form link. The motor has 11.0 compression, needs to run on pump gas, and pull to 6000+. They came back with the following cam: 248/258 duration @ .050, .624/622 lift, 112 LSA. I asked how much vacuum that would produce and they said 6-9 inches. I'm concerned that will not be enough vacuum for headlight/wiper doors, idle quality etc. I asked them how to get more vacuum and the response was "problem is your compression ratio and wanting 14 inches of vacuum. To get more vacuum you need a smaller cam which will cause preignition with that CR."

Any comments / recommendations greatly appreciated. Chris

 

You will be happy to know that you're not the first person with that problem : https://www.summitracing.com/search/...=vacuum%20pump

 

I concur with Crower, they are an excellent choice. Bruce Crower was an engine genius, I'm sure it rubbed off on his kids.
I'm not sure anyone knows a magic vacum number for brakes and headlights, but it may not be as high as you think.

 

Didn't Crower invent some new kind of engine? A six stroke engine, or something like that?

 

nice 1 hp/inch hyd roller. GM doesn't like to give away engines under warranty. so they design cams to not beat the valvetrain to death. you need the front of the block drilled for the cam retainer. most are. waaaaay better than that damn cam button. https://paceperformance.com/i-625508...zz502-502.html

 

A 5 cycle and it made perfect sense. Back in the 70:s during the gas crisis he developed a. Kit that made 14-1 compression but ran on. Crappy gas made. Better power. And got better mileage. The power stroke stayed the same but the intake stroke was. Cut. In half. I put that system in a Plymouth wagon with a 440 and it pulled my race car really well.

 

I recently had a new cam ground by Racer Brown cams in Baltimore. The did some cams for me back in the day. Jim Do well is a great guy and has been doing it for longer than most of you guys have been alive. He grinds each cam himself, and isn't really expensive.
racer Brown ground all Chrysler's performance cams from the 60's to the 80's everyone from cotton Owens to Richard Petty and Sox and Martin used thier stuff. Small operation now,, but high quality.

 

I agree with their cam selection 100% and especially their comments. (But if you are going to go with one of their cams you really should get the billet steel option, not the std iron core, it has too many problems)

You are really boxing yourself into an almost impossible situation trying to satisfy all three of those requirements. Something has to give or you get pre-ignition. The problem is the static compression. It's just too high for today's street gasolines.
CCs recommendation cuts your detonation problems down with a bigger overlap cam. That'll work but with ow vacuum and rougher than stock L71 idle. It'll rev tho and you have the gears for it.

Another way is to lower the compression. Have your machinist check / cc everything and figure out your actual compression, it is likely only 10.5 or so even with stock pistons.
But that is still probably too high with street gas and iron heads. I ran that in my 11:1 LT-1 and needed to pull the timing back 8 degrees to stop the pinging (28-30 total and that killed 25-30 HP and really took off it's "edge" but it still ran great. You would probably be in the same boat.

If the bores are still perfectly useable, I would strongly consider another set of pistons to drop the static to 10:1 That would be a great use of $3-400? and you would make more HP than the timing retarded 11:1 motor. It also opens up your cam selection a lot. With old school iron heads you really want to keep your DCR (dynamic) below 8.2 for street gas. That is done by carefully balancing your cam IVC pt against the static CR. Wallace Racing has an excellent calculator online for DCR. The cam and the CR must be selected together at this level.

With a lower CR I think you can run a slightly milder cam to bring up the idle vac. 14 is an unnecessarily high number, it should run fine with 10-12" at low rpm. Changing the low idle rpm of 750 to 850 could gain you 2" right there. And you will need to run 10" of vacuum advance at idle as well, that will also raise it, if you were not doing that already. Mine gave 15" of vac at 850 rpm with 35 degrees advance.. So you could go a little bigger than my 230 degree intake duration. I would keep it between there and the factory 242, not over. That was CCs way of dropping the DCR.

What kind of vac at idle did you get dead stock? Your preferred HR style cams all have faster ramps than old school GM (shorter adv dur but same .050) and that makes more idle vac with the same overlap. The you can tighten up the LC from 114 to 110 and make more power with more overlap.

I think mine is a little small for what you say you are looking for (230/240 but SR). So I would recommend something in the 240 intake range, with more exhaust, like 248-250. With faster ramps and a tighter 110 LC it should idle pretty close to stock, have the vac you are looking for, and a little more overlap than stock, but not much.. My 454 peaks at 5600, your 427 should peak higher anyway like at 6000 with the same cam and maybe 6200 with the above one

***Use really good hydraulic rollers and springs so it does not pump up at 6200.****

So I recommend select the pistons and the camshaft at the same time to wind up with 8.0-8.2 DCR. That is most likely going to mean a piston change.

You'll love it way better that way than a timing restricted or over-cammed (duration) low vac combo!

And do not be afraid of a SR in that range. It will make more vac due to even faster ramps, but it will needs stronger springs. And it is less money and will valve float less than a HR.

 

Ok, so I decided to drop CR to10.0 with new pistons. I contacted Crane and Comp for recommendations. I'd like a hydraulic roller to that pulls hard to 6200+rpm, yet makes enough vacuum for decent idle and operating headlight/wiper doors. Interestingly they both came back with "Marine" cams.

Crane: ZHR-296-2S-12-IG. 10.0 CR, 2200-6200rpm, 234/242ex, 610/632ex, 112 LSA

Comp: XM 296HR-12. 10.0 CR, 2800-6200rpm, 242/248ex, 566/566ex, 112 LSA

A few observations: both have 112 LSA for vacuum, the Crane has milder durations but bigger lift.

Bigger lift...is it worth it? Will that make noticeably more power? Drawbacks are stiffer springs? Is that too much lift for the stock valve covers?

Thanks in advance as always.

 

Dropping the CR was a good move. Now you have better cam selection. Now your cam selections are getting closer together as well. The one will idle a little rougher than the other, and rev a little better upstairs. With HR cam make sure you run really good Hydraulic roller lifters. Get some recommendations and go with the best.
It is not the valve lift that interferes with the stock valve covers it is the roller rockers. I run .635 lift SR under stock height rockers. It can be done. Use good stainless rockers, they're smaller. It's the polylocks that are really the problem. Stock ones will not fit. There are some short ones available (Crower maybe, I may even have a set around here if you want). My machinist just took the stock polyloks and shaved a little off of them to make them clear. It was .15 or .20" or similar.

Make sure you get springs carefully matched to the cam and the lifters.

If you call Crane or Comp they may be able to tell you an example of what vac to expect. FYI Mine was in the 15-17 range at 850 with a 230 dur. I could have gone a little bigger.

Plug those cam numbers into a good Dynamic Compresion Calculator like Wallace Racing, and make sure it is 8.0 or 8.2 or lower. Duration strongly affects this, intake lobe centerline, even advancing or retarding the cam

 

Ok, just completed the dyno run. Custom Comp grind of 230/230 duration, 570/570 lift at 10.5 CR. 16 inches of vacuum at 850 rpm.

 

Sounds like you nailed a great combination! And it sounds great!

Now you are killing us with anticipation....how much power did it make .... complete with the stock cast iron manifolds?

 

this thread is worthless without numbers!