Hi all,

been gathering parts for this swap for quite some time but just finally bought the big ticket item: ported heads. Now that I have enough details about the rest of hardware, it's time to pick a cam. I've emailed many of the major cam providers but thought I'd ask the pros here for some advice as well. I've read through just about every cam, dyno, and track post I could manage on this and other forums plus respected magaines, but sometimes it's hard to separate concrete good advice and scientific testing from the nont-so-good-evidence that's out there, so I thought I'd start my own thread.

Ok, so here some details. '95 Z/28 Convertible, CPT 4l60e, 2800 stall, full boltons, upgraded street suspension. The goal of my build isn't peak HP but torque torque torque! This car is my wife's daily driver, we cruise in it, take long trips, sit in traffic jams, drive in the snow: we want a fun ride. Part-throttle response, decent idle and vacuum, cruising economy, and emissions are all concerns. Reliability is also a priority, so I don't want to rev real high to get into the meat of the powerband.

Rev limiter will be set to 6200 but I wouldn't mind have optimum shift point around 5800-6000 for those blasts down the track. I know lots of people spin to 6300 on the stock bottom end (or higher) with no problems, and that's great for track performance but realistically the engine rarely even sees 5k on the street with its current mostly stock power levels, so my focus is clearly not a big cam.

The torque converter locks up at 1300 RPM and typical cruising is 1500-2500 RPM so ideally I'd like good throttle response in that range; for real acceleration the torque converter flashes to 3000, so I'm not sure what's ideal for a desired torque peak as it relates to part-throttle response and overall WOT performance. I'm playing with simulators but they simulate WOT; I've never read anything (and I've been looking) that compares a WOT dyno run with parth throtle response, economy, and torque. I assume they are all related but I don't have any good facts.

Stock ported heads w/ LT4 sized intake and exhaust valves (2.00/1.55), flowed:
Lift Intake exhaust
0.2 140 105
.3 200 140
.4 240 170
.5 270 190
.6 280 195

I'll be topping those heads with Speed-Pro 1.6 NSA full roller rockers, 7/16 studs, and a choice of two valve springs:
Beehive style springs that are installed on the heads
O.D. 1.290"
I.D. 0.885"
Install - 1.800" 130 lbs
At 1.200" - 318 lbs
Rate - 313.3 lbs/in
Coil bind height - 1.140"
As installed, I'm told they are at 165lb seat pressure, 400lbs open; unknown locks, steel retainers, locators

Dual Damper Spring
O.D. 1.464" (I.D. outer 1.080")
I.D. 0.724"
Install - 1.900" 138 lbs
At 1.250" - 383 lbs
Rate - 377 lbs/in
Coil bind height - 1.200"
Comp Cams - Locks - 611-16 (10 degree)
Comp Cams - Retainers - 740-16
Comp Cams - Locators - 4781 - 16

I orignially bought the dual springs with the intention of A) getting a spare set of heads to port and then when finished B) running a cam with wild lobes; but the beehives came already installed on the set of heads I purchased so I have an extra option. I know for one thing, Comp recommends using the beehives with their XFI line, but I'm not sure if non-behives are OK as long as they have the necessary pressures, or if it's more a harmonic resonance and weight consideration that requires the beehives. Keep in mind, I won't be spinning this to the moon, so I'm not really sure what spring is best.

I'd like to use those heads to the best of their flow capabilities with fast opening ramp rates, slightly gentler closing rates for noise and reduced wear, have the right LSA to pass emissions without the EGR system, increase efficiency a bit with a DCR around 9.0:1 for use with 93 octane and a 160* thermostat. I know SCR can be bumped to a max of 11.1:1 with thinner head gaskets so I shouldn't have a problem getting the required SCR dialed in, especially since the cam I choose probably won't have too much overlap.

So, what do you all recommend? My leanings right now after my own research are the comp XFI line (either the 252, 260, or 268), lunati VooDoo (also thinking EFI line, but don't know too much about it; is it competition for the XFI?), and similar offerings from crane and crower (which as far as I can tell have older-tech lobes, which is not necessarily a negative). But like I said, it's a bit hard to find detailed, scientific information about "what cam is best", "what lobe designes are best", etc since most people are either hardcore racers that don't have the same goals I do, or just tried one cam and said it was great (regardless of what other threads or advice says that choice was wrong). HP/Torque estimates are fun too, I'd guesstimate upper 300s for RWHP? Sims are nice to play with, even Comp's CamQuest which seems very optimistic; how unrealistic is 400 tq 400 hp with my goals in mind?

Thanks all in advance! I don't post too much here but have been using the search function for years, and mostly finding everything I needed to know was already answered somewhere.

 

You may get 20 people that reply to this thread but I can tell you there are only a handful of guys on this board that can give you an answer that's worth more than a grain of salt.

If you talked to the guys at comp cams and told them what your goals are, or other cam builders, you should trust them.

It sounds like you know exactly what you want so when you speak to comp tell them your goals and they'll be able to recommend a cam I'm sure you'll be happy with.

I got my cam from a member here. It was custom made by NuTek and the spec's are in my sig. The cam is awesome and has power all the way to 6800 (I usually only take it to 6500).

You may want to give them a call and see what spec's they recommend based on what you want, as my cam from them has made me very happy.

 

Thanks, I'll check out NuTek. Do you know what power you're putting down with that 226/231 cam, and what your heads flow?

 

Comp Cams help line is pretty useless. I would not rely on them. They just plug what you tell them into their "Cam Quest" program, which you apparently already have. You have to know one of tech (not sales) people at Comp to get any decent info out of them. There are plenty of people who will spec out a cam to your needs, it will cost a few bucks. [I] can't shill for specific vendors, but there are plenty out there. Google "custom cams" for a sample.

I can give you some advice if you want. PM me.

Rich

 

The other thing I'm considering is just sticking with the stock cam. One thing I'm worried about is port velocity; the high lift from the heads is mostly non-conducive to my goal of lots of low-end torque, unless I keep overlap in check (which of course limits scavenging at higher RPM and trades off upper RPM performance, which I'm OK with). It doesn't have to pull tree stumps off idle, but I do want it to be efficient (if not necessarily powerful) in the 1800-2200 RPM range which is where it lives cruising on the highway. The meat of the powerband can start around 3000 since that's where it flashes to when the TC unlocks, but the car spends lots of time on the highway so it needs to be good on gas.

Keeping the stock cam is certainly easier, and it'll also benefit from the 1.6 rockers and I could use a thinner head gasket to get the compression up a bit (if necessary). I'm willing to spend the money on a custom camshaft and the time to install it and do everything right, but only if it's going to be a significant improvement. While I'm in there I'd replace timing chain and sprockets, lifters, etc, and all the little things add up. Plus I can always add the cam later too if I am not satisfied with performance. This would give me a good baseline to start from, and I'd rather be unsatisfied with stock cam performance than be unsatisfied with too large a cam. I've head it's always best to go with too small a cam rather than too large.

I remember reading about various 1/4 records for various stock components, but can't seem to find much for fastest stock-cam LT1 times. I found some nice collections here and here, but most people when changing heads change the cam too. Does anyone happen to remember or have a link saved? Maybe results from the past LTX shootouts?

Also interesting is that I haven't heard back from any of the cam manufacturers I emailed, with basically the same info as in my first post. I believe I contacted Comp, Crane, Lunati, and maybe Crower. Oh well.

 

You have the wrong idea about lift. The SBC is notoriously "undervalved". Well, just about any 2V engine is. In addition, there is a lot of valve shrouding, that is why there is benefit from as much lift as is practical, especially on the intake side. The limits are the need to keep duration in check - a cam lobe can only be so steep.

I am sorry I didn't respond to your PM. I try not to get to specific in these threads because I don't like to get into discussions/arguments with ignorant people. But you need a cam with intake duration in the low to mid 210's and about 10 degrees more exhaust duration. The LSA should be ~112 degrees. You seem stuck on Comp, so here is what you should get.

Intake/Exhaust
lobes 3190/3314
214/224 @ 0.050"
.565/.536" (1.6 rockers)
112 degree LSA
108 degree ICL (4 degrees advance ground in)


ps: you didn't listen to what I said about cam help lines, which are generally useless. If you want professional advice on a cam you will need to pay for it or know someone at one of the cam companies.

Rich

 

My CompCam "502" passed CA smog with 218/224. It had great mid-torque. Something to consider...
360 RWHP / 360 RWTQ

 

I should add that there are stock cammed N/A cars running damn near in the 6s in the 1/8th.

OP, it sounds to me like you're trying to reinvent the wheel. What I would do is just research what other people have built and how they like it, then roll with it. I find that you have to find a balance between real-world experience from other LT1 enthusiasts and professional advice. In most cases, you can get professional advice from LT1 enthusiasts, which is the most advantageous.

For example, Rich.

 

What he wants seems to me like the lpe 211/219 cam.

 

The ideas in the last couple of posts are goiod.

Rich

 

I like both Rich's advice, also the CC502 is a nice choice. Back when my car was a dailydriver, it had the the "Hotcam" which nobody likes on the forums but I really liked the driveability, performance and even fuel mileage. The car ran low 12's on motor and low 11's on a little n2o, then drive back and forth to work everyday. I should have kept it that way actually. LOL would have save me alot of money but the desire to go faster got me. Later

 

What?

 

that completely defeats the purpose of a message board, of course some people are ignorant but that is just life

people correcting each other is how everyone learns. including yourself. remember the other week when you told someone that he would not be able to tune a car with a 109 lsa or make it idle. when you were corrected you learned something and besides if you had just pm'd him you would have passed on some terrible misinformation and no one would have had an opportunity to correct you

OP, if i were you i would be contacting the custom cam grinder of your choice and talk with them extensively about what you want and what you ultimate goals are

 

I would go with something like the LPE 211/219 but with it custom tailored to your heads.

I would talk to LE/AI, both are not the best cam knowledge people/places to talk to but they know LT1's. Few shops deal with them anymore due how easy it is to make big HP with the LSx motor.

I would also call the major F body shops, they are focused on LSx now but at one point they did build lots of LT1's.


For not wanting the all power in the world you sure got a dam good set of heads. They would really show their potential at 6800-7k, but i am sure you will make good power with the lower shift point.

 

For some reason, I don't say him saying that!