I just got off the phone with Comp's Cam Help. They suggested the XE 249-12 cam for my 305. It is soon to have headers, it has a Performer intake, Flowmaster Force2 cat back, 700r-4, and will have 3.4? gears. I have to leave the computer on for now, but when I retire from the Air Force next fall, I will take it off the computer depending on where we move to. Are they being conservative? I was looking at the XE 262H, but now I am wondering if that is too much? I wouldn't think so, but I will let people who know more than me give their opinion. Here is the spec card on the
XE-249 and the XE-262 . Let me know what you think.

THANKS!
Mark

 

Nevermind, I mistyped in the search, and that's why I didn't find anything. If you still feel like answering, I would still appreciate it.

Mark

 

They tend to be somewhat conservative. They would rather that your car run a little slower, but be on the "safe" side as far as emissions and tuning issues.

A LG4 auto runs alot beter with a XE256. A XE262 is a bit too much in an auto car, without a real loose converter, really good exhaust, and more gear than that.

 

My one experience with the Comp Cams XE series has shown me that they are more aggressive than their numbers indicate.

When I switched from a Crane with 216* @ .050 to a Comp XE with 224* .050 duration the change was a LOT more than jsut 8* of duration would suggest. The power moved "upstairs" considerably and idle vacuum and quality went downhill considerably. More than I had expected.

I would think the XE 262 (218* duration @ .050) in a little 305 with auto trans would be sorta "ragged edge" in terms of idle quality and snappy around-town torque.

 

I'm with RB. Every time I've called to discuss cam recommendations, they've been a little "chicken". I think they may just have a chart of recommendations that doesn't vary much from the catalog, and stick with that. Even after discussing head port volumes, changed runner positions, intake modifications, valve sizes, etcetera, they seem to stick with the "chart".

They probably avoid suits and warranty claims that way.

 

XE 256 it is!

Mark

 

Here's a chart from DD2000. Try not to look at the actual numbers so much as the torque curves.

I used the two cams you gave the specs for. Notice how the peak HP and every RPM above peak HP of the 262 is only slightly higher than the 249 (the 249 is the dotted line), but the torque below that is higher with the 249. HP above peak isn't used very often so I think you'd be better off with the 249.

I think they want to make your car perform on the street well, and torque does that. Plus lack of torque is something the 305 suffers from anyway.

 

Wow! I wouldn't have thought that the smaller cam would have more under the curve like that. I assume that would help the vacuum also. I wonder how it sounds compared to the stocker that is in there now? How accurate is Desktop Dyno? That looks like a HUGE torque and horsepower increase over my stock 165 hp and 285ish torque.

Thanks for the Dyno chart! Thank you all for your help!

Mark

 

Hey AJ, how did you get the dyno 1 and dyno 2 to be on the same page? I have never done that with the DD 2000.

 

Smaller cams build torque in the lower rpm range. Bigger cams build hp in the higher rpm range. It's a tradeoff, more lowend tq or more highend hp. The lower duration will also help the vacumn too. IIRC the XE262 doesn't make a whole lot of vacumn on a 305. With a new cam you will notice a huge increase in power over the old peanut cam. I'd go with the XE256 since you're probably running stock heads and your rearend isn't geared very high. I think the XE262 would be a little much, especially in downtown traffic.

 

I just figured it out. I wish that I had known about this after several engines I have built. I always printed out the graphs and put the one on top of the other and held it up to a light.

 

In my opinion TPI is the ideal design for a really quick street car. Which will also turn half way decent E.T.'s. G.M. used that to put a stock 305 TPI in 1990 into the 13's. Now someone takes that same car modifies the lower end. makes it biger and stronger and they stick in the wrong cam and run ET's that would make me burn my car and leave it at the track. They cry induction limited.. Are they ? The car ran high 13's or low 14's berfore on induction limited. it runs low 15's now ? I think it's because the cam destroys the calibration of what the TPI is all about. I been studing the set ups on here for a while I don't see that Comp cams makes a true TPI cam. They Every car that has a boat load of money in it and runs crap for ET's with a TPI induction unit on it almost always carry the same charicteristic. A comp cam. Induction limited is a joke of your cam isn't right.
Something to think about is this. Max volumetric effieciency is at peak torque. Very few street cars that are like 350 cubic inches actually move 350 cubic inches of air. They usually are more like 80% of that. That gives most a 273 cubic inch engine or less. If you have ever felt the cam come in a carb'd hipo car it's when it's pulling max efficiency which will accomidate the pull into the 7000 grand area if it can take that much R's. This street car utilizes the efficiency to the point that horsepower takes over. It still may not hit max V.E. but it's fast because when it gets into a higher rpm range it's moving air. . NowTPI... Fast port volocity and make room for the most air volume you can get. Porting of heads, intake and add some headers. Big valve heads if possible. Now pick a cam that is a TPI cam or designed to use with a high torque curve in mind with fuel injection. You should not feel the cam come in and it will rap quick. The torque ceiling will cross the horsepower ceiling at almost the same place. around 4500 to 5000 rpm and the air flow will run out about then too. It all happens quickly and the end result is unreal quickness. Reason, The efficiency is above 80 % maybe closer to 100. This will result in way better than average E.T.'s when compaired to lastnight's e.t. on here. Way better...This is for those who have poor times and those who want to chose a camshaft. think about all this ahead of time. A Lt1 cam, and most other GM cams are designed for a flat torque curve that come on early and utilizes air flow as a whole at a higher RPM level. They are not designed to run with a TPI system but still will work. Taking all this into account I did this.....

- 355ci, WS6, 5speed -
* Ported & Polished Big Valve Cylinder Heads (Cast # 993)
* 2.02 & 1.6 Manley Pro-Flo Valves
* Harland Sharp 1.6 Ratio Roller Rockers
* Crane Valve Springs and Retainers
* G.M.P.P. Ram Jet Roller Cam
* Crane Roller Lifters
* Speed Pro/TRW 1.25 Dome Forged Pistons
* Windage Tray
* Lightweight Nodular 16lb Flywheel (Came Stock)

* Induction - Ported and Gasket Matched
Plentum
Manifold
Runners
52mm Holley Throttle Body
Custom Built Adjustable Fuel Pressure Regulator
#19 GPH Injectors running at 50lbs

* Exhaust All New
Edlebrock Chrome T.E.S. Headers
High-Flow 3" Carsound Cat
Dynomax 3" Exhaust Tubing and Tail Pipes
A 3" Flowmaster American Thunder Muffler

 

So what does the setup run?

 

This is kinda lame but I have not run it yet. I have had 3 cars including this one that were pretty fast. 1st car was a Dart 340 sport 12.90's, A 68 Camaro 13.50's with a powergluid trans no less and this one. This car 90 WS6 5.0 - 5 speed dual cat car was a runner from the factory and I've had it since new. I spent a lot of time studing pricable and I've been a auto tech for 30 years on top of that. I watch high dollar failures on here and whatched what they have done upon failing. I listen to Lingenfelter and Emanual for performance and I believe I've figured out what they did from the factory with TPI as it progressed and tried to explain it the best I can. The car... It's shockingly quick for a mostly stock modified chevy car. Oh, I just flat blew my cousuns drawers off his z28 with a aluminum head, tpi vette motor in it with a automatic... guess what.. comp cam.. I'll get some numbers when time permits..