New Member - 1988 IROC

Hey everyone! I am new here and wanted to introduce myself.

I have been out of the car scene for many years and finally have the time and a little extra pocket money to invest in a car to play around with. I got it for $6700, I think thats pretty fair for what is in it.

I recently purchased a 1988 IROC Camaro off Craigslist. It has a 454 big block shoehorned into it, actual 9.3:1 compression, Holley 780 Vac Sec, pretty beefy hydraulic cam, HEI. TCI TH350 with 2800 RPM stall. 4.10 gears. Headers, line lock, cage, racing seats, 5 point. The builder is making a packet to mail to me with all the receipts for parts and machine work. So I will have all the little details then.

It is currently setup for the 1/4 mile strip. Has passed tech at Bandimere. It supposedly has only 5 break in passes on the build. So I am still taking it pretty easy on her but I can tel she pulls pretty hard.

My goal is to make it a bit more streetable by changing to a 4L80e (over drive), if I can swing it I may go with a TCI 6x and get the close ratio 6 speed gears. Definitely want a line lock. Probably change the open headers to a set of magna flow's with electric cutouts. Definitely want a stronger rear end, with disc brakes.

I would like to eventually have a fuel injection system, MSD ignition with 2 step, maybe a little shot of gas for those hard times lol.

The engine is a 1978 truck block with peanut port heads that have been worked pretty hard to increase flow. I will just run this build as it is until it shits the bed, then I would like to go with a 572 crate motor. For now I will focus on all the other goodies that need to be done, making sure that things stay together when I do change the motor.

Anyways I am sure I will be here asking many questions and learning from other builds.

Welcome Aboard. Nice to see you here. The car sounds like a beast!

Welcome from central Iowa!

Welcome aboard.

"pretty beefy hydraulic cam"

You probably will not like using a hot rod cam with an overdrive transmission.

The idea of an overdrive trans is to reduce the rpm's of the motor at cruise speeds, for an increase in fuel economy. Problem with a hot rod cam is that it does not want to make power in the range of rpm's where the auto trans wants to run......and if the cam is not efficient in the cruise range, then you'll likely be using more fuel than you would with a standard 3-speed transmission.

There is a range of about 500 rpm's from where a cam begins making power to where it is "up on the cam" and contributing to increased power in the motor. The efficiency range of most cams is about 3000 rpm's. In other words, a cam will make power from 800 (idle) to 3800 or from 1000 to 4000 or from 1500 to 4500 or from 2000 to 5000 or from 2500 to 5500 or from 3000 to 6000. Let's say you wanted to make your power at 2000 rpm's with an overdrive transmission. OK then, you'd want to begin making power with the cam at about 1500 rpm's, so that at 2000, the motor would be up on the cam and everything would be working as it should be. That cam would be rated to make power from 1500 to about 4500. Some cam grinders will try to cheat and tell you that their cam will be effective in a 4000 or 4500 rpm range. Bull Hockey. It will not. A 3000 rpm range is realistic, with a leap to 3250 if you are enchanted with the cam grinder.

Now, on the other hand, you decide that I'm full of the aforementioned Bull Hockey and decide to use the cam of your choice. After talking it over with the experts down at the Sonic Drive-In, you decide that you will purchase a stick with a range of 2500 to 6500, because this grinder really likes his products and claims a longer range of power for his products, a 4000 rpm range. OK, fair enough.

Now, using the aforementioned lead of 500 rpm's, remember if you want power at 3000, you use a cam that begins making power at 2500, you slide the killer stick into the motor and take off on a trip. What do you discover? Well, you probably discover that the motor doesn't have the power to pull the hat off your head at your assigned cruising rpm of 2000 and further, fuel mileage is in the toilet. Not quite what you expected, huh?

I have talked on forums to fellows who use cams that begin making power at 4000 and swear that their results are good with an overdrive transmission. I just smile and go to the next thread.

OK, you have some facts and figures to chew on. Make up your own mind as to what to do.

If you're ever in doubt about why something is one way or the other, take a look at the OEM equivalent of what you want to do. They are in business to make money with a product that works for everyone in the car market. Check out any new car with an overdrive transmission and listen to the idle quality. You are likely NOT to hear any cam lope from the motor because of what I have just taught you and because the intake valve duration is no more than 204 degrees, making for a smooth idle.
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The cam is a comp cams xtreme energy 284H.

I was wondering about the engine being within it's powerband in OD.

I was doing the math and the OD would take me from 3200 down to 2400 RPM at 65 MPH, thats not counting a little torque converter slip, say another 300 RPM? I had planned that i would only drop it into high gear when at highway speeds, as it is now I am afraid to take it on the highway as it's just hard on the motor. Speed limits here are 75 on the interstate, that would be 3700 down to 2750 RPM with OD. I definitely don't see me running the OD except when rolling at a speed that would give me at least 2500 RPM.

What do you think? I want to keep the 4.10:1 differential performance at the strip and not wear my motor out getting there lol.

Thanks for your time btw. When I was deciding to join this forum it was your posts that most impressed me. You help a lot of people with your extensive knowledge.

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Originally Posted by Renfro

The cam is a comp cams xtreme energy 284H.

I was wondering about the engine being within it's powerband in OD.

I was doing the math and the OD would take me from 3200 down to 2400 RPM at 65 MPH, thats not counting a little torque converter slip, say another 300 RPM? I had planned that i would only drop it into high gear when at highway speeds, as it is now I am afraid to take it on the highway as it's just hard on the motor. Speed limits here are 75 on the interstate, that would be 3700 down to 2750 RPM with OD. I definitely don't see me running the OD except when rolling at a speed that would give me at least 2500 RPM.

What do you think? I want to keep the 4.10:1 differential performance at the strip and not wear my motor out getting there lol.

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http://www.compcams.com/Technical/Dy...84H-10_001.asp
Here are some dyno results on that cam. You can see that they began reading it at 2500......
If I just wanted to keep the r's down for longevity and was not too concerned about mileage, I'd use the motor as is.

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If you want to simply lower cruising or highway rpm's perhaps changing the rear axle ratio would be easier.?
Maybe something in the 3.7 to 3.9 ratio would be better suited? Just a thought.

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Originally Posted by 34_40

If you want to simply lower cruising or highway rpm's perhaps changing the rear axle ratio would be easier.?
Maybe something in the 3.7 to 3.9 ratio would be better suited? Just a thought.

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I hear ya, I just want to keep the strip performance of the 4.1 gears. I figure with the OD transmission I could get the best of both worlds. It is mostly a track car but I do like to drive it a little around town and to the strip. The 3.73 gears wouldn't really drop the RPM that much but they would hurt my track times.

I do plan to eventually do a major change to the car and stuff a 572 in there with EFI, with a little less radical hydraulic cam and I kinda want the TCI 6x transmission with trans brake. Winter time project. The 572 may have enough HP to push it down the track with some higher gears, according to my numbers it would like something around the 3.73 range due to the extra HP, vehicle weight and finish line RPM of 6k. As it stands with the current motor the 4.1 gears get me across the finish line at just over 6k RPM.

Nice! Hard to believe these cars are 30+ years old. I vividly remember when they were new.

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Originally Posted by falconvan

Nice! Hard to believe these cars are 30+ years old. I vividly remember when they were new.

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I agree, I had a 1984 5.7L, red with t-tops, bought it new. It was a slug though, those were bad years for performance.

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Originally Posted by Renfro

I agree, I had a 1984 5.7L, red with t-tops, bought it new. It was a slug though, those were bad years for performance.

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We have an 82 z28 with a stock 305,it's definitely a car you don't want to get cocky with lol