# Need old isky info



## David 389 (Apr 1, 2011)

I'll keep this as brief as possible. Many moons ago I had a 1966 GTO 389 that I built myself in 1973. At that time, the phrase "3/4 race cam" was common to use and I purchased what was called a 3/4 race Isky cam. I do not care to get into a discussion of the term "3/4 race cam "....I've already heard it all! Anyway, I really liked that cam and how my entire motor performed when I was through doing my build.
Now that I'm getting old, I finally will be able to do something I've been wanting to do most of my life since I no longer have that GTO and sold it in 1975. I will be building a 389 motor again and it has to be as close as possible to my original build as I can accomplish...other than less compression. I have a lot of knowledge on motors and Pontiac vintage v-8's, also my son is into it and has a nice '71 Firebird Formula with a very nicely built 428. I'm hoping someone out there has an old Isky catalog from the late 60's to early 70's and will be able to give me the specs on the cam I had. I will need ALL specs so I can find something as close to it as possible. I have tried to contact Isky 3 times via email and received absolutely no reply. At this point I'm angry with them and have heard since Isky's kid took over things aren't the same...including quality. Back in the day, Isky was the best. I am NOT willing to entertain the suggestion of going with a more modern grind cam. I realize that there are many cams out there that would be somewhat better grinds...but I have my own personal reasons for sticking with a very similar grind cam to my old Isky cam. I know it wasn't a real wild cam, actually just moderate but it worked perfect for me. 
I'm looking forward to knowing the specs of that great old cam. If I had to guess I'd say it may have been something like 212 duration @.050" with .440" lift and may have been a single pattern, not sure, and have no idea what the lobe seperation was. The cam was actually fairly mild but worked very, very well for me and had a nice lumpy idle and plenty of vacuum. Thanks, David.


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## geeteeohguy (Feb 2, 2008)

David, I feel your pain. I'm running a 389 that I built in 1981 in my '65 4 speed tripower GTO. The engine has about 50k miles on it, and runs really strong still, all these years later. I bought this car way back when for nothing and just kept it. When I built the motor, I used a huge Sig Erson cam that's still in the car. 12 inches of vacuum, and really lopey. Here's the thing: I need race gas to drive the car, and it's a street car. The compression is too high. The old style "big" cams and the factory Pontiac High Performance cams were designed to work with HIGH COMPRESSION. If you run a 9 to 1 motor with one of these cams, it will not produce the best power/economy/drivability. You need high compression for these old grinds, and with that, race gas. There is a silver lining: you can use one of the Comp Cams XE grinds (like a 262 or 268) that fills the cylinders more efficiently in a 9:1 motor. I reciently built a '66 389 for a friend's GTO, and he's running dished pistons (9:!) , an XE268 cam, and a single 4 barrel. His car runs on regular fuel (87-89 octane) and screams. It runs just as hard as my race-gas, tripower 389 (al least it seems to....no race yet!) and it's dependable and sounds mean. In know you want to stick with an old Isky cam, but I would suggest that if you do, build it all original and commit yourself to race gas. We liked the way the low compression/XE cam combo turned out so much, we're helping a friend build an identical combo for his '65 GTO. Have fun!


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## David 389 (Apr 1, 2011)

geeteeohguy said:


> David, I feel your pain. I'm running a 389 that I built in 1981 in my '65 4 speed tripower GTO. The engine has about 50k miles on it, and runs really strong still, all these years later. I bought this car way back when for nothing and just kept it. When I built the motor, I used a huge Sig Erson cam that's still in the car. 12 inches of vacuum, and really lopey. Here's the thing: I need race gas to drive the car, and it's a street car. The compression is too high. The old style "big" cams and the factory Pontiac High Performance cams were designed to work with HIGH COMPRESSION. If you run a 9 to 1 motor with one of these cams, it will not produce the best power/economy/drivability. You need high compression for these old grinds, and with that, race gas. There is a silver lining: you can use one of the Comp Cams XE grinds (like a 262 or 268) that fills the cylinders more efficiently in a 9:1 motor. I reciently built a '66 389 for a friend's GTO, and he's running dished pistons (9:!) , an XE268 cam, and a single 4 barrel. His car runs on regular fuel (87-89 octane) and screams. It runs just as hard as my race-gas, tripower 389 (al least it seems to....no race yet!) and it's dependable and sounds mean. In know you want to stick with an old Isky cam, but I would suggest that if you do, build it all original and commit yourself to race gas. We liked the way the low compression/XE cam combo turned out so much, we're helping a friend build an identical combo for his '65 GTO. Have fun!


Thanks for the info geeteeohguy. You bring up some good points, but I'm not sure I agree with you entirely in this case. You reference a "huge Sig Erson cam" in your car, but the Isky cam I reference is not "huge" in my opinion and may not compare well to your Sig Erson cam. The 10.25 comp. ratio motor (many times actually more like 10.00:1) will run fantastic at 9.3-9.5:1 on premium pump gas with a moderate old 3/4 race grind...I just need the exact specs and I'm still hoping someone can give them to me. I do know about the Comp Cams grinds you mention and may have to go that route if need be, but I'd reallt prefer to stick with my plan since I'm really not lowering the CR a tremendous amount. To repeat myself, I really don't think the Isky cam I need the specs for was a "huge old grind". I have read some books on the subject and I do understand what you are referring to....I'm just not confident that my Isky cam falls into that "huge" category.


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## 66tempestGT (Nov 28, 2009)

in on one. :cheers


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## 05GTO (Oct 6, 2004)

Look at the ISK-901271



> Excellent mid-range performance. Fair idle. Stock converter. 9-10.5 comp. .221/.221,.465/.465,.108.


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## JustAl (Mar 20, 2010)

Hi David, First off I can't help with the cam specs, but take a look at the H.A.M.B site ( Hokey Ass Message Board). Lots of old school guys hang out there and maybe one has an old catalog laying around. One thing though, anything over 9.5:1 compression ratio with iron heads is asking for trouble. Dentonation is a problem, sometimes it can't be heard, but the continous effects can break piston rings or lands or worse over time. Retro is neat, but the new cam profiles are superior.


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## geeteeohguy (Feb 2, 2008)

If Mr' P Body chimes in, he'll set things straight, as will Bear! David, more information is on the way, I'm sure. I'm out the door to screw around with the distributor advance on that "huge old grind" 389!!!!


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