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PowerPack Heads on a low compression 350.

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Old 11-12-2017, 05:23 PM   #1
Jna_1991
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Default PowerPack Heads on a low compression 350.

I called up the guys that built our motor for corrvette center in Colorado Springs to repair a spun bearing in my mothers 81 corvette. To make a long story short. I was told by Rich(the owner of corvettecenter) they were going to mildly up the compression and put a bigger cam with the rebuild. So whatever that meant they forgot to pass the info along to the builder.I called the motor builder. Stock 12.3cc dish pistons and a stock 390/410 cam. Just one more issue among the many we had with CorvetteCenter. I would not trust them to tune up my push lawn mower(story for another post).

So getting to the point. My thought is to temporarily up the low end seat of your pants feel with what I have, I am going to use the powerpack small valve heads off of my 327. I know the valves are small for a 350 but I am looking to up my idle-4500 torque ratings. From my understanding it will increase the velocity of the intake valves and make a very snappy low rpm motor. I can not find very much on this subject but what I have found is positive. So basically I am interested in anyone who has done this before. Not just opinions per say. I will be using an lunati barebones cam (10120101LK) the largest with a stock converter(which is relatively mild). I will eventually upgrade to a set of aftermarket heads unless I really love the setup and the gas mileage I get with the powerpacks.

FYI: I am aware of the lack of accessory holes and have made custom brackets.
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Old 11-12-2017, 05:43 PM   #2
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I have used PP heads on a low comp 350, but haven't done a "before/after" comparison. We used that engine in a streetstock and with a circle track cam. It's the smaller combustion chambers helping the lower end power , not the smaller valves. (the only good heads we had at the time)
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Old 11-12-2017, 06:13 PM   #3
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Thanks for the info, Did you feel that the heads and motor worked well together though? In your opinion would it make a good street car setup?
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Old 11-12-2017, 06:39 PM   #4
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Quote:
Originally Posted by Jna_1991 View Post
I called up the guys that built our motor for corrvette center in Colorado Springs to repair a spun bearing in my mothers 81 corvette. To make a long story short. I was told by Rich(the owner of corvettecenter) they were going to mildly up the compression and put a bigger cam with the rebuild. So whatever that meant they forgot to pass the info along to the builder.I called the motor builder. Stock 12.3cc dish pistons and a stock 390/410 cam. Just one more issue among the many we had with CorvetteCenter. I would not trust them to tune up my push lawn mower(story for another post).

So getting to the point. My thought is to temporarily up the low end seat of your pants feel with what I have, I am going to use the powerpack small valve heads off of my 327. I know the valves are small for a 350 but I am looking to up my idle-4500 torque ratings. From my understanding it will increase the velocity of the intake valves and make a very snappy low rpm motor. I can not find very much on this subject but what I have found is positive. So basically I am interested in anyone who has done this before. Not just opinions per say. I will be using an lunati barebones cam (10120101LK) the largest with a stock converter(which is relatively mild). I will eventually upgrade to a set of aftermarket heads unless I really love the setup and the gas mileage I get with the powerpacks.

FYI: I am aware of the lack of accessory holes and have made custom brackets.

The so-called "power pack" heads used on the 283's didn't have any accessory bolt holes on the ends. If you want more low end install a TH700R4 and a set of 3.70's.
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Old 11-12-2017, 06:53 PM   #5
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Thanks for the info, Did you feel that the heads and motor worked well together though? In your opinion would it make a good street car setup?
Yes you'll be fine, never notice the loss below 4,000 rpm likely, but above that yes. Your bigger than stock cam will mask part of that, but of course will hurt the low end itself.
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Old 11-12-2017, 07:11 PM   #6
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Ok thanks. I tried to aim for a slightly bigger cam that will work well idle-4500. Which is about where my car shifts now anyway. Hopefully this will work out well then. Just looking for someone with actual experience. Thanks again.
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Old 11-12-2017, 08:53 PM   #7
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Hi
I put some small valve 305 heads on a 75 corvette (L48 I guess).
The smog heads were cracked and I’d had the heads previously rebuilt.
The increase in compression really woke the car up.
It smoked the 255 tires from a standing start and was a piece of cake to drift.
It was in the process of being sold so I didn’t get to drive it at high speed.

HTH
Mitch
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Old 11-12-2017, 09:11 PM   #8
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Thanks guys, I know there was more options with the better flowing 305 HO heads that are newer then my 68 powerpacks. Although I hope my results are similar to Terminal_Crazys.

The main reason I am doing this is the 327 that I built had other problems.( My friend advised me to reuse stock rod bolts...never again). So the heads are rebuilt and I have them (0 cost). I only plan to put new howards stockish upgrade springs.

NeverTooOld I do plan a 700r4 swap at a later date. At that point I will buy a higher stall and build a new 350 in a vortec block with a roller cam. This is just for the next year or two to give me a little more power in this fuel crisis area corvette.The assumed 8:2:1 (probably less) static compression is not doing it for me. Also I already have brackets figured out as the 327 is in the car atm.

Thanks again for the info. I just really wanted to see if anyone had done something similar and there results.

Last edited by Jna_1991; 11-14-2017 at 01:16 AM.
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Old 11-14-2017, 02:06 PM   #9
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If youre getting a roller block dont waste your time with either of those heads, get some vortecs youre so much better off.
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Old 11-14-2017, 02:37 PM   #10
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If youre getting a roller block dont waste your time with either of those heads, get some vortecs youre so much better off.
You increase torque by increasing cylinder fill. The higher compression from PP heads may give an off idle increase in power from more compression, but will be all downhill from there.

The vortec head will also increase compression, but will also increase airflow dramatically over both your original heads and the power pack heads and will give you a good power increase throughout the rpm range. They are still a small port head, so are not going to hurt bottom end.

Mike
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Old 11-14-2017, 07:44 PM   #11
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Seems like many have missed the original question. He just wanted to know who had used the power pack heads and what they experienced. He already has the heads and is going to use them. Not ready to invest in new parts at the moment.
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Old 11-14-2017, 09:10 PM   #12
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So getting to the point. My thought is to temporarily up the low end seat of your pants feel with what I have, I am going to use the powerpack small valve heads off of my 327. I know the valves are small for a 350 but I am looking to up my idle-4500 torque ratings. From my understanding it will increase the velocity of the intake valves and make a very snappy low rpm motor. I can not find very much on this subject but what I have found is positive. So basically I am interested in anyone who has done this before.
Your assessment is correct. I do not have personal experience with the PP heads but I do have the modern equivalent with "128" heads installed on my 350. Great low end from the high compression (small cc chamber) and small runners but power will fall off at higher rpms over 4500 or so. Feels good tooling around town, short shifting with my 3.36 gears, I wouldn't want to drag race anyone past 30 mph though.

Just know that the PP heads will not have hardened valve seats so you will need to run a lead substitute. at $4-5 a bottle there goes any savings from gas mileage.

I would sell them to someone doing a restoration and use the money to get some used "113" heads. Same benefits but will provide more power in the upper rpm ranges, save 50# and they have hardened valve seats.

Last edited by Dynra Rockets; 11-14-2017 at 09:17 PM.
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