Technical power pak heads

hello I was given some chevy heads a set of 441s, a set of 896 pwer paks and a set of 520 power paks. the 441s very good condition the 896s look like new after cleaning I see someone has installed 1.94 valves in them and also some deshrouding for the intake valve upper area. they also have no exhaust valve rotators and some odd looking retainers n there are spacers under the valve springs( I ***ume because the bigger valves were put in an raised the valve.) I have a 74 350 for the heads stock 4 releif pistons .020 below deck this is a low use engine maybe 500 mles a year. am leaning towards the power pak heads for more compression. do i need to clean up the cly head chambers to lower compression or just use premuim fuel ? also will a stock cam work in this engine ? thanks

 

.020 below, are the true flat top pistons? Or the ones that have a ridge around them and then another .030-.040 or so where the pistons are flat with the valve reliefs?

 

Ok they have the dish n 4 valve reliefs

 

Show you what I mean. My finger in on the “ridge” that sits roughly .020 in the hole. You can see the rest is much lower. This piston yields about 9:1 with 64 cc heads in a 350

 

they have the ridge I had used a comp calculator came up with like 10 to 1 I can reck I used 6cc for valve reliefs, .020 below deck, 60cc for head , .038 head gasket I am just looking for a decent motor to pull a old truck or car body around thanks

 

I think, the piston I showed has about 16 cc of volume. Also the 9:1 I mentioned is with a .022? As I recall, maybe .025 compressed head gasket.

 

thank what I have so no worries about to much compression my heads are 60 cc I think I can do a somewhat accurate head volume ck with a sheet of plastic n a medical sryinge

 

Yes. Should get you better than quoted sites, especially since large valves were put in the PP heads. As I recall they were on the mid to high 50cc range. I think (not sure) the 441’s were used in the late 60’s/ early 70’s?
But yes, be prudent and figure it all out beforehand

 

so my 441 heads (76cc) would flow better but have alot less compression n less pulling power ?

 

Well, now you are getting out of my league. I’ve no idea on flow v velocity at different cam lifts on the heads you have.
Eventually if we keep bumping this thread up, someone that knows will come along

 

well thanks, I will sort it all out in time

 

It’s Sunday, getting late to boot. Bump you post up in the am

 

Proper squish is more important than a half point in compression.Pistons .022 down, steel shim gasket, will give a decent .045 squish and reduce possible detonation, better throttle response ,especially on mid octane fuel..

 

have been reading up on squish. thanks. (also have owned several triumph, bsa bikes 67 daytona 500, bsa 441 victor, driven nortons (combat) royal enfields (750 intercepter) )

 

For 500 miles a year I would run the 441.

Unless you have other wild modifications like cam headers dual plane intake etc the compression bump won't do much. Depends on the whole combo.

 

yes, this stuff is not as easy as just bolting stuff on plus no acc. holes in old heads. Are the 896 n 520 heads worth anything besides s**** ?

 

For a 283 they are..I have a set that I am saving for a 283 block.

 

ok i'll keep them 896s show very little wear the 520s have the smaller valves. maybe a 283 eng will show up in my area I was reading that a 283 with small valve heads can get very good fuel economy thanks

 

What's the LSA on your camshaft?110 or less don't worry about spark knock.
112 or more and 9:1 CR....??( with reg. or mid-grade fuel?)
6sally6

 

Yes. It will be very anemic in power and fuel economy will be terrible. With your short block you should be looking for 1.94 int. and 1.5 exh valves with no more than 68 cc combustion chambers ( 64 would be better).

 

Am not going to use the 75cc 441 heads. am ckn around. I did get a cc setup here n measured the 896 heads at 60cc also did the dish 4 relief pistons n got 12cc. there is a auto recyler close by n have vortecs and the "swirl port' truck heads. I can pull for 40 a head plus 30 day exchange. the smog heads are a waste of time

 

prices went up
CYLINDER HEAD (30 Day Returns)

$58.60
Core Price: $5.00


ENGINE (30 Day Returns)

$214.84
Core Price: $35.00

 

Sounds like the 896 is your best choice. Running regular gas should work fine . Maybe another cam with more lift and/or 1.6 ratio rocker arms. Good work on finding what your volume numbers are.

 

been reading up on chev heads, these smog 75cc heads are really not good for much unless you have higher compresson pistons. better to buy better heads.

 

I have a 355 with flat top pistons and ran 993 heads with 76 Cc chambers...
I could spin my tires easy... car ran fine.

I changed heads because the cam I had wanted at least 9.5 compression.
Depending on your combo, which we don't know you could be fine with those heads.

 

I have only the stock camshaft at this point but got some corvette header 1980's ? i cut the sir tubes off n welded up I bought a motorhome n drove it 30 miles home n pulled eng n trans It ran fine no smoking or overheating

 

was given a "like new" camshaft (RV) which was installed with new chain but will change eg was dissembled oil galleys cleaned new cam bearing s main n rod bearings It ran maybe a hour when I got it unstuck from ice n snow drove home no issues shifted fine pd 250.00 for it n sold s**** body n frame

 

Those Are dished.... so even with 64 Cc heads your compression is still 9 to 1