[Rapdron]

I'm getting to the point in the restoration of my 67 GTO ht of needing to install a motor in the car.
Since the original 400 HO motor is long gone, I picked up a 69 428 2 bolt mains with #46 heads, factory intake & Q-jet. I bought a summit 2801 cam kit & Coyles roller chain kit from Scott at Summit & a set of ceramic coated Dougs headers so far. It will be backed by a m-20 & a stock 3;55 8.2 posi. The car also has ps, pdb & a/c.
I want to hopefully just hone & ring the block & have the crank either polished or cut & have the rods rebuilt with ARP bolts. The motor is a complete 64,000 running motor which will only be used at cruise nites & summer weekend cruises to the New Jesey shore. I need to have the heads done, but my question is do I keep these small valve heads or get another set of heads to lower compression for pump gas?
Any & all suggestions will be appreciated.

[Rapdron]

I'm getting to the point in the restoration of my 67 GTO ht of needing to install a motor in the car.
Since the original 400 HO motor is long gone, I picked up a 69 428 2 bolt mains with #46 heads, factory intake & Q-jet. I bought a summit 2801 cam kit & Coyles roller chain kit from Scott at Summit & a set of ceramic coated Dougs headers so far. It will be backed by a m-20 & a stock 3;55 8.2 posi. The car also has ps, pdb & a/c.
I want to hopefully just hone & ring the block & have the crank either polished or cut & have the rods rebuilt with ARP bolts. The motor is a complete 64,000 running motor which will only be used at cruise nites & summer weekend cruises to the New Jesey shore. I need to have the heads done, but my question is do I keep these small valve heads or get another set of heads to lower compression for pump gas?
Any & all suggestions will be appreciated.

[travelinscout]

I have a 69 GP with the 428. I am also running the 46 heads and m-40 auto trans. I went with the 2802 cam and it was a real dog at first. Once I put in the conti converter 2200-2400 stall, it is now a rocket. I have 3.23 gears and nhave no problem lighting them up. As far as compression goes, I like things original so I am running about 10.5-1. Way too much for even super unleaded. The only thing that gets rid of the pinging for me is 2.5 gallons of 112 race gas in each tank. The car loves it and it runs awesome. When I did my motor, it was a 65k mile original car, I left the crank, pistons, rods alone. I replaced everything else. So far its been about 1000 miles and the car is great. Best of luck with your goat. Take care of that motor, there arent that many of them left anymore.

[grandville455]

Hey scout how's the car running ?You have any pics of her?

[b-man]

Find a set of 6X-4 or 5C-4 350 heads, the 94cc chambers can be cut down to about 85ccs which would net you a nice 8.8:1 compression ratio. Along with the 2801 cam you'll have nice runner.

Keep the small-valve #46 heads for a future 350 engine build. I bought a '69 2-bolt main 428 just like yours, it was still running but smoking. During the teardown I saw that it had broken rings and ring lands on the #8 piston, no doubt due to detonating on today's low-octane fuels. I gave the #46 heads to my brother and they were put to good use on a nice-running 350 that we pieced together.

[travelinscout]

Running great Grandville. Havent driven it much lately because of gas prices and mostly because it was 107 here yesterday.

[grandville455]

Man thats nice!!!!!

[Rapdron]

b-man
How much would the 6x-4 heads have to be cut to bring the compression level to 8.8:1. Would my intake also need to be cut? What years were they made & are there any years better than others?
Thanks for yur help
Ron

[Cliff R]

The 428's are the "odd ball" engines. To keep the compression ratios on par the factory used dished pistons in them. I had two different 428 engines in the Ventura prior to the current 455. The first 428 was topped with milled #96 heads and used the 744 cam, the second one milled 6X-4's with an HC01A cam. The static CR on both was around 8.8 to 1. The second engine ran better than the first one, but neither one delivered the type of power that I was looking for. I was also not at all impressed with the 744 cam, rough idle, a tad "soggy" off the line and didn't pull all that well on the top end. Looking back, I don't think I had enough static compression for it. The HC01A cam idled better and made power across the rpm range. The best ET I managed with them was 13.47 @ 104mph. If I were to build another 428, it would have have at least 10 to 1 CR and a bit more cam. These engines love to rev. Aside from having limited choices for pistons, a very good way to go.....Cliff

[Skip Fix]

I believe SRP has flat top pistons for 428s. Ross can make a dish at whatever specs from SD,KRE,Butler,Dude etc fro reasonable and still use the small cc heads and get an exact compression ratio you want for the street.Then you just have piston expense and not head and piston expense.

A friend had a 428 short block with the old UD 288/296 cam with moderate compression that always ran well in the 12s.

[b-man]

Ron,
Both Cliff and Skip have made excellent points, but since I figured you were intent on keeping the original stock pistons I suggested a head swap.

Nothing wrong with building a 428 with between 8.5:1 and 9:1 compression for a cruiser. For ultimate performance on premium pump gas (hopefully 93 octane is available) 10:1 compression is a good thing.

If your engine combo is very carefully built to use that much compression (piston at zero deck, polished chambers/piston tops, cam carefully chosen) and your tuning abilites are up to it, do it. Otherwise running a 'safer' lower ratio might be more prudent.

The '75 5C-4 heads and the '76 -'77 6X-4 heads came on 350 engines. All are equal in performance, take your pick. Usually milling them .060 will get you what you want (.005 mill removes 1cc as a general guideline). The intake side of the head will need to be milled the same amount (don't mill the sealing area for the valley pan).

The 5C/6X heads have 2.11 intake valves, screw-in rocker studs and hardened exhaust seats, your current heads don't. Your current heads would be on the ragged edge for pump gas use, for a mild build I say give up a point of compression and enjoy the drive.

[tom s]

If you can find a set of TRWs,they can be D shaped dished,I have had 2 sets done.Usually about $80 set.Tom

[Rapdron]

Thanks for all the suggestions. I will try locally to find a set of heads & send them to Hansen Machine for milling.
B-man, I need to kep this on a budget with 2 kids in college at the same time!

[Brian '74]

Rapdron,
KB now has pistons for the 428s. They are flat tops w/ the 2 valve reliefs and are priced reasonably.

BTW, Before you buy a set of heads and send them to Hansen's, why don't you see what he has in stock. I was going to go see Larry today but had been tied up here. I could go there tomorrow and see what heads he has for you. I have a set of 7K3's there that I am not going to use, if you are interested.

[pvan]

428's need compression to run hard.

Cliff is right about the 28 motor. I learned the expensive way how to make one run. On my first rebuild four years ago to make it run on pump gas I lowered the compression to 8 to 1 with a 214@.050 and 444 lift cam and it was a docile V-8 that was very smooth running but uneventful.
I was disappointed in the performance so last summer I really researched the 28 engine and came to the conclusion that it's design needed over 10 to 1 compression with a bigger cam in order to run. I had my 16's milled and ported, put 30 over forged NOS pistons and comp cams 280h cam. I did a ton of other machine work and now it runs hard. If I don't keep a close eye on it the rpm will easily go north of 6,000, I have had it at 6,200rpm more then once not on purpose, it loves to rev... and it also makes good power right off idle. I just finished installing 200hp of juice and it is a handful even though its a heavy weight.
Unless you are willing to build a 28 with compression over 10 to 1 thus requiring mixing 93 with race gas you likely can't get one to run hard unless you pack air to a lower compression version.
Like Cliff says the 28 is an engine all by itself and not for everyone.

[tom s]

my 434in motor with iron heads that flo in the 260 range,248@50 roller and 9.5CR made 478HP with a pair of 600AFBs.Pushes a 3640lb car to 112MPH.Dont think it is too bad for a pump gas street motor.IMHO,Tom

[pvan]

TomS you got a serious pump gas motor.

I am only saying what I believe from building the same 28 twice. I now have 70cc 16's and probably close to 11 to 1 compression.
Your post proves that there is more then one way to build a hot 28 motor.
I just like high compression 28's, but I also respect that you got the job done with lower compression, likely a tougher task.

[tom s]

stock 428 30 over TRW forged pistons with a D shape dish.Heads that flo in the 260 range,small solid roller.The motor has been in the car about 6 years and will be pulled in the next month or so to be freshened up.Tom

[Rapdron]

67_428_FBird
You have mail!
Thanks, Ron

[76TA428]

You guys seem to know a good bit about building a good running 428. I've got a .030 over 428 in a 79 trans am. I want this thing to run 11's to start but my 46 heads are hodling me up right now. I'm going to rebuild it with the 46's right now just to get the thing running. I dont mind high compression at all, I planned on using a 50/50 mix of 93 and 110 sunoco anyway for the t rack. This will be a streetable drag racer. I'm looking for the best heads in your opinions and general tips on building up the 428. If you dont want to post feel free to email. All my buddies run chevy's and know nothing when it comes to pontiac engines.
tib_003@yahoo.com