[roy381]

Hi folks I'm looking to rebuild a 73' standard bore 455 short block .I have a set of 6x-4 heads(need rebuild) and a 72' cast iron intake going to mate with a th400.A good friend supplying the machine work.Its going into a street 67 tempest clone. My thought is to go with forged rods and pistons.Looking for 400 plus HP.I have a $2500 budget maybe a bit more.

Lets hear what you think.

Thanks in advance!

[mechanic17]

Hey, Welcome!

With that budget, it'll be nice to have a "Good friend" doing machine work. Machine shop bills will eat half your budget and more, and you need the $$ for parts!

6x-4s should work nicely with a 455--somewhere in the 9 to 9.5 static CR range. You can choose a cam and springs to maximize that with the help of the cam gurus up here. An 041 factory cam/ Rhoads lifters will get you to 400hp, but a modern grind might suit that compression better.

For now, I'd concentrate on the short block. Magnaflux it first, and check the bore tapers. If it passes. . .You'll want flat top pistons--do a mockup assembly with the actual crank and rods you'll be using ($3-400--Ace or Ebay. I don't recommend Scat as the side clearance is too wide.) Then you'll know what needs to be skimmed off the deck to zero it. With a .042 head gasket, you'll be right on the money for quench distance.

If the heads need to be decked too, so much the better. More compression. If they are too beat up, just buy another set for a few hundred--I would not bet the farm on that particular set of heads--there are plenty of 6Xs out there (that set probably came off a 350).

Later you can see what trick parts the budget will stand--aftermarket oil pan, 1.65 rockers, aluminum intake, that kind of stuff. $2500 will not get you deep into this stuff, so your '72 intake would be better kept in favor of a decent carb.

Good luck.

[steve25]

Some 375 HP can be had easy with the those heads in stock form and with out anywhere near a crazy cam, but if you want more than the exh valves should be stepped up to the standard 1.77" size and the exh ports atleast bowl ported to take advantage of the bigger valves.
Be sure with eitheir valve size used that the main exh seat when the valve job is done is .080" wide and you will have no issues with no lead gas.
With eitheir size exh valve have the valve back cut to a 30 degree which will leave your main seat ( the 45 degree) at a .090" width if you can, or atleast match the .080" width in the head.
If you keep the stock 1.66" valve do not do a multi angle job on the head, as this will only make it harder to get the needed .080" wide seat, plus but into the ports high lift airflow numbers as the multi angle valve will sink the valve alot!
With the 1.77" valve you can do a 2 angle valve job and the second cut used should be a bottom cut of 60 degrees, this will give a good combination for better high lift and low lift flow.
Whatever you do sink as much money as you can into the bottom end like you are with the needed rods and such, you can always then pull the heads to up grade them and leave the good short block in the boiler room!
If your Tempest has at least 3.08 rear gears you will be quite happy, but with the torque of the 455 in the least a set of hop stop bars will be needed on the rear!

[Cliff R]

Most 6X-4 heads will come in around 92cc on the chambers, I've seen samples as high at 96cc, but most have been at or very close to 92cc.

We usually have them cut some to clean them up, leaving them around 88-90cc or so, and open them up for the larger 1.77 exhaust valves.

The compression ratio when used on a 455 with flat top pistons will be closer to 10 to 1 rather than 9 to 1.

I've built and dyno'd a number of these engines, and they will make at or very close to 1hp/cid with very little porting of the heads. A few steps to get the heads up to 230cfm or so results in 450hp with the right cam.

For cam choice, the Crower 60919 or factory 041 would top my list. I'd install Rhoad's lifters on it, and use high ratio rocker arms like the Harland Sharp's or Crane 1.73 Ford rockers. This will mimic the power of a hydraulic roller cam at much less cost.

For rods and pistons the readily available low cost "H" beams are fine, and there are quite a few good choices for pistons. I would NOT use the Speed Pro's, they are an old/obsolete design with heavy pins. Upgrade to the KB forgings or equivalent. Icon, Ross and several other really nice pistons are out there as well, and they will take the modern ring packs.

Deck/square for zero as mentioned, and use the Felpro blue head gaskets at .039" crush. You don't need the 1016's, the stock ones in a standard kit are fine for the power level.

We also use and recommend aftermarket oil pans. My first choice is the Morroso pan, Canton makes a nice one as well. No need to go broke or use any fancy parts internally past the rods, pistons and ring pack. The factory 455 cranks are excellent, stock Melling oil pump, and Cloyes factory wide link plate timing set. The aftermarket 9 keyway roller sets are OK, but I've had several of them stretch out WAY too much for my liking, so went back to the link plate sets, although cam degreeing is a tad more complicated using offset cam/crank keys.

Buy good pushrods, the stock replacement type are marginal for these engines. Comp Cams .080" wall are good parts, I use and prefer the stronger .118-.120" stuff for these engines. I say this due to evidence of pushrod "flexing" when we've pulled these engines down for any reason, although we've never had any failures with the good .080" wall stuff.

Stock intake is PLENTY, I use one on my own engine making a lot more power, and a factory Q-jet and HEI distributor. Nothing aftermarket will run any faster or last nearly as well in long term use. MSD's are OK, but offer NOTHING on the dyno in measured improved performance. Same thing with carburetors, none of them will outrun a correctly tuned factory q-jet anyplace, they just use more fuel for "normal" driving.

My old 455 engine was the test "mule" for the KRE heads a few years back, here's a link to the articles:

http://www.highperformancepontiac.co..._dyno_results/

http://www.highperformancepontiac.co...track_results/

Hope this helps some......Cliff

[mechanic17]

Cliff, I see COMP CAMS #7262-16 are the 5/16 .080" wall standard length pushrods. I believe I had to order custom length with my 1.65 rockers and having the decking done, etc.

Anyone know the best place for custom length pushrods with thick walls? The standard ones are $100 per set. I don't think the guy's budget (or mine) will stand $200.

How much are you guys paying for valve seat and guide work?

[Cliff R]

I haven't been able to use a "standard" length pushrod in many years. Decking/squaring, valve length, rocker arm choice, etc, will require a special length pushrod about 19 times out of 20, at least from what I've seen here.....Cliff

[Blued and Painted]

Before you get started, plan on doubling your budget.

[zeebo]

cliff, what do you need to do to measure for the correct length pushrods? thanks

[72LuxuryLeMansLa.]

Originally Posted by zeebo

cliff, what do you need to do to measure for the correct length pushrods? thanks

http://www.summitracing.com/parts/cca-7702-1/overview/

[David Brown]

Is that the right rod? It is for 6.8 to 7.8 length. I have a 7704 which is 8.8 to 9.8. Standard pushrod length (1970) is 9.17 for a 455.

But on this topic, because I have never measured the rods, what valve spring do I use to check the length and where can I buy one?

[Cliff R]

Measuring for pushrods takes minutes. I take one full turn down on the hydraulic lifters and turn the engine few a few times after marking the valve stem tips with a magic market.

Record the measurement, then add in the plunger travel left from one full turn till bottomed out. This is easily determined by putting a dial indicator on the pushrod end of the rocker arm, and turning the adjustment nuts till the lifters are bottomed out. Otherwise you are going to have to build yourself a solid lifter from a hydraulic one with one full turn of plunger travel in it.

There are so many potential combinations out there these days the pushrod length can be all over the map, so fully expect to be buying a custom length set. We just move on up to the thicker ones these days, they aren't that much more money than the .080" versions......Cliff

[72LuxuryLeMansLa.]

Originally Posted by David Brown

Is that the right rod? It is for 6.8 to 7.8 length. I have a 7704 which is 8.8 to 9.8. Standard pushrod length (1970) is 9.17 for a 455.

But on this topic, because I have never measured the rods, what valve spring do I use to check the length and where can I buy one?

David I didn't mean that one in particular, just that I will be using this type of checker. I should have waited until I drank my coffee to post.

[Bruce Meyer]

Originally Posted by Blued and Painted

Before you get started, plan on doubling your budget.

That's no joke. 2500 will get eaten up from machining alone.

[66 Gas Tires Oil]

i just did my 1975 455 block with 48 heads got custom pistons to make 9.5 comp. the machine shop charged $65 an hour. with only a plate hone, line bore, head port, vavle job and all the necessary block prep and cleanning the oil galleys. the machine shop bill was $2008. because someone tryed to recently rebuild it, i did not need a timing set or an oil pump. the parts came to $2800. i supplied the parts that is with some scat rods on amazon and ross pistons and diligent shopping. good luck with $2500. what ever part you skip or step you miss that will break so you got to do it right. i suggest you save up some more and use good parts too.

Jim

[roy381]

Originally Posted by Bruce Meyer

That's no joke. 2500 will get eaten up from machining alone.

Thank for the input guys.I am doing some contruction work on a friend of a friends machine shop so we have a bartering thing going. Saving me the cash for the machine work.I don't have much knowledge on the engine end so im relying on what I read.So any and all input is greatly appreciated! Like I sad $2500 maybe a bit more for parts.

[demonic68]

Call the boys at Butler performance they will get ya the right stuff I even got them to give me a package deal on my hole order my order was about 3k but I got a lot more than just rods and pistons

[7t8ta]

Quick question on two of the replys (Cliff R & Mechanic17) both of you guys mentioned aftermarket oil pans, wondering what that does for performance. Cliff mentioned Moroso, which one in particular they have a few. Thanks in advance.

[72LuxuryLeMansLa.]

Originally Posted by 7t8ta

Quick question on two of the replys (Cliff R & Mechanic17) both of you guys mentioned aftermarket oil pans, wondering what that does for performance. Cliff mentioned Moroso, which one in particular they have a few. Thanks in advance.

The better pans will provide two main benefits over stock pans. The first and I think most important is they have baffles in the sump that keep the oil pump pick up screen submerged in oil. During hard acceleration and cornering the oil will climb or slosh up the side of the pan and can temporarily allow the engine to loose pressure. The other benefit is extra oil. More oil provides better cooling and also prevents oil starvation with higher volume pumps and slow oil drain back to the pan.
I am shopping for an oil pan myself. One pan that was recommended and the one I am leaning towards is the Canton 15-452 https://www.cantonracingproducts.com...LY-GTO-RR-PAN/

I would also like some feedback on which pans people use.

[PONTIAC DUDE]

Budget mods:

A baffled pan, windage tray and crank scraper will control your oil for street and mild strip usage.
Put a .060 washer under the oil pump spring and your ready to rock & roll.

Elongate the bearing feed holes and make sure no flashing keeps the flow across the area.

The aftermarket replacement FORGED con rods are actually cheaper to replace then resizing and installing ARP rod bolts, etc.
Have it balanced.
Weakest link in a performance Pontiac engine is the valve train. Moly pushrods and aftermarket rockers are a must. Reline up the guide plate flanges to make sure the rocker tip lines up correctly.

Cut valve guides for a Teflon/viton boot seal.

Lots of other items can be addressed when building a non stock engine for longevity.