[JLMounce]

Try as I might, I simply have not been able to get the 455 in my Firebird to work on anything near the pump gas we have available around here.

When the tune up on the engine is where it needs to be, it runs great. Good off idle response, runs cool, no hiccups or other issues. The problem however is that at nearly 11:1 compression it detonates under wide open or near wide open throttle.

Even with a mix of 91 and 100 octane (usually 50/50) in the tank, I have to neuter the tune to get it to stop detonating. The engine likes about 35/36 degrees of total, but I have to bring this down to around 30 total and give it a rich WOT tune-up to prevent detonation.

When I do that, the car runs hot, smelly and rough.

With that being the case, there's just no way around it, I need to ditch the #62's and go a 91 octane friendly head and compression ratio. There's nobody around my area still doing these things that I would trust with a set of heads, so I've looked at outfits like SD Performance, Butler etc. The price difference between a worked set of heads and a good rebuilt stock setup is about double.

For those of you who've gone the ported iron heads route, given the price of entry, would you do it again, or would you just go with a good factory rebuild? Yeah I realize I'm giving up some power, but as it is right now, I can't use the power I have without risk of destroying the engine.

[ponyakr]

I'll just throw out a couple of ideas, which you may have already thought of.

Instead of using 100 octane to mix, how about some 108 octane race gas, for mixing. That's what I did with my last bracket 455. It had #215 heads, so probably over 11:1 CR. Mixed it with 93 pump gas. Worked fine. Ran 7.30's in 1/8 mile. But, the 108 cost $11 a gal at the time.

Or, I recently ask about octane booster. Several said the Torco brand works good. It is said to raise pump gas to over 100 octane. I haven't tried any yet, but have a can ordered. Don't know that it will be any cheaper, but should be more convenient than buying 108 to mix.

http://www.amazon.com/Torco-Accelera.../dp/B004ZO3VN0

Another brand booster that is supposed to work is called "Race Gas"--race fuel concentrate.

http://www.jegs.com/i/Race-Gas/814/1...ductId=3410293

A properly built set of 6x-8 heads might fix your problem, and be cheaper than a professional port job.

Seems to me that for the price the big boys charge for a port job, some KRE D-ports would be a better value. But, that's just an opinion.

By the way, have you already thought about a cam change that could possibly help the situation some ? Considered E-85 ?

Hey, just some ideas that might help. Hope you find a good solution.

[tom s]

Your best bet would be a stock set oh KRE alu D port heads.The cheaper deal is a set of SD ported iron heads with what ever CR he think you need.Im sure you would like not to have to screw with mixing gas and just pull into any gas station and buy what you need.Remember there is also detonation you can't hear so get to it before you bang the bearings out of it.JMO,Tom

[68WarDog]

Having been there, done that some years ago. I went for #96cc 7K3 heads. Unless you have an aggressive cam, stock 6X or 71 year 96 heads are good for 455 pump gas street combos.

[JLMounce]

Originally Posted by tom s

Your best bet would be a stock set oh KRE alu D port heads.The cheaper deal is a set of SD ported iron heads with what ever CR he think you need.Im sure you would like not to have to screw with mixing gas and just pull into any gas station and buy what you need.Remember there is also detonation you can't hear so get to it before you bang the bearings out of it.JMO,Tom

Yes, this is precisely the case. My car is predominantly a street car. While I have 100 octane close to me, it's $7.53 per gallon and the next closest pump that carries anything close is about 70 miles away.

Price of entry is a concern, otherwise I'd put a set of SD prepped KRE D-ports and an old faithful cam in the car.

Either way I will likely need a cam swap as well. I don't know what's in there right now, but it doesn't sound nearly as radical as it should for only producing 8" of vacuum at idle (7" with the timing backed out). So I'll need to factor in that cost as well.

[roy381]

I believe the op is asking if optimal compression is achieved whether iron or aluminum is porting worth the expense given a street car?

If im wrong my apoligies

[goatless]

Is it worth the $$$ to get ported heads vs. stock rebuild? That depends on you. How do you use the car? With any decent 455 build (ported or unported) you're going to have enough power to do just about anything you want to do… on the street. If you're looking for a lower ET at the strip then ported heads are the way to go.

[JLMounce]

The car is mostly just a fun street car. While it may see the strip on occasion, nothing more than a tech and test or bracket race. The car is more setup for autocross anyhow. Basically what I'm wanting is a reliable engine that will motivate the car well and run on fuel from any gas station I visit.

[wheneaglesfly]

Since Your 455 is Built and Running its not easy now to make Design parts changes.

The best solution is to Run 100 % Straight Race Fuel.
110 Motor Octane.

100 LL Aviation Fuel untcut run 100% straight is the #2 solution .

If you daily drive then it won't be practical for long.
$200 to fill the 20-25 gallon gas tank on 110 Motor octane Race fuel.

This a complicated Topic...Running High compression Pontiac V8 vintage iron heads with 10.75 -13.0 :1 static compression on.the street.
Todays Piss water pump gas too.

I have been down this road prior.

Race gas wad 2.99 per gallon then too.


There is Static Compression.
Dynamic Compression .
Effective compression.
Effective compression is most accurate. Takes into account the Volumetric efficiencey of the engine.

[tom s]

The 455 I had in my bird had a moderate hyd roller with 9.5 CR with 48 stock heads and it was all the HP I needed.I think it was in the 430 HP with factory 69 intake and carb.Tom

[tharkun8]

Call Bill Arnold in Arvada. Mountain High Performance.

He's built engines for half of the CO POCI chapter.
He has my 66 389 now and 2 other engines of mine.

His main business is building racing truck diesel
engines but he still builds Pontiacs when he can.

He can do any engine work you need semi-locally.. save
on shipping.

John

[wheneaglesfly]

If you can maintain 140-160 F water temps all the time it will help trying to run on pump gas 91-93 in your iron #62 headed.
Not so easy to do for most.
When you run water temps this cool you must change oil every 100 miles.
To remove the condensation buildup.
Water vapor never fully boils away like 195F-200F.

[wheneaglesfly]

When ypu have time this weekend take a cranking compression test of. your engine.

Let me know what you have exact for readings.
I want 7-8 cranking puff readings.

180-190 Psi is about Max with 91-93 octane non ethanol gasoline.
Tune must be perfect.

Aluminum heads & EFI Corporate Chevy the Limit is 195-200 psi.

[wheneaglesfly]

Another solution is to run.on.E85- E100 fuel.
Entire fuel system must be redesigned.
Think RACE DRAG CAR ALL OUT.

[wheneaglesfly]

Pontiacs have a High Volumetric efficiency .
Better than most Chevy bone stock.

Calculated ideal dynamic compression ratio can be a mile off.
EFFECTIVE COMPRESSION IS WHAT HAPPENS WOT.

[b-man]

A good rebuild on iron heads, with all new parts and all the needed machine work done including installing hardened exhaust seats easily eclipses the thousand dollar mark.

Porting work adds roughly another $500 for something in the 240cfm range (intake flow).

So for around $1500 you'll end up with a nice set of heads that'll satisfy your need for speed.

Have the work done on a set of 6X-8 castings and strive to keep the compression in the 9 to 9.25:1 range. No need to push the envelope.

My last 'high-performance' low-compression 455 had a meager 8.6:1 compression ratio. I had it in a fairly light bracket car (3550# with driver), it was geared for the track (3.89) and had slicks for reliable/good traction. It ran in the 12.0s at over 110 MPH. This was a used short block (original pistons/bearings, etc) with used #197 HO heads (lightly cleaned-up ports), nothing was fresh other than the cam, valve springs, timing chain and oil pump.

You don't need to push the limits with compression to have a fun, fast street engine.

[beemergary]

I run Jack Podels tetraethyl lead in my 67 gto-61 tempest 421 sd 127 heads and 63 tempest 421 sd 980 milled heads. About $ .25 a gal. to 93 octane. Haven't bought a case for a couple yrs. now. Can make 103 but I usually make a little less. 8 oz. to 10 gal.

[wheneaglesfly]

I recently dropped in A High Compression Engine into my 1963 Grand Prix.
Not Pontiac V8.
Not Chevy.
A 1965 Oldsmobile 425 A With 10.25 :1 static factory compression .
It runs great on 91 octane Gas.
I did it because I had the engine since 2011.

I had a 455 Tripower 1973 4X engine in it years ago.
Spun #2 main bearing street racing above 120.

Dropped in a 403 olds.
Wore it out.

425 olds now.
My tested Cranking compression is 180 psi .
Obtained 4-5 puffs.

I have a 455Pontiac for my '63 GP.
Build later in 2016.

[Sprocket]

The porting isn't the problem, it's the 11:1 compression (and with iron heads). Cam design can also make the problem better or worse. Generally, you need to keep static compression in the mid-high 9's with iron heads and low-mid 10's with aluminum heads to maintain premium fuel compatibility. Get some ported heads with a chamber size conducive to pump fuel usage and all will be well - or get some dished pistons to go with your heads. Even a mild 066 factory cam will detonate like crazy with factory 10:1 and 10.25:1 compression (partly because it builds a lot of dynamic compression).

[torqhead]

Originally Posted by JLMounce

The car is mostly just a fun street car. While it may see the strip on occasion, nothing more than a tech and test or bracket race. The car is more setup for autocross anyhow. Basically what I'm wanting is a reliable engine that will motivate the car well and run on fuel from any gas station I visit.

Jason, I've been down this exact path. Bottom line is you can't run those #62's on a 455 and expect to use pump gas. I made the decision to go the aluminum route, KRE's. If you're going to keep it iron headed you'll need to be around the 9-9.5 compression, anything more than you'll have a sledgehammer. Save yourself some pain, if you want to keep the power up on the higher side then you should go aluminum.