[HWYSTR455]

Originally Posted by lust4speed

#62 heads when they started life came right in about 75cc's, and after a normal cleanup mill, they are probably down to 72cc's. Even with the pistons down in the hole .012" your compression ratio is going to be slightly over 10:1 (and if zero decked, you are at 10.3:1). No amount of game playing with gaskets or cams is going to be a solution for your pinging. Increasing combustion volume is the only tried and true solution - so either larger iron chamber heads or dished pistons...

That pretty much covers it.

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[Chris65LeMans]

What's your rear end gear? If you're running a 2.56 and are looking for better acceleration, lower gears are a lot cheaper than pulling the engine and starting to throw parts at it.

[etd66ss]

Originally Posted by Chris65LeMans

What's your rear end gear? If you're running a 2.56 and are looking for better acceleration, lower gears are a lot cheaper than pulling the engine and starting to throw parts at it.

I have 3.23 gears.

I was given another suggestion, to run E85 with this combo, it is like 106 octane.

Does this make sense?

[Chris65LeMans]

Define "performs like a dog" Is it "only" managing 13 second quarter miles, or does it take 8 seconds to hit 60 mph?

What kind of driving will you be doing? Just around town, or spending hours on the freeway?

I haven't heard that about E85, but I'm not a fuel expert.

[etd66ss]

Define "performs like a dog"

I can't break the tires loose.

What kind of driving will you be doing? Just around town, or spending hours on the freeway?

Around town and to work, but not on the freeway, not without overdrive.

[post toastie]

Try having the carb rebuilt or putting a better carb on it.

[etd66ss]

Originally Posted by post toastie

Try having the carb rebuilt or putting a better carb on it.

That seems like just throwing money at the wrong part of the problem? If #62 heads + very mild cam = bad build for 93 octane, I don't really see what buying a new carb is going to do.

I think I will investigate this 106 octane E85 pathway. If I can setup a Q-Jet for E85, I will try that. I might have to replace all the fuel hose in the car but that is no big deal. Lots of E85 gas pumps up here, and way more affordable than 100 octane racing gas.

[Burningbird]

Could this be the Crane RV cam previous owner chose? http://m.summitracing.com/parts/crn-283901 (260 advertised duration).

Using this cam and 10.1:1 SCR I get 8:43:1 DCR with Wallace racing's dynamic compression ratio calculator. With the Summit 2802 cam (298 advertised duration) I get 7:12:1 DCR. Please correct me if I'm wrong?

[etd66ss]

Originally Posted by Burningbird

Could this be the Crane RV cam previous owner chose? http://m.summitracing.com/parts/crn-283901 (260 advertised duration).

Using this cam and 10.1:1 SCR I get 8:43:1 DCR with Wallace racing's dynamic compression ratio calculator. With the Summit 2802 cam (298 advertised duration) I get 7:12:1 DCR. Please correct me if I'm wrong?

The engine builder could not give me the part number of the Crane RV cam used, he said it was one that way "lying around in the shop" and the prev owner chose it because it was only going to cost him $50 and it was a very mild cam (which is what the prev owner wanted). All I got from the engine builders memory is that it was ~212/215 @ .050.

[HWYSTR455]

Originally Posted by Burningbird

Could this be the Crane RV cam previous owner chose? http://m.summitracing.com/parts/crn-283901 (260 advertised duration).

Using this cam and 10.1:1 SCR I get 8:43:1 DCR with Wallace racing's dynamic compression ratio calculator. With the Summit 2802 cam (298 advertised duration) I get 7:12:1 DCR. Please correct me if I'm wrong?

True, based on 10:1, BUT, that is the lowest estimated SCR, and could be as high as 10.3 or 10.4 SCR.

Without knowing the deck height and actual head CC, it's a crap shoot. Not to mention if it has the rebuilder special pistons or not. If that's the case, the only thing I see that will help is the other heads.

You can try a dance around with all the crutches, but I say it will just add to your frustrations while killing time and money.

.

[etd66ss]

You can try a dance around with all the crutches, but I say it will just add to your frustrations while killing time and money.

What about the 106 octane E85 idea?

I found some guys who have successfully jetted their Quadrajets to run E85. I have a couple Quadrajets to try this with. It might be my winter project.

[FrankieFeenixx]

The E85 should solve the problem with pinging that you're having. It will also allow you to bump the timing to where it should be, most likely vastly improving the power output of the motor. It will also run cooler than on gasoline. Actually, on E85, you ideally want even more compression than what you're running right now, but that's not a major issue. The main issue with E85 is availability. If it's widely sold in your area, then no problem there. You'll use a bit more fuel also, so may need to upgrade fuel delivery (pump, lines, etc).

[etd66ss]

Originally Posted by FrankieFeenixx

The E85 should solve the problem with pinging that you're having. It will also allow you to bump the timing to where it should be, most likely vastly improving the power output of the motor. It will also run cooler than on gasoline. Actually, on E85, you ideally want even more compression than what you're running right now, but that's not a major issue. The main issue with E85 is availability. If it's widely sold in your area, then no problem there. You'll use a bit more fuel also, so may need to upgrade fuel delivery (pump, lines, etc).

Sounds like this is the plan if I can find the information I need to jet a Q-Jet for E85. I'll also look into a larger supply line. It's something I can try without digging into the motor. There are a lot of E85 pumps up my way.

[rohrt]

Originally Posted by etd66ss

Ok so, I just got off the phone with the engine builder.

There is more to the story.

Last year the prev owner brought in the GTO to his shop to get the "rebuilt" 400 running better. The more the shop investigated the engine, the more it became apparent the prev rebuild was not a rebuild, but thrown together with used parts, a quick hone job and what he called "crap cast pistons". So this guy rebuilt the engine. The owner wanted the high compression heads and a very mild cam. The builder told him this would require higher octane fuel, but that's what the owner wanted.

He could not give me any part numbers, but said they bored the engine and put in TRW flat top pistons and a Crane RV cam that had lesser specs than the 1972 067 cam. All he could remember about the cam is that is was about 212/215 @ .050.

The car came in to his shop with what he called a butchered Q-Jet that he fixed up the best he could, and it already had the HEI which he said still needed work when the car left but the owner didn't want anymore work done to it.

He told me the compression is definitely over 10:1, and even if I put a bigger cam in it, it still could have detonation issues on 93 octane.

Was it TRW forged pistons? If so not a bad way to go.

Originally Posted by etd66ss

So just changing the cam to something like this is not an option?: http://www.competitionproducts.com/H.../#.VdM8bE2FNus


I've already got a 66 Chevelle project $$$ so won't be doing a long block for this car anytime soon. I'd think to get the original heads in order I'm looking at more $$$ than a cam change.

Doesn't look like a bad cam on paper. However since there are so many that are happy with the 2802 why not got that route.

Originally Posted by Lee

I'd use readily available dished pistons to knock the compression ratio down to about 9.0:1

You can SELL the 62 heads for enough money to offset most of the cost of getting the 7K3's prepped. I agree with HWYSTR455. The best solution for your situation is another set of heads.

Maybe consider getting a set of CNC'ed heads from Dave @ SD Performance. They will flow better than either set you currently have (more power) and he can help you size the combustion chamber to get you the compression ratio you would like to have.

The SD Performance CNC of the chamber is my choice here but also the most expensive. I think DCI can do this work too.

Originally Posted by etd66ss

I guess maybe I need to be schooled on flat top vs. dished. Flat top pistons still have milled pockets for the valves right? I guess I am a bit confused. I was told flat tops are better for quench and detonation when compared to dished.

So what I am hearing is, with the combo of my heads and pistons, there is no good cam solution for 93 octane for this engine.

Flat tops for Pontiac will have valve reliefs. Some have two some like the TRWs will have 4 and then you have the worst pistons ever made with eight. A dished piston will have a big pocket in them.

Originally Posted by crm318

X2 on the Summit 2802. I have a .060 400 with 16 heads and 10:1 compression. The car runs great, granted, I have a 2500 converter and 3:73 gears. I think it's worth it for $115.

Sounds like your best first step would be the 2802 cam swap. Even if you had head work done latter you would have a good cam for it.

[post toastie]

The car came in to his shop with what he called a butchered Q-Jet that he fixed up the best he could, and it already had the HEI which he said still needed work when the car left but the owner didn't want anymore work done to it.

If your carb isn't getting full throttle or needs rebuild or just needs to be thrown out. This is where the performance starts lousy carb lousy performance

[Squidward]

As far as carbs go, I put on a new Quick Fuel Hot Rod series 780 cfm vac secondary carb. Out of the box performance was awesome. I think I dialed in idle speed just a touch, idle mixture screws no more than 1/8 from factory settings, and both floats maybe a 1/2 turn.

I was tired of playing with old crap, wondering if the initial jet/rod/etc. setup was right for my combo, and tired of not knowing what level of molestation my carb suffered over the course of 40 years.

That cam doesn't look that soft. I ran an 066 cam in a 400, 73 Formula with 3.08 gears. The 066 is a softer cam than the one mentioned above. I didn't have much of a problem getting with it, and running easy 15's.

[etd66ss]

That cam doesn't look that soft. I ran an 066 cam in a 400, 73 Formula with 3.08 gears. The 066 is a softer cam than the one mentioned above. I didn't have much of a problem getting with it, and running easy 15's.

With high compression heads on 93 octane? Because that is my issue.

If your carb isn't getting full throttle or needs rebuild or just needs to be thrown out.

I guess I have not seen any major issues with the carb yet other than having a hard time getting the choke to work reliably.

[Squidward]

Originally Posted by etd66ss

With high compression heads on 93 octane? Because that is my issue.



I guess I have not seen any major issues with the carb yet other than having a hard time getting the choke to work reliably.

No. Low compression, maybe 8:1 with wishful thinking. Just trying to benchmark the performance, because lower compression allowed me to put in more timing and run crappier gas, but all at the expense of degraded performance. It sounds like you have an idea about the timing, and have decent confidence with the carb. To me it sounds like the wild card is the unknown cam, and what its specs really are. Or, maybe the cam timing.

Used engines with unknown build parameters suck. But your build IMO appears sound according to the numbers.

I have a local friend who just put together a 400 build with 62 heads, qjet, 2802 cam, and HEI. It's in a 4 spd 69 'bird, with 3.73's. I can ask him his timing specs. I know he fought some pinging and had to carefully manage his timing. He was running a mix of premium with a little racing gas. IIRC, I think he put in around 32 total. But I know this: He clearly stated he was going to seriously detune before he let his 16 year old drive it, because it was way more car than the lad could handle.

[etd66ss]

Originally Posted by Squidward

No. Low compression, maybe 8:1 with wishful thinking. Just trying to benchmark the performance, because lower compression allowed me to put in more timing and run crappier gas, but all at the expense of degraded performance. It sounds like you have an idea about the timing, and have decent confidence with the carb. To me it sounds like the wild card is the unknown cam, and what its specs really are. Or, maybe the cam timing.

Used engines with unknown build parameters suck. But your build IMO appears sound according to the numbers.

I have a local friend who just put together a 400 build with 62 heads, qjet, 2802 cam, and HEI. It's in a 4 spd 69 'bird, with 3.73's. I can ask him his timing specs. I know he fought some pinging and had to carefully manage his timing. He was running a mix of premium with a little racing gas. IIRC, I think he put in around 32 total. But I know this: He clearly stated he was going to seriously detune before he let his 16 year old drive it, because it was way more car than the lad could handle.

It would be really great if you could ask him about what he went through to time that thing

[HWYSTR455]

Originally Posted by Squidward

...He was running a mix of premium with a little racing gas....

That's how he managed it.

You can dial the timing back to manage it too, but both are crutches.

As for E85, from what I understand, there's no way to know if you're getting a consistent mix, it's all over the board. Look at some of the guys over on pro-touring who are running boost and you will see the challenges there.

My last 400 was .030 over, TRWs, 62s (or 16s, I forget, but no diff), and was at 9.97 SCR. I ran a 228/236 114 Crane cam similar to the 2802. 3000 stall and 373 gears. I ran 30-32 total, and it was a struggle to keep it from pinging. Get a tank of gas where it's off a little, pings, hot day, pings, engine temps raise a little, pings, 3 people in the car, pings, and once it pings, like noses over, getting it to stop pinging was tough. I went through all the tricks, ran it rich, slowed advance, 160 stat, you name it, I tried it. Constant battle, and made the car no fun to drive. But, when it did run right, like in the fall, cool air, it was a handful. It can be done, but does that sound like fun to you, constantly battling it?

.