Crate engine swap advise please?

[MadOgre]

OK. Where do I get a new HEI? OEM?

http://www.jegs.com/i/Accel/110/59107C/10002/-1

http://www.msdignition.com/Products...eet_Fire_Chevrolet_V8_GM_HEI_Distributor.aspx

http://www.summitracing.com/int/search/product-line/summit-racing-blueprinted-hei-distributors

 

[rich weyand]

OK. Where do I get a new HEI? OEM?

This one looks right. Has the adjustable vacuum can. Just dial it in to 7.5 crankshaft (15 camshaft) degrees using a timing light. The instructions say to hook it to ported vacuum, which is nonsense. Connect it to manifold vacuum, the driver's side port of the Edelbrock.

http://www.jegs.com/i/JEGS-Performance-Products/555/40002/10002/-1?parentProductId=#moreDetails

 

[MadOgre]

Ya that would do

 

[rich weyand]

The Summit one MO pointed to looks OK too.
http://www.summitracing.com/parts/sum-850001r/overview/

 

[rich weyand]

I would just stay away from the ****-bang stuff. The problem with a fully adjustable gizmo is you have to fully adjust it.

 

[73 C10]

The Summit one MO pointed to looks OK too.
http://www.summitracing.com/parts/sum-850001r/overview/

OK. If it's agreed that I should start here. I'll order it tonight, might have it tomorrow.

 

[73 C10]

OK. It's in. Next.

The old one was f**kd. The mech was stuck for some reason. I'll check it out later. So there was VA only.

Anyway, timed it to 12*, no vac., port plugged, 1000 RPM.

18" vac with screws 1 3/4 turns out at 550 RPM. The needle bounces right along with the murmer.

I got the Blueprint Summit.
Paperwork says mech advance is 6* @ 900, 8* to 10* @ 1200 RPM. Max of 10* to 11* at 1500 RPM. Vac advance is 10*. Set vac can fully counter clockwise.

I took it for a spin and it definatly ran a bit smoother through the neighbor hood but kinda doggy running up to 45 MPH. And still a murmer. No knock.

I guess I should bump the timimng up to 16*?

It still smells like fuel. I'll get a regulator.

 

[rich weyand]

OK, couple things.

18" of vacuum means you should be running the 8" step-up springs in the Edelbrock. I stretched mine so they rested at 1/4" longer than they came at, to get closer to 9". The rule of thumb is the springs should be 1/2 of your idle vacuum, so that's why I say switch to the 8", and maybe even stretch them. As it is now, you are in the cruise circuit all the time, and with those needles, it means you are running lean as hell. That's why it is doggy right now. You need the more powerful springs to force the step-up pistons up and get into the thin part of the needle when you get on the throttle.

That's your biggest problem right now.

I would still try the needles I suggested above, as well.

Those advance numbers sound like camshaft degrees, which is the way distributors are traditionally specced. Normally you figure 20* of mechanical, and 15* to 25* of vacuum advance. Those are crankshaft degrees. But 10*-11* mechanical and 10* vacuum advance sound like camshaft degrees, which are half as much. Does it say in the instructions which degrees they are talking about? You can check this by noting the timing, then plugging in the vacuum and noting the timing again. You should be able to see whether the timing with the VA hooked up moves 10* or 20*.

My own recommendation is 20 crankshaft degrees mechanical (10* on the cam) and 16 to 24 camshaft degrees vacuum advance (8* to 12* on the cam). That's the range of most GM applications with the HEI. If those numbers you quoted are camshaft numbers, which I strongly suspect they are, you are right on the money.

12* base is OK. With 20* mechanical, that's 32* total advance with the throttle open at rpm, and 52* at cruise, which is about as high as you want to go, and also gives your best mileage. You could try for 16* base later, to get 36* base + mechanical, which is the maximum horsepower/torque point at rpm with the throttle open for GM V8s, but then you need to back the vacuum advance down a bit to keep base+mechanical+vacuum (cruise) at 52. That is, as you increase base timing for more advance during acceleration, you need to bake off vacuum advance to keep cruise timing the same. Make sense?

 

[Old77]

Rich....I just want to say I really enjoy reading your posts. You are a wealth of good information, sir

 

[MadOgre]

 

[MadOgre]

OK, couple things.

18" of vacuum means you should be running the 8" step-up springs in the Edelbrock. I stretched mine so they rested at 1/4" longer than they came at, to get closer to 9". The rule of thumb is the springs should be 1/2 of your idle vacuum, so that's why I say switch to the 8", and maybe even stretch them. As it is now, you are in the cruise circuit all the time, and with those needles, it means you are running lean as hell. That's why it is doggy right now. You need the more powerful springs to force the step-up pistons up and get into the thin part of the needle when you get on the throttle.

That's your biggest problem right now.

I would still try the needles I suggested above, as well.

Those advance numbers sound like camshaft degrees, which is the way distributors are traditionally specced. Normally you figure 20* of mechanical, and 15* to 25* of vacuum advance. Those are crankshaft degrees. But 10*-11* mechanical and 10* vacuum advance sound like camshaft degrees, which are half as much. Does it say in the instructions which degrees they are talking about? You can check this by noting the timing, then plugging in the vacuum and noting the timing again. You should be able to see whether the timing with the VA hooked up moves 10* or 20*.

My own recommendation is 20 crankshaft degrees mechanical (10* on the cam) and 16 to 24 camshaft degrees vacuum advance (8* to 12* on the cam). That's the range of most GM applications with the HEI. If those numbers you quoted are camshaft numbers, which I strongly suspect they are, you are right on the money.

12* base is OK. With 20* mechanical, that's 32* total advance with the throttle open at rpm, and 52* at cruise, which is about as high as you want to go, and also gives your best mileage. You could try for 16* base later, to get 36* base + mechanical, which is the maximum horsepower/torque point at rpm with the throttle open for GM V8s, but then you need to back the vacuum advance down a bit to keep base+mechanical+vacuum (cruise) at 52. That is, as you increase base timing for more advance during acceleration, you need to bake off vacuum advance to keep cruise timing the same. Make sense?

I find it hard to believe he's pulling 18" at idle with a lopey cam. But if he is then ya go with the stronger springs for sure. Hes still lean though. Maybe not as much as I would have thought though.

I would still like to see a fuel regulator with a fuel filter inline before it. Probably why he's smelling gas.

 

[Georgeb]

Rich....I just want to say I really enjoy reading your posts. You are a wealth of good information, sir

2X^^ makes me want to scrap the stupid TBI on my truck and tune a Q-Jet with a standard HEI!

 

[Old77]

2X^^ makes me want to scrap the stupid TBI on my truck and tune a Q-Jet with a standard HEI!

Careful, George...you'll make @MadOgre puke .....after he edits his original post of nonsense

 

[Georgeb]

Careful, George...you'll make @MadOgre puke .....after he edits his original post of nonsense

My TBI makes me want to puke!!

 

[Old77]

My TBI makes me want to puke!!

LOL I hear ya. When they're up to snuff they're great and super reliable but when you start to have little nit picky issues they can sometimes be hard to track down and makes it frustrating.