454 tune

[TBART70]

I just finished the install of a jasper 400hp 454 in a 71 Chevelle.
It has a small camshaft. Hydraulic roller .510 lift 210* duration @ .050.

I put an AED 750 cfm DP carb on it. Full MSD igniton, RPM air gap with open spacer. I set the timing at 14* initial 18 in dist. It has a TKO 600 with 3.31 gears.

I'm not impressed with it. It is kind of slugish out of the hole but as mph and rpm climb it gets better. I think it needs a jet change, but it is pretty close.

I might speed up the distributor curve, AED actually tells you the MSD out of the box has too slow a curve, so I did what they said. MSD does it so you don't have detonation.

I also think it needs more gear in back. maybe 3.73.

What does everybody think.

[My427stang]

The first no-brainer stop would be to make sure you are getting full throttle.

Second, I agree that the first tuning stop is the timing curve.

I'd set it up with 14 initial, 22 mechanical, all in by no later than 2800 RPM, as it is, its probably not coming in until 4000, stock MSDs are pitifully slow.

That should wake it up a bit.

After that a gear change would help, but not critical, a TKO-600 with 2.87 gear and a 3.31 = 9.5 SLR (starting line ratio) that's not horrible

However, ultimately a 3.73 would be a good choice because it will make 5th gear much more friendly, and the by product is good stuff in the lower gears

However, timing curve first, especially if its a low compression motor.

Later you may want to look into getting a more manly camshaft :)

[TBART70]

The first no-brainer stop would be to make sure you are getting full throttle.

It is getting full throttle




I'd set it up with 14 initial, 22 mechanical, all in by no later than 2800 RPM, as it is, its probably not coming in until 4000, stock MSDs are pitifully slow.

It's all in by 3000, I set it up a little faster, I was thinking the same thing and putting a little more in the distributor.

It has 9.5 to 1 comp

I didn't pic the motor, my buddy did. I found out the cam specs after the fact when I went to order the carb I got the specs and was like this thing making 400 hp no way. I'm not thrilled with Jasper at this moment. The quality control on this thing is so-so.


thanks for the response I'll have to mess with it.
-Tom

[68Formula]

In addition to intial and total timing My427stang suggested, make sure it doesn't come in too soon either (so probably all in by 2600-3000rpm). I'd take off the open spacer, it somewhat defeats the advantage of a dual plane intake like your AirGap.

Is it sluggish at full and part throttle or just part throttle? Are you running vacuum advance?

If the QC doesn't look so great, it makes me wonder if they degreed the camshaft properly or just lined up the dots and hoped with all the tolerances and QC of the subcomponents that it was setup right. In general, many are finding the "line up the dots" ends up a few degrees off with todays components. Your dots could be lined up, but the cam still retarded a few degrees.

[TBART70]

I was going to put on my 4 hole spacer and see if it makes it better, it is sluggish at part throttle more than full. But it seems to get a little better with higher rpm and mile per hour.

[Trackman]

Put the 4 hole spacer on .
Are you running vacuum advance?
I bet it will like more initial, more like 20 plus
32 total is fine.

[TBART70]

I changed the curve to a lighter set of springs, and added a little more advance to the dizzy. Now it has 21* in the dizzy and 14 initial, I will probably add a little more initial. I changed out the spacer for the four hole. It ran a little better but before I could get a good drive in the throttle stuck and so did the rear float. I fixed that and then the clutched messed up again. Once I fix that we will see. I think I need to jet down the primaries a touch.

No vacuum advance.

[68Formula]

I think with 21 centrifugal if you increase your initial, you'll have too much total. Instead of a lighter set of springs, go back to the old ones, and just increase your initial. Remember increasing your initial means you'll have that much more at each point anyway.

[Trackman]

Increase your initial. Keep your total the same. That will require changing the bushing.
Doesn't sound like a race car so you should run a vacuum advance distributor.
Iron heads? I have been told 32 -34 total is max. I run 32
If you had a vac dizzy you have high 20's at idle and high 40's for cruise. That 454 will like that.
I run 3.73 with my tko. Cruise at 75mph @ 2-2100.. nice
I would like to try some 3.55's to try to fix some of my wheel spin in the first few gears. Probably help in the mpg area too.

[MonzaRacer]

Forget the "rules"
I ran my 402 with 10.5 to 1 zero deck block and the heads look milled when I bought them.
I have right now it has a Lunati cam in the .501 lift range but I also ran this setup with my Chet Herbert Roller too and every other cam its had.
I set it up with a stock type HEI, all I the trouble I have ever had with HEI dists are being born out as 2 people I know have removed them for stockers(remans).
I dial in 16 to 20 initial, run the centrifugal with stock weights and light springs from a recurve kit and hook my Vacuum advance up to manifold vacuum.
I ran nearly 60 degrees of total, use a 31 ,35 or 37 shooter, either drill or replace the shooter screw with hollow one.
I have had best luck with black cam in hole 1. adjust the pump arm after resetting the idle with vac advance hooked up, so it has on barely noticeable looseness. This means if you can see arm just move your good, if it has a lot of slop it wont work.
A 454 with a 750 will probably need some where in the range of 78s to 85s in front, a 4.5 PV and keep adding secondary jets till it slows down.
Secondaries MAY need to be cracked a tiny bit more if you have idle adjustment issues. But before messing with secondary blades you can drill a 1/32 hole centered in the front part of the throttle blades and increase its size if need be but dont get carried away.
Secondary accelerator pump arm adjust same way but you only want enough shooter in back to kill the bog of opening.
With a 454 at 9.5 it has a large open combustion chamber it can handle some timing.
Personally the best distributors I have are the cruddiest!
But wire brush and silver paint makes then look new!
Good Luck and dont be afraid to throw some timing at it. Too many people dont and wonder whats up!

[68Formula]

Iron heads? I have been told 32 -34 total is max. I run 32

I'd like to clarify this, as this statement could be misleading. The material of the heads should not be what dictates the maximum timing. If it is then it's because insufficient octane is being used for that particular combination.

Assuming you've used the proper octane for the compression ratio, quench and head material, the optimum ignition timing (one that makes maximum brake torque at the higher rpms/loads) is dependent on what happens in the combustion chamber. By this I mean, bore size, quench distance, crevice volume, spark plug angle/location and chamber shape. Chamber shape being one of the major factors.

(Note, I referenced quench twice. Excessive quench can not only cause pre-detonation, but also affects speed of the flame front.)

In general (again, those other camber factors play a small role), old-school (typical mid-late 60s and earlier) closed chamber heads usually like upwards of 40 degrees lead.
https://static1.pt-content.com/images/pt/2010/09/imagesqtbnANd9GcSPz2cd2NwwOnJwdx_rZfXX3S-1.jpg

Later open chambers typically like 34-36 degrees,
https://static1.pt-content.com/images/pt/2010/09/imagesqtbnANd9GcSvglzVZrdMk4JGEx3r5Q2zxU-1.jpg

Modern heads typically like 30-32 degrees
https://static1.pt-content.com/images/pt/2010/09/imagesqtbnANd9GcTG6erHAqMnlADM2lZLG5xqwG-1.jpg


These may be where the "iron heads like" comes from, as most modern heads are now aluminum. So the majority iron heads tend to fall into the open chamber category.

That being said, each combination of components is a little different, so you'll need to experiment to find out what is best for yours.

And as far as what is the best initial timing and curve rate, the camshaft plays a large role in this. Again, you have to tune what is best for your combination.

On a mostly street vehicle, you would be best served using a distributor with vacuum advance. Not only will improve fuel economy quite a bit, but the light/moderate tip in throttle response as well.

[TBART70]

thanks for the responses, I'm up in the air about the vacuum advance. I still have to get the clutch issues ironed out so I can really drive this thing.

[TBART70]

Finally got in a decent drive, It runs pretty good. Checked the timing before I left. Total is 36*, 14 initial and 22 dizzy. It is all in by 2500, I might change out one spring for the heavier one just to see what it does. Filled the tank up with 93 octane. It was a little damp so I didn't jump on it. I did get out on the highway, it seems to need a little more gear off the line. Once it gets going it seems to pull pretty good to 5500 rpm. Did about 65-70 mph. From 50 to 70 it pulled pretty strong in fourth. I still have a clutch issue, it seems to be bending the bracket on the frame rail. I wonder if the metal of the aftermarket bracket is weak. I welded the whole bracket this time and it still seems to be bending.

thanks for the help.

[TBART70]

I bumped it up o 40* and it got much better, I might have to change the secondary squirt-er to a larger one. I ordered a dist with vacuum advance today. I may or may not use it.

[TBART70]

Did a check of TDC with a piston stop. The tab is off 4*.

I put in the vacuum advance dist. and timed it to 43 degrees. No pinging at all. With the tab being off, that would make it 39*'s total at 2600 rpm. They told me 32* to 34*.

[My427stang]

If you have a chamber without much movement (not zero decked, not much squish, poor quench pad, inefficient chamber, etc) it'll want more timing. I would expect that's the case with a reconditioned engine.

If you are sure it isn't pinging, let it have the timing it wants. It may even be less compression than you think.

Sounds like you are getting there.

The next step if you wanted to get fancy would be to pull the heads, measure the chambers and the deck clearance and figure out your true static compression, then look at an online calculator to calculate dynamic compression ratio.

My guess is you have less compression than you think, and advancing the cam would bring your vacuum (and torque) up some, but at this point it sounds like you are doing pretty well, the cost/benefit may not be worth it