Lateral-g Forums - Asphalt Modified Discussion

Lateral-g Forums (https://www.lateral-g.net/forums/index.php)

- Race Cars and Modern Pro-Street (https://www.lateral-g.net/forums/forumdisplay.php?f=57)

- - Asphalt Modified Discussion (https://www.lateral-g.net/forums/showthread.php?t=45094)

Quote:

Originally Posted by ccracin (Post 537364)

Just checking in Ron. Did you go to speedweeks this year?

Sorry about that Chad. My girls had 3 days off & took me to the snow. Have you ever seen a fat boy sled down a steep mountain side? :confused59:

I'm just heard back from my guy at Comp Cams, so I'll post up the details today.

Hey Chad,

First, everything I'm recommending is based off of 1.65 roller rockers (Crower stainless are my recommendation by far).

-----------------------------------------------------------------------

If the timeline requires an "off the shelf" camshaft, I recommend:
Comp Cams Grind: 286XOS
* Careful, there are two versions - Get PN: 12-657-5

Duration @ .050: Int=256° Exh=262°
106° LSA (Lobe Separation Angle)
Install this cam at 6° advanced

Lobe lift: Int=366" Exh=.362"
Valve lift with 1.65 Rockers: Int=604" Exh=.597"
* Actually slightly different with hot lash calculated in.

-----------------------------------------------------------------------

But what it really needs is a custom grind. Same price, just takes a while longer to get.

The cam profile I recommend includes the intake lobe profile from the cam above ... 286XOS ... and the exhaust lobe profile from the 290XOS ... with a wider LSA at 108°.

The specs would look like this:

Duration @ .050: Int=256° Exh=266°
108° LSA (Lobe Separation Angle)
Install this cam at 6° advanced

Lobe lift: Int=366" Exh=.366"
Valve lift with 1.65 Rockers: Int=604" Exh=.604"
* Actually slightly different with hot lash calculated in.

-----------------------------------------------------------------------

With either cam at 6° advance, you may need to flycut the intake valve pocket on the piston a bit more. Maybe not. Ideally, you want .090" on the intake & .110" on the exhaust.

-----------------------------------------------------------------------

More tips:
a. You do need to run the carb spacer they allow.
b. Run gapless piston rings (to get all the dynamic compression possible) with a low tension oil ring (for less parasitic loss).
c. The exhaust will be critical to maximum power. I'll map it out next & make a separate post.

-----------------------------------------------------------------------

This dyno curve shows the off-the-shelf cam & the custom cam. The difference from 5250 rpm & up is key to a fast race car down the straights. This is the middle of the 3 cam profiles I was considering.

It will not be a torque monster. But it won't be lame either. the key to being fast with this combo is to gear the car to hit the 6300 rpm rev limiter 4-6' before the lift point.

The throttle won't be as sensitive. The car won't be edgy on exit about tire spin. The driver won't have to egg-shell the throttle. The driver will be able to roll the throttle on early & rapidly ... starting the acceleration ramp earlier.

From corner exit to the the next turn, it will be the best combo, if geared correctly.

Quote:

Originally Posted by Ron Sutton (Post 537385)

Every time I go sledding with my girls! :hello:

Coming down the hill is fun, hauling me, my sled, and their 2 sleds back up the hill is the issue! :waveflag:

No apologies necessary, i'll never argue over time with the family. I have my twins to chase around as well.

You went to the snow and I am desperately trying to get away from it!

I appreciate the time, I'm anxious just from curiosity. I don't have any skin in the game, but my friend that owns the cars texted last night to see where I was with it. He's ready to go. LOL Daytona has him all revved up!

Ok, the exhaust is critical. Can't stress that enough.

If they can find, or afford to have built, a 4-2-1 header set-up, that would be optimum. I'd be happy to map a system out for you. But I suspect not, so I've outlined a 4-1 exhaust system.

The headers need to be "Step headers" starting with a 1-5/8" primaries out of the head & stepping up to 1-3/4". 34"-36" long primary tubes.

FYI: All the dimensions after the primary header tubes ... are measured from the end of the primary tubes up inside the collector.

The collector needs to be 3" in diameter ... with a true "merge collector" diameter of 2-1/2" installed at 9.9"± from the end of the primary tubes. People often confuse collectors with merge collectors because the names are similar. A true merge collector necks down at a specific point & then necks back up. See the attached photos.

If the merge collector is designed correctly ...
* The 4 tubes come into the necked down area of the collector at a 10° to 15° angle
* There is a "merge tip" at the end of the primary header tubes, in the middle of the 4 tubes, that comes to a point.
* The collector necks down & then necks back up, forming a venturi.

I like, use & recommend Dynatech merge collectors & headers. They have the best "affordable" merge collectors. There are places that build merge collectors costing insane money that work about the same as the lesser expensive Dynatech versions. Warning: There are a lot of inferior designs that cost the same & even more.

For this application, the centerline of that venturi neck down needs to be at 9.9"± from the end of the primary header tubes.

The front edge of the opening of the H-pipe needs to be at 19.8"± from the end of the primary tubes. This one is very sensitive. Don't vary more than a half inch at most. Less is better.

The X-pipe (photo at bottom right) needs to be centered at 39.6"± from the end of the primary tubes. This one is less sensitive ... and inch or two either direction is ok.

The mufflers need to be centered at 79.2"± from the end of the primary tubes if possible. This is getting close to the suspension. If this won't work, they may need to eliminate the X-pipe & place the mufflers at 39.6"±. Unless they're running a "straight through" type of muffler, then placement is a non-issue.

If you need to vary from these dimensions, don't vary much, as you are upsetting the exhaust pulse timing. If you need to vary a lot ... let's talk first. It is better to have no H-pipe or X-pipe ... then to have them in the opposite location from optimum.

Quote:

Originally Posted by ccracin (Post 537795)

Ok, Ron, I have taken it all in. This is great information. I am going to recommend the custom cam. I hope they can get it in time. This is what I came up with for the part and grind number of the cam you suggested. I got this from the master lobe catalog.

Part# 12-000-5
Grind # CS 6263/6414-S108

With regard to the exhaust, I am not sure they will be able to go this route at first. I will find out what they have now. I know it is not a crossover system. I think if I can get them to do most of this on the engine, the budget may take a beating. What do you think we can get away with at a bare minimum?
I probably should know what they have first. So find out & list it on here. If they can't afford step-headers, they need to go with the 1-3/4" straight headers. If they run 1-5/8" primaries the cam & headers will be working against each other. Just know they are giving up some low end power with 1-3/4" straight versus 1-5/8"-to-1-3/4" step headers.

An less expensive alternative to true merge collectors are "Insertable Collector Reducers". (Photo at bottom of page)

They basically slide into the 3" collector material & run a few welds to hold it in place centered at 9.9" from the end of the primary tubes. I've used them with some positive results when the exhaust was too tight to fit a merge collector in there.

An H-pipe is dirt cheap. It is the same 3" tubing as the exhaust. When I re-read my initial exhaust post #4 ... I saw I worded it incorrectly & went back to change it. (The corrections/additions are in red) You want to weld the H-pipe in so the leading edge of the H-pipe is at 19.8".

The rest of the exhaust needs to be 3" too. If it's smaller, that will not work with this cam cambo.

How about the carb? Anything I should tell them to pay attention to? I would can provide here will be greatly appreciated.
I can't tell you what the specs need to be, but the carb is critical in two areas. Obviously, ANYTHING that can be done legally to increase airflow is a priority. Get with a proven carb guy known for building good gauge legal GAS 2-barrels.

The second part if getting the fuel curve correct. This is all internal with orfices & bleeeds. How we do this is running the exact engine on the dyno for 12-20 hours with the carb guy tweaking the curve & making runs until the fuel curve, idle quality, throttle response & power are optimum. The challenge is they can't afford to do this. So they just need to get with that proven gas 2-barrel carb guy & trust his work.

Do you have a recommended vendor for a blue printed oil pump?
The Melling Select pumps are pretty good out of the box, but being frank, we still disassemble them, check for imperfections & deburr them. Precision Oil Pumps blueprints Melling select oil pumps & offers them ready to go for what I think is a pretty good price. Their website is here.

They are not allowed the E-Curve Dizzy. Any options there?
I did not see a distributor rule. If you can run any MSD billet racing distributor, that would be my pick. They have hardened shafts & 2 shaft bearings. There are other brands too.

But if they require OEM distributors ... I assume they allow you to run HEI distributors. Performance Distributors offers their "DUI" distributor ... which is basically a HEI clone ... with the best HEI distributor parts (coil, pickup, caps, rotors, etc.)

I have mixed feelings here. Where rules allow any distributor ... and where there are no rules ... I wouldn't run the DUI distributor because there are much superior options for literally a few dollars more.

I have ran the DUI distributor a LOT and get good performance out them ... especially 7000 rpm & below. My qualm with them is the fast wear rate of the non hardened shafts. I had to rebuild the DUI distributors every season & put in new shafts. Otherwise the shaft "wobbles" and timing is erratic.

So DUI is the best option if you can not run a racing distributor. Be prepared to rebuild with new shafts every off season.

As far as the timing curve ... run biggest weights & softest springs so the timing curve is extremely quick. Set the total timing at 37° to start & tune from there.

Thanks.

You're welcome.

Ron,

Let's start with the distributor. There is no distributor rule per say, but there is a rule that does not allow electronic timing control or retard boxes. That's why I said I didn't believe the E-Curve dizzy would be allowed. I understand the goal here and will help them come up with a solution that best fits the budget.

With regard to the exhaust, here is what they have. The headers are Shoenfeld stepped but are not crossovers. They are 1 5/8" primary tubes stepped to 1 3/4". The 1 5/8" tubes are 16" long with a total tube length of 38 1/2". They have standard 4 into one 3" collector about 8" long then into the Sheonfeld slip on mufflers. They are 3' in and out with 3 1/2" bodies. They are mounted right to the end of the collectors.

Thoughts?

Thanks!

Hey Chad,

Quote:

Originally Posted by ccracin (Post 538127)

Ron,

Let's start with the distributor. There is no distributor rule per say, but there is a rule that does not allow electronic timing control or retard boxes. That's why I said I didn't believe the E-Curve dizzy would be allowed. I understand the goal here and will help them come up with a solution that best fits the budget.
OK. Got it. Get a "self contained racing distributor" that doesn't require an external controller or amplifier ... with a sealed bearing that the shaft spins on. MSD makes them as well as Accel & Mallory.

With regard to the exhaust, here is what they have. The headers are Shoenfeld stepped but are not crossovers.
Crossover not needed.

They are 1 5/8" primary tubes stepped to 1 3/4". The 1 5/8" tubes are 16" long with a total tube length of 38 1/2". They have standard 4 into one 3" collector about 8" long then into the Sheonfeld slip on mufflers. They are 3' in and out with 3 1/2" bodies. They are mounted right to the end of the collectors.

Thoughts?

Thanks!

The easy, low budget solution is ...
a. Keep the headers.

b. Use 3" exhaust tubing for the dual exhaust.

c. Place the center of Insertable Collector Reducers with 2.5" ID at 9.9" from the end of the primary tubes.

d. Add a H-pipe inbetween the dual exhaust with the front edge of the opening of the H-pipe 19.8"± from the end of the primary tubes.

For anyone following along with us, how we place "straight through" mufflers in the exhaust system is different than how we place mufflers with chambers. "Straight through" mufflers act much like straight exhaust tubing, so the placement isn't critical. Chamber mufflers are different, as the exhaust gases are traveling further ... and in some chamber muffler designs ... there is expansion.

e. Chad, since they have straight through type mufflers, attach the mufflers after the H-pipe & try to keep the end of the mufflers (where the exhaust exits into the air) around 37-43" from the end of the primary tubes.

So I have a quick update for you Ron. I think what you have helped me with here is going to work out better than I even imagined. So, I took all the information from the thread and typed up basically an outline for them starting with the block and moving on. I sent it over to them and let them chew on it. They are both professional mechanics and own a garage, but they are not engine guys. I think what really hit home was how many details need to be addressed to really make the most of the rules. I told them they could go one of 2 ways. I would help them execute this plan and try to stay on budget. The other was I would get them in touch with the guy I think makes the best power in our area for these types of engines and they can say the hell with the budget and put a hammer in the car. They asked for the introduction and dropped their engine off at his shop today! LOL I'll keep you posted on the progress. Thanks very much!

You have me wanting to take the parts I have around the shop and putting a motor together to sell. It might be easier to clean the shop up that way!