Help me plan my race car project
 

This is possibly my first real post in the Race section. :3gears:


I’m a few years away from being able to retire, and I want to build a dedicated drag car and get into bracket racing. Looking back at my GTO project, I realize that I wasted a lot of $$ by changing directions multiple times, so for this project I want to develop a solid plan before I start and then stick to it. Once I have a good strategy, I will begin collecting parts as money allows and start the build when I am ready.
There isn’t really a specific budget, but I want to keep costs reasonable as I will only be able to do 4-5 races a summer due to the few events/tracks up where I live (all are 1/8 mile). I already have a stash of parts to use as a starting point, and want to plan the build around them to keep costs down. Being a bracket car, I’m looking for a strong, reliable and consistent setup.

What I have to work with so far:

-79 Trans Am rolling chassis with 10 bolt rear (assume I will use 28” slicks or drag radials)
-factory 2 bolt 481988 block
-“as cast" round port Speedmaster 72cc heads
-forged 3” main, 4.250” crank
-forged 6.800” I-Beam rods
-factory 1970 dual plane intake (planning to do the Cliff/SD mods to it)
-800CFM Q-jet
-Turbo 400 transmission that I will rebuild with appropriate parts & shift kit

Assuming 91 octane/10% ethanol for fuel, I am looking for input on:

-recommended camshaft type & specs that complement the heads/intake/carb I will be using (note: I have no plans to port the SM heads and will run them as delivered other than swapping springs as required.) The heads are reported to flow 289/202CFM at .600 lift and I want a cam that will fully use the airflow capability with either 1.5 or 1.65 rockers. I'm OK with solid lifters if that saves some $$. If a flat tappet cam will get me where I need to be that is great; a roller cam is also not out of the question if needed.
-recommended target compression for the cam/engine/fuel combo
-recommended size of round port headers to match the combo (I see Doug’s has 2 sizes for round ports to fit in 2nd gen F bodies)
-recommend rear gear ratio
-recommended stall speed for converter
-I plan to install main studs. Are 4 bolt splayed caps needed at this level?
-block fill required or recommended?

-anything else I should know? J

I appreciate that most of you have spent years to get your combo’s dialed in, and any advice to get me on the right track is appreciated. Bear with me as I ask a lot of dumb questions along the way. Pontiac powered race cars are few and far between up here so hoping to represent the tribe :canada2:

If your 10-bolt is stock, the first thing I'd do is get a consultation going with Strange or Moser about upgrading. Stock axles won't survive with slicks. The conversation will be upgrading your 10-bolt vs switching to something else. Include your driveshaft and u-joints in that conversation. Sounds like you have the benefit of time to ponder alternatives.

Give lots of attention to bulletproof reliability so you'll have more fun and less frustration.

Eric

Hi Eric,

Thanks for responding. My initial plan was to upgrade the 8.5" 10 bolt with better axles, welded tubes, C-clip eliminators, a support cover, and a spool. Driveshaft would be an upgraded unit with 1350 joints and matching yokes on the trans/differential. Having zero racing experience, I am not sure if this is a reasonable plan or not.

You might want to look at a TrueTrac over the spool. It will make everything easier and should be plenty strong for your power level and weight. I'd also investigate using the 30 spline version (28 stock) and take advantage of the bigger axles just Incase you up the power level down the road.

IMO a Nitrided SFT camshaft with quality lifters is the best option for reliability for a dual purpose vehicle.

Thanks Paul. I had planned on 30 spline axles anyway so will look into the TrueTrac.

Built the short block strong and with light internals so it works best for you money input and with it being built strong you up the motors power level safely with better top end parts and not loose sleep at night.

1) use hard block to make a fill up to the bottom of the water pump passages.
Believe it or not even a street motor will run a minimum of 10 degrees cooler by doing this and the bottom of your cylinder bores will not get chewed up especially if you run crank strokes longer then 4.00”.

2) run longer Aluminum rods ( greater then 6.625” along with the needed pistons ) to maximize internal weight reduction.

Why is this a big deal you might ask.
The reason is that every pound of rotational weight reduction increases vehicle performance a minimum of 4 to up to 10 times more than that same amount of weight reduction done any where else on the car.

You will be stunned at how much faster the motor buzzes up and that faster rpm gain translates directly into the vehicle accelerating faster.

Hi Steve,

Thanks for the suggestion on block fill. For the rods, I already have a set of 6.8" steel rods that I will be using.

Your plan sounds reasonable.
I'm using a TrueTrac differential in my road race car based on recommendations from other road racers. No track time yet to report on. I can imagine it might be easier to drive on a drag strip with inconsistent prep?? If a car with a spool has sticky track under one tire and less traction on the other side, it definitely will try to steer the car.

FWIW,
Eric

Great info. The closest "track" is actually an air strip that gets closed down 2 weekends a summer and turned into an eighth mile strip. Consistent traction is one of my concerns so this is a good consideration.

Hop stop bars are an easy to install traction aid for a coil spring rear car.

Keep the rear sway bar on also since that helps .

Buy a race car that’s already built and proven from someone who’s retiring from racing.

For 25 to 50k you can buy a 100 to 200k car and start racing next week.

But what’s the fun in that? ;)

I would build the rear end/ rear suspension/trans and driveshaft ready for 10.00 and then use what you have for a motor with a big SFT cam/lifters. Then later when you have more money you can upgrade your motor to go faster. My rear is a 1972 10-bolt with a Strange spool, Strange billet bearing caps, Ford ends welded on, tubes welded to center, Moser 33 spline axles and an aluminum cover with bearing cap preloads. I use Caltracs with split mono leafs but was using stock leaf springs and cheap traction bars down to 10.4. With the motor parts you have you should be able to get down to 11.00 or slightly faster with the right converter. You should put a rollbar in right away. It's always an evolutionary process unless like Bman said you can buy a ready to race car for 30K and go low tens to high nines right away and save money in the end.

LOL, that goes against everything I believe in...building things IS the fun part! :) Winters are long, I need something to keep me busy!!

The need for a rollbar was something I was wondering about. If I can build the car to get into the 11's in the 1/4 that would be awesome. I believe I would need a roll bar if quicker than 11.50 in the 1/4, but not aware of what the equivalent requirement is for the 1/8th. I will consider one regardless as I think it could help stiffen up the chassis.

^^^^^^^

This

Sounds great on paper but I'm unlikely to squirrel away 25K without the wife finding out, and Chevy power is most common up here and not my style. :)

I already have the car and 30% of the hard parts so really wanting to move in that direction. Growing the parts stash one pay at a time is more likely to get approval (forgiveness).

So camshafts....since no one has recommended one, maybe I should start with what I was thinking and get some feedback from there.

With a 4.155" bore and 4.250" stroke I come up with 461 cubic inches, practically the same as the 463 in my GTO. I have the 230/236 Stump Puller in that motor with 1.65 rockers, ram air manifolds and 3" exhaust, 800 Qjet and a factory intake modified by SD. It pulls like crazy...so something similar or a step up seems like a place to start for a fun bracket motor.

Considering this will be a track car, idle & vaccum are not as big a concern. The SM heads appear to have about a 70% intake to exhaust ratio at .5 to .6 lift so thinking a dual pattern cam still needed. With a Qjet and modified intake + headers, is a 246/253 cam on the small side or about right? I believe compression should be somewhere around 10.5-1 for 91 octane. This is similar duration to SDs Road Paver cams and see several members using them in 455-463 street cars with 6X heads and better. I'm not scared of slightly more cam if it is a logical thing to do. I realize the intake is a limiting factor but it is a place to start.

Thanks

Tell wifey it’ll be cheaper in the long run and that you’re selling all your stuff and that Firebird to get a better car.

She’ll come around.

Asking for forgiveness is always easier than asking for permission. :)

On this we definitely agree!

If your only planning on 11's for ET, should be really easy.
But usually the bug to go quicker and faster comes quickly.

Also, havew to decide if you want it still streetable, or towing it to the track.
Towing it it can be made very fast easier.

Roller cam for sure either way, solid probably better. (just my 2cents)
With the TA, the leafspring setup is easy to work for 10/11 second times.
Faster than that ladder bar or 4 link would be better for strength and adjustability.
Narrowing the rear and tubbing then comes into play.
Then more money.


:D

Blowing 25k or more on a car that has once run fast times but just needs a drivetrain now and you will have learned nothing!

There no feeling of accomplishment to it.

Now if you have been there already and just want to get back into it as fast and cheaply as possible, then that’s fine.

A simple motor build making all of 450 hp should get you well into the 11s.

Dan Whittmore had a customer who he built a racing engine for that decided he just had to have aluminum rods. So, Dan rebuilt the engine, same cam, top end, compression ratio but with aluminum rods.
Ran the same ETs when done. Did rev quicker when not under a load. But down the track ran the same.

The plan is to tow it to the track, I already have a car hauler trailer and there is zero intention to drive on the street.

You could do the cal-trac type of traction control on the rear for starters. It should work good for the ET's wanted plus more. If (or when) you decide you need more tire (slicks) than will fit in the wheel well, then tubs and narrowed rear with 4link or ladder bar setup.


The roller cam will help quite a bit, with a good higher stall converter. With a reasonable rear gear, it should run great in the eighth. Eighth mile will be easier on the engine/tranny also. TH400 with a good transbrake setup will make for a consistent and fast car.


:)

[QUOTE=johnta1;6531930]If your only planning on 11's for ET, should be really easy./QUOTE]

It's not that I am planning on "only 11's", I'm more about doing a build that complements the 461 cubes with the parts I already have. If I could build a 10 second car that was reliable using stock leaf springs, no tubs, etc., then I likely would.

I was thinking (I guess naively) that many would chime in with cam suggestions that I could consider and plan my build around as a starting point.

I was looking at cal-tracs, thanks for the info.

Someone may have already suggested this but a call to Bullit or Lunati or whatever cam manufacturer you choose would be a good starting point. Give them the parts you are working with and your goals and see what they would recommend. The intake will be a limiting factor but not too much in the modified form you mentioned. Off the top of my head I would think a cam in the 248/254 duration would be in the ball park. Maybe .550 lift. As your combo evolves you can always upgrade the cam as needed. Also, with the 461 I would go with 1&7/8" headers and 3" exhaust to cover future needs; may not make much difference with your current combo but at some point they will be needed. And as others have said don't skimp on the drive line. On my 79 with the 463 I am running a beefed up 8.5 with Strange 30 spline axles, the housing cover and True Trac differential, aluminum drive shaft and 1350 u-joints. As to traction you might want to look at the Smith Racecraft Assassin Bars. Similar setup as the Cal Tracs but more adjustable and a little easier to install. I run them with stock leaf springs and drag radials successfully. On a side note I think the rollbar rule for 1/8 mile is 7.35 or quicker.

Thank you for the info. Much appreciated.

If you are planning on only tracking the car....get the car on a diet. Every 100 lbs will get you quicker.

Glass hood
Gut the interior....all the seats ( i leave the carpet in and use a race style seat. huge
cut out the door guards
drop bumpers and replace with glass
remove exhaust system
replace side glass with lexan
remove front wheel wells.
Take off stuff like wiper motors etc
convert engine to electric waterpump.
Install electric fuel pump

AND get a holly carb for your engine. Im gonna get flammed here, but at the track its way easier to jet up/down, ajust air bleeds etc between rounds
Remove front sway bar
replace brakes with light weight discs with good calipers
light weight wheels
grind off the old rust prventative
replace fuel tank with 5 gallon cell
move battery to the trunk
add a light weight starter
consider removing the alternator and charging the battery between rounds

500 lbs will get you a half second in the 1320

You do not need a roller cam, billet caps or block fill to get what you are after.
You can do them if you want but its expensive and can be a pain. Studs and 2 bolt are fine
I would call Tim at Bullet and get a custom sft cam.
Would not mess with iron intake either, you are bracket racing.
Those Tomahawk knock off intakes work good enough and are cheap, fit you shaker too. I ran one down to 11 flat and 9-1. (but with roller cam)
Get a 850/950 Holley carb too.
Do not skimp on a converter. Lane at PTC will hook you up.
Might want to get in touch with Paul K here. Hook you up with some pistons and advice. I would get some Total Seal rings with port slots too.

Back at it
 

Back at this, and have collected all the parts to build the motor this winter.

Build will be a 400 block, 4.250" forged stroker crank, SM 72cc heads, Ross .040" dished pistons (dish still to be determined), forged I beam rods, Bullet SR cam 255*/263* @ .050 on a 110 LSA with .605" lift.

I have two 400 blocks I can use, both cast # 481988. One is a 1971 and the other is 1973. I looked them over very well before picking one to send to the machine shop, and upon visual inspection, it looked like the 1973 block would be better. I will post some pics to show the differences, then get to the sonic results.

First thing I noticed was that the 71 block did not have the "00" casting in the valley, where the 73 block did. The pic on the left is the 71 block.

Looking further at the castings, they are very different in how the molds were created, and the 73 block is thicker in many areas around the mains compared to the 71.

The 71 block is on the left. Note that the area between the main and cam bores is scalloped with less material, but still appears to have reinforcement ribs where needed. Also note the slight undercut below the main cap surface. The 73 block has a lot more metal here, so I thought it would be better.

Next thing I noticed was that the 73 block had more material under the bores where the oil galley is located. On that block, there is a bevelled area between the bottom of the bores and the lifters. On the 71 block, there is less material and you can actually see the rounded shape that was cast for the oil galley to be inside.

The other difference was how the mold went together and where the parting line is for the cylinder bores. The 73 block has the casting inline with the crank (not on the thrust side), whereas the 71 block has the casting line on the thrust side of the bores with a noticeable mark that could act as a stress riser. This made me think the 73 block would be better.

I also noted that the 71 block casting surface is much smoother than the 73 casting. Not sure if the 71 was poured in a better mold?

The 71 block is on the left.

Looking at the area where the motor mounts are located, I saw another difference.

The 71 block has a bar or lug running below the pan rail where the bolt bosses are, whereas the 73 block has an individual bump where each boss is located. This made me think the 71 was stronger in this area.

Looking at the bulkheads for the mains, the 73 is almost a straight casting and has more material from the main cap mounting surface down to the bores and cam area. the 71 block has material removed and instead of just a straight casting there appears to be strategically placed ribs. Even though the 71 block looks stronger where the mounts are, I thought the 73 would be stronger in the mains area due to more material.

The 71 block is on the left.

Pick a block!
 

Lastly, I weighed both blocks to see if there was a difference...there sure was. Using a digital bathroom scale, the 71 block weighed 192 lbs vs the 73 block that weighed 201 pounds. This was with all the same items still installed like caps, bearings, frost plugs, etc. 9 pounds is a lot!

Visually, other than the motor mount bosses, the 73 block looked stronger. More material in the main bulkheads, more material under the bores/around the oil galleys, and parting lines not on the thrust side of the cylinders.

So I sent the 73 block away for bake/blast/mag and sonic check, and got results that are not great...the right bank appears to have core shift and with the required 0.040" overbore, losing .020 per side puts the thrust sides at around .110". Cylinder #7 is also very thin on one side. Spoke with the machinist, he said he could move the bores around to keep as much material as possible, but that will require additional setup and cost.

Note that I do plan to use block fill.

Here are the sonic readings.

Try again
 

I only want to do this once, so I sent the 71 block in for the same work to see if it was better, thinking I will use whichever one is better in the bore area.

The 71 is better. Cylinder #5 & 7 have thin areas on the non-thrust side, but I can get at least .145" on all thrust sides without moving any bores around, and more if I do.

Here are the sonic results for the 71 block.

So...looking for advice to make sure I am on the right track.

While the 71 block is thinner in several areas, it has thicker bores. Should that be my primary concern? Is there any reason I should use the thicker/heavier 73 block?

If the 71 block is the way to go, is a .145" finished wall thickness on the thrust side more than enough, or should I pay extra to move a particular bore to get a certain thickness?

Appreciate your feedback.

Biggest question is how fast do you want to go?And then what safety equipment you will need-ie a roll bar or cage.
Keeping the Speedmaster or even brand name Edelbrock heads unported unless the car goes on a BIG diet you won;t need to worry about it.
My current 0.030 455 in my 78 Trans Am full factory interior AC box still on but no condenser up front with light ProStar wheels and 9" radial no tube slicks weighed 3750lbwith my 150 lb butt in it. Good air-a rarity here ran 10.90s @124mph. Ported E heads Ultradyne hydraulic flat tappet 239/247 @0.050 and 1.65 HS rocker on exhaust 1.8 Crowers on intakes. Ported Torker II and a Holley 4781 850 DP jetted on e click lean form factory. 2" Hooker Super Comp 4202 headers into 3" X and ultraflows 3" tailpipes. 4.10s and a 10" Continental convertor.

Previous 455 similar but a roller cam and aluminum rods ran about the same but had a 5000 stall and 4.56s. Similar times but a faster 1.5 60ft and 6.9 @ 100 1/8. STOCK 10 bolt 28 spline axles Eaton posi . Just freshened rear last year and dropped back to 3.42s for street upgrading to 30 spline Eaton and axles but factory axles looked fine no twist. LOTS of 1/4 mile passes on the rear. I does has 79-81 rear discs so kind of c clip eliminators. years ago I asked Tom at Tom's differenitals about new axles said if you are using the stock posi it will break before the stock axles. The Eaton was stronger.

Rear springs were the trick to hooking up over traction bars . Tri City "Launcher" springs that lots of NHRA Stockers used before caltracs came out. Built like the old Mopar Super stock springs with second and third leaves going further up second under spring eye. Now Caltracs and their split springs are the best what I have ion the IA/Camaor.

To slow it down with no roll bar I added back the heavier 8" Snowflakes with 235 60 -15 fronts and heavier DOT 275-60-15 M/T rear tires and put the spare back in it. Ran 11.50s @117 in Texas heat all day long WITH an air filter in the Shaker.

I would add C clip eliminator and good axles and a decent Eaton posi or trutrac and go 30 spline. Most the bearing and axles are identical to 30 spline 12 bolts other than the C clip button is thinner.Strange has or had a C clip eliminator that uses the taper Ford 3.150 bearing that is better at side loads if you are on the street any. You won't break the 10 bolt! Most leaf spring cars are not going to spin the axle tubes as easily as a coil spring car. If you have the tubes welded be sure they use a jig to keep them straight. I have seen 9 second F bodies using a 10 bolt rear.

First motor with the roller cam I ran a ported Pontiac HO intake and a Carb Shop worked over 73 SD Q jet. Swapping at the track with an adapter and 850 demon DP picked up 0.3 seconds! Swapping on the Torker II picked up even more but not done at the track. Holley?Demons much easier to tune at the track than pulling the top off a Qjet-otherwise on a Q jet you are just changing secondary rods. And using a wiode band th BS about primary jets/rods don;t do much on a Qjet is just wrong they do!

Forgot just a 2 bolt main 455 block.

3X B man!Tom

I am far past the point of considering the purchase of an existing race car. I'm building my own and have collected all the parts over the past year so let's focus on helping me achieve that. Tragically, my wife passed away unexpectedly in July and my car hobby and two Labrador retrievers are pretty much what is getting me through this, so....

....I would like to focus on my recent posts about which block is best to use for this build.

Thank you

Regarding Skips post, I have upgraded 30 spline axles and and Truetrac for the differential.

I would let your machinist tell you which one HE would machine and build.Tom

Sorry to hear about your wife. I would be a mess, she is everything to me.
I run a 73 stroked 400 block and all is good.
71s bore numbers do look nice though.

Thanks Tom.

When I picked up the 73 block and we reviewed the numbers, the machinist said he was most concerned about the #7 wall with a .107" thickness (non-thrust side) knowing I would be using a .040" overbore. He said if I was filling the block (I am), and shifted the bore over to keep as much wall as possible, I should be OK and we could probably keep it at .100". But that still leaves other bores (#4 & 6) with a finished thickness of .110" and .108" on the thrust sides unless I relocate those bores. If the bores are shifted, around .120" is the most I can get on the thrust side.

Maybe I should ask this a different way:

-what is the minimum recommended wall thickness on the thrust side when building a 500-550HP bracket motor?

-has anyone encountered block issues such as broken or cracked main bulkheads with the style of casting that this 71 block has, at this power level?

I should clarify that I don't see anything "wrong" with the 71 block, it is not a bad design like the 557 block, but in comparison to the 73 block it does have this different design with some thinner areas. Interestingly, not only are the cast surfaces smoother, but the block seems more dense in some way, tapping it has more of a ring that the 73 block does. I have read many posts that the blocks got thinner and lighter as time went on in the 70's, but that is not the case comparing these two examples.

Thanks. Do you know or recall if your casting is the same as the one I have? Having only these two to compare, I am not sure if there were other mold styles used in 73 or if what i have is the only type.

Just use hard block to fill the water jacket up to just below the front of the block water pump holes and then the machine shop can bore away without off set boring .

You will gain ring seal and better cooling from this mod.

Hard block will raise oil temps!Tom

I will take a look when I get a chance.
Few pics of my block.

Thanks for the pics Dragncar, my 73 casting is the same as yours. The identifying feature is the parting line from the casting and how the main/cam area is one piece.

I came across these pics below in a post from GRX back in 2006 that was about block differences. They are representative of my 71 block on the left and my 73 block on the right.

Michael, my machinist always told me that he would not recommend starting a performance build with less that .180" on the thrust side. Your machinist was OK with your numbers?

Also, what airport races do you plan an doing. I've done 7 or 8. Raced at Kirkland Lake, Northbay on the hill , and Elliott Lake. Been over 10 years since I did one.
They were all a blast. Just a totally different environment than racing my local track (Shannonvlle). Have always wanted to go back to another

Glenn