[JLMounce]

Originally Posted by Skippy597

Just called molnar and put my info on the list for the 4" crank with bbc rod journals. Gonna go with 6.8 rods.

Really shooting for 500 hp, I'm pretty sure I can get there with a street 433 and then spray a 150 shot on the strip.

Thanks guys.

1.15 hp/cid is more than achievable, even streetably. I think you'll be happy in this direction, especially with the TKX and the high 3 series gear you're planning.

Should be a fun street car!

[turbo69bird]

Originally Posted by mgarblik

I think this very well sums up your choice. I just finished a 468 and have it back in the car. 4.181x4.25. I already had a billet crank left over from the Boss Bird funny car so that made the decision for me. I wanted the engine to really "zing", so I used a solid flat tappet cam and light rotating assembly. Didn't really matter, it's done making power at 5900 RPM. I had anticipated it zipping right to 6300-6400 RPM. Has a nice, broad torque curve. Just depends on what you want. I would tend to favor the shorter stroke with the stick trans and the desire to spray in the near future.

Kinda curious Why would the stick trans factor into it? I mean you dint see pro stock racers building 433 inch motors for their stick cars?
Not trying to give you a hard time just wondering what your thought process is on that.

[Skip Fix]

I have a set of 6.8 rods to use in my planned 4" stroke motor.

[Skippy597]

Originally Posted by Skip Fix

I have a set of 6.8 rods to use in my planned 4" stroke motor.

What pistons are you gonna go with skip and what heads / chamber size?

Running the 6.8 rods on a 4"stroke there's not a lot of options, icon makes a flattop that will require 87 cc chamber size.

So to pose another question forgetting about rod length and saying I wanted to run a off the shelf piston is it better to run a smaller chamber and a dished piston or a larger chamber and a flat top?

I've done some reading but haven't found much on the subject, seems the larger chamber is theory would allow the valves to flow more since they would be unshrouded, and I know flat tops are typically desirable. But I've also read that the smaller chambers tend to be more efficient and that dishes to a degree do not have a negative effect.

What's everyone's thoughts on this?

[racerboy]

Originally Posted by Skippy597

Just called molnar and put my info on the list for the 4" crank with bbc rod journals. Gonna go with 6.8 rods.

Really shooting for 500 hp, I'm pretty sure I can get there with a street 433 and then spray a 150 shot on the strip.

Thanks guys.

Skippy
You and I are building very similar engines, or at least short blocks. I’m on the Molnar list as well for a crank and set of rods and literally just picked up my WS block from machine shop today. I’m planning on going with my original #12 heads, but will definitely be watching this thread. This is the original RAIII that came out of my ‘70 Trans Am. Like others mentioned, I didn’t want to go with a 4.25 stroker because this is a stick car (M21) with a 3.73 rear.


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[mgarblik]

Originally Posted by turbo69bird

Kinda curious Why would the stick trans factor into it? I mean you dint see pro stock racers building 433 inch motors for their stick cars?
Not trying to give you a hard time just wondering what your thought process is on that.

My thought process was that I was cheap. I already had a billet crankshaft that was 4.25" stroke. Tried to sell it for over a year. It needed some repair on the mains but I couldn't get enough for it to buy a Chinese forged 4" crank. So I fixed it and used it. My engine is in a 62 Catalina street car. The torque of the 4.25" stroke overpowers the skinny 6" wide, 15" diameter tires. Only so much you can do with all that torque and the gearing in a 4-speed. I think it could have been managed better with a torque converter. No big deal really, puts on a hell of a smoke show with those street tires. Peak torque is at 4800 RPM. No real way to even roll into the throttle without torching the tires in 1st or second gear. Good problem to have I guess.

[Skippy597]

Originally Posted by racerboy

Skippy
You and I are building very similar engines, or at least short blocks. I’m on the Molnar list as well for a crank and set of rods and literally just picked up my WS block from machine shop today. I’m planning on going with my original #12 heads, but will definitely be watching this thread. This is the original RAIII that came out of my ‘70 Trans Am. Like others mentioned, I didn’t want to go with a 4.25 stroker because this is a stick car (M21) with a 3.73 rear.


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Sounds like a good combo. Are your heads ported? And did you go with the 6.625 rod from molnar? And what pistons are you gonna run? And what cam if you don't mind me asking.

[tom s]

Just put my 455 WS 69 engine back in my 69 Bird.4.21 3 in crank,bone stock 48s with 3,31s in the back and a TKO 500.Hope to fire it up tomorrow.Tom

[tom s]

Pic

[turbo69bird]

Originally Posted by mgarblik

My thought process was that I was cheap. I already had a billet crankshaft that was 4.25" stroke. Tried to sell it for over a year. It needed some repair on the mains but I couldn't get enough for it to buy a Chinese forged 4" crank. So I fixed it and used it. My engine is in a 62 Catalina street car. The torque of the 4.25" stroke overpowers the skinny 6" wide, 15" diameter tires. Only so much you can do with all that torque and the gearing in a 4-speed. I think it could have been managed better with a torque converter. No big deal really, puts on a hell of a smoke show with those street tires. Peak torque is at 4800 RPM. No real way to even roll into the throttle without torching the tires in 1st or second gear. Good problem to have I guess.

No I meant for this new build if it was a stick use the 4 inch stroke Vs the 4.25 stroke of it was a auto. That’s how I understood what someone said,z. Which didn’t make any sense to me . Being cheap if I had the crank already makes perfect $en$e to me I’d do the same thing. ��

[Skippy597]

Looking at piston options it seems that it's far more viable to go with a 6.625 rod and use something like the dss 14cc dish pistons with a 72cc head and get a good 10.3ish:1cr. If I were to go with a 6.8 I'd be limited to running only a flattop from either icon or racetec for an off the shelf piston. Now that is fine but would force me to run an 87 cc head and knock compression just below 10:1. Seems that if I don't want to shell out the money for a custom piston I should go with the shorter rod since I think the half a point in compression will make a bigger difference than the slightly longer rod will ever make.

[PAUL K]

Originally Posted by turbo69bird

No I meant for this new build if it was a stick use the 4 inch stroke Vs the 4.25 stroke of it was a auto. That’s how I understood what someone said,z. Which didn’t make any sense to me . Being cheap if I had the crank already makes perfect $en$e to me I’d do the same thing. ��

A 4" stroke engine usually has a wider power band, more fun to drive with a stick. The 4.25 engine usually develops more torque and will make things harder on the driveline, mainly the transmission.

[Skip Fix]

Originally Posted by Skippy597

What pistons are you gonna go with skip and what heads / chamber size?

Running the 6.8 rods on a 4"stroke there's not a lot of options, icon makes a flattop that will require 87 cc chamber size.

So to pose another question forgetting about rod length and saying I wanted to run a off the shelf piston is it better to run a smaller chamber and a dished piston or a larger chamber and a flat top?

I've done some reading but haven't found much on the subject, seems the larger chamber is theory would allow the valves to flow more since they would be unshrouded, and I know flat tops are typically desirable. But I've also read that the smaller chambers tend to be more efficient and that dishes to a degree do not have a negative effect.

What's everyone's thoughts on this?

Probably my RAIV heads 69cc chambers so will need a good dish to run pump gas.

[mgarblik]

Originally Posted by PAUL K

A 4" stroke engine usually has a wider power band, more fun to drive with a stick. The 4.25 engine usually develops more torque and will make things harder on the driveline, mainly the transmission.

This is basically my feeling too. No hard scientific data. In the driveline, the Muncie or T-10 with a single disc clutch is the weak link. Those little lightweight transmissions were never intended for 500+ ft. lbs. of torque. The only saving grace was the tiny lousy tires the cars came with back in the day. Good pair of tires and the transmission becomes a basket of aluminum cole slaw. A turbo 400 with the right converter can control and use more of that brute torque. But I love stick cars for street fun. In the end, probably doesn't make a big difference, more based on how you drive it.

[Formulajones]

Less and less people are running muncies these days anyway. Pretty much reserved for the restoration purists and cars that don't do much driving.
Shucks the prices I saw for muncies at the swap this weekend doesn't even make them a viable choice anymore.

Nearly everyone anymore that actually drives their cars or even races them on occasion are going with a much more durable 5 or 6 speed setup so the thought of a manual trans being a weak link isn't much of an issue these days.

[mgarblik]

Originally Posted by Formulajones

Less and less people are running muncies these days anyway. Pretty much reserved for the restoration purists and cars that don't do much driving.
Shucks the prices I saw for muncies at the swap this weekend doesn't even make them a viable choice anymore.

Nearly everyone anymore that actually drives their cars or even races them on occasion are going with a much more durable 5 or 6 speed setup so the thought of a manual trans being a weak link isn't much of an issue these days.

I would love to upgrade to a TKX 5-speed in my car. But like many people my age, I have a bunch of Muncie and BW-T10 stuff laying around here in good condition. (for now). I was picking them up in good used condition for never more than $100.00 a pop. A long tail might bring $150-200. Those days are long gone, of course. Once my current, fresh Muncie blows apart, I will seriously look at a 5-speed upgrade. I plan to drive my car several thousand miles a year now and run the Hot Rod Power Tour with it . That one event is over 1000 miles, typically. The ability to knock one apart with a pair of snap ring pliers, a 1/2" and 9/16" wrench and a hammer is still attractive to me. Not going to overhaul a TKX with 4 tools!

[Formulajones]

Originally Posted by mgarblik

I would love to upgrade to a TKX 5-speed in my car. But like many people my age, I have a bunch of Muncie and BW-T10 stuff laying around here in good condition. (for now). I was picking them up in good used condition for never more than $100.00 a pop. A long tail might bring $150-200. Those days are long gone, of course. Once my current, fresh Muncie blows apart, I will seriously look at a 5-speed upgrade. I plan to drive my car several thousand miles a year now and run the Hot Rod Power Tour with it . That one event is over 1000 miles, typically. The ability to knock one apart with a pair of snap ring pliers, a 1/2" and 9/16" wrench and a hammer is still attractive to me. Not going to overhaul a TKX with 4 tools!

Completely understand. I have 3 spare muncies still laying around, one car still running one that isn't driven much. Back when they were cheap to buy they made sense. Spares I have would keep me alive a long time if I chose to keep running them. The last several years I've just geared more towards the 5 speeds as I found myself driving the cars more and more. I don't have to worry about breakage so much anymore either.

I just couldn't get over the $1500+ asking prices of the muncies currently at the swap yesterday, and that was just M-20 stuff. Some of the prices were even higher. They no longer make a lot of sense to me at those prices.

[Skip Fix]

I think on my old 409 stick race car the lighter aluminum flywheel helped the hit on the trans and pumpkin 10 bolt. not enough to prevent ripping out all the ring gear bolts when I had a 4.11 with a spacer plate-how I learned about spacer plates vs thick gears.

Have a couple of muncies, and ST10 also to use up. Richmond 5 speed"race" trans too.

[surfsama]

Originally Posted by Skippy597

Just called molnar and put my info on the list for the 4" crank with bbc rod journals. Gonna go with 6.8 rods.

Really shooting for 500 hp, I'm pretty sure I can get there with a street 433 and then spray a 150 shot on the strip.

Thanks guys.

500 hp at the flywheel or wheels? I run a 433 that puts down 505 hp at the wheels with nothing crazy so that shouldn't be tough.

[Dragncar]

Originally Posted by mgarblik

This is basically my feeling too. No hard scientific data. In the driveline, the Muncie or T-10 with a single disc clutch is the weak link. Those little lightweight transmissions were never intended for 500+ ft. lbs. of torque. The only saving grace was the tiny lousy tires the cars came with back in the day. Good pair of tires and the transmission becomes a basket of aluminum cole slaw. A turbo 400 with the right converter can control and use more of that brute torque. But I love stick cars for street fun. In the end, probably doesn't make a big difference, more based on how you drive it.

I went through the Muncie breaking thing back in High School. I solved it by putting a Ford Top Loader trans in. Twice the weight but much tougher.
Shifted great, even used the stock 69 GTO console.
I never did see how quick I could get down the track with it. Hid a T400 in it by that time.
Used to be a big manual trans guy. Still am.