Fresh 350 in a 74 Chevelle

by bigredlaguna Sun Sep 18, 2016 12:42 pm

Just got done R&R the engine in my daughter's car. Tuned as well as I can without dyno time. It is a vortec headed 350 with a xr258hr-10 cam. The trans is a th350, gear ratio is a 2.73 open differential (I haven't verified this, but the rpm to speed puts it in this range). The tires are 265 50r15 at all four corners. The suspension is stock with new bushings. We went to a local 1/8 mile drag race at an old WWII airstrip and had a blast. We were one of the slowest cars there, but could have been competitive with more cars had the car not spun so badly from the start.

There is not a timing system at this place, so the best estimate for et based on some videos is anywhere from 10.9 to a best of about 9.5 seconds in the 1/8. My daughter and I both drove the car, with her getting the most passes. This is her first time participating in drag racing and she obtained the best time with modulating the throttle to start. I kept getting too aggressive and would just spin through first gear. However, it seemed that the track itself was improving as time went on. We were some of the first ones to race and the weather was overcast/foggy just before racing commenced with sunshine the rest of the day.

The car is perfect for a cruiser, which is what she wants to do mostly with it, but what would be the first thing you would do for better traction? I have a few ideas and suggestions already from some fellows that were there, but would also like to hear from folks here also. I'll figure out how to get some videos on here in a bit, so you can see what is going on.

by bigredlaguna Sun Sep 18, 2016 2:02 pm

by bigredlaguna Sun Sep 18, 2016 2:05 pm

This was the best run she made

by bigredlaguna Sun Sep 18, 2016 2:35 pm

The other 74 had a big block (don't know the ci, but I don't think the engine was original to the car), th350, and 3.15 gears with the spider gears welded

by wbaker01 Sun Sep 18, 2016 9:36 pm

Best investment would be a posi unit (not the cheapest though). You can also play with air pressure but trying to put power through one tire makes things pretty rough..

by bracketchev1221 Mon Sep 19, 2016 6:26 am

An old unused runway is probably going to be covered with dust and dirt. Second, I would skip any water burnouts with street tires. The tires only trap water and when they get hot they release all the road oils they have absorbed rather than get sticky. I agree that the posi will distribute the power evenly and help, but also don't get overly excited to powerbrake it on the line. It loads the chassis and the only thing to take the hit is the tires instead of the suspension.

by bigredlaguna Mon Sep 19, 2016 10:51 pm

Thanks guys. That is consistent with the advice I got at the event.

I think she will only want to track the car one or two times a year. Maybe even just at this venue since it is fairly close. So here are my thoughts on getting this car to hook up with the gear ratio in it now.

1. Mini spool. This can be changed out at the track and eliminate the need to obtain a trailer. Since the car will not see much track time in reality, and the open differential is not a liability for a cruiser.

2. 275 50r15 drag radial tires. I suspect that any of them would be good for this car, but some input would be appreciated.

I figure these two things could be done with brand new stuff for about 500 dollars and a little bit of sweat equity from me.

3. No spool, but use an air bag on the right side to keep the right tire on the ground. The drag radials will happen either way.

I am not opposed to getting a posi unit, but I am also looking to be cost effective for her as she will be on the hook for this stuff if/when she decides to upgrade things.

by bracketchev1221 Tue Sep 20, 2016 5:36 am

I'm going to advise against the mini spool for 2 reasons, it puts all the load on the crosspin that it was never designed to have and you don't want to be pulling the differential cover and pulling axles to go to the track. You'll either give up on doing it or wind up leaving it in. I would spend the money once and put in a decent posi unit that will work all the time and make going to the track fun instead of work. Second, if the tires are as big as you say, you may want to consider installing a set of 3.42 gears. It will make the car more responsive and not be terrible for a highway cruiser. Finally, if you plan on using the drag tires on the car all the time, then yes a drag radial would be the way to go. If you plan on swapping tires for the track, then go with a bias ply tire. If you plan on racing on poorly prepped surfaces the majority of the time, a drag radial really isn't going to help. For example, if you watch the video of the other big block Malibu that you raced, in the screen shot you posted, you can still see the sidewall wrinkled on the Hoosier street slicks he was running. Without being able to initially load a radial on poor track prep they will spin just like street tires. A Bias slick will be more forgiving with the softer sidewall.

by Joe73 Tue Sep 20, 2016 6:37 am

bracketchev1221 wrote:I'm going to advise against the mini spool for 2 reasons, it puts all the load on the crosspin that it was never designed to have and you don't want to be pulling the differential cover and pulling axles to go to the track. You'll either give up on doing it or wind up leaving it in. I would spend the money once and put in a decent posi unit that will work all the time and make going to the track fun instead of work. Second, if the tires are as big as you say, you may want to consider installing a set of 3.42 gears. It will make the car more responsive and not be terrible for a highway cruiser. Finally, if you plan on using the drag tires on the car all the time, then yes a drag radial would be the way to go. If you plan on swapping tires for the track, then go with a bias ply tire. If you plan on racing on poorly prepped surfaces the majority of the time, a drag radial really isn't going to help. For example, if you watch the video of the other big block Malibu that you raced, in the screen shot you posted, you can still see the sidewall wrinkled on the Hoosier street slicks he was running. Without being able to initially load a radial on poor track prep they will spin just like street tires. A Bias slick will be more forgiving with the softer sidewall.

X2 on all the above !!!

by bigredlaguna Tue Sep 20, 2016 9:59 am

The tires on the car now are only 25.5" tall. The 275 50 drag tire is only 26" tall. So I don't think the tire size will hurt it much at this point. I would not put a taller tire on it without a gear change. I have a couple of 8" wide rally rims so I would be changing tires at the track.

Sounds like bias ply for the tires then. There is a good track at Great Bend, Ks that is a full 1/4 mile with timing lights that is about 2 hrs drive from here. We may go there for some concrete numbers instead of guessing at times.

I ultimately think that the car needs an overdrive transmission and a better gear with posi. I would like to be able to get it to handle a full throttle launch. The power figures I have found on the internet for the head/cam combo suggest that it should make 300 horse power or better, with close to 400 ft/lbs torque. I think it is a reasonable goal to get it to be able to handle that.

by bracketchev1221 Tue Sep 20, 2016 1:28 pm

Like I said, the bias tire will be your best bet. Also, on the starting line, bring the rpm up only as high to prevent an off idle stumble if needed. The suspension is there to handle the hit of the torque from the engine. And if you torque the body over powerbraking it, the only thing to take the hit is the tire. And most times they will just spin at that point. The airbag is another good idea, though I'm not positive at your hp it will help anything. In a Chevelle body style with the 4 link suspension, with enough hp it will try to rotate over on the passenger side. However, when it does that it tries to suck the passenger side tire UP into the body and unload the suspension. My car years ago with the air out of the airbag would put the driver side tire 18" in the air with the passenger side on the ground. But that was going 11.20's at 118 mph as well.

by Hs1973 Wed Sep 21, 2016 2:31 pm

Just a heads up. If you need a posi at a decent Price, try and look for a posi unit from trans am/ camaro 70-1980 i just put a used posi unit in my original rear Axel. It was not that hard as it seems and less than 400 dollars with all new bearings and such. I Found a 3:42 gear and posi from a 79 trans am. I bought the whole Axel that Way i could tjeck the pattern and start the setup with the original shims. That made it fairly easy to set up and the Price was ok. The Price also make it easier to pound on it cause If it breaks it dosent cost an arm and a leg to fix it again. The posi units are plentyfull in junkyards, and fits right over in our axel housings If it is a 8,5 10 bolt. Strength wise the 10 bolt 8.5 is almost just as stronger as the 12 bolt. Google super chevy artikel on the 8.5 10 bolt build, they explain really good what to look for and so. So that is a cheap Way to get a strong rear that is cheap enough that you can drive the snot out of it without crying snot If it breaks.

by bigredlaguna Wed Sep 21, 2016 6:12 pm

Believe me, if I find a deal on some good used parts like that, I will likely jump on it. I'll update this thread when/if something changes.

by bigredlaguna Mon Feb 06, 2017 10:44 pm

Look at what I have.

Fresh 350 in a 74 Chevelle Img_2010

Auburn posi and 3.42/1 gears. Just got the new bearing kit for it the other day.

There is another fun drag day on 4/22, and I hope to have this together with a better set of tires by then.

by bigredlaguna Sun Feb 12, 2017 7:02 pm

Pulled the cover off before doing anything and found no c-clips.
Can I still use the Auburn unit? It was made for a c-clip axle. I do have some c-clip axles, can they be used or are the bearing ends too different?

by Joe73 Sun Feb 12, 2017 7:09 pm

C-clips or no C-clips does not matter. Difference between the two is how the axle is held in the rear. C-clips on the end of the axle like most chevys or 4 bolts on the backing plate like BOP do it.
Your good to go with what you have.

by bigredlaguna Sun Feb 12, 2017 7:17 pm

by bigredlaguna Mon Mar 06, 2017 2:32 am

Amazing what a wire wheel can do for these old things

Fresh 350 in a 74 Chevelle Img_2010

by bigredlaguna Mon Mar 06, 2017 2:34 am

I did get the limited slip carrier installed. Just getting some of the small stuff tended to.

by S3SS Wed Mar 08, 2017 10:12 pm

Nice..The BEST thing to change the performance of my laguna, el camino and chevelle was install posi with 3:42 gears. It took it from a sleeper to a contender. It literally woke the car up out on the line.

by bigredlaguna Sat Mar 11, 2017 10:44 pm

Well.....crap.

I got the axle back in the car and am ready to test drive it and the transmission completely lunched itself. All I did was back it out of the garage and put it in drive. Still had to push it back in the garage with my pickup due to living on an incline.

Hopefully I can get something together before the fun drags.

by Joe73 Sun Mar 12, 2017 7:26 am

S3SS wrote:Nice..The BEST thing to change the performance of my laguna, el camino and chevelle was install posi with 3:42 gears. It took it from a sleeper to a contender. It literally woke the car up out on the line.

I agree !!!! I always tell people the same thing. Yes, more power is great, but you need gears. Gears will wake up any car.

by S3SS Sun Mar 12, 2017 7:47 am

I wish I would of done this when I was first introduced to the G3's in the mid eighties. It was always about more power yet the gears were the one thing that made a very noticeable difference.

Joe73 wrote:
S3SS wrote:Nice..The BEST thing to change the performance of my laguna, el camino and chevelle was install posi with 3:42 gears. It took it from a sleeper to a contender. It literally woke the car up out on the line.

I agree !!!! I always tell people the same thing. Yes, more power is great, but you need gears. Gears will wake up any car.

I

by fasrnur Sun Mar 12, 2017 3:21 pm

The combination of more torque and a different gear ratio will help get our big old boats rolling SO much quicker. I can't wait to see what gears are in mine. It seems to do alright off the line. I can't believe it has anything higher than a 3.08 gear in it. And no, I haven't had the cover off yet. In time. Very Happy

by bigredlaguna Sun Mar 19, 2017 1:35 pm

Just for kicks, I'm going to put up the axle code for the axle that was in this car.

The AC means 2.74 open, the O is for Oldsmobile, And 247 is I'm assuming is a production date like Feb of 1974, 7th day perhaps.

Fresh 350 in a 74 Chevelle 74_axl10

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