[74Xr7302]

hello everyone, i have a 1974 XR7 with a 1971 302 in it, motor came out of a boat, correct rotation also. i repalced the marine cam with crane cam p/n 444232, also swaped the stock heads for edelbrock rpm performer heads p/n 60259,and edelbrock performer intake,1.6 roller rockers, gear driven timing, stock pistons, rods, crank, water pump, high vol oil pump, holly 750cfm dual feed, HEI dizzy, with MSD coil in cap, and picking up the 6a msd box p/n 6200 in about an hour. long tube headers 2 1/4 to 3. 18in pipe then 18in purple hornys. and stock starter and stock fuel pump. 3/8 fuel line.

my question is i also have another crank (scat forged steel p/n 9351w10) im wondering A. will it fit B. if so what would be the correct rod length if i still used stock pistons, seeing that i have a brand new set of forged ones in a box on the shelf?

all of these parts came from summit, so how well are they working together? any help would be great. thanks a million

building for drag!!!!!!

 

[1970fastcat]

Crank will not work, it is for a 351 windsor. A 302 can't handle a 3.85 stroke.

Also, I would consider changing the gear drive out for a chain set. Gear drives are bad news, especially on a street driven car.

 

[ZMAN]

Crank will not work, it is for a 351 windsor. A 302 can't handle a 3.85 stroke.

Also, I would consider changing the gear drive out for a chain set. Gear drives are bad news, especially on a street driven car.

I heard gear drives are noisy, what's the bad.

 

[cougarshaman]

Forged pistons on the shelf should be in the engine. Stock pistons are a major weak link as are rods.
HV oil pump should have a deep sump pan to draw from.

 

[74Xr7302]

well an update the 6a msd box is in and she is running great couldn't be happier with the noticable differance in spark!!! as far as the gear drive, i chose summits noisy gear cause i like the way they sound, i had one in my 86 t-bird (turbo 302 swap) and i never had a broke or streched chain, nor does it ever jump teeth. and its my belief that enjoying your car is just important as it performing well. so noisy gear is the way for me, and this is a track car build, its not a 10 sec car yet, but in time she'll get there.

thanks for the crank info, ill use it in a windsor block i got. and the pistons on the shelf are for the 351, the xr7's block has yet to be bored, but that is next season, i've not taken this car down the track, yet so its off to the tune shop, after i find a torque converter, i'm thinking a 2000 - 2400 should suit my cam well.

 

[1970fastcat]

I heard gear drives are noisy, what's the bad.

There are 3 main reasons I took mine out before I even had 100 miles on it.

1. Without a fixer idler gear, meaning it had 2 floating gears between the crank and cam gears, it had way too much play and was causing my timing to jump around at revs. If it makes the timing jump, then you know it is making the cam timing jump too.

2. It transfers vibrations back and forth between the crank and valve train. Not good for lifters and cam lobes. The "noise" you hear from the gears is caused by vibrations. If it is that noisy then that tells you how much vibration is being transfered to the valve train.

3. The aforementioned floating idler gears get bound up between the crank and cam gear, causing excessive bearing wear. If you just think about how they work, it all makes sense. The crank gear turns the idler gear hard enough that it tries to ride up and in between the 2 gears, causing the crank to be pushed to the 4 o'clock position, and the cam gear to be pushed into the 3 o'clock position. This causes the bearings and journals to wear excessively in these spots. This is not as much of a problem with the fixed idler gear setups, but this isn't the type of set we are talking about here.

All of this is a non-issue with a chain setup. I got the gear drive for mine for the same reasons, then discovered these issues and learned more about them. I went with an AMP timing set, the ones that all the Cleveland racers use. I have 650 pound springs and was told that it would be a non-issue with chain stretch. The owner told me that out of all the chain sets he has sold, he has sold very little replacement chains, with most folks running loads more spring pressure than me.

I would look into a set from Rollmaster or Australian Muscle Parts. They are more expensive than a Cloyes, but much better quality.

 

[ZMAN]

There are 3 main reasons I took mine out before I even had 100 miles on it.

1. Without a fixer idler gear, meaning it had 2 floating gears between the crank and cam gears, it had way too much play and was causing my timing to jump around at revs. If it makes the timing jump, then you know it is making the cam timing jump too.

2. It transfers vibrations back and forth between the crank and valve train. Not good for lifters and cam lobes. The "noise" you hear from the gears is caused by vibrations. If it is that noisy then that tells you how much vibration is being transfered to the valve train.

3. The aforementioned floating idler gears get bound up between the crank and cam gear, causing excessive bearing wear. If you just think about how they work, it all makes sense. The crank gear turns the idler gear hard enough that it tries to ride up and in between the 2 gears, causing the crank to be pushed to the 4 o'clock position, and the cam gear to be pushed into the 3 o'clock position. This causes the bearings and journals to wear excessively in these spots. This is not as much of a problem with the fixed idler gear setups, but this isn't the type of set we are talking about here.

All of this is a non-issue with a chain setup. I got the gear drive for mine for the same reasons, then discovered these issues and learned more about them. I went with an AMP timing set, the ones that all the Cleveland racers use. I have 650 pound springs and was told that it would be a non-issue with chain stretch. The owner told me that out of all the chain sets he has sold, he has sold very little replacement chains, with most folks running loads more spring pressure than me.

I would look into a set from Rollmaster or Australian Muscle Parts. They are more expensive than a Cloyes, but much better quality.

That all makes perfect sense.
Thanks for the info.

 

[74Xr7302]

so then all in all, i have a pretty good set up besides the crank that wont fit, replacing the stock pistons rods, and crank, and the gear drive idler gears need to be fixed to prevent vibration and such. does anyone know how much hp/tq a 71 302 boat engine can handle, because if it is weaker then some of the newer ones or cyl. walls are thinner etc... i do not want to waste time and money on the bore, and machine work if its not worth it.

 

[Floorit]

1970Fastcat - Outstanding info on the gear drive. I was about to order one for my 69 351 4V, but I think I'll stay with a chain now. Thanks for the insight.

 

[Smith Brother]

I can tell you that every time a gear drive car pulls into a outside car show, everyone LOOKS UP, SHAKES THEIR HEADS, and thinks, WHY? IMO.

But each to his/her own.

Dale in Indy

 

[cougarshaman]

All factory 302 blocks have limitations. Generally, the limit is about 500-550hp or so.

I'd go with a 460 based engine in that '74. $:lb/ft ratio is way better.