Big Block Conversion

[KEITH'S75CUSTOM]

originally posted by STOVEBOLT

4th Gen Big Block Conversion..

On my 77 I used the 520-2455-1 Hooker Competition's (for 70/72 BB Camaro) ceramic coated 2" primaries, fit great and I used the 305 motor mounts. 3rd gen BB mounts offset the motor to passenger side (not needed on 4th gen because they are front steer) and don't believe the Headers will clear the shock tower on passenger side if used.

You do have to grind a little off the corner of drivers side (clam part) of the motor mount (per instructions) easiest to fit on engine stand.

I also used the Hooker reducers, they are heavier gage and welded, rather than the thinner flanged slip joint junk.

Also used the Flo-Master Thunder Exhaust System for 67/68 Camaro (crossover, twin 40s, dumps down behind rear wheels) fit and sound great.

If you have a non/air car you will need to change the heater core to a BB core (Same as 67/68 BB Camaro) Original Parts Depot has them with the little trim plate. http://www.frontiernet.net/~irishhills/core.jpg

My car was non/air (smaller narrow radiator) so I cut out the right side of the core support to use the wider size air rad. and used a 4 core air rad., with the top hold down support from an air/car, also used a stock air/car shroud (with a little trimming on rad. side) I did have trouble with the stock GM clutch fan clipping the top of the shroud and found another stock clutch fan 1" smaller in diameter that corrected the problem.

Also if you use a TH-400 you will need to move the cross-member back to the next set of holes in the frame. (mine had the extra holes but I hear some don't) also using a TH-400 you will need a fine spline yoke, the one I found was 1" shorter than the yoke on my 305 car, but the TH-400 is 1" longer so it worked out perfect.

Other than that it's pretty straight forward bolt in.

[Nova Bob]

all very good and useful info.....thanks Keith.

[Pop-A-Top]

Can someone confirm that for a similar planned SB to BB conversion in a 3rd gen, is the issue of whether or not the heater core/box has to be changed in a non/AC car because the non/AC radiator will not have the capacity to cool a BB? I'm hoping to avoid having to change my heater system as part of my conversion, and would rather deal with a radiator change, if that is the issue.

Thanks,

Mike
Tennessee

[StoveBolt]

Can someone confirm that for a similar planned SB to BB conversion in a 3rd gen, is the issue of whether or not the heater core/box has to be changed in a non/AC car because the non/AC radiator will not have the capacity to cool a BB? I'm hoping to avoid having to change my heater system as part of my conversion, and would rather deal with a radiator change, if that is the issue. (67/68 BB Camaro core will work)

Thanks,

Mike
Tennessee


It's a clearance problem with the core tubes/hoses clearing the head, with a BB core the tubes come out the other end of the core (closer to the passenger side) use the same heater box but with a BB core. (67/68 BB Camaro core will work)
http://www.frontiernet.net/~irishhills/core.jpg

Edit: Still have to change the radiator to a higher capacity (4 core or aluminum)

Also on a 3rd gen you will have to use BB motor mounts to offset the motor, so the headers will clear the steering box and use headers for a 1st gen camaro.

[Pop-A-Top]

I've read and discussed the various issues associated with the conversion that was completed on my car this week. I figured for what it was worth, I'd share a few details of my project. The shop could not get the BB frame mounts to work. They even tried switching them. In each instance, there was a conflict with the manual steering box. They then tried the original SB frame mounts. Everything cleared. Somewhere in the archives I read someone else solved the same problem in this manner. We did not change to a BB heater box. The hoses are very close to the passenger side head, but they clear. As for the distributor, we converted to an HEI, a regular, rather large distributor head. Again, it's a close fit, but it does fit, without distorting the firewall in any manner. We changed from a 350 ci to a 402 ci. I had new Hedmann ceramic headers, which fit very nicely without any conflict. I had all new 2.5" aluminized pipe with the 'H' pipe configuration installed while it was in the shop. I pick up the car on Monday and the shop owner has driven it a couple of times and said it's running great. I can't wait to drive it. I have done nothing to my stock SB radiator. The new motor has a clutch fan arrangement with no BB shroud yet and a short water pump. I'm anticipating cooling issues when the weather gets warm. I considered buying a BB shroud and continue with this mechanical fan. But, something tells me I probably should get a quality aluminum radiator and use electric fans, and do away with the mechanical fan. If anyone has a good cooling set that would work for me for sale, let me know. I believe this might be the way to go. Maybe this information will help some other newbie toying with a similar conversion...Mike, Nashville, TN area

[StoveBolt]

Interesting, I have never done a BB 3rd gen Nova, but have done a 1st gen camaro switch and with the understanding they have the same subframe, steering etc. I'm surprised.

[Green Dragon]

On our 69 - an original 6 cyl car - we used the original 6 cyl motor mounts for the 402, over the counter ( at the time) TH400 trans crossmember, and 'swap meet Camaro BB headers '.
manual brakes, manual steering - NO clearance issues.

We also ran a stock ( auto parts store replacement ) V8 radiator ( the standard width one, not the slightly wider 'a/C' version ) .

402 LS3/ TH40, 10" converter, 4:10 posi = very quick, no overheating issues ( although note this was NOT street driven other than up and down the street in fornt of dad's shop :) .

not sure why there'd be a n issue with the BB mounts, all they do is move the motor FORWARD ( over my 56 cyl mounts anyways ) and slightly tilted for clearance... in fact an early super stock 'trick' was to use the 6 cyl mounts to gain an ever-so-slight rearward movement of the motor for weight transfer, not sure if that minimal ammount made much difference, but when you;re talking thousandths of a sec to win or loose... who knows. ..

your mileage may vary, but worked for us.

~ AL

(couple pics of the 69 on my cardomain page, under 'Sailoral " )

[taz3]

BB mounts move the engine to the pass side as well as the 400 TH crossmember,for some reason some guys have made it work not using BB mounts,but if power steering is invovled it is an issue.The size and brand of header also matter.My power steer 69 BB car has less room then my manual steering BB car.Both OE BB cars.

The front steer is much better in the 4th gens

[StoveBolt]

Crossmember Info when using a TH400 in a 4th gen...

http://stevesnovasite.com/forums/showthread.php?t=59821

[1977Chad350]

hi keth what size was the clutch fan that you used?