SU Carbs

[Stubby]

I have been kicking around the multi carb idea and I did some measuring on the Datsun Zcar intake and it looks like anyone who has cut the log off of their head could possibly cut and widen a Zcar intake and bolt on a pair of SU carbs. The intake port araingment is the same, but the port centerlines are approx. 1in less on the Z intake. You would have to make two cuts on each manifold halve, cut two spacers and weld the whole thing back together. I am posting this because I have seen several pics on different post of cut up log heads. I don't have time to pursue right now. I do have a Z EFI intake and a dual carb setup If anyone needs measurements.

 

[xctasy]

You are on the right track. The Ford engine breaths from the right, while the Datsun breaths from the left.

The Datsun engine as 3.98 and 3.96 bore spoacings, while the Ford is 4.08". However, the chopped up log head only differs a small amount from the Datsun item.

Since aluminum is easy to cut and TIG weld, and the basic dimesions are close, you will be okay if you separate the centre branch, and adjust the spacings so each port gets a good shot of fuel air mix.

Heres my LD 28 diesel intake which I'm fitting to my log head.

http://img.photobucket.com/albums/v223/ ... C02649.jpg


The L28 is a 240/260/280Z engine with the same OHC set-up as the gasoline Datsuns. I had one in my Falcon 500 before the X-flow and AOD went in.

http://img.photobucket.com/albums/v223/ ... C02237.jpg

http://img.photobucket.com/albums/v223/ ... C02628.jpg

 

[ASMART]

Xtaxi: How do you go about rigging a place to bolt the manifold to after you saw off the log?

 

[Stubby]

I have not personaly cut one yet. I have seen pics of several on different post and I don't think it would to difficult to put a flange on it either by brazing or bolting. It would be a tedious job but anything is possible if you don't know any better. The EFI intake that I have for the Zcar has been modified for a Holley and Rochester 2barrels. Ther was a slight problem with it wanting to ocasionaly fouling the #6 plug, so I ran a copper tube thru the block off plate on the front of the log, made a long loop around thr floor of the plenum back out the plate and circulated hot water thru it. I feel the problem was the distance the mixture had to travel combined with the large plenum/low velocity. The fact that the Holley isn't the best atomiser didn't help. We then installed an Edelbrock a/f moniter and dialed in the Holley, It was a wild ride!!! My fatherinlaw was never content with good enough so I adapted the carb flange to fit a Rochester 2G and repeated the tuning process. Awesome power and milage was good. Then I found the dual SU setup with headers. We pulled them installed them on the Z, and I think He was a little dissapointed. The power was great but he didn't get to tune them. The a/f meter said they were perfect and we havn.'t turned a screw on them since. If they are that trouble free they would make an awesome setup on a mustang.

 

[xctasy]

Easy, ASAMRT.

I have made an item to sort that out. Once I've got my US transmission up and running, I'm then doing durability tests on my log head conversion stuff I promised years back.

Watch this space.

 

[Stubby]

The heat tube seemed to fix it just fine. Any fuel that tries to puddle is vaporised. It would probably work better with more velocity, and heat the fuel right under the carb. I thought about cutting it open and using epoxy to reduce plenum volume and radius runner entries, and we probably would have if I had not found the SU setup. Other than the total distance for the fuel to travel it is still better than a log head. The long runners help bottom end I am sure.