center main strap

[pikeyboy]

Just wondering how many people would recomend using a steel four bolt center main strap on a 1380 race A series race engine. Is it an over engineering approach and a bit of a waste of money, will the std cap with a surface ground finish on the top and a steel bar be sufficent?

any opinions welcome

thanks pikey

[markelvin]

I ceritainly would

[fwdracer]

If you are having the block line bored anyway then the 4-bolt centre cap is a good investment. It may apear expensive, but start totalling up all the components in the gearbox/sump should the crank decide to let go.

[cooperman]

If you want to really rev it, it's s must. The 'A-Plus' block is better than the early ones, but still it's a wise precaution to add the strap.
The only 'big' block which doesn't really need one is the genuine Cooper 'S' block, but they are as rare as rocking horse droppings these days.

[pikeyboy]

thanks for the swift replies fella's

cooper man, what do you mean by really rev it? I'm prob only going to set the limiter at 7500 as i'm going for a 649 type cam as i preffer a bit more grunt lower down, would you say thats considered really reving it? I think from bill richards site he only seems to use a strap.

[fwdracer]

Mini Miglia's run STR930 (AKA modern 649) Cam and regularly see 8000rpm. Your rpm will only be limited by the breathing potential of your induction sytem/head/exhaust. A strap should be the absolute minimum.

[pikeyboy]

ahhhhh see what you mean now.

I've been used to running in a road going class that only allowed std 1 1/4 inch SU's with std size valve head. I've just moved upto the road modified class with 1380cc 45 DCOE webber, longman GT15 head etc so i guess this will rev like a good un compared to my old spec engine. I used to get to about 7500rpm in that but it felt a bit strained and didnt go any better. I hadnt factored in the better breathing of my new set up.

Re the cam I'm going for one of those STR930 swiftune jobbies is that a good choice?

[cooperman]

That sounds like an ideal cam.The old 649 was, IMHO, getting a bit old and cam technology has moved on a lot since 1964.
For 7500 on a non-'S' block a centre strap is a minimum and you might consider other mods as well like a wedged crank, 4-bolt centre main bearing cap (line bored to suit), lightened and polished rods, tuftrided crank (or a billet steel one), etc. It's expensive, but still cheaper than snapping a crank or putting a rod down through the gearbox thus scrapping the entire engine/transmission unit.

[fwdracer]

649 - Inlet 50-70 / 81-51 Exhaust
STR(MM)930 - Inlet 50-70 / 75-45 Exhaust

Any other info on the application such as Final Drive Ratio? Programmed ignition etc?

Edited by fwdracer on Tuesday 12th December 13:43