Engine tuning

[rgh0]

Remember if you increase the cubic capacity without also increasing the breathing capacity of the head your gains will be less than than expected.

A cleaned up big valve head with a high lift short duration cam and right carbs and exhaust will breath into the 150 to 160 hp region. It will get to the 170 to 180 hp region with a top quality porting job and larger valves and the best cams.

Getting above 150 hp requires revs above 6500 rpm or capacity above 1600 cc.

The breathing capacity of the best original head with the best porting is around 180 hp no matter what the cams, capacity or revs you put under it, may be a little more if you have a Hart head with fuel injection and 1600 cc plus 9500 rpm. The McCoy conversion or the new cast heads from SAS , QED or Dave Bean will do more with the right cams, big capacity or big revs but the dollars are rapidly going up when you enter this territory

cheers
Rohan

[2cams70]

A cleaned up big valve head with a high lift short duration cam and right carbs and exhaust will breath into the 150 to 160 hp region. It will get to the 170 to 180 hp region with a top quality porting job and larger valves and the best cams.

Getting above 150 hp requires revs above 6500 rpm or capacity above 1600 cc.

The breathing capacity of the best original head with the best porting is around 180 hp no matter what the cams, capacity or revs you put under it, may be a little more if you have a Hart head with fuel injection and 1600 cc plus 9500 rpm. The McCoy conversion or the new cast heads from SAS , QED or Dave Bean will do more with the right cams, big capacity or big revs but the dollars are rapidly going up when you enter this territory

Yes but my argument is that if you take a standard small valve head and don't do any work on it and just bolt it onto a big capacity block your gains will be less than expected. If around 140HP is the target then the QED 420 cams are fine with extra some head work done (which you'd still need to do for a large cubic engine anyway) and still retain a relatively untouched bottom end.

There are quite few cars that have lost some of their sporty character by going to larger capacity engines - eg.

Mazda MX5 1.6 versus 1.8L
Honda S2000 2.0L versus 2.2L

[rgh0]

I dont disagree but the type of modest head mods and cam changes I described will be limited by revs or capacity not by the head itself and capable of more than the 140 to 150 hp range with a bigger than 1600 cc engine or more than 6500 rpm bottom end.

cheers
Rohan

[Dieschelan]

You can certainly develop the earlier engines as much as the later ones. How much money you want to spend will determine how much reliable HP you can get.

If you're car has its original engine it may be nice to keep that so you have something to drive while you build a big engine to swap in and have something to go back in if you ever want to return it to original as others have said.

cheers
Rohan

What is the best Tuning combination for a 4 bolt crank with 125e cons?
Are 140-150 hp to much power for this engine? Is not better and safer less power? Is there neccesary to do many modification from S/E cams to sprint?
I’m thinking in a 120-135 hp engine ...

Cheers

Diego