Carbed and FI cam difference

[zoe60]

I may have found something out by accident. I have an '89 LX that I bought in 2006 (carbed). It had a cracked block so I bought an Aspire engine and installed it using the Aspire hla rockers and the Festy camshaft (originally with mechanical lifters). The cam is stamped with a "B101". Then I switched to a 1st gen B6 from an '89 Mazda 323. Hla lifters like before with the B101 cam. This car has had a rough idle and low vacuum (16 inches and jiggling needle) it seems like ever since I bought it. (of course the original motor was screwed) Yesterday I was playing in the garage and found a cam that I bought at Pull a part 2 years ago but never installed it. It was from a '91 Festy and the casting number is "B308". I went ahead and put it in and viola! 20 inches of vacuum and the idle was smooth! I think it may be important to use the correct cam with the correct lifters. Don't mix a carbed cam with HLA's and vice versa. I know someone will say I must have been off a tooth or something but over the years I have checked for that about 6 times. I hope this helps someone.

[getnpsi]

Fi and carb cams are the same. The fi festy has a fuel pump lobe still. Its the whole aspire cam design that is not

[sketchman]

^X2

I've used all 3 types of rockers on the same cam. No issues. I think something else was going on here.

[zoe60]

I always thought so too. Just thought I would throw it out there. The cam is the only thing I changed and it solved a big problem I've had with this car. Almost didn't post this but I thought it might help someone. I always blamed it on the intake but it runs fine with it now. I know I'm not gonna put the B101 cam back in! It will be interesting to see what it does to my fuel economy.

[1chrisapple]

well if it solved ur problem with rough idle and low vacuum then it don't matter what everyone else says at least u got her going better than ever.anybody have proof the cams are the same between them other than the fact they used them and they worked .lol

[sketchman]

I think Matt posted that they are the same, IIRC. When he first started here and someone said there should be a difference. Lemme search.

EDIT: My apologies. Brain fart. See correct info below. Specs are valve lift.

hyd '90-'93 B3 .374 IN .378 EX
mech '88-'89 mechanical has slightly less lift typically .008-.012
hyd roller '94-'97 .382 lift IN/EX

So almost the same.

[zoe60]

well if it solved ur problem with rough idle and low vacuum then it don't matter what everyone else says at least u got her going better than ever.anybody have proof the cams are the same between them other than the fact they used them and they worked .lol

Yeah, I'm no mechanical engineer and I know nothing about measuring cam lobes but I just drove a hundred miles and the difference is night and day. Who knows, it could have been something else that I mistakenly did. When I got home I threw my B101 cam in the trash!

[sketchman]

My thinking was that it could have been a more worn cam. Especially with the sliding rockers. Then when you changed to a slightly larger engine the problem was more noticeable. IDK, though. I could see that if the mech cam is already a TINY bit smaller to begin with, that after 100s of Ks of running then put into a bigger engine it would show more. But again, that's just speculation.

[bravekozak]

Does anyone remember of the top of their head what the fms performance and competition cam lifts were?

[sketchman]

Just found some by accident.

FMS Comp Cam .449" IN .445" EX

Again lift at valve.

[getnpsi]

Is there an oversize exhaust valve available for B3 or b6?

[sketchman]

Matt's valves.