i was out working on the DOHC today just turning screws and a friend of mine with a carbed 350 vortec fiero said that by doing the cam timing i lost some torque which i know i did but seeing that i have never driven a DOHC in a fiero is it better 0-60 than a DOHC without the cam timing ???
i have the mod done already but you know how all v8 guys are, they are all about torque but i am a high revver.

has anyone on here had like a before and after DOHC first without cam timing then with????

thanks all

Edited for context.

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[This message has been edited by Phaeton (edited 07-17-2004).]

Phaeton, He's talking about retarding the exhaust cam 13 degrees, it's supposed to give you more horses up top but less torque lower down. The engines are supposed to be non interference but I hope I never have to test that theory. Also there is very little in the way of performance equipment for this engine so any custom cam is going to be waaaaaaaay expensive.

Personally, I've left mine alone until I get it running right, ruddy code 42 is back, arrrgggghhhh....

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Dave E

www.ltlfrari.com

[This message has been edited by ltlfrari (edited 07-16-2004).]

There is a thread on 60*V6 about custom cams for the DOHC.

http://60degreev6.com/forum/viewtopic.php?t=1759&postdays=0&postorder=asc&start=0

Someones been playing with his Desktop Dyno and posted a graph (page 5) showing "advertised stock", "actual stock", W41 Quad 4 profile and the 13* retard. Cams will get you more at the top end, but you lose a lot at the bottom.

I was considering doing my cams but I think I'll do the 13* instead.

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1988 GT, 5-speed, white, beechwood leather, trying to get my 3.4 DOHC put together.

[This message has been edited by sspeedstreet (edited 07-16-2004).]

do the cam retard mod. its worth it in a fiero. A fiero is lightweight and can sacrifice some low end torque for more top end hp. It will be beneficial for you to do so.

good luck

I too would like to hear from someone with first hand before and after knowlege. If not, I guess i'll be the first . Might be a good thinng, because I try to take a lot of pics, and right now I wish somone had a thread on the adjustment with lots of pics, so I could get a good idea of what to do. but again, if it doesnt exist, I guess I'll make one when the time comes

on that graph what is "official GM" and "W41"?????

i see what the other 2 are though but it seems that hp is raised a LOT!!!

I have never driven a 3.4 DOHC equipped Fiero or other car with the 13 degree mod, but I have driven several with the non-modded engines and this is my take:

From what I have been hearing, this is a mod you don't want to do unless this is going to be a purpose built all-out top speed vehicle. The reason I say this is because even mated to a getrag or muncie, the 3.4 DOHC in stock form doesn't even match the accelleration of a stock 2.8L before 3200 rpm. I would imagine that doing the cam timing mod would make this engine such a turd around town you would hate to drive it on a daily basis. Out on the highway you would be ok and I am sure it would be a lot of fun. In stock form the 3.4 DOHC offers a good balance between top end power and drivability. The majority of the people I have met over the years who own Fieros don't even go much more than 10 MPH over the highway speed limit anyway so the cam timing mod would be a waste if you drive like one of these people.

On the other hand if you drive it like you stole it and like to frequently "stretch the legs" of your Fiero then by all means it will probably be a worthwhile mod. Just keep in mind you still have to get out of grandma's way when the light turns green.

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power corrupts. absolute power corrupts absolutely.

Custom Chip Burning | Fiero Engine Conversions | Turbocharging | www.gmtuners.com

I'm not sure I would bet my stock 2.8L against a stock 3.4L DOHC. I've driven several (one often) and I still think the DOHC would take it at every turn.

I've driven two Fiero's with DOHC's and some serious cam timing changes (Mike Smith's is one). By the time you were getting any significant improvement in the top end, the driveability below 3000 was attrocious. Not just a loss of power but the engine would buck and bog. I would improve the breathing the best you can and leave the timing alone, otherwise spring for some new camshafts with the grind you want.

IMHO

TK

quote Originally posted by Exotic Rida: on that graph what is "official GM" and "W41"????? i see what the other 2 are though but it seems that hp is raised a LOT!!!

Summed up; What is advertised as the cam specs and what are actually measured on the cams are not the same. The "W41" specs are the ones that came on the Quad 4 engine that are kind of the outer limits of specs that he's been playing with just to see what's possible.

Read through the thread for an expaination of "Official GM" and "W41".

If you go to link above, itll explain the GM and W41, but basicaly speedstreet got it.
If you look at the HP graph though, it would definitly be worth it, but I think you might see bigger losses in a torque graph.

quote Originally posted by TK: I would improve the breathing the best you can and leave the timing alone, otherwise spring for some new camshafts with the grind you want. IMHO TK

I think that is the key to getting more power out of this engine, new cams. There is a problem however. The 3.4 DOHC engine uses hydraulic lifters that are not adjustible. This means you would probably not have good luck regrinding stock cams because the stock lifters would not be able to compensate effectively. Perhaps someone has a lead on aftermarket cams or lifters?

FYI Quad4 and 3.4 DOHC lifters are nearly Identicle, the quad 4 lifters have a slightly shorter skirt on them, they also seem softer to push the plunger in on. You CANNOT increase the lift on the 3.4 DOHC cam's. First the lobes peak at .370" lift, that peak is only .020 short of the overall diameter of the cam. Since these cams are inserted long way's as opposed to having little caps holding them in, The peaks should not be raised. (you would have to finnagle the cams into the housing If that's even possible) You can however decrease the diameter of the base circle. Then you have a much bigger problem because the bucket lifter will no longer reach the cam through the duration of the base circle. You can pretty much scrap that Idea, not to mension you do NOT want to put any additional load on the cam belt, because that WLL become the weakest link. But there is plenty of room for increases in duration though
Personally, I had driven my 3.4 DOHC powered Fiero with the 13º Exhaust cam retard. Didn't much care for it. The gains were negligable, but the engine Idled with a harsh vibration. When I turned the cams back to factory, I was MUCH more pleased to have it back to nornal. My 3.4 DOHC had plenty of torque IMHO. I had no problem lighting up the tires on demand. This was with an automatic (never going to make that mistake again!)

another little fact, Quad 4 valves are almost Identicle to the 3.4 DOHC's, the only difference's are that the stem is approximatly ¼" longer then the 3.4 DOHC's, and the Q4 exhaust valves are flat as opposed to tuliped. Maybe there is a way to take the cams diameter down a whole bunch to have it reground with the base circle 1/4" shorter... Nah.

The way I see it, All you have to do is decrease compression alittle and then apply boost, Its pretty easy to dial in the cams for boost when you have fully adjustable cams from the factory...