Bang-for-the-Buck

[jeremylmartin]

I just got my 79 spider a few weeks ago. Given that it is winter I figure it is a good time to work on it. I asked a similar question before but have narrowed down my expectations since then and would like some more input before I make a final choice. I'm not looking to milk every last HP out of the engine but am trying to find a balanced approach to increase the power. My understanding is that the 79 is one of the weakest from the factory. I want to only do the items that give the best bang for the buck. I am not really looking for better top end speed but for a better acceleration (and maybe a bit better on the top end - I got most of my speeding out of my system in my younger days). I know there is likely no "silver" bullet but is there any one "big" improvement I can do while the others I have read about are more just icing on the cake? (I don't need to have smog checks done on the car so the smog stuff can (and likely will) all go.

1. Change the carb to an EMPI 32/36 but keep stock intake/exhaust the same (my thought is that this alone might be sufficient?)
2. Do the EMPI 32/36 carb and change intake manifold to a single plane but leave the exhaust stock
3. Do the EMPI 32/36 carb and single plane intake and 4-2-1 exhaust (I think mine is a 4-1) and 2"+ pipe
4. Consider a 34adf?? (worth the cost for my desired results??)

Is there a combination here that I am missing that would be a good bank-for-the-buck modification? Is this the type of thing where none of these alone is much of an improvement - so it is better to do all or none? I am open to any ideas but would like to keep it as simple and cost effective as possible.

[BEEK]

the 32/36 or the 34 adf are both good choices. you will need to replace the intake though to take advantage of either carb. the egr is easy to block off on the exhaust side. i would replace the manifold with a 4-2-1 type with down pipe, or a header

[rodman]

the 32/36 or the 34 adf are both good choices. you will need to replace the intake though to take advantage of either carb. the egr is easy to block off on the exhaust side. i would replace the manifold with a 4-2-1 type with down pipe, or a header

Was waiting for you too chime in ( Richard ) lol

[jeremylmartin]

Thanks, Beek. So the intake swap needs to be done in conjunction with the carb upgrade? Could I do just this (carb&intake) and see decent improvement or would the upgraded carb be significantly restricted by the stock exhaust?

[bobplyler]

I just changed the carb, and it makes a large difference even without changing the manifold. The 79 already has a 4-2-1 exhaust.

[narfire]

I mentioned this in another thred , but I gave a fellow a hand with his 79 in changing to a single plane from a 77 I think and a 34 dmsa carb. He had the 4-2-1 exhaust. He noticed a marked improvement in performance. I think his next plan is go to a 1800 head. The 34adf is great but expensive. Perhaps there might be a 34 dmsa out there or reading here,the 32/36 seems a popular swap as well.

[BEEK]

yes, you need to replace the carb and intake as a unit. some 79 spiders had a 4-1 exhaust manifold. they may be a california emissions version, im not sure. but i have seen them both ways. if you have a 4-2-1 manifold / down pipe then stick with that, until you are ready to go further. to narfire, i dont feel that replacing a 2.0 head with a 1.8 head will be a noticable gain. the couple of cc's difference will raise the compression ever so slightly. but the shrouding of the intake valve in the 1.8 head may take away anything you would gain and maybe more.

[jeremylmartin]

Thanks for all the help everyone. I think mine was bought new in California. I am new to all of this but the exhaust manifold has a pipe coming from each cylinder and then goes into one pipe were the exhaust hooks up. I assume this is a 4-1? The 4-2-1 would converge into 2 separate pipes before going to the exhaust pipe?

[jeremylmartin]

I just changed the carb, and it makes a large difference even without changing the manifold. The 79 already has a 4-2-1 exhaust.

Are you saying you didn't change the intake manifold or are you referring to the exhaust? I like the idea of just adding an upgraded carb as a 1st step but as beek pointed out (and I think I have read it elsewhere) the intake should be done as well. bobplyer - is yours a 79? Did you take the smog stuff off?

[Daniel]

replacing the dual plane manifold with the single is a waste of time if your just upgrading the carb and maybe exhaust
it's a popular myth around here that its needed to see a improvement in performance. I replaced my 79 carb is a 34
and was very happy with the upgrade.

[jeremylmartin]

Thank you for the input Daniel the Bandit...(reminds me of a trip I took to yellow stone on a Suzuki Bandit 1200 motorcycle - screaming across the Idaho farmland at 140 mph - but I've mellowed out since then)...anyway, back on topic. Did you go with the 34 carb over the 32/36 for any specific reason? The 34 is more expensive but I might go for it if it will provide a better fit, performance or reliability.

[Daniel]

I had a 34 that needed to be rebuilt the 79 was stock so it was a good match

[Daniel]

140? way to fast for me on a bike back in 89 i had a new 750 ninja i decided to race a corvette getting on the fwy
as we approached 135 mph my front wheel started to wobble, Ive heard of the problem but never seen or experienced
that before. Scared the living day lights out of me. I had a lot of fun on dirt bikes and ATVs the street bike was fun
as well I just can't see myself buying another I had a few close calls even while doing the speed limit.

[jeremylmartin]

I actually only reached that speed for a few seconds before the front started coming up and I got freaked out. Sold the motorcycle to buy an engagement ring and the rest is history. I'm a family man now and the Fiat suits me just fine. Thanks again for the input!

[rodman]

http://www.youtube.com/watch?v=MyxJCENkjCA