Hey All, in need of a little advise.
1979 spider 2000, carbureted
Recently blew my head gasket and in the process of replacing it have decided to port and polish the head and manifolds and install is single pane intake with a 34 dsma carb off of a 1976 1800. ive decided to have the head resurfaced even though i cant measure any warp but theres a few nicks and i am considering smoothing the chamber and would like to offset any loss in compression that comes with that. Perhaps I could even end up with slightly higher compression net. Also, i plan to remove the cat.
My question is when i get this thing back together with the new carb and better flow there is likely to be some tuning required on the 34 dsma, as its used to the 1800cc stock engine. I figure it'll be good to start thinking about that process and gather the likely jets that may need to be swapped out to get it running right.
I am sure many of you have done a similar upgrade and i would appreciate it if you could share your thoughts / theories / experiences...
Sure excited to see how this thing goes as i've already felt pretty zippy with my stock 77.6 hp, hoping i can get it well above 100.
performance tune briefing needed
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fiatfactory
- Posts: 506
- Joined: Sun Jun 13, 2010 11:22 pm
- Your car is a: 1970 128
Re: performance tune briefing needed
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Last edited by fiatfactory on Tue Jul 02, 2019 11:14 am, edited 1 time in total.
nothing to see here... move along.
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baltobernie
- Patron 2020
- Posts: 3466
- Joined: Sun Nov 25, 2007 6:00 pm
- Your car is a: 1973 Spider [sold]
- Location: Baltimore, MD
Re: performance tune briefing needed
Can't speak to your 34 DSMA, as I went with another carb, but you will need larger jets. Tuning is hit-and-miss without a wideband O2 meter, but it can be done by an experienced mechanic.
Use caution with porting and polishing. You want to remove only imperfections in the combustion chamber. Do not touch the exhaust ports; the head port is supposed to be smaller than the exhaust header. That "flange" helps to prevent spent gas from being sucked back into the combustion chamber. Be very careful also with the intake manifold/intake port. Enlarging the mating surfaces of these openings will result in loss of velocity in this area, which is more harmful than most restrictions you will find. The whole intake stream, BTW, should be finished in 50-60 grit paper; this surface helps to even the mixture. Just remember you're not building a race motor, and the stuff you see on the car TV shows does not apply.
+1 with fiatfactory re: exhaust manifold. Without a 4-2-1 exhaust, you're not going to see much improvement.
Use caution with porting and polishing. You want to remove only imperfections in the combustion chamber. Do not touch the exhaust ports; the head port is supposed to be smaller than the exhaust header. That "flange" helps to prevent spent gas from being sucked back into the combustion chamber. Be very careful also with the intake manifold/intake port. Enlarging the mating surfaces of these openings will result in loss of velocity in this area, which is more harmful than most restrictions you will find. The whole intake stream, BTW, should be finished in 50-60 grit paper; this surface helps to even the mixture. Just remember you're not building a race motor, and the stuff you see on the car TV shows does not apply.
+1 with fiatfactory re: exhaust manifold. Without a 4-2-1 exhaust, you're not going to see much improvement.
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majicwrench
Re: performance tune briefing needed
Just a quick note on head surfacing...if it doesn't need it, please consider NOT doing it. Has it been done before?? Will it need to be done in the future?? Once you shave the heaad you change the cam timing, among other things. If it's flat, leave it alone.
Keith
Keith