Kalel, please don't think you're being ganged up on here. We're all genuinely interested in what's going on with this engine. You're trying something out of the ordinary, so there's bound to be hiccups.
There are fellas in this thread who know a hundred times more about engines than me... but we're all here to learn, and to share what we know.
I agree I learn new stuff everyday That's why I posted this for other thoughts about things It took more than one person to make a engine from the start
Hey Superman! Green Lantern here. The short block you are using has a much faster piston speed per degree of crankshaft rotation. At 10* before TDC the 3.5L rotating assembly is traveling 41fpm faster and past TDC to 75* the piston velocity is at 455fpm faster and the piston is 0.153" deeper in the bore compared to the 2.8L. Another factor is the discrepancy in combustion chamber size. The aluminum head at about 23cc and the iron at about 54cc, that's a bit more than double the size. Ad to that the difference in piston shape, the 3.5L having a dish adding more real state to the mixture compared to the flat top of the 2.8L. Al these differences combined have increased the amount of space that the flame has to travel and knowing the flame travels at one speed the one thing we can do is move the point at which that flame starts. Also if you are using the exhaust system from the 2.8L, that will aggravate the problem because since there is more air mass in, the result will be an increase in volume of exhaust gasses. The restrictive exhaust with its added back pressure will not allowed the gasses to escape as fast and residual unburnt gas can accumulate and burn in the exhaust. I had the same problem when I build my 3.7L. What I did was use a infrared thermometer and play with the timing until I had about 550 to 612F, and for my engine that is the sweet spot. I use E85 by the way. Good luck!
Are you looking at exhaust temp And adjusting timing until you reach desired temp ?
Yes, but the temp should be measured with the infrared meter at the closest point of the header to the head. It is more accurate if you have an individual style exhaust manifold like a header.
start the engine and let it idle until you see them glow red. Measure at every exhaust header runner and all should be withing 20-50F regardless of the peak temperature. You want to see 740-780F for gasoline at idle. Glowing of the manifolds at WOT is normal but at idle is no bueno. Advance the timing until you get to the 740-780F range. If you can't get down to that range the the problem is somewhere else. Maybe restricted injectors or you have the wrong fuel pressure for those bigger injectors.
[This message has been edited by La fiera (edited 05-29-2023).]
Hell it may have a vacuum leak I forgot I plugged the iac hole in the throttle body to make it run It's been 2 1/2 years since I done this motor and put it in the car and just now getting back to it I owe my on mechanic shop and it hard to get time to work on my on stuff
I have a 2005 Cadillac CTS 3.6l I would love to put in it I stripped the whole car took the harness all modules the dash the column every thing out of the caddy just need a front wheel drive transmission for it I also have a 2000 Camero 3800 engine I could do a swap on
Hell it may have a vacuum leak I forgot I plugged the iac hole in the throttle body to make it run It's been 2 1/2 years since I done this motor and put it in the car and just now getting back to it I owe my on mechanic shop and it hard to get time to work on my on stuff
I understand! I had my own shop for 7 years and sold it because if you are in the business to fix vehicles the right way and you are making money, you are doing something very illegal. That's what I learned.
I have a 2005 Cadillac CTS 3.6l I would love to put in it I stripped the whole car took the harness all modules the dash the column every thing out of the caddy just need a front wheel drive transmission for it I also have a 2000 Camero 3800 engine I could do a swap
The problem is that if you haven't solved the problem for the 3.5L and now you want to install a 3.6L or a 3.8L to compensate for your lack of knowledge because you couldn't solve the problem with the 3.5L says a lot about you regardless of how many years you have of experience.
