| Re: 4 Bolt Main Corvette Block versus Splayed Caps 2bolt LTx |
Subject: Re: 4 Bolt Main Corvette Block versus Splayed Caps 2bolt LTx by JAKEJR on 2010/10/2 15:34:34 BTW, I'm in the process of going through much the same things as you are so I figured I share what I'm doing. I'm in the parts selection process to build my son a 415 LT1 for his 96 Vette. Since it's HIS car, I've been trying to get a good handle on how he wants the engine to perform - off idle torque, idle quality, exhaust note (you know how young guys are about that - 23), etc. We don't have tail-pipe in my County, just ALDL connection for SES codes. So I've got a bit of a break there. I've got Engine Analyzer Pro's simulation program which is supposed to be one of the best on the market for data input, etc. I've been plotting in various cam profiles to see what the differences there are in their various characteristics. I'm pulling them out of CompCam's latest catalog right now. I changed his heads (Dart Pro 1s; 180 cc, actually 189.8 when measured by me), cam and rockers last summer on his stock bottom end 350 and now we're going up in CID. I had a custom CompCams grind made for the 350, so I'm using it's characteristics as a base line for a new cam. That is, to see if a new cam is what's called for. What I've done is plug in all the specs on his 350, as it is now, and ran a simulation then saved it for graphing. I then created the new 415 engine on the program but with the same HR that's in his 350 now. Then I did a comparison of the two. From that point I plugged in the specs of many different CompCams offerings so as see what difference, if any, they'd make when installed in the new 415. I then used EAP's auto chain function to have the program automatically play with the duration specs in 4 degree increments. I'm also playing with LSA differences; then rocker ratio differences, etc., etc. What I'm primarily interested in are the DIFFERENCES between them - not the accuracy of the numbers, themselves. See what I mean? If I run different cam specs that show an average of, say, 20 lb/ft torque and/or HP increase from the cam he's now running, then I'll know I'm moving in the "right" direction. That is unless the DCR goes too high or something like that. Lots of variables to juggle, LOL. After all the research I did last year, I decided on a single pattern profile and he's been happy with it, but going up 65 inches may make a significant enough difference to call for another profile - and, yea, another $300, LOL I just began the EAP Chain function yesterday and, right now, I'm in the same range as you are for a cam- the 218/224 - 224/230 - 230/236 @ .050 area. Since his car is a DD, there are a lot of variables to be considered, a lot other things just merely looking at torque and HP. I installed a set of Dart Pro 1s on his 350 last year and used the flow numbers from a few different sites (not just Dart's) to get a representative idea of their flow range (not much difference from Dart's #s I might add.) Anyway, I used EAP's percentage CFM flow feature to increase head flow CFM in 5% increments to see if there'd be justification to have his stock 180 cc Darts ported to achieve a 5% flow increase. I'm looking at the cost/benefit side of the picture on that. In other words, I'm trying to see if it would be of a cost benefit to have them ported for the power increase that it would provide. So far it seems doing that wouldn't be worth the cost. I'm still in the analysis part though, so I haven't made a decision on that. May well turn out to be the same as with the cam. Hope some of this helps. Jake |
