Fairly new on here. Been lurkin the last several months ever since I bought a 460 jetboat and been upgrading it. Just bought a super deal on a new BDS blower kit and Edelbrock heads still in boxes for $3500 for a winter project on the boat.
I have had a 6-71 blown T bucket for years. I question why using a 108 lobe center cam? When I first installed the blower on the bucket I had 10 1/2 hypert. pistons and kept the 108 cam to help blow the charge out the exhaust (as well as running underdriven). But once I rebuilt the motor with the good stuff I went with a good 114 cam and I am 12% overdriven. Been running that for many years now and man is it fun. The blower really tames down a 108 cam, while a 114 cam sounds and lopes great. Personally I would not go back to a 108 cam.
BT
The 108 cam is for a JET BOAT, not a street rod. Close lobe centers narrows the power band and PEAKS the power in a specific RPM range. The jet drive does not need blower power at 2000 RPMs, so why have the rod bearings get pounded at low RPMs? I think YOU called it right when you pointed out "10 1/2 pistons/108 cam." (underdriven ???) Then you go on to say, the 114 cam sounds and lopes great. (that's what you really wanted, right?) I'm glad that you have what you want! BUT, this jet boat motor isn't anywhere near a street rod motor. He is asking for a motor that "runs well and LASTS !" 108 centers will treat the rod and main bearings with respect while giving MAXIMUM POWER where the pump needs it. Lastly, 12% overdriven would be too much for this "pump gas blower motor", considering it needs about 8.00 to 1 static compression. A 'reasonable' 6-71 @ 5% over should give about 6lbs max boost. (with correct carb sizing) The motor should see that boost from 3000 RPMs thru 7000 RPMs and @ 32 degrees of spark timing, do it on 91 PUMP GAS. If he can keep the water temps under 180 (F) and the oil temps under 240 (F), this motor should last 3 seasons. After the third season it will need #1, 16 new valve springs. #2, reset/replace timing chain (stretch). #3, inspect bearings. #4 new gaskets/seals. #5, carb rebuilds. I know these things to be true from my experience. PS if you want the "blower surge" at idle, just turn the idle mix screws out 1/2 turn (all the way around) it'll SURGE then!
thanks for the explanation. Wasn't tryin to give ya a hard time. Just curious why a 108 and not a 112 or 114? I figured it had sumptin to do with being in a jetboat and not on da street.
This new blower deal I happened to run into I just could not pass up on for the price. I plan on keeping the motor fairly stock and the blower at 1 to 1 or underdriven. Besides I can always stick the blower on my 29 sedan BBC project with another intake if need be.
BT
This is an open forum, as I post, you ask and so on. You stated facts (as I did) and so we exchange ideas/experiences. I have no problem going deeper into what I think works in these motors. Let's keep the dialog going.
Let's keep the dialog going.
Yah, what George said. Let's keep this going.
How bout this one,
I understand how they work and the benefit of cooling the charge after you've heated the heck out of it by building boost, but for your run of the mill blown jet that limits it's hard charges to short distances (think drag races), is there that big of a benefit to an intercooler or are they really for those guys that stay in it for long distances (building tons of engine heat)......?
Sorry for the silly question....john
I just typed out a big long 'deal' (BTU's, inlet temps VS EGT's) on this subject and it "fell off the planet". This happens (to me) on this site all the time. NEVER anywhere else, just here. Sorry, I don't want to waste any more time here. I'm over on V-driveboat.com (with a lot of very smart people) and I never have trouble posting there. "jrork" you know where I'll be. SORRY
Longer runs are benified more by intercooling than short bursts. Some cars and boats benefit more than others. In the case of my 25 daytona, I am able to run 11-12 lbs boost on 87 octane pump gas. Before the intercooler I needed 91 with a splash of av-gas. My street/strip Nova runs no cooler and likes 1/3 av to 2/3 pump gas, but I burn much less fuel in it than the boat. TIMINATOR
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