Inliners International Forums General Discussion Hi Performance Building a 302 GMC for LSR

I agree that the 8.125" rod hurt my low end TQ but felt the longer rod and reduced compression distance would allow me to drasticly reduce the piston, rod and pin weight and make life a lot easier on the crank. By the way, the piston is a custom JE with a 50cc dome. I couldn't find an OEM piston with enough dome to get the compression I wanted. With this combination I saved more than 1.25 pounds per piston/rod/pin.

Another factor is our rules that require a bias ply tire with a maximum tread width of 6 inches. Traction off the line is a problem and tire spin in first gear is excessive, but taking off in second bogs the engine. I wish the rules allowed an automatic tranny. Some of the guys are running automatics and can control wheel spin much better. Their also a few tenths quicker even though our car miles per hour much better.

I'm going to try the 4x1 header and I think it will pick up the TQ quite a bit.

Thanks for the comments, Ron

The reason I say that is because despite all the talk, I have never seen actual dyno runs to support any meaningful horsepower/torque differences. Here's an article to contemplate.

http://www.iskycams.com/techtips.php#2005

I'm not trying to be argumentative here, I just would like to see how much we are talking about.

I've never personally dynoed an engine with different rod ratios. From the tests I've seen the HP & TQ numbers are VERY close, typically <1 percent difference. I'm sure there are specific applications where different rod ratios would be worth the effort. However, on the GMC the piston/rod/pin weight savings over shadowed all else. There are so many other areas to address with this engine that rod ratio is a very low priority.

The distributor gear and cam gear were destroyed the last trip down the strip. So I build an external oil pump (BB Chrysler) and distributor drive thats driven off the front of the engine with a Gilmer belt. I fired the engine and set the timing and everything looks good...no leaks and 60 psi of oil pressure. If I knew how to post pictures on here I'd show what it looks like. If someone will let me send them the pictures they can post them.
That is if anyone's interested.

Ron

Pics would always be great, I dont know how to post them either, as i've had several 292 race engine pics I thought would be good to share....

Ron, I've got the pictures you sent me, give me a bit, I'll post them.

Gottum

I can't seem to find the pics of the rods though.

I remember one that had the stock rod & piston laid out next to the 'new' rod and piston, but I as yet haven't found it in my stuff.

Here

I for one would be very interested. I just happen to have that very pump assembly on my bench right now!

guy's,
ron sent me these pics of the oil/ distributor system for his kickin jimmy.






all you have to do is sign up with imageshack and install their free software. upload your images and then it is copy and pasting after that. i always send the thumbnail version so people with slow internet do not have problems. tom

I'd like to see more pictures of Ron's racer!

Well naturally the more aggressive the profile is on the camshaft contributes to it. But making a change of over 1" inch in length to the connecting rods might have had some part in it as well.....ya think!

The mechanical engineers that have worked with the Winston Cup engine builders i've worked with, have explained it to me in terms that still border on a thesis level. Many times if they cant dazzle you with brilliance, they will baffle you with BS! Sometimes you would get an actual answer to a question, other times they would do that, usually meaning, you don't need to know! First, their main focus is on making the most HP and torque in the engines operating RPM range, usually between 7500-9000 RPM on Super Speedway motors, and around 6500-8500 on Short track engines. So what the engine does below that range, doesn't really concern them that much. They have done so much R&D in the R/L, that they have done exhaustive dyno and cam testing for all possible rod lengths(starting with 6.125" and going to 6.350" with rods made for lengths every .050 in between)and stroke combos. All that with no definintive answer as to why the loss of torque really occurs,other than it does, and they can prove it does. But that loss doesn't affect them, because it happens much lower in the RPM range than concerns them. Im sure that with the same R&D and dyno time that they spend with their engine programs, Ron could probably recoup what was lost, but he would have to know what he lost to begin with, and establish a baseline to compare.

Panic,

The pump is internally vented to the suction side and I figured if the pump could supply steady pressure to a BB Chrysler at RPM, it surely can handle my little GMC at 6000 RPM.

I agree about the scoop....but, my partners aren't gearheads and just wanted it to look pretty. The mirror finish is handy for them to comb their hair. I didn't have a vote on that since I'm bald.

Actually the whole car is a sort of compromise since there are 5 partners on the car. Kinda like someone once stated......the camel is really a horse designed by a committee. Overall, I'm very satisfied with all the partners contribution to the project.

Changes will be made as necessary when (IF) someone goes faster than we do.

Ron

That's gonna take some doin'.

I thought the Ramchargers were combating an oil starvation issue abbove 5000 RPM (and winding it a fair ways past that) when they came out with their bigger pickup tube? Or was I mis informed?