combo advice

Hi Guys,

I'm helping my father with his drag car. I know it's Brand X, but the question is still relevant. The car combo is a 4link, '66 Chevy II with a Heidt's coil-over front end. It currently sits on 31x14 tires with a 'glide and a 5.14 gear, approximately 2500lbs. I have a line on a very fresh 312" sbc comp engine. It was built and maintained by a very well known and successful Comp Eliminator racer. It is a 13 degree head combo. We were originally going with a 393" combo which is a high-winder but nothing like this 312. Other than going to a deeper rear gear, I'm looking for some advice on converter shops to key on for a foot-brake combo like this. I've done tons of reading and opinions on the net are like belly buttons on who is good, bad, or up and down. The rpm range of the engine will be about 8k-9800rpm. I haven't pulled the trigger on it yet, because I'm not convinced its a better option for us than a 393 combo with 15 degree heads. What is making me even consider it is the price. I understand the level of maintenance to be expected, what we were already planning on was going to be a heavy-effort combo too. I just wonder how the reduced torque in the smaller engine will narrow or widen the window to perfect the way the suspension works. I would think the reduced torque would soften it up, but only if the converter is spot-on.

Thanks

Tough choice since you don't know the intimate details on either engine. If both engines are built correctly then either one would work. Personally I prefer the bigger engine with more torque but some people love the smaller engines with the super peaky power curve. Either combo can go fast and there are lots of examples at the track. Best bet is to talk to someone with a very similar car to see who they like for torque converters. Lots of people can make torque converters so I always tell people to find a vendor who they like talking to since you'll be talking to them a lot. It often takes at least 2 or 3 converters before you find one that really works for you.

If it were me, I would put it on a dyno (I am bias) and get some numbers before talking to a converter guy, unless you like pulling transmissions and shipping converters back and forth.

Joe

A-1 with a 7" converter. They want dyno specs to set up for the right set up where possible.

Hi Andy,

The 312 makes 760hp with that higher rpm window. The 393 would be a tick over 800hp, but the rpm window would be 1000rpm lower.

IMO pretty simple choice, A1 as high winding SB's are their bread and butter. They would want a dyno sheet or at the very least some previous performance numbers and details. But I can tell you the dyno sheet is a much better start. Those two engines will require two different converters, just to much stroke difference to not require two.

That's what I'm looking for, thank you. I felt we would have to move from an 8" converter down to a 7" converter as well with this combo. Our current SLR is 9.05....I think that might be a bit light for the 312's manners, so the gear change would bring it to 10.91. That and the right 7" converter might be able to print some respectable 60ft times with the 4 link where it's happy.

Thanks Al, I was just typing that last response as yours posted. I was hoping you would post, as I know you have a pretty intense small block combo. I do have access to a dyno sheet. Feel free to weigh in on my SLR thoughts

A lot of factors play in slr numbers, IMO there is no "magic slr". Don't get to hung up on it its gonna want what it wants based on power numbers and where they occur. That little engine is likely going to want a fair amount MORE slr than the bigger armed one for sure. This is pretty much and apples to oranges deal honestly. I am sure the TQ numbers are significantly different in number and RPM. Id think that little engine would want to be over 11 for sure

Thanks for the advice, greatly appreciated

Happy to help anyway I can. feel free to PM me if oyou like happy to look over data etc..

Will do