What do you think of my combo?

[mikemustang289]

I posted this in 5.0 tech but this is more classic oriented since this motor is going into my 68'

Here is my current combo which has run a best of 14.5 @ 96 on an easy launch

68 Mustang Coupe, 289, .030 flattops, 9.1:1 CR, stock rods w/ARP, Ported Windsor D0OE, 1.85/1.55, Crane [email protected], .498/.498, RPM Intake, Longtubes, Bigs 650 DP, T5Z w/.059 OD, 9" Locker, 4.30 gears, 31 spline moser axles. full MSD.

Ok. so here is the combo I am building

306 roller, 9.2:1 CR, ARP everything, AFR 185's, Jay Allen cam: base specs: 218/224 552/541 114LSA, RPM Intake, 650DP, T5Z, 4.30 gears, 9" 31spline locker, 26X10.5 E.t. Streets, MSD.

Jay didn't give me full valve timing specs yet but from what he said his cam would outperform the XE274hr that I was going to run, he said it is less agressive but would increase the dynamic compression to ~165-170 psi and require 91-93 octane. I trust what he says but I was always under the impression that more power came from bigger a bigger cam.

I'm curious what you guys think my new combo will put down and how much I will gain e.t. wise, or any suggesstions before I finish putting the engine together. Goal starting out in this build was low-mid 12's.

 

[mustangdave]

You need a better intake, the regular rpm will choke that engine.

 

[12sec67]

with 4.30's, mustangdave i feel is correct. you'll need to get at least a Victor Jr. style intake.

 

[Jc69Stang]

Yup on the intake, a Vic Jr would compliment that nicely. Those are some steep gears. You drive it on the street much?

 

[302 coupe]

I'd be expecting 12.30-12.40 area at the track, depending on weight, regardless of which intake is used. I think the strengths of each intake will balance out the performance of one over the other. Rpm will pull harder to 5k, Vic jr pulls harder over 5K, with the 4.30 gear you'll probably be splitting the rpm range. Being as how you already have the rpm, use it. If it nosedives at around 5200 rpm or so, consider switching. or you could go to a 4.10 gear, keep the rpm intake, and still run about the same ET. Or instead of the gear, go to a 28" tire, it will most likely all even out pretty close.

 

[SoCalCruising]

I think the reason for the "smallish" cam is the low compression ratio you plan. A bigger cam would bleed off too much compression. I suspect that if you bump up the compression, your cam grinder would also bump up the duration. Then you would have more power without too much dynamic compression for 91 octane.

 

[mikemustang289]

thanks for the suggestions. the T5z has a 2.95 first and mine's built with a 0.59:1 OD so the 4.30 gears act very similar to 3.73's with a stock T5. Only real difference is 2nd,3rd,4th are a little steeper.

I figured I would trap around 105-108 area and that puts me at 58-5900 at the finish. I will switch to a taller tire if needed.

I'm not too worried about the compression, If I had the choice I would have went with different pistons with less of a dish but the AFR's have the smallest chamber's 58cc, so im pretty much stuck with that ratio. This was kind of a budget build, I had bought the shortblock for a good price and decided to build around that.