LT1 & LT4 Head Flow Results

This page is a compilation of information from all over the web, various magazine articles and various folks who have had their heads flowed. It seems the more data accumulated, the more error shows up in the tests.  I cannot attest to the validity of the data, it is here for review and to offer assistance in head / porting selection.  The math used to generate a flow index is a result of several intelligent folks trying to classify the data, if may or may not be applicable, but serves it's purpose

Flow Index = (.300 * 4) + (.400 * 2) + (.500 / 7)
Flow Index = (flow @ * 4) + (flow@ * 2) +( flow@ / 7)

Potential HP based on Airflow (Hot Rod, Jun '99, p74):
Airflow at 28" of water x 0.257 x number of cylinders = potential HP
or required airflow based on HP:
HP / 0.257 / cylinders = required airflow  (see below)

"Flow Index" refers to a formula Jody helped devise to compare driveability between the different cylinder heads. The formula is:
(cfm at .300 lift x 4) + (cfm at .400 lift x 2) + cfm at .500 lift
-------------------------------------------------------------------------
7
Higher airflow numbers at less than peak lift imply more usable hp and torque, since the valves are cycled twice through these values with every cam rotation; flow numbers at highest lift are achieved only once for every cam rotation. This influences peak hp, but doesn't reflect overall driveability and throttle response. The index model attempts to take these factors into account.

(Car Craft, Feb ‘99, p88) Determining peak HP rpm based on peak head flow numbers. These numbers are based on flow measured at a 28" depression.
The formula is: (flow in cfm / 1.68 * 2000) / (Displacement ci / number of cylinders) = rpm.
(flow in cfm / 1.68 * 2000) / (350 ci / 8 cylinders) = rpm
(flow in cfm / 1.68 * 2000) / (43.75) = rpm

HP

Airflow

300

146

350

170

400

195

450

219

Much of this   LT1 data complied by Jody Shapiro & Glen Swartz
Email: jshapiro@netgate.net
or
Email: GISwartz@aol.com

Also...Dan Wicker had a hand in establishing the flow index math
Email: dwicker@premierhome.net

Impala Head Data from Randy Acorcey (NAISSO Digest) furnished by Mike  Reily

Manufacturer and Model
(valve size) if given

Intake - Lift

Exhaust - Lift

Flow Index (I)

Peak HP RPM (350)

Potential HP

Exhaust Intake (Index#) %

Flow Index (E)

0.100

0.200

0.300

0.400

0.500

0.600

0.100

0.200

0.300

0.400

0.500

0.600

TPIS-Stock GM LT1

58.0

113.0

167.0

203.0

212.0

47.0

97.0

133.0

152.0

160.0

1104.3

5768.7

435.9

77.8%

858.9

MD Perf-Stock GM LT1

59.5

120.2

171.5

199.6

212.4

201.7

44.4

91.5

118.1

137.8

148.9

153.9

1115.5

5779.6

436.7

69.0%

769.3

Unk-Stock GM LT1

63.0

126.0

180.0

206.0

206.0

206.0

47.0

97.0

122.0

145.0

171.0

178.0

1161.4

5605.4

423.5

69.1%

802.4

Hot Rod-Stock GM LT1

117.0

165.0

187.0

195.0

195.0

89.0

121.0

130.0

133.0

136.0

1061.9

5306.1

400.9

71.9%

763.0

Avg-Stock LT1 (above) (1.94)

60.2

119.1

170.9

198.9

206.4

200.9

46.1

93.6

123.5

141.2

153.2

156.0

1110.8

5615.0

424.3

71.9%

798.4

LT1 Cast Iron Stock (Impala 94/5)

55.0

119.0

179.0

214.0

230.0

48.0

91.0

128.0

140.0

147.0

1112.4

5576.5

472.9

70.4%

783.3

LT1 Cast Iron Stock (Impala 96)

58.0

117.0

174.0

207.0

221.0

57.0

107.0

135.0

146.0

150.0

1111.6

5525.8

454.4

70.8%

786.8

LT4 GM Stock (CHP mag)

147.0

197.0

230.0

250.0

243.0

109.0

133.0

159.0

172.0

177.0

1283.7

6802.7

514.0

68.1%

874.6

LT4 GM Stock (TPIS) (2.00)

56.0

119.0

179.0

218.0

241.0

232.0

47.0

102.0

140.0

164.0

176.0

182.0

1186.4

6557.8

495.5

77.0%

913.1

LT4 GM Stock (Morgan Motorports)

69.2

150.0

194.6

225.7

235.5

237.0

1263.4

6408.2

484.2

AFR 190 (HotRod)

126.0

198.0

243.0

268.0

262.0

102.0

150.0

175.0

190.0

194.0

1316.3

7292.5

551.0

74.2%

977.1

AFR LT1 190cc Street (from ARF web) (2.02")

129.0

195.0

240.0

260.0

262.0

108.0

156.0

178.0

190.0

194.0

1297.1

7074.8

534.6

77.6%

1007.1

AFR LT1 190cc Comp.(from ARF web) (2.02")

135.0

201.0

243.0

264.0

276.0

110.0

157.0

180.0

195.0

276.0

1327.7

7183.7

542.8

76.5%

1015.9

AFR LT4 195cc Street (from ARF web) (2.02")

132.0

198.0

240.0

260.0

262.0

108.0

156.0

178.0

190.0

194.0

1309.1

7074.8

534.6

76.9%

1007.1

AFR LT4 195cc Comp.(from ARF web) (2.02")

135.0

201.0

249.0

275.0

280.0

110.0

157.0

180.0

195.0

208.0

1341.3

7483.0

565.4

75.7%

1015.9

Blackstone--improved

CNC Heads

67.0

124.0

182.0

233.0

267.0

270.0

53.0

114.0

158.0

187.0

196.0

199.0

1232.1

7265.3

549.0

83.9%

1034.0

Dominion 32 valve

107.6

188.8

254.6

294.5

314.5

325.0

92.1

165.6

204.2

239.7

259.4

270.7

1652.3

8557.8

646.6

80.7%

1333.3

DRM CNC'd

71.0

144.0

199.0

237.0

258.0

267.0

80.0

132.0

172.0

194.0

202.0

208.0

1306.9

7020.4

530.4

84.5%

1104.9

Flo-Tech LT1

63.0

138.0

202.0

245.0

265.0

269.0

53.0

119.0

157.0

185.0

200.0

208.0

1335.9

7210.9

544.8

76.8%

1026.6

GTP Stage II LT1 (Blackstone test)

70.0

122.0

186.0

222.0

254.0

266.0

51.0

115.0

145.0

176.0

204.0

217.0

1224.3

6911.6

522.2

78.5%

961.1

GTP LT1 (Morgan Motorsports stage unknown)

72.4

138.5

188.6

228.9

257.6

247.9

1249.0

7009.5

529.6

GTP Stage II LT4 (2.02)

66.9

137.5

193.5

236.3

265.6

280.2

56.7

112.0

148.4

183.7

198.9

208.1

1284.5

7227.2

546.1

77.0%

989.4

GTP StageII LT4 (by Chris B)

64.5

135.6

192.3

239.5

269.4

283.9

54.5

111.4

147.0

183.5

202.1

222.1

1286.7

7330.6

553.9

76.5%

983.9

GTP LT4 (Morgan Motorsports stage unknown)

77.1

147.8

195.4

231.8

263.7

278.2

1282.9

7175.5

542.2

GTP Race LT4

147.0

207.0

262.5

300.0

312.9

126.8

160.0

196.5

220.0

232.9

1395.9

8163.3

616.8

76.3%

1064.4

Larry Kurek LT1(1.94)

56.3

120.8

176.8

214.7

225.4

220.0

43.9

84.8

112.4

134.3

147.9

155.8

1168.8

6133.3

463.4

63.3%

739.3

Larry Kurek(2) LT1(1.94 Manley RaceFlo)

62.0

132.0

186.0

219.0

235.0

226.0

45.0

92.0

124.0

149.0

165.0

169.0

1215.6

6394.6

483.2

67.3%

817.6

Larry Kurek(3) LT1(2.0 Ferrara)

71.0

138.0

188.0

225.0

242.0

232.0

60.0

116.0

146.0

168.0

174.0

179.0

1236.6

6585.0

497.6

76.4%

944.9

Larry Kurek(4) LT1(1.94 stock)

66.0

132.0

184.0

219.0

247.0

235.0

45.0

91.0

117.0

138.0

155.0

166.0

1209.3

6721.1

507.8

63.4%

766.1

Lingenfelter

197.0

236.0

252.0

261.0

151.0

185.0

190.0

207.0

1296.0

6857.1

518.1

77.2%

1001.1

MD Performance LT1 (1.94)

65.1

128.8

183.9

221.5

247.9

233.7

57.6

103.3

135.3

154.6

164.4

172.0

1214.0

6745.6

509.7

72.0%

873.9

Modern Musclecar LT1

67.0

135.3

199.0

240.6

271.9

284.9

51.5

117.2

154.8

180.1

199.7

203.8

1316.0

7398.6

559.0

76.6%

1007.9

Modern Musclecar LT1 (Quoc - flowed locally)

61.0

132.4

183.0

223.0

250.2

256.5

47.4

105.7

146.8

176.8

200.8

213.2

1213.7

6808.2

514.4

79.9%

969.5

Morgan Motorsports LT4

72.9

142.0

195.5

242.5

267.6

280.5

1305.2

7281.6

550.2

MTI (GTP ported)

193.0

233.0

262.0

273.0

152.0

177.0

189.0

193.0

1275.4

7129.3

538.7

77.5%

989.0

Ronald Trigg (custom port)

160.0

230.0

267.0

280.0

285.0

109.0

148.0

188.0

206.0

215.0

1494.0

7619.0

575.7

66.8%

997.4

TPIS ("cleaned up") LT1

67.0

136.0

200.0

230.0

251.0

263.0

56.0

117.0

150.0

171.0

182.0

191.0

1295.9

6829.9

516.1

74.7%

968.0

TPIS-Ported LT1

63.0

129.0

192.0

238.0

260.0

258.0

53.0

107.0

138.0

171.0

185.0

194.0

1281.1

7074.8

534.6

71.8%

920.4

TPIS-Ported LT4

56.0

123.0

196.0

235.0

261.0